trumpf tlf laser kap4 e

T195EN04.doc Criteria for the evaluation of laser cuts 4-1

Chapter 4

Criteria for the evaluation oflaser cuts

1. How is the quality of cut evaluated? ........................... 4-2

2. Burr formation................................................................ 4-3

3. Kerf.................................................................................. 4-4

4. Pittings............................................................................ 4-6

5. Standard roughness...................................................... 4-7

6. Groove lag ...................................................................... 4-9

7. Perpendicularity and slant tolerance......................... 4-10

8. Evaluation table ........................................................... 4-12

4-2 Criteria for the evaluation of laser cuts T195EN04.doc

1. How is the quality of cut evaluated?

DIN EN ISO 9013:2000 The standard DIN EN ISO 9013 is a summary of and also asubstitute for the standards DIN EN ISO 9013:1995-05"Oxyacetylene (flame) cutting", DIN 2310-4 "Plasma cutting" andDIN 2310-5 "Laser cutting of metallic materials". In addition, thecontent of these standards has been revised.

DIN EN ISO 9013:2000 gives terminological definitions anddescribes criteria for evaluating the quality of cutting surfaces,quality classification and the dimensional tolerance. It applies e. g.in the case of laser beam cuts for material thickness of between0.5 mm and 40 mm.

TRUMPF criteria TRUMPF applies the following criteria for the evaluation of cuttingresults which deviate in part from DIN EN ISO 9013:2000:

• Burr formation (slag formation or melt drops)• Kerf• Pittings• Groove lag n• Standard roughness Rz5

• Perpendicularity and slant tolerance u

A definition and description of the methods used in measuring ordetermining the criteria above is provided on the following pages.

The evaluation table at the end of the chapter is intended for useas a master template, so that data required for the evaluation ofthe quality of cut is saved.


2. Burr formation

Example: mild steel, sheet thickness 15 mm, focus position +5 Fig. 25110

Example: mild steel, sheet thickness 15 mm, focus position –1 Fig. 25111

Example: Stainless steel, sheet thickness 8 mm, focus position –4 Fig. 25112

Definition Burr formation can refer to• a highly adherent burr which cannot be removed without

further treatmentor• a slag which is adherent but can be easily removed without

further treatment.

Determining theburr formation

The burr formation is evaluated visually and described in words.The dimension of the burr is dependent on the focus position,amongst other things.

• "Bead burr": beadlike or drop-like burr, with a polished metallicsurface; highly adherent burr

• "Crumble burr": Melt adheres in the form of fine, crumbly burr,easier to remove than "sharp burr"

• "Sharp burr": Whisker-like, rough and sharp-edged burr; highlyadherent in parts. The underside of the cut surface is rough.


Example: stainless steel, sheet thickness 8 mm, focus position –11 Fig. 25113

3. Kerf

The kerf - also referred to as the kerf breadth - is given in [mm].

Rectangle with slit: measuring the kerf Fig. 25395

• "Sharp burr": fine but sharp-edged burr, whisker-like andadhering to the underside.

Definition Laser cutting produces a kerf which is usually narrower at thebottom of the cut than at the top.

Measuring the kerf The kerf is measured in the slit of a rectangle (see Fig. 25395).

12

1 Slit 2 Workpiece


Measuring the kerf Fig. 25396

Material Sheet thickness[mm]

Kerf[mm]

Mild steel (QSt 37-2) 1 - 34 - 6-1520

0.150.2 - 0.30.35 - 0.4

0.5

Stainless steel(1.4301), high-pressurecutting with N2

1 - 3

4 - 810 - 12

0.15

0.20.5

Aluminium alloys(AlMg3, AlMgSi1), high-pressure cutting with N2

1 - 34 - 8

0.150.2 - 0.3

A value is determined with the aid of a feeler gauge: Depth ofpenetration s (see Fig. 25396)

2

s

1 Workpiece s Sheet thickness = depth ofpenetration

2 Feeler gauge

With material strengths of more than 3 mm, the exact measure-ment of the kerf is carried out by cutting a rectangle and using theslide gauge to measure the edge length. The difference to theprogrammed length of the rectangle is the kerf.

