milling cast iron materials with ceramic, pcbn and …

MILLING CAST IRON MATERIALS WITH CERAMIC, PCBN AND CERMET CUTTING MATERIALS

WHITE PAPER

OF SOLUTIONSDISCOVER A MULTITUDE

Published by:CeramTec GmbHSPK Cutting Tools Division Hauptstrasse 5673061 Ebersbach [email protected] Author: Joachim Beck/[email protected]

This publication constitutes a general, non-binding, informational document. The contents reflect the view of the Cutting Tools department of CeramTec GmbH at the time of publication. This information has been created with the utmost care. However, no claims are made regarding accuracy, completeness and/or currency. In particular. this publication cannot take into account particular conditions that may arise in individual cases. The reader therefore uses this document at his/her own responsibility. All liability is excluded. All rights, including whole or partial reproduction, are reserved for CeramTec GmbH.

Published: 06/2014

CONTENTS

Introduction ...................................................................................................................... 5

Milling with Ceramic Cutting Materials ............................................................................. 5 - 6

Types of Cast Iron Materials ................................................................................................... 7

Cast Iron Microstructures and Machability .............................................................................. 8

Designation System for Cast Iron ............................................................................................ 9

Machining Cast Iron Materials ............................................................................................. 10

Machining of:

- Grey Cast Iron ............................................................................................................ 11

- Ductile Cast Iron ........................................................................................................... 12

- Austempered Ductile Iron, ADI ...................................................................................... 12

- High-Silicon Cast Iron ................................................................................................... 13

- Compacted Graphite Iron .............................................................................................. 13

- Chilled Cast Iron ........................................................................................................... 14

Cutting Materials for Milling and their Properties ............................................... 15

Ceramic Cutting Materials for Milling ............................................................................ 16 - 20

PcBN Cutting Materials for Milling ................................................................................ 21 - 22

Cermets for Milling ....................................................................................................... 23 - 24

Milling Tools from SPK Cutting Tools ................................................................................... 25

SPK Series of Milling Cutters ......................................................................................... 26 - 31

Application Recommendations ............................................................................................. 32

1

2

Basics for Milling ........................................................................................................... 33

Climb/Conventional Milling ................................................................................................. 34

Size and Position of Milling Cutter ................................................................................ 35 - 37

Exit angle of Insert .............................................................................................................. 37

Pitch of the Milling Cutter ................................................................................................... 38

Number of Inserts Engaged ................................................................................................. 39

Approach Angle, Cutting Forces and Chip Thickness ..................................................... 40 - 41

Calculating the Machine Power ........................................................................................... 42

Surface Quality during Milling ....................................................................................... 42 - 43

Formulas, Units and Tips .............................................................................................. 44 - 46

Troubleshooting .................................................................................................................. 47

DIN 8030 Dimension Table .................................................................................................. 48

About SPK Cutting Tools from CeramTec GmbH ................................................................... 49

Achieving Milling Success .................................................................................................... 50

3

Milling White Paper 5

INTRODUCTION

In order to ensure successful and efficient use

of machine tools, the user must first have de-

tailed knowledge of the properties and possible

applications of the available cutting materials

and tools. The wide range of available cutting

materials – including carbides, ceramics, PcBN,

PCD and Cermets – combined with the nu-

merous possible coatings for these materials,

requires that the user has detailed knowledge

in order to implement the most technologically

sound and most efficient machining solution

within a production process.

This White Paper from SPK Cutting Tools within

CeramTec GmbH explains how to use inserts

made of ceramic cutting materials, PcBN and

Cermets for the milling of cast iron compo-

nents as well as how to use the corresponding

milling cutters. The goal is to provide the user

with basic knowledge on milling with ceramics,

PcBN and Cermets, to assist the user in decid-

ing on the appropriate cutting material, insert

geometry and milling cutter for a particular

milling project and to explain to the user how

to implement these in a production process.

MILLING WITH CERAMIC CUTTING MATERIALS

For more than 20 years, milling with ceramic cutting materials has been one of the most established and well-developed machining processes. Modern ceramic high-performance cutting (HPC) materials and milling cutters with HPC inserts now offer the highest levels of process reliability within a milling application.

Handling and using milling cutters that operate with ceramic inserts is now just as simple and reliable as handling and using milling cutters that operate with carbide inserts. The difference between milling with carbide inserts and milling with inserts made from ce-ramic materials lies in the performance of the cutting materials and the possible pairings between cutting materials and workpiece materials. When compared to carbides, ceramic cutting materials allow for significantly higher cutting speed. The higher cutting speed leads to significantly higher machine pro-

ductivity per unit of time. A higher machining speed in-creases the productivity of the machining process, since the output per unit of time is substantially increased. This results in a wide range of additional advantages.

The most important are summarized here:

∙ Higher output per unit of time.∙ Reduction in milling costs due to the reduced amount of time that each milling machine requires for a single

component.∙ Possible increased flexibility in milling machine usage.∙ Capacity of the milling machine is shifted toward higher production quantities and the milling machine can be used to complete additional orders or to finish higher batch sizes per working shift.

11


When milling with ceramic cutting materials, however, there are limitations regarding which cutting materials can be paired with which workpiece materials. Ceramic cutting materials are suited for cast iron materials and for chilled cast iron. In some cases, ceramics can also be used to mill certain steel materials. The same applies to certain aluminium materials. This White Paper from SPK Cutting Tools provides information on perform-ing milling work with the following types of grey iron: grey cast iron (GJL), ductile cast iron (GJS), compacted graphite iron (CGI, also known as GJV), austempered ductile iron (ADI) and high-silicon cast iron. Cast steel, white cast iron and chilled cast iron are not addressed. Our Solution Team would be happy to assist you with your questions regarding additional milling applications with ceramic cutting materials.

You can contact our Solution Team at the following address: [email protected]

Another significant advantage when using ceramic cutting materials is that cutting fluids are not required. This results in further advantages, which are briefly summarized here:∙ No cutting fluids required∙ No costs for disposal of cutting fluids∙ Chips are not soiled with cutting fluid

However, modern thermal-shock-resistant ceramics can also be used for wet machining, when needed. It must be noted, though, that using cutting fluids reduces the service life of the milling system by approximately 20%. Mixed wet-dry machining can also be achieved with high process reliability.

As with the cutting materials, milling cutters and in-sert geometries have been continuously refined over the years. Modern ceramic varieties are tough, highly impact resistant and resistant to thermal shocks, and they are available in a range of insert designs that are tailored to the particular application. Negative and positive inserts with a hole or notch are available as standard. For example, you can now employ positive octagonal inserts of type OEHX, i.e., inserts that are

fixed via hole clamping and have a clearance angle of 20°, for use in rough milling with high process reliabili-ty, with cutting depths up to 4 mm and with a feed rate per tooth of 0.3 mm. Other standard designs include in-serts with various lenght wiper facets and a wide range of edge preparations for the cutting inserts. Depending on the design of the milling cutter, the inserts can be fixed using wedge clamp, screw clamp or a clamping element. All types of clamping are suitable for both roughing and finishing operations.

Cartridge-based milling cutters, milling cutters with fixed insert pocket seats and cutters with adjustable pocket seats are mainstays in the CeramTec portfolio of milling cutters. This means that the optimal milling cutter is always available for every operation, wheth-er face milling, groove milling, 90° shoulder milling, plunge milling, high-feed milling, roughing or finishing.In addition, the availability of custom milling cutters and geometries expands the possible applications for using milling cutters with ceramic inserts. SPK Cutting Tools part of CeramTec GmbH excels in this area as well, with extensive experience designing inserts and milling cut-ters and comprehensive knowledge of customer needs. The many satisfied customers who use these tools in their daily production attest to the outstanding process reliability and efficiency that is achieved by using ce-ramic cutting materials in standard or custom solutions.

In terms of outlook, the field of milling with ceramic cutting materials still has much untapped potential. SPK Cutting Tools part of CeramTec GmbH is working to unlock this potential for use in practical milling oper-ations by continuously refining ceramic cutting materi-als, cutting geometries and milling cutter designs.


TYPES OF CAST IRON MATERIALS

Cast iron is a general term for iron-carbon alloys with a proportion of carbon between 2 and 5% and with other added alloy elements, primarily silicon, manga-nese, phosphorous and sulphur, with silicon being the most important alloy element and the element with the highest proportion in the composition.

Additional alloy additives such as chromium, nickel and molybdenum improve the properties of the cast iron with regards to heat resistance and corrosion. These are considered special forms of cast iron. The name grey iron is derived from the color that appears on a fracture surface. White cast iron and grey iron differ in this characteristic.

CAST IRONMATERIALS

SOLIDIFICATION

CARBONCONTENT

CARBON

APPEARANCE OF FRACTURE SURFACE

FURTHERTREATMENT

Annealed in

e.g. lower

Mg andTi content

e.g. lower Mg

content

Highly alloyedwith

Meta-stable Stable

Cast steel White cast iron

Greycast iron

Specialcast iron

Bound in cementite Predominately as graphite or pearlite

White White Grey

<2% 2.4%-4.5% 2.5%-5% 1.5%-3.5%

Chilledcast iron Si Al CrHypoeutectic

white cast ironGrey

cast ironCompacted

graphite iron

Ductile cast iron

Oxidativeatmosphere

Neutralatmosphere

Blackheartmalleable cast

iron

Whiteheart malleable cast

iron


The metallic matrix of a cast iron alloy depends to a large degree on the alloy composition and the solidi-fication. The matrix that results can be represented in practical terms by the following Greiner-Klingenstein diagram. In this diagram, the resulting microstructure of the cast iron is displayed as a function of the cooling conditions. If the cooling conditions are not artificially influenced, they correspond to the wall thickness of the workpiece. The diagram displays the total proportion of carbon and silicon together. Since this total proportion greatly in-fluences the deposition of graphite, connections have been drawn between the total proportion and various wall thicknesses.

Areas I, II, IIb and III are of importance for milling work with ceramic, PcBN and Cermet cutting materials. All areas up to area I result in grey iron. Area I results in white cast iron. As you can see from the diagram, the cutting materials are primarily used to machine white, pearlitic, pearlitic-ferritic and ferritic matrices with in-tercalated graphite.White matrix – The carbon is bound as iron carbide, making fracture surfaces appear white instead of grey. This document will focus on chilled cast iron, which has a high proportion of cementite (Fe3C) that is interca-lated in the matrix as carbide. The intercalated carbide subjects milling inserts to high wear, and increased cutting forces can result. These forces increase as the

hardness of the workpiece increases. Pearlitic matrices are a mixture of ferrite and ce-mentite. During machining, they result in highly abrasive wear and lead to increased machining forc-es because the cementite has a high hardness value (HV~1100). However, this matrix tends to exhibit few burrs and favourable chip formation. Ferritic matrices have low hardness and strength and exhibit good ductility. However, they tend to be more difficult to machine because they produce longer chips and can develop a built-up edge. Burr formation on the workpiece is improved as a result of the ferrite properties. The surface quality greatly depends on the cutting parameters, the balance of forces at the point of contact and the geometry of the cutting edge.

As described above, the composition of the particular matrix of grey iron has a large influence on the ma-chinability. The intercalated graphite also has a large influence on machining. The most important factors are how finely the graphite is distributed and the form of the graphite. In principle, the graphite works to reduce friction between the cutting material and the workpiece material. In addition, the intercalation of the graphite disrupts the continuity of the metallic matrix. These dis-ruptions lead to chips that break quickly and tend to produce lower machining forces.

Wall thickness in mm

(Car

bon+

Silic

on-)

cont

ent i

n %

7.0

5.0

6.0

4.0

0,0 10 20 30 40 50

L L+P Pearlite+CG F+P+CG Ferrite+CG

60 70

Casting range

I IIa II IIb III

Cast iron matrices:

I White

IIa Mottled

II Pearlitic

IIb Pearlitic-ferritic

III Ferritic

CAST IRON MICROSTRUCTURES AND MACHINABILITY


DESIGNATION SYSTEM FOR CAST IRON

Cast irons are described in European standard EN 1560 according to their performance characteristics or using material numbers. The following diagram shows the designation scheme for the system of standards. The standard permits abbreviated designations, which con-sist of the positions 1, 2, 3 and 5. Such an example is EN-GJL-HB190. All additional information is optional. For machining, it is helpful to know at least position 4, since this indicates the matrix structure.

Information regarding the hardness or the tensile strength does not say anything about the microstruc-ture, but this information can be used to determine the K factor (see page 42). It is also permissible to enter the tensile strength for the hardness in position 5.

Pos. 3: Graphite structure

L LamellarS SpheroidalM Temper carbon (malleable)V VermicularN Free of graphite, ledeburiticY Special structure

Pos. 5: Production of test sample

S Separately cast test sampleU Cast-on test sampleC Test sample cut from a casting

Pos. 5: Test temperature range

RT Room temperatureLT Low temperature

Pos. 4: Micro/macrostructure

A AusteniticF FerriticP PearliticM MartensiticL LedeburiticQ QuenchedT Quenched and temperedB BlackheartW Whiteheart

EN standardCast ironGraphite structure, carbon structure (spheroidal graphite)Microstructure or macrostructure, if necessary (ferritic)

Classification by mechanical properties - Tensile strength in N/mm2

- Elongation at fracture in % - Production of cast test sample (cast-on sample) - Temperature range for required impact resistance (low temp.)

Or chemical compositionAdditional requirements, if necessary (heat treated)

No blank spacesPos.

Desig.

1 2 3 4 5 6

EN- GJ S F -350-22U-LT -H


MACHINING CAST IRON MATERIALS

Before we discuss the machining behaviour of various common cast iron and their sub-types, we present gen-eral information on the machining of cast iron work-pieces below.

When you are considering workpieces for milling work, for example a gearbox housing, these will be character-ised by different wall thicknesses and typically a num-ber of interruptions in the form of circles or grooves. As described above, the resulting microstructure depends on the cooling conditions. Different wall thicknesses within a workpiece also cool differently. This also ap-plies to the edges of holes or grooves. This leads to an inhomogeneous microstructure within a workpiece, which results in different hardness and matrix zones. During machining, the cutting material continuously comes into contact with an inhomogeneous workpiece material that contains zones that can lead to increased wear.

During machining, cast iron behaves as follows:

∙ Short chips form, primarily discontinuous chips.∙ Cast iron is machined dry, although wet machining is also possible.

∙ Different types of cast iron require adjustments to the cutting material and tailoring of the cutting data.

∙ The casting skin can contain high levels of contamina-tion, which leads to increased wear.

EFFECT OF MATERIAL HARDNESS

When cast irons are machined, harder materials put in-creased demands on the cutting material regarding its wear characteristics. The hardness range of cast iron extends from HB 125 for GJL to an HB hardness of 480 for ADI. In case of unfavourable cooling conditions, primarily cooling that is too fast, iron carbide forms (Fe3C). This is very hard, is very abrasive during machining and can decrease the service life of machine tools significantly.MACHINABILI

TY OF


Short material designation

Old DIN standard 1691

Machinability

Area of application

Microstructure components

Brinell hardness HB

MACHINABILITY OF GREY CAST IRON

In general, grey iron is good for machining. Grey iron has a matrix similar to steel, a matrix which is interrupt-ed by intercalated graphite flakes. During machining, discontinuous or segmental chips are formed. This results in moderate machining forces. Due to the production of discontinuous chips, break-age may occur along the workpiece edge as the cutter leaves the workpiece if the cutting parameters are not

correct. The main cause of wear during machining is abrasion. The surface quality of a GJL workpiece is determined by the cutting data, the production process used and the fineness of the microstructure, i.e., the size and distri-bution of the intercalated graphite. The cutting ma-terials SL500, SL808, WBN101, WBN115, SH2, SC60 and SC7015 are available for machining.

EN-GJL-150 EN-GJL-200 EN-GJL-200 EN-GJL-300 EN-GJL-350

GG 15 GG 20 GG 25 GG 30 GG 35

Very good Very good Very good Very good Good

Thin-walled parts down to 10 mm in general ma-chinery, etc.

Pumps, fixtures, etc.

down to 20 mm

Compressors, cylinder

pistons, etc. down to 30 mm

> 30 mm for turbines,

presses, tables, etc.

Machine frames, ma-chine parts

Ferritic/pearlitic Pearlitic

125 - 205 150 - 230 180 - 250 200 - 275 210 - 250


MACHINABILITY OF DUCTILE CAST IRON

GJS workpieces with higher tensile strength are not very good for machining. Types with low strength pri-marily produce helical chips that break easily as a re-sult of the intercalated graphite. Components with a predominantly or highly ferritic matrix can cause higher tool flank wear during machining, and a built-up edge can easily form. In addition, soft microstructures in-

MACHINABILITY OF AUSTEMPEREDDUCTILE IRON, ADI

Austempered ductile iron is created by heat treat-ing GJS cast iron. This produces a material with very good mechanical properties: high toughness, tensile strength, wear resistance and hardness with good elongation properties.

Insert life is reduced by approximately 40 to 50% when components made from ADI materials are machined. As with GJS materials, ADI materials produce chips that

crease the strain on the cutting edge during milling. For GJS types with higher strength, these effects are mini-mized. In this case, the tool wear and the cutting forces increase as the strength or the proportion of pearlite in the workpiece material increases. This leads to in-creased wear due to abrasion. The ceramics SL808, SL854C and SL858C are suitable cutting materi-als for such tasks, as are the Cermet types SC60 and SC7015.

break easily during machining. ADI materials with high-er strength, such as EN-GJS-1200 .. or EN-GJS-1400 .., tend to exhibit build-ups of free carbide, which have a higher hardness and lead to increased abrasive wear.The good mechanical properties of ADI lead to higher thermal and mechanical strain on the cutting edge. The shape of the chip limits the wear on the cutting edge and the rake face. The cutting material SL858C is suitable for machining ADI.