Example:Programmed edge length: 100 mmMeasured edge length: 99.7 mmDetermined kerf: 0.3 mm

TRUMPF standard values for kerf width can be found in the datacollection for your machine.

Example: Entries from the data collection for TC L 2530,TC L 3030, TC L 4030, TC L 6030 with SINUMERIK 840D controlsystem and TLF 3000 turbo


4. Pittings

Pitting Fig. 25397

Erosions Fig. 25398

Definition Pittings are erosions of irregular width, depth and form whichinterrupt an otherwise regular cutting surface (see Fig. 25397).

1

2 3

3

4

1 Cutting beam direction 3 Pittings

2 Workpiece 4 Cutting direction

Determining When determining the quality of cut, the features of the pittingspresent are visually evaluated and described in words. If no pittingis detectable, this criterion is ignored.

Erosions arising, for example, from changes of direction, are listedseparately.

2 3

3

4

1 Cutting beam direction 3 Erosions

2 Workpiece 4 Cutting direction


5. Standard roughness

Sketch showing roughness: enlarged top view Fig. 25246

The standard roughness Rz5 is the arithmetic mean calculated fromthe roughness (scallop height) of five consecutive, representative,individual measured sections. The roughness is stated in [µm].

Schematic diagram: Roughness over five individual measured sections Fig. 25454

The point at which the roughness is measured is dependent on thesheet thickness s and the material type. TRUMPF deviates fromthe standard by measuring at positions which visually seem todemonstrate the highest degree of roughness. The standardprocedure is to use the upper third of the top of the cut as themeasuring point.

Definition of roughness Roughness = groove depth

12

3

1 Roughness 3 Kerf

2 Workpiece

l1 l2

ln

Zl1Zl2 Zl3 Zl4

Zl5

l3 l4 l5

Zl1 to Zl5 Roughness of individualsections

ln Whole measured section

l1 to l5 Individual measuredsections

Measuring the standardroughness R

The standard roughness Rz5 is measured e. g. with a brushanalyzer corresponding to ISO 3274. The measuring itself iscarried out at continuous distances in the cutting direction, inaccordance with ISO 4288.


s [mm]Measuringpoint

*) [mm]

Mild steel

Measuring point[mm]

Stainless steel

Measuring point[mm]

Aluminium

1 -0.5 -0.5 -0.52 -1 -1 -13 -2 -1 -24 -2.6 -2.6 -2.65 -3.3 -1.6 -3.36 -4 -4 -48 -5.3 -7 -5.310 -1 -9 -12 -1 -11 -15 -1 - -20 -1 - -

The maximum roughness creeps from the lower to the upperside of the sheet in the case of mild steel with a thickness of> 8 mm. This is not the case with Stainless steel andaluminium.

Sheetthickness

[mm]

Mild steel,maximum

values Rz [µm]

Stainless steel,maximum

values Rz [µm]

Aluminium,maximum

values Rz [µm]1 9 6 18

1.5 8 - 132 15 10 17

2.5 7 - 143 17 10 224 5 10 205 6 10 196 6 13 148 7 19 4610 28 43 -12 23 38 -15 28 - -20 28 - -

These values are standard values determined on the basisof the current state of the technology.

*)

The measuring points for mild steel, Stainless steel and aluminium given in the table refer to the top edge of the sheet.Example: -0.5 means 0.5 mm below the top edge of the sheet (=beam entry side).

The following table shows the Measuring point for theroughness, which depends on the sheet thickness and materialtype. These values are to be regarded as standard values for thetechnology in its current state. They were determined on the basisof a TLF 4000 turbo.

Standard values forroughness Rz

In the following table, maximum values for the standard roughnessare given, for your orientation. These values were determined byTRUMPF based on a TLF 4000 turbo.


6. Groove lag

Measuring groove lag Fig. 25399

Pittings Pittings must be dealt with separately, as they cannot be calculatedby measuring the roughness. The expansions of the pitting exceedthe range of the measuring device.