Machinability

Area of application

Microstructure components

Brinell hardness HB


Old DIN standard 1691

Machinability

Area of application

EN-GJS-400-15 EN-GJS-500-7 EN-GJS-600-3 EN-GJS-700-2 EN-GJS-800-2

GGG 40 GGG 50 GGG 60 GGG 70 GGG 80

Very good Good Good Moderate Moderate

General machinery

construction, nozzle rings,

housings, pad-dle wheels

General automobile

and machinery construction,

supports, casing pipe

General automobile

and machinery construction,

pistons, flywheels

General automobile

and machinery construction, cam disks,

gearwheels, suitable for temperable

parts

General machinery

constructionGearwheelsAutomobile construction

Predominantly ferritic

Ferritic/pearlitic Ferritic/pearlitic Ferritic/pearlitic Pearlitic

135 - 185 150 - 220 200 - 250 220 - 280 250 - 330


Microstructure

Machinability

Brinell hardness HB

EN-GJS-800-8 EN-GJS-1000-5 EN-GJS-1200-2 EN-GJS-1400-0

Austenitic/ferritic Austenitic/ferritic Austenitic/ferritic Austenitic/ferritic

Moderate Moderate Unfavourable Unfavourable

260 - 320 300 - 360 340 - 440 380 - 480


MACHINING HIGH-SILICON CAST IRON, A DUCTILE CAST IRON MATERIAL

High-silicon cast iron belongs to the ductile cast iron family. It is distinguished by significantly improved me-chanical properties: significantly higher yield strength and increased elongation at fracture with significant-ly lower weight. High-silicon cast iron materials have

MACHINABILITY OF COMPACTED GRAPHITE IRON

CGI (GJV) materials are fundamentally more abrasive due to the dendritic form of their embedded graphite. The ductile properties of CGI (GJV) also increase the friction coefficients between the cutting material and the workpiece material. This significantly increases the thermal and abrasive strain on the cutting edge. This promotes higher wear on the flank surface. This effect is higher with higher cutting speeds. In addition, the lack of manganese sulphide means that a protective

a ferritic matrix. Ferritic matrices are easier and less complex to machine compared to standard ductile cast iron, which causes higher tool wear due to the hard cementite intercalated along with the pearlitic com-ponents. High-silicon materials can therefore increase tool life significantly, i.e., up to 50% depending on the particular application. The cutting materials SL808, SL850C and SL858C are suitable for such appli-cations.

coating does not form on the insert, which promotes diffusive wear. The cutting materials SL854C and SL850C are recommended.

CGI (GJV) microstructures come in various forms. CGI (GJV) workpieces with a pearlite content of approxi-mately 90% are most common in industrial practice. Common workpieces include motor blocks and cylinder heads.


Microstructure

Machinability

Brinell hardness HB

EN-GJS-450-18 EN-GJS-500-14 EN-GJS-600-10

Ferritic Ferritic Ferritic

Good Good Good

170 - 200 185 - 215 200 - 230


Microstructure

Machinability

Brinell hardness HB

GJV-300 GJV-350 GJV-400 GJV-450 GJV-500

Predominantly ferritic

Ferritic/pearlitic Ferritic/pearliticPredominantly

ferriticPredominantly

ferritic

Good Moderate Moderate Unfavourable Unfavourable

140 - 210 160 - 220 180 - 240 200 - 250 220 - 260


CHILLED CAST IRON

The hard, ferritic matrix places high strain on the cut-ting edges. Therefore, it is important that the milling cutter position be optimised and the path overlap be adjusted in order to minimise the strain on the cutting edge. Because of the high hardness, the cutting materials WBN101 and SH2 are suitable for milling such materials.

Effect of the casting skinThe casting skin on cast iron materials plays a large role in machining. Because of non-metal deposits, an altered microstructure and scaling, the skin composi-tion is unfavourable for ceramic cutting materials. The ceramic cutting edge is subjected to high wear and may in some cases fail if sand is embedded in or has pene-trated the outside edge of the material.


CUTTING MATERIALS FOR MILLING AND THEIR PROPERTIES

Section 2 of this White Paper discusses the high-performance ceramic, PcBN and Cermet cutting materials available from the Cutting Tools department of CeramTec GmbH for the machining of cast iron materials.The following table provides an overview of the cutting materials currently available (Spring 2014) from SPK Cutting Tools: 22Assignment of cutting materials to workpiece materials

*See list of steels in section on Cermet cutting materials

GJL GJS CGI (GJV) ADI Si GJS Chilled cast iron Steels*

Cutting Materials for Milling

The wide range of cutting materials available from CeramTec includes both coated and uncoated grades. These materials can differ significantly based on the particular combination of base substrate and coating. The range of combinations determines the possible ap-plications of the cutting material. The applications for the CeramTec cutting materials will be explored in more detail below.

In general, though, all ceramic cutting materials are employed as high-performance cutting materials and allow for very high cutting speed during milling, as mentioned above. In order to ensure efficiency and process reliability dur-ing milling, it is crucial to match the cutting material to the workpiece material. The following table provides information on which pairings of cutting material and workpiece material provide optimal milling results.

Uncoated ceramic Coated ceramic PcBN Cermet

SH 2 SL850C

SL500 SL854C WBN101 SC60SL808 SL858C WBN 115 SC7015

SH 2 SL808 SL850C SL858C SL850C SH 2 SC60SL500 SL850C SL854C SL854C WBN115 SC7015SL808 SL854C SL858C SL858C

SL850C SL858C

SL854C SC7015SL858C SC60

WBN101WBN115


SPK CERAMIC VARIETIES

This cutting material is a silicon-nitride ceramic. Sil-icon-nitride ceramics exhibit good toughness and are resistant to thermal shocks. These two properties make it possible to perform highly interrupted cutting and to use cutting fluids. Because of its wear characteristics and the rounded cutting edges that are employed, this

cutting material is suitable for rough milling and for rough finishing. With this material, GJL workpieces can be machined to surface qualities with a Ra ≥ 6.3 µm.

Grey cast iron Recommended values for roughing with ap < 4 mm

SL808 is an α/β SiAlON. It is distinguished by a core that is quite tough for ceramic cutting materials and a wear-resistant surface. The composition of the cutting material and the resulting wear characteristics mean this material can also be used for milling GJS workpiec-es.

Overall, SL808 is suitable for roughing and rough fin-ishing and for producing Ra values ≥ 6.3 µm for GJL and GJS workpieces with the highest cutting speeds.

Grey cast iron Recommended values for roughing, ap < 5 mm, Ra = 6.3 - 12.5 µm

Ductile cast iron Recommended values for roughing, ap < 5 mm, Ra = 6.3 - 12.5 µm

GJL vc recommended value vc total range fz recommended value fz total range

Hardness (HB) m/min m/min mm/z 43°/45° 75° 88°/90°190-210 1200 800-1000 0.18 0.12-0.30 0.12-0.20 0.12-0.22220-240 1000 500-1300 0.18 0.12-0.30 0.12-0.20 0.12-0.22250-280 800 400-1200 0.18 0.12-0.30 0.12-0.20 0.12-0.22


UTS Rm (N/mm2) m/min m/min mm/z 43°/45° 75° 88°/90°

400-500 800 600-1000 0.18 0.15-0.30 0.12-0.20 0.14-0.21500-700 700 500-800 0.18 0.15-0.30 0.12-0.20 0.14-0.21


GJS vc recommended value vc total range fz recommended value fz total range


The SH2 cutting material is a mixed ceramic. Mixed ceramics are distinguished by their hardness and their outstanding edge stability. Modern mixed ceramics ex-hibit a high toughness and are therefore best suited for

finish milling and fine finishing of GJL and chilled-cast-iron workpieces without cutting fluids. Surface qualities of Ra ≥ 0.8 µm are possible with high process reliability.

SL 850C consists of a multi-layered TiCN coating on a silicon-nitride base substrate. With this combination of base substrate and coating, GJL workpieces can be

semi-finished to surface qualities of Ra ≥ 3.2 µm, and GJS, CGI (GJV) and high-silicon GJS materials can be rough finished to surface qualities of Ra ≥ 6.3 µm.

GJL vc recommended value vc total range fz total range



Grey cast iron Recommended values for finishing, ap = 0.1 - 0.5 mm, surface qualities of Ra ≥ 0.8 µm

GJN (chilled cast iron) vc recommended value vc total range fz total range

GJN (chilled cast iron) vc recommended value vc total range fz total range

Cast HRC m/min m/min mm/z35-40 300 100-450 0.10 0.05-0.1540-45 300 100-450 0.10 0.05-0.1545-55 250 80-400 0.10 0.05-0.15

Hardened HRC m/min m/min mm/z55-63 250 80-400 0.10 0.05-0.1558-64 200 80-350 0.10 0.05-0.1560-65 180 80-300 0.10 0.05-0.15

Chilled cast ironRecommended values for finish milling, ap < 2 mm, Ra = 1.6 - 3.2 µm

Recommended values for finish milling, ap < 2 mm, Ra = 1.6 - 3.2 µm



fz recommended value





The silicon-nitride base substrate of SL854C is covered with a TiCN coating. With this coating, GJL workpieces can be semi-finished and GJS workpieces can be rough

finished with surface qualities of Ra ≥ 3.2 µm for GJL and Ra ≥ 6.3 µm for GJS. The same applies to CGI (GJV), ADI and high-silicon cast iron materials.


400-500 800 600-1000 0.16 0.15-0.30 0.12-0.25 0.12-0.20500-700 700 500-800 0.16 0.15-0.30 0.12-0.25 0.12-0.20

Ductile cast ironRecommended values for rough finishing, ap = 0.5 - 1.0 mm, surface qualities of Ra ≥ 6.3 µm


300 800 500-1000 0.2 0.12-0.22 0.12-0.22 0.12-0.22350-400 600 400-800 0.18 0.12-0.20 0.12-0.20 0.12-0.20450-500 400 200-600 0.16 0.12-0.16 0.12-0.20 0.12-0.20

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

450 1500 800-1100 0.18 0.10-0.22 0.10-0.22 0.12-0.22500 1500 800-1000 0.16 0.10-0.20 0.10-0.20 0.12-0.22600 1200 800-900 0.16 0.10-0.20 0.10-0.20 0.12-0.22

Compacted graphite ironRecommended values for roughing, ap < 5 mm, Ra = 6.3 - 12.5 µm

High-silicon ductile cast iron Recommended values for roughing, ap < 5 mm, Ra = 6.3 - 12.5 µm

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

400-500 800 600-1000 0.16 0.15-0.30 0.12-0.25 0.12-0.20500-700 700 500-800 0.16 0.15-0.30 0.12-0.25 0.12-0.20



GJS vc recommended value vc total range fz recommended value fz total range



GJS vc recommended value vc total range fz total range

CGI (GJV) vc recommended value vc total range fz total range

GJS (high-silicon) vc recommended value vc total range fz total range





This ceramic cutting material also has an α/β SiAlON ceramic base substrate, but it is coated with aluminium oxide. SL858C is thus specialised for rough finishing of

GJS workpieces. This cutting material can also be used for milling GJL, CGI (GJV), ADI and high-silicon work-pieces.

CGI (GJV) vc recommended value vc total range fz recommended value fz total range

GJS high-silicon vc total range fz total range


300 800 500-1000 0.18 0.12-0.22 0.12-0.22 0.12-0.22350-400 600 400-800 0.16 0.12-0.20 0.12-0.20 0.12-0.18450-500 400 200-600 0.14 0.12-0.16 0.10-0.20 0.12-0.18

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

450 1500 800-2000 0.16 0.10-0.20 0.10-0.16 0.12-0.22500 1500 800-2000 0.16 0.10-0.20 0.10-0.16 0.12-0.22600 1200 800-2000 0.16 0.10-0.20 0.10-0.16 0.12-0.22




400-500 800 600-1000 0.16 0.15-0.30 0.12-0.25 0.12-0.20500-700 700 500-800 0.16 0.15-0.30 0.12-0.25 0.12-0.20




Grey cast iron Recommended values for semi-finishing, ap = 0.5 - 1.0 mm, surface qualities of Ra ≥ 3.2 µm

vc recommended value

fz recommendedvalue

GJS vc total range fz total rangevc recommended value

fz recommendedvalue


GJS high-silicon vc total range fz total range

CGI vc total range fz total range

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

450 1500 800-2000 0.16 0.10-0.20 0.10-0.15 0.12-0.22500 1500 800-2000 0.16 0.10-0.20 0.10-0.15 0.12-0.22600 1200 800-2000 0.16 0.10-0.20 0.10-0.15 0.12-0.22

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

300 800 500-1000 0.2 0.12-0.22 0.12-0.22 0.12-0.22350-400 600 400-800 0.18 0.12-0.20 0.12-0.20 0.12-0.20450-500 400 200-600 0.16 0.12-0.16 0.12-0.20 0.12-0.20


ADI vc recommended value vc total range fz recommended value fz total range

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

800 600 450-720 0.14 0.08-0.22 0.12-0.22 0.10-0.201000 500 400-700 0.14 0.08-0.20 0.12-0.20 0.10-0.181200 400 350-600 0.12 0.06-0.12 0.08-0.20 0.08-0.161400 320 120-500 0.1 0.06-0.12 0.08-0.15 0.08-0.12

Austempered ductile cast iron Recommended values for roughing, ap < 5 mm, Ra = 6.3 - 12.5 µm







PCBN CUTTING MATERIALS FOR MILLING

PcBN cutting materials, with their very good wear characteristics and good edge stability, are equally suited for both roughing and finish-ing of GJL workpieces. For one, they allow you to achieve high removal rates. They also allow you to achieve finely finished surfaces with Ra values up to 0.5 µm.

WBN101 materials from SPK Cutting Tools are effective for rough finishing up to fine finishing of GJL workpieces.





Hardness (HB) m/min m/min mm/z 43°/45° 75° 88°/90°190-210 1500 800-2000 0.14 0.10-0.20 0.10-0.15 0.08-0.15220-240 1200 500-1500 0.14 0.10-0.20 0.10-0.15 0.08-0.15


Grey cast iron Recommended values for roughing, ap < 5 mm, surface qualities of Ra = 6.3 - 12.5 µm

Recommended values for semi-finishing, ap = 0.5 - 2.0 mm, surface qualities of Ra ≥ 3.2 µm

Recommended values for fine finishing, ap = 0.1 - 0.5 mm, surface qualities of Ra ≥ 0.5 µm





The WBN115 PcBN variety from SPK is primarily suit-ed for roughing and finishing, as well as for machining hardened castings.




Grey cast iron Recommended values for roughing, ap < 5 mm, surface qualities of Ra = 6.3 - 12.5 µm

Recommended values for semi-finishing, ap = 0.5 - 2.0 mm, surface qualities of Ra ≥ 3.2 µm








Hardened castings vc recommended value vc total range fz total range

Hardness (Shore C) m/min m/min mm/z68 250 80-400 0.10 0.05-0.1573 250 80-400 0.10 0.05-0.1580 220 80-300 0.10 0.05-0.1587 200 80-300 0.10 0.05-0.1593 180 80-250 0.10 0.05-0.15

Hardened castingsRecommended values for finishing and fine finishing, ap = 0.1 - 0.5 mm, surface qualities of Ra = 0.8 - 3.2 µm



CERMETS FOR MILLING

Cermet cutting materials can be categorised as hard-metal cutting materials, since non-oxide ceramics such as TiC or TiN are employed as a wear-resistant base material and embedded in a metallic binder, usually nickel. This cutting material exhibits very high edge stability and moderate toughness.

These properties make Cermets excellently suit-ed for the finishing and fine finishing of GJS, steels from the case construction and free-ma-chining groups as well as case-hardening and tempering steels.

The SC60 type from SPK is effective for semi-finishing, since it exhibits comparatively high toughness.

Tensile strength vc recommended value vc total range fz total range


UTS (N/mm2) m/min m/min mm/z 43°/45° 75° 88°/90°300-600 350 250-450 0.20 0.15-0.30 0.10-0.25 0.08-0.20600-800 300 200-350 0.20 0.15-0.30 0.10-0.25 0.08-0.20

UTS (N/mm2) m/min m/min mm/z 43°/45° 75° 88°/90°600-900 250 100-350 0.20 0.15-0.30 0.10-0.25 0.08-0.20

900-1300 200 100-250 0.20 0.15-0.30 0.10-0.25 0.08-0.20

Case-construction and free-machining steelsRecommended values for roughing and semi-finishing, ap < 5 mm, surface qualities of Ra = 6.3 - 12.5 µm

Case-hardening and tempering steelsRecommended values for roughing and semi-finishing, ap < 5 mm, surface qualities of Ra = 6.3 - 12.5 µm


400-500 500 350-600 0.12 0.10-0.20 0.10-0.15 0.08-0.15500-700 400 250-500 0.12 0.10-0.20 0.10-0.20 0.08-0.15

Ductile cast iron Recommended values for finishing, ap < 1 mm, Ra = 0.8 - 1.6 µm



GJL vc recommended value vc total range fz total rangefz recommended value


SC7015, in contrast, is primarily used in the finishing and fine finishing of GJS as well as case-construction

and free-machining steels.

UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

400-500 500 350-600 0.12 0.10-0.20 0.10-0.15 0.08-0.15500-700 400 250-500 0.12 0.10-0.20 0.10-0.15 0.08-0.15


UTS Rm (N/mm2)

m/min m/min mm/z 43°/45° 75° 88°/90°

400-500 500 350-600 0.10 0.08-0.20 0.08-0.15 0.05-0.12500-700 400 250-500 0.10 0.08-0.20 0.08-0.15 0.05-0.12



UTS (N/mm2) m/min m/min mm/z 43°/45° 75° 88°/90°600-900 350 250-400 0.10 0.08-0.15 0.05-0.12 0.05-0.12

900-1300 250 200-300 0.10 0.08-0.15 0.05-0.12 0.05-0.12

Ductile cast iron Recommended values for finish milling, ap = 0.5 - 1.0 mm, surface qualities of Ra ≥ 3.2 µm

Case-construction and free-machining steelsRecommended values for finish milling, ap = 0.5 - 1.0 mm, surface qualities of Ra ≥ 3.2 µm



Case-hardening and tempering steelsRecommended values for finish milling, ap = 0.5 - 1.0 mm, surface qualities of Ra ≥ 3.2 µm













fz z recommended value


MILLING TOOLS FROM SPK CUTTING TOOLS

This section deals with the various families of milling cutters from CeramTec, presenting the main applications of these cutters and their ad-vantages. Three basic types of milling cutters can be distinguished based on the way in which the inserts are fixed: milling cutters with wedge clamping, milling cutters with screw clamping and milling cutters for which a clamping ele-ment is used to fix the inserts. It must be noted, however, that the way in which the inserts are fixed does not imply anything about the main applications of an SPK milling system.