Definition In laser cutting, the edges of the workpiece have a characteristicgrooved pattern. At low cutting speeds, the grooves run almostparallel to the laser beam. As the cutting speed increases, thegrooves bend away from the direction of cutting.Groove lag n refers to the greatest distance between two drag linesin the direction of the cut.

Measuring n The groove lag is evaluated visually.

The evaluation is carried out on a photo or cut sample with the aidof a magnifying glass or stereo microscope. A reference line isused for assistance (see Fig. 25399).

n

1

2

3

4

5

1 Reference line 4 Cutting direction

2 Workpiece 5 Drag lines

3 Groove width n Groove lag


7. Perpendicularity and slant tolerance

The perpendicularity and slant tolerance encompasses thedeviation from both straightness and flatness.

The perpendicularity and slant tolerance are measured in [mm] inthe case of perpendicular cuts or bevel cuts.

Bevel cut:

s 1

u

s

s

s Sheet thickness

u Perpendicularity tolerance

1 Reference area in which the measurement is carried out.

∆s Dimension by which the reference range of the perpendicularity tolerance isreduced. This dimension varies with the sheet thickness:

Perpendicularity and slant tolerance Fig. 3800, 11181, 11182, 25243

Definition The perpendicularity and slant tolerance u is the distance betweentwo parallel straight lines between which the cutting surface profilemust lie at the theoretically correct angle - i.e. at 90° in the case ofperpendicular cuts.

Perpendicular cut:


TRUMPF’s values are based on the TC L 3030 and TLF 3800 turbo.The values are represented in the following diagram:

u [mm] Edge angle S [mm] Sheet thickness

Edge bevels for mild and stainless steel and aluminium Fig. 25393EN

DIN EN ISO 9013:2000 classifies three ranges for laser cutting:Range 1 to 3.

Deviating from the standard, TRUMPF defines three ranges fromthe following formulas, dependent on the material:

Formula for upper limit

Mild steel (flamecutting)

Stainless steel (laserfusion cutting)

Aluminium (laserfusion cutting)

u = 0.05 + 0.01s s = sheet thickness

u = 0.005 + 0.033s

u = 0.03 + 0.035s

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

0 5 10 15 20 25

u [m

m]

Mild steel (St)

Stainless steel (VA)

Aluminium (Alu)

Upper limit St

Upper limit VA

Upper limit Alu


8. Evaluation table

General data

Date: Person responsible:

Material type: Cutting speed:

Laser type: Lens:

Laser power: Focus position:

Gating frequency: Nozzle geometry:

Cutting gas pressure: Nozzle stand-off:

Cutting gas:

Data calculated

Mate-rialthick-ness[mm]

Kerf[mm]

Rough-ness[µm]

Groovelag(yes/no,minor/major)

Perpen-dicularitytolerance[mm]

Pittings(yes/no,sporadic/frequent)

Erosionfollowingchange ofdirection(yes/no)

Actualradiusafter 90°change indirection[mm]

Other

Remarks:

From:

Technical informationLaser processingTLF laser: Basics, installation and useEdition: 10/2000

Ordering informationPlease state the title of the document, the language required, and the date of issue.TRUMPF Werkzeugmaschinen GmbH + Co. KGD-71254 DitzingenJohann-Maus-Straße 2Phone (0 71 56) 3 03-0Fax (0 71 56) 3 03-5 40Internet: http://www.trumpf.come-mail: [email protected]

The document was drawn up in the Technical Documentation of TRUMPFWerkzeugmaschinen GmbH + Co. KG.All rights to this documentation, especially the rights of reproduction and distribution as wellas that of translation are retained by TRUMPF Werkzeugmaschinen GmbH + Co. KG, evenin the case of notifications of protective privilege. Without previous written consent ofTRUMPF Werkzeugmaschinen GmbH + Co. KG, no part of the documentation, no matter inwhich form, may be reproduced or processed, copied or distributed using electronicsystems. Subject to technical modifications or errors.© TRUMPF Werkzeugmaschinen GmbH + Co. KGTRUMPF Werkzeugmaschinen GmbH + Co. is not liable for any errors in thisdocumentation. Liability for direct and indirect damage or injury resulting from the delivery oruse of this documentation is excluded, in so far as this is legally permissible.

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