As mentioned above, the possible applications of a milling system are determined by the basic design of the milling cutter, the combination of angles of the insert seating (axial and radial rake angle, setting angle, approach angle), the insert geometry and the cutting material.The following table provides a brief overview of the possible machining applications and milling cutter types for roughing and finishing appli-cations. The table thus allows a first selection of milling cutters for the particular milling task.

ROUGHING FINISHING

TYPES PFK90R-AMPFK88R-AMPFK75R-AMPFK45R-AM

PFK47R-AMPFLSP13/88°PFLSP13/75°PFLSP13/45°

PFLOP-06 PFLOE-06 PFLON-06 BFLSP13/75°PMK88R-AM PMKS88R-AM

PDK88R-AM PEK88R-AM MFS88-M4

MILLING CUTTERS

APPLICATION

Roug

h fa

cing

Fini

sh f

acin

g

Squa

re-s

houl

der

mill

ing

Gro

ove

mill

ing

Hel

ical

mill

ing

Hig

h-fe

ed m

illin

g

Primary application Additional application

8888

75 CP75

4545


AREAS OF APPLICATION

The PFK series of milling cutters constitutes a univer-sal milling system. They operate with insert approach angles of 90, 88, 75 or 45 degrees. This milling sys-tem can be used for face milling, shoulder milling and groove milling. The PFK series is used primarily for rough milling.

PRODUCT DESCRIPTION ∙ PFK milling cutters employ negative inserts that are fixed in the pocket seat using wedge clamps.

∙ This series is highly precise in terms of axial and radial run-out, which means it can also be used for rough finishing and can achieve surfaces with Ra values ≥ 6.3 µm.

∙ The PFK90TN series allows you to mill 90° shoulders using 6-edged T-inserts, which are also available with a wiper facet.

∙ The PFK47HN milling cutters employ efficient, 12-edged HNGX inserts.

∙ The PFK88SN, PFK75SN and PFK45SN milling cutters employ 8-edged, SNG inserts. These are available with wiper edges, in ZZ (wiper) variants and with var-ious edge geometries.

ADVANTAGES

Coated and uncoated ceramic, PcBN and Cermet cut-ting materials are available. This allows you to mill GJL materials, GJS materials, case-construction and free-machining steels as well as case-hardening and tempering steels with high process reliability.The wide selection of cutting materials and cutting edge geometries ensure that the milling process is efficient and tailored to the application. Another ad-vantage is that milling applications can be carried out either wet or dry.

SPK SERIES OF MILLING CUTTERS

The following is a brief description of the ap-plications for the SPK series of milling cutters and provides more detailed information so that you can select the correct SPK milling cutter for your application:

Face millingRa ≥ 6.3 µmExtremely efficientIndividual and series productionISO-P + ISO-K application groups

vc = 600 - 1200 m/minfz = 0.14 - 0.3 mmap = up to 5 mm

12.5 6.3

Face millingRa ≥ 6.3 µmExtremely efficientIndividual and series productionISO-P + ISO-K application groupsWiper edges and ZZ geometries


12.5 6.3

Face millingRa ≥ 6.3 µmExtremely efficientIndividual and series productionISO-P + ISO-K application groups


12.5 6.3

Face millingRa ≥ 6.3 µmExtremely efficientIndividual and series productionISO-P + ISO-K application groupsWiper edges and ZZ geometries


12.5 6.3

Face millingShoulder millingGroove millingRa ≥ 6.3 µmExtremely efficientIndividual and series productionISO-P + ISO-K application groups


12.5 6.3

-Milling cutters



PFL milling cutters are designed for rough face milling and semi-finishing of any contour with high feed-ad-vance speeds and with thin-walled or relatively unsta-ble components.

PRODUCT DESCRIPTION ∙ The milling cutters can be delivered in standard diam-eters of 50 to 250 mm with the standard pitch.

∙ The PFL88SP, PFL75SP and PFL45SP milling systems are available with an insert approach angle of 88°, 75° or 45° and operate with four sided positive inserts that are fixed via screw clamping.

∙ The PFL43OP system operates with positive, octago-nal inserts that are also fixed via screw clamping.

ADVANTAGES

The name of the PFL milling system says it all. It is a uni-versal milling system that allows you to perform even difficult roughing operations with high cutting speeds and with the highest process reliability. The designs of the milling cutter and the insert clamping allow you to execute even long and wide milling paths with excel-lent flatness and generate semi-finished surfaces with Ra values of 6.3 µm.

Face millingRoughing and semi-finishing Ra ≥ 6.3 µmExtremely efficientIndividual and series productionISO-K application groupLower cutting forcesMinimized power consumptionLower noise emission


12.5 6.3



12.5 6.3



12.5 6.3

-Milling cutters



The PFL43OE milling cutters can be used wherever thin-walled or unstable workpieces are to be face milled with high cutting data and process reliability. If you are using a milling machine with lower spindle power, the PFL43OE milling system provides you with all the bene-fits of fast and efficient machining with ceramic cutting materials and high process reliability.

PRODUCT DESCRIPTION ∙ The PFL43OE milling cutters are equipped with oc-tagonal inserts of type OEHX, which are fixed using screw clamps.

∙ The milling cutters are available in diameters of 50 to 200 mm.


The PFL43ON milling cutters are designed for effi-cient, high-performance rough face milling of cast iron workpieces. The PFL43ON is equipped with 16-edged ONHQ inserts.

PRODUCT DESCRIPTION ∙ The ONHQ inserts are fixed using screw clamps.∙ The PFL43ON is available with diameters from 63 to 160 mm as standard.

The low cutting forces of the PFL43OE milling cutters are specially suited for applications involving thin-walled or unstable components, a sub-optimal clamp-ing set-up or lower spindle power.

ADVANTAGES

ADVANTAGES

Extremely stable negative inserts with 16 economical cutting edges made from high-performance ceramic make the PFL43ON a milling system with outstanding efficiency.

Face millingRoughing and semi-finishing Ra ≥ 6.3 µmExtremely efficientIndividual and series productionISO-K application groupLow cutting forcesFor milling machines with lower spindle powerLow noise emission


12.5 6.3

Face millingRoughing and semi-finishing Ra ≥ 6.3 µmExtremely efficientIndividual and series productionISO-K application group


12.5 6.3



The BFLSX is a high-feed and helical milling system.

PRODUCT DESCRIPTION ∙ The milling cutter is available in standard diameters of 63, 80 and 100 mm. SPHX inserts are fixed using screw clamps.

ADVANTAGES

The BFLSX milling system is the top choice for all ap-plications where milling work is to be carried out with high productivity and low costs. Its outstanding radial and axial run-out mean it can be used for semi- finish-ing within a work process for surface qualities with Ra values ≥ 6.3 µm.

High-feed millingHelical millingExtremely efficientIndividual and series productionISO-K application groupRa ≥ 6.3 µmUse of ZZ geometries


12.5 6.3



The PDKSN series of milling cutters is a high-perfor-mance face-milling system that produces perfect, finely finished surfaces with an Ra value ≥ 0.5 µm.

PRODUCT DESCRIPTION ∙ Depending on the size of the milling cutter, the

PDKSN has 1 to 3 insert pocket seats that can be adjusted in the Z-direction.

∙ The fixed insert pocket seats have an approach an-gle of 88°, while the adjustable pocket seats have an angle of 90°.

∙ The inserts in the 88° insert pocket seats perform the cutting work in the feed direction, and the inserts in the 90° pocket seats ensure the high surface quality.

∙ The PDKSN milling cutters are available in sizes from 63 to 250 mm as standard. Custom diameters are also possible.


The PMKSN is a finish-milling cutter that can produce surface qualities with Ra values ≥ 0.8 µm. It can also carry out rough-finishing tasks with high process relia-bility. The PMKSSN, with a coarse pitch, can be used to achieve maximum cutting depths or to machine thin-walled components.

PRODUCT DESCRIPTION ∙ Depending on the diameter of the milling cutter, 1 to 3 insert pocket seats can be adjusted in the Z-direction.

∙ All insert pocket seats have an approach angle of 88° and are fixed using wedge clamping.

∙ The milling cutters are available in diameters of 50 - 250 mm with standard pitch.

∙ For the coarse pitch, sizes of 63 to 260 mm are avail-able.

ADVANTAGES

The exact axial run-out of the inserts can be set with minimal effort. The PMKSN milling cutters operate with 8-edged, S-shaped inserts, which are available in coat-ed or uncoated ceramic, PcBN and Cermet. The inserts are also available with the ZZ (wiper) geometry.

ADVANTAGES

The PDKSN milling cutters operate with 8 cutting edg-es, which can be made of coated or uncoated ceramic, PcBN or Cermet. By mixing cutting materials, for exam-ple PcBN for ensuring surface quality and ceramic for the cutting work, you can effectively reduce the cost of cutting materials for finishing processes.Even milling cutters with large diameters are quickly ready for operation, since the axial run-out for finishing is set by adjusting a maximum of 3 inserts.

Face millingFine finishing, Ra ≥ 0.8 µmRough finishing Extremely efficientIndividual and series productionISO-P + ISO-K application groups

Face millingFine finishing Ra ≥ 0.5 µm extremely efficientIndividual and series productionISO-P + ISO-K application groups

vc = 700 - 1000 m/minfz = 0.16 - 0.2 mmap = 0.5 - 1.0 mm

vc = 700 - 1000 m/minfz = 0.12 - 0.25 mmap = 0.1 - 0.8 mm

3.2 6.8

1.6 0.5



The MFSSN is an adjustable, cartridge-based finish-milling cutter for finish facing that can achieve surface qualities with an Ra ≥ 0.8 µm.

PRODUCT DESCRIPTION ∙ With MFSSN, all cartridges can be set with a single setting screw to ensure optimal axial run-out.

∙ The MFSSN range of milling cutters have an 88° approach angle as standard.

∙ The inserts on MFSSN milling cutters are fixed with a clamping element.

∙ The milling cutters are available in diameters of 80 to 250 mm.


The PEKSN is a finish-milling cutter for finish facing with surface qualities Ra ≥ 0.8 µm.

PRODUCT DESCRIPTION ∙ With PEKSN, all insert pocket seats can be adjusted in the Z-direction using a tapered screw. This ensures extremely precise axial run-out for all inserts. The inserts of the PEKSN work with an approach angle of 88°.

∙ The milling cutters are available in diameters of 50 to 250 mm as standard.

ADVANTAGES

The minimal work required to set the axial run-out and a single setting screw per insert seating make this mill-ing cutter extremely user friendly. The PEKSN operates with 8-edged inserts that are available in a wide range of cutting materials, specifically coated or uncoated ce-ramic, PcBN and Cermet. Both the wiper-edge and ZZ (wiper) insert geometries are available.

ADVANTAGES

The MFSSN is distinguished by its sturdy design and the low effort required to set the axial run-out. All MFSSN milling cutters can be equipped with a finishing car-tridge, which has an insert approach angle of 90° and operates with S-shaped milling inserts. The wide range of cutting materials for the MFSSN, including coated and uncoated ceramics, PcBN and Cermets, demon-strates the wide range of face-milling applications for which this milling cutter is suitable.

Face millingFinishing, Ra ≥ 0.8 µm Extremely efficientIndividual and series production ISO-P + ISO-K application groups

vc = 700 - 1000 m/minfz = 0.12 - 0.2 mmap = 0.5 - 1.0 mm

3.2 0.8

Face millingFinishing, Ra ≥ 0.8 µmExtremely efficientIndividual and series productionISO-P + ISO-K application groups

vc = 500 - 800 m/minfz = 0.10 - 0.25 mmap = 0.1 - 1.0 mm

3.2 0.8


APPLICATION RECOMMENDATIONS

Overall milling set-upTo begin the application recommendations, it is helpful to first have a look at the overall set-up for the milling work and to check for possi-ble problem areas.You should note that, as a rule, the overall set-up should be stable during milling work. A stable overall set-up is essential to obtain max-imum performance from the cutting materials and milling cutters and to achieve the desired

results in terms of surface quality and planarity.The following table is intended as a short check list that can be used to inspect the most impor-tant points.

Machine situation

Stable milling machine designSufficient spindle power

Instructions for calculating the spindle power are on page 42

Closed working spaceGood vibration damping

Clamping set-up

Ensure that the workpiece is stably clamped

Note the distribution of forces from climb and conventional milling Pages 33 and 34

Component stability

Thin-walled componentNote the influence of milling cutter design

(approach angle, insert geometry) and climb/conventional milling on cutting forces

Unstable componentNote the influence of milling cutter design

(approach angle, insert geometry) and climb/conventional milling on cutting forces

Stable component

Holder for milling cutterAvoid excessive projection

Observe dimension table DIN 8030 on page 48

High-performance cutting materials

Selection of cutting materials according to component material and use of

cutting fluidBeginning on page 15

Milling insert geometry

Selection according to surface requirements Pages 42 and 43

Selection according to cutting forces Pages 40 and 41

Selection of milling cutterSelection according to machining task Pages 35 to 39

Selection according to cutting forces Pages 33 to 39

Criterion Additional information

Instructions for troubleshooting during milling on page 47


3ment). The following figure shows the chip cross sec-tion that results during milling due to this over-lapping movement.

3Feed direction

fz

fz

BASICS FOR MILLING

In order to go deeper into the topic of milling, it is useful to understand the cutting path that occurs during milling. This allows many prob-lems to be clarified quickly and easily.It is well known that the tool rotates during milling. The rotation of the milling cutter caus-es the cutting edge to trace a circular path. The workpiece itself follows a longitudinal path (feeding movement), which for face milling is perpendicular to the axis of rotation of the mill-ing cutter. This causes overlapping movement to occur at the cutting point (cycloidal move-

Cross section of the material removed by one tooth

As can be seen by the three colours of the chip, chip formation can be divided into three areas:

Blue area: Area of the entry cut. The chip is initially very thin and because a lot of friction arises initially, there is a risk here that chip welding can occur and transfer heat to the insert and the workpiece. A hard-ening of the material can occur in this entry zone. This hardening lessens as the chip cross section increases.

Grey area: In this area, the chip cross section corre-sponds to the feed rate per tooth (fz). The forces pri-marily work in the direction opposite the feed direction.

Red area: In the exit area, the chip cross section de-creases quickly and any heat transfer is minimised. However, the cutting forces are perpendicular to the feed direction.

The chip formation has been described here for conven-tional milling.


A favourable alternative to conventional mill-ing is climb milling. The chip cross section that forms during this method is the same as for con-ventional milling. However, the red area is now the entry zone and the blue area is the exit zone.

Red area: The impact strain on the insert and the workpiece material is high here. If the size and position

of the milling cutter are optimal, the insert meets the workpiece with full width, fz, and full depth, ap, upon impact.

Blue area: The chip cross section shrinks as the insert is leaving the material. Heat transfer to the insert and the workpiece are minimized, as is hardening of the workpiece material.

resulting force

forces on the workpiece

resulting force

forces on the workpiece

Table feed directionConventional milling

Feed directionfz

fz

Table feed directionClimb milling

CUTTING FORCES

During climb milling, the forces act more in the feed direction and press the workpiece into the clamping

device, with conventional milling the forces act more to pull the part from the clamping device.


SIZE AND POSITION OF THE MILLING CUTTER

The blue area in the following figure shows the part of the chip cross section that should be aimed for in an optimal milling situation. This shows that the entry and exit points are important factors during milling.

Cross section of the material removed by one tooth

It is therefore important to approach the desired blue area as closely as possible. The variables to adjust here are the milling cutter position and the milling cutter di-ameter. The optimal diameter for the milling cutter during face milling depends on the width of material to be milled.2 basic cases can be distinguished:

Case 1:Narrow milling paths that can be machined with a sin-gle cut. In this case, the rule of thumb is that the milling cutter should be 1.5 times larger than the width of the milling path. For example, if the width of the milling path is 80 mm, the diameter of the milling cutter should be about 125 mm (A).

Case 2:Wide milling paths that require multiple cuts to ma-chine. In this case (B), the milling machine, the clamp-ing set-up and the stability of the component must first be taken into account.

a) Machine rigidity, spindle power and the holder for the milling cutter: You must select a milling cutter width

that corresponds to the spindle power (see page 42) and the rigidity of the holder.

b) Clamping set-up: Note the primary direction of the machining forces.

c) Thin-walled and unstable components: Note the sta-bility of the component.

As a rule, approximately 2/3 of the milling cutter should be engaged in this case. For example, if a milling cutter has a diameter of 250 mm, you can calculate a desired contact width of 166 mm. The width of the milling path can also be increased (overlapping milling paths) depending on the machine situation. However, as a rule of thumb, overlaps of more than 80% are not recommended. If the correct milling cutter diameter is not available, approximately 25% of the milling cutter should not be engaged (C). The number of milling paths must then be selected accordingly.

fz

fz

Feed direction

Conventional milling


(A) Desirable (B) Undesirable (C) Milling cutter position

The position of the milling cutter should always be slightly off centre, since the cutting length per insert is shortest here. As shown, in (C) the entry and exit points of the cut lead to good chip formation and mod-erate impact strain in this case. If the cutter is positioned centrally, the radial forces at the entry and exit points will be equal. Since the entry and exit cuts do not occur simultaneously, this can lead to vibrations. As a result the spindle of the milling ma-chine can be damaged, the wear on the insert increases and the surface quality worsens (B).

When a cutting edge makes contact with the material to be machined, it is subjected to high strain, which is determined by the workpiece material, the type of cutting and the chip cross section.

Workpiece feeddirection



80 mm 125 mm1/4 of themilling cutter

ø 125 mmø 125 mm

ae


The images on page 36 indicate that favourable or unfavourable balances of forces at the entry and exit

points can result from the chosen amount of overlap. 3 cases are used to demonstrate the major influencing factors.

Position of the milling cutter centre Impact strain Chip thickness Strain on insert

Moderate Moderate

Very high. The impact strain is absorbed by the tip, the weakest point of the insert upon entry and exit.

Very highCorresponds

to fz

The strain on the insert is the highest, but strain is exerted on the rake face of the insert in proportion to the chip thickness h. This reduces the strain on the fragile tip, since during entry and exit the rake face is subjected to strain over a length given by fz, starting from the tip down.

Moderate Moderate

Soft entry cut strain is exerted further back on the insert. The problem here is that burrs can form on the edge of the workpiece and that the insert is subjected to higher strain upon exiting the workpiece.

EXIT ANGLE

The angle at which the insert exits the workpiece influ-ences the amount of burr formation. In case of a neg-ative exit angle, the remaining material may bend. As the insert continues its path, this remaining material is dragged along the end face of the cutting edge (and may be stretched). A part of the deformed material then remains on the edge of the workpiece as a burr.

In this process, additional tensile forces are exerted on the end face of the cutting edge, which causes addi-tional strain. The insert should exit the workpiece with a positive angle relative to the cutting edge. This leaves more ma-terial remaining at the workpiece edge, which can be more easily removed.

Centre of milling cutter

Positive exit angle

Centre of milling cutter

Negative exit angle

All

exam

ples

are

clim

b m

illin

g


PITCH OF THE MILLING CUTTER

The pitch of a milling cutter is defined by the number of milling inserts in the cutter. The three categories are coarse pitch, normal pitch and fine pitch. The number of teeth and feet per tooth are needed to determine the table feed rate. The key value here is the number of teeth that are in contact with the workpiece at the same time (zc = effective number of teeth).

MACHINING FORCESDURING MILLING

Cutting forces change continuously during a milling process, both in terms of magnitude and direction. The most important factors and their influence on the process are described be-low. The focus is on those factors that result from the geometry of the milling cutter and the insert. Factors that depend on the material to be machined (toughness, hardness, material

behaviour during removal, etc.) are briefly ex-plained on p. 42 within the calculation of spin-dle power.The main factors are the pitch of the milling cutter and the approach angle of the insert.

Coarse pitches are suitable for general milling tasks with relatively low machine power.Normal pitch – The impact forces during the entry cut are reduced because more inserts are in contact with the workpiece. However, the necessary spindle power increases because the radial machining forces increase.

Fine pitch is especially suited for applications with many interruptions in cutting along the milling path, high table-feed rates, moderate cutting depths and suf-ficient spindle power.

Coarse pitch Normal pitch Fine pitch

Cutting forces Low Moderate High

Machine power Low Moderate High

Feed rate per tooth High Moderate Low

Table feed rate Moderate Moderate High

Milling forces High Moderate Lower

Number of interruptions in cut-ting along the milling path

Few Moderate Many


NUMBER OF INSERTS ENGAGED

The number of inserts that are simultaneously in con-tact with the workpiece is determined by the number of inserts on the milling cutter and the overlap angle α. The angle α depends on the overlap distance ae and the effective diameter of the milling cutter Dc.

This can be calculated by the formula Zc = Z x α°/360°.It follows that the same effects described above also apply for milling cutters with fine, normal and coarse pitches.

Diagram for calculating the number of inserts involved in a cut

α = engagement angleα 1= angle between centre line of milling cutter and milling cutter radius at the peripheral point of the exit or entry cutae = width of cutDc = effective diameter of milling cutter

Dβ

α

Table feed direction

ae

ae-Dc 2


APPROACH ANGLE, CUTTING FORCES AND CHIP THICKNESS

The distribution of forces in the axial and radial direc-tions depends on the approach angle of the insert. The approach angle of the insert also defines the chip thick-ness h. Inversely, the chip thickness (h) is determined by the approach angle of the insert and the parameters with which the insert contacts the workpiece surface. The chip thickness decreases as the approach angle decreases. A smaller approach angle means that a

greater length of the cutting edge is in contact with the workpiece. As the angle at which the insert meets the workpiece decreases, the radial forces acting op-posite the feed direction decrease proportionately (left figure below); accordingly, the axial forces acting in the direction of the spindle increase proportionately (right figure below).

Approach angle Advantages Effects Distribution of forces

90°

75°

RELATIONSHIP BETWEEN APPROACH ANGLE AND DISTRIBUTION OF FORCES:

∙ For 90° shoulders

∙ Suitable for thin-walled

components, since the force

mainly acts opposite the feed

direction

∙ Highest radial machining forces

∙ Cutting tip subjected to very

high cutting forces during the

entry cut

∙ Probable burr formation and

breakout during exit cut

∙ For rough machining

∙ Reduced strain on cutting tip

during the entry cut

∙ Better balance of radial and

axial forces

∙ Optimal ratio of cutting depth

to insert size

∙ High radial machining forces

∙ Cutting tip subjected to high

cutting forces during the entry cut

∙ Probable burr formation during

exit cut

∙ Greater headspace needed

at entry and exit cut points –

collision with clamping device

possible

∙ Limited cutting depths

∙ Balanced distribution between

axial and radial cutting forces

∙ Minimised impact strain on

cutting tip during the entry cut

∙ Suitable for brittle materials

∙ Breakage/burr formation can

be avoided

∙ High table feed rates possible

45°

10°

90°

fzh

ap

45°fzh

ap

75°

90°


Approach angle Chip thickness h

90° h = fz

75° h = 0.96 x fz 45° h = 0.707x fz

10° h = 0.18 x fz

Round inserts = ( iC2 * (iC-2ap)2 *fz)-2

The correction factors for calculating the chip thickness h apply for the case where the milling cutter is centred.

The correction factor clearly shows that the chip thick-ness h decreases as the approach angle decreases. A smaller chip thickness h means that higher feed ad-vance speeds can be employed and that productivity can be increased.In general the chip thickness h can be calculated:h = sin Kr ∙ fz

Round inserts

10° ∙ For the highest table feed rates

∙ Suitable for plunge milling

∙ Axial cutting forces predominate

∙ Minimal tendency toward vibration

∙ Suitable for many applications

and materials

∙ Formation of thin chips allows

for high feed rates

∙ Magnitude of cutting force de-

pends on depth of engagement

∙ Burrs formed

∙ High axial strain on the spindle

bearings

∙ Stable components and

equipment required

∙ Moderate strain on spindle

CHIP THICKNESS h AS A FUNCTION OF APPROACH ANGLE

Approach angle Advantages Effects Distribution of forces

fz

ap

45°

30°100% Spanlast75%

50%25%

10°

fzh ap

90° 10°


CALCULATION OF THE MACHINE POWER

In order to determine the necessary spindle power, you must first calculate the machining volume (Q). The ma-chining volume is also a measure of the efficiency of the machining process. The unit of measurement is mm3/min. The higher the machining volume, the faster the work-piece can be machined.

Machining volume QThe machining volume can be calculated as follows, ac-cording to the approach angle:Q = h ∙ vf (mm2 x mm/min)

In general, the machining volume can also be calculat-ed using the contact width ae:Q = ap ∙ ae ∙ vf (mm3/min)

Calculation of the drive power Pc

For a simplified calculation of the required spindle po-wer, the machining volume Q can be used as an output variable:Q = ap ∙ ae ∙ vf (mm3/min)

The cutting performance Pc can then be calculated as: Pc = Q

K

K = a workpiece material depending specific chip remo-val volume.

SURFACE QUALITY DURING MILLING

The surface quality that results when a workpiece is milled is a critical measure for assessing the quality of the manufacturing process. For milling with ceramics, PcBN and Cermets, surface qualities with roughness values (Ra) of less than 0.5 up to 12.5 can be achieved with high process reliability. In addition to roughness, waviness and flatness are also important values for surface quality.

The spindle power can be caluclated with: Pc = [W],

Respectively: Pc = [kW]

The following table gives the K factor for different workpiece hardness for the GJL, GJS and malleable cast iron types.

k c follows from the formula K =

That implies the required drive power Pm with an effi-ciency factor ( = 0,75 - 0,90) can be calculated with: Pm = [kW]

The values that can be achieved depend on many factors:

Rigidity of the machine, spindle parameters, clamping set-up, machinability of the workpiece material, cutting speed and cutting depth, milling cutter design, design of cutting edge, wear characteristics/current wear of the insert

ap ∙ ae ∙ vf ∙ kc

60 ∙ 103

ap ∙ ae ∙ vf ∙ kc

60 ∙ 106

GJL and GJS kc factor [N/mm2]

GJL 150 1.500GJL 200 1.800GJL 250 2.100GJS 400 1.800GJS 500 1.850GJS 600 3.100GJS 700 3.200

Approximated value h = 0,10 mm

1 kc

Pc


One of the most important ways to influence the sur-face quality is in the preparation of the cutting edge.The following table shows the options.

The figures demonstrate how the various designs of milling cutters and inserts can affect the surface quality.There are further options for improving the surface quality. One such option is increasing the cutting speed while reducing the feed rate. However, this can lead to problems with heat removal. The heat transfer into the workpiece is higher, and the thermal load on the insert also increases.

The axial run-out of the milling head has a significant effect on the surface quality. A precise axial run-out produces significantly higher surface qualities.Finely finished surfaces can be best achieved using in-serts with a wiper design and milling cutters with insert seatings that can be adjusted in the Z-direction. The adjustable insert pocket seats are equipped with ZZ inserts and protrude in the Z-direction from 0.025 to 0.1 mm.

Design of the cutting edge

∙ Pronounced feed marks

∙ For rough surfaces

∙ Moderate feed marks

∙ Produces rough surfaces

∙ Inserts with wiper-edge and wiper (ZZ)

designs create minimal feed marks

∙ Depending on the design of the cutting edge,

surface qualities with Ra values less than 0.5

can be achieved

∙ Round inserts create a uniform wave profile

Because of how these inserts contact the work-

piece, surfaces with rough-finishing qualities can

be achieved

Small corner radius

With wiper edge

Large corner radius

Round inserts


FORMULAS, UNITS AND TIPS

The application recommendations in section 3 provide important fundamentals for milling cast iron materials with ceramic, PcBN and Cermet cutting materials. This White Paper presents the most important application recommendations. We recommend taking advantage of the extensive practical experience of our Solution Team when designing your milling projects.

ABBRAVIATIONS AND UNITS

Dc = diameter mmlm = length machined mmDe = effective diameter mmap = cutting depth mm

ae = overlap distance mmvc = cutting speed m/minQ = machining volume cm3/minTc = contact time minzn = number of inserts pieces

fz = feed rate per tooth mmf

n = feed rate per revolution mm

vf = feed advance speed (table feed rate) mm/minh = chip thickness mm

zc = number of teeth engaged pieceskc1 = specific cutting force N/mm2

n = spindle speed rpmPc = cutting power kWn = efficiency

Kr = approach angle degreesvc0 = cutting speed constantmc = increase in specific cutting force (kc) as a function of chip thicknessiC = insert diameter

Contact us at [email protected]


FORMULAS FOR CALCULATING MILLING QUANTITIES

Cutting speed (m/min):

Spindle speed (rpm):

Feed advance speed(table feed rate) (mm/min):

Feed rate per tooth (mm/min):

Feed rate per revolution (mm/rev):

Machining volume (cm3):

Median chip thickness (mm)(peripheral and face milling)when aQ / Dc ≤ 0.1:

Median chip thickness (mm)when aQ / Dc ≥ 0.1:

Machining time (min):

Drive power (kW):

LIST OF ABBREVIATIONS

fz

fz

fzh

ap

vc = π ∙ Dc ∙ n

1000

n = vc ∙ 1000

π ∙ Dc

Q = ap ∙ ae ∙ vf

1000

Pc = ap ∙ ae ∙ vf ∙ kc

60 ∙ 106 ∙

fn = vf n

Tc =lm

vf

fz =vf

n ∙ zn

vf = fz ∙ n ∙ zn

hm = fz ae

Dc

hm = sin Kf ∙ 180 ∙ ae ∙ fz

ae

Dcπ ∙ Dc ∙ arcsin


FORMULAS FOR FACE MILLING WITH NEGATIVE AND POSITIVE INSERTS:

FACE MILLING WITH ROUND INSERTS

Max. diameter for a given cutting depth (mm):

Centred milling, feed rate per tooth (mm/tooth):

Max. diameter for a given cutting depth (mm):

Centred milling, feed rate per tooth (mm/tooth):

fz

ap

fzh ap

Dc = D + 2 ∙ ap

tan

fz = h

sin

Dc = D + iC2 - (iC - 2ap)2

fz = iC ∙ h

2 ∙ ap ∙ iC - ap2


Measure

Problem Problem area

Increasing tool flank wear *1

Inappropriate cutting data

Inappropriate tool shape/RI *2

Wear on the clamping surface



Breakage on cutting edge



Poor surface quality



Burr formation



Edge breakage Workpiece



Poor planarity/parallelism



Heavy rattling/vibrations



Swit

ch t

o a

hard

er m

ater

ial

Swit

ch t

o a

mor

e du

ctile

mat

eria

l

Cutt

ing

spee

d Vc

Feed

rat

e pe

r to

oth

fz

Cutt

ing

dept

h ap

Chec

k cu

ttin

g w

idth

ae

Corn

er r

adiu

s

Chec

k w

orkp

iece

cla

mpi

ng

Wip

er Z

Z

Clea

ranc

e an

gle

Cham

fer

*1 Use C2 geometry*2 RI = replaceable insert

TROUBLESHOOTING


Holder shape B

w

D = 100 mm

Holder shape C

D = 160 mm

Holder shape B

D = 125 mm

Holder shape C

D = 200 - 250 mm

Holder shape C

D = 315 mm

Holder shape A

D = 50 mm - 63 mm

Holder shape A

D = 80 mm

32

D

14.4

8.30

40

D

16,4

9,5

14,5

66,7

6018

101,6

D

25,7

14,0

6018

22

101,6

177,8

D

25,7

14,0

22

11

D

10.4

6.55

27

14

D

12.4

7.00

40

D

16,4

9,5

DIN 8030 DIMENSION TABLE


For over 50 years, precision tools from CeramTec have been an inte-gral part of highly productive ma-chining solutions for components from the automotive industry. With

our tool solutions, the implementation of concrete cost savings and increased productivity is always top priority. Component examples: Brake discs, gear components, fly wheels, clutch plates, brake components, drive shafts, hydraulic elements, engine/motor components.

Manufacturing complex components made of different materials with ex-treme precision and optimal surface quality in an economic way – that is the basic structure of require-

ments for which we work together with our customers to create innovative, cost-efficient machining solutions. Component examples: gearbox housing, flanges, guides, shafts, rollers.

Surface quality, tolerances and the service time of the cutting materi-als are the standards for quality for hard machining. Our unique range of cutting materials made of PcBN and

ceramics, together with our perfectly matched tools, set the bar in this industry. In practice, this results in highly efficient and cost-effective machining.Component examples: Gear wheels, shafts, large gear-box components, bearing rings and rolling elements.

In the field of wind energy, spe-cial machining solutions are often required because the components involved are frequently very large. Strict tolerance requirements and a

high level of surface quality place exceptional demands on the cutting materials and tool holders. By observing and analysing the determining factors for machining, we are able to provide our customers with extremely efficient and cost-effective machining solutions. Component examples: Rotor flanges, rotor blade con-nections, planetary gear holders, gearbox housings, gear components.

ABOUT SPK CUTTING TOOLS FROM CERAMTEC GMBH

SPK tools provide the manufacturing industry with a wide range of state-of-the-art cutting materials, coat-ings, insert geometries and tool holder systems to cre-ate optimal solutions for machining tasks. These tools make it possible to manufacture products that are characterised by extremely high precision in limited tol-erance ranges and perfectly matched surface qualities.Efficient implementation of these attributes is primarily influenced by two factors: the performance of the ma-

chining tools and the amount of practical knowledge regarding the use of our precision tools, whereby prac-tical knowledge is becoming increasingly important. It brings together cutting materials and tools with the materials, components and the machine situation to create processes with increased productivity and reli-ability.

AUTOMOTIVE INDUSTRY

MACHINERY AND PLANT ENGINEERING

GEARBOX, DRIVE TECHNOLOGY AND BEARING INDUSTRY

The aerospace industry places ex-tremely high demands on machining. In this field, machining capacity and process safety are the decisive pa-rameters, and our CSA cutting mate-

rials together with our Monsoon Tool Technology tools are the optimal solution. Component examples: Jet engine components such as blisks.

AEROSPACE

WIND ENERGY

OF SOLUTIONSDISCOVER A MULTITUDE

MACHINING SOLUTIONS FOR INDUSTRIAL SECTORS


ACHIEVING MILLING SUCCESS

When you are starting your next milling project, consider the following services provided by our Solution Team to assist you throughout the entire milling process:∙ Selection of the cutting material and the milling system ∙ Determination of the optimal cutting parameters∙ On-site support during production

Milling systems from SPK Cutting Tools provide you with a wider range of solutions and allow you to complete your milling tasks more successfully and more efficiently than when using conventional milling cutters.

Contact our Solution [email protected]

CeramTec GmbHSPK Cutting Tools DivisionHauptstrasse 5673061 Ebersbach/FilsGermany

Tel.: +49 7163 166 - 239Fax: +49 7163 166 - [email protected] / www.ceramtec.com

milling cast iron materials with ceramic, pcbn and …

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