form tool design procedures

8/19/2019 Form Tool Design PROCEDURES

1/15

Assignment on-

DESIGN OF FORMING TOOLS

Abstract — A form tool is precision-ground into a pattern that resembles the part to

be formed. The form tool can be used as a single operation and therefore eliminate

many other operations from the slides (front, rear and/or vertical) and the turret, such as

box tools. A form tool turns one or more diameters hile feeding into the or!. "efore

the use of form tools, diameters ere turned by multiple slide and turret operations,

and thus too! more or! to ma!e the part.

INTRODUCTION —

#esigning a forming tool is one of vital factor of tool engineering, hich must be

!non by every design engineer. $orming a tool means giving a particular and useful

shape ith re%uired dimensions to the part. The part formed by forming operation is

generally ta!es the shape of the dir or punch. &n the forming operation, the metal flo

is not uniform and locali'ed to some extent, depending upon the shape of the or! piece.

"ending along a large radius in a straight line may also be referred to as a forming

operation. &t is difficult to distinguish beteen a bending and forming tools. $orming

operation may be simple and extremely complicated.

A form tool is precision-ground into a pattern that resembles the part to be formed.

The form tool can be used as a single operation and therefore eliminate many other

operations from the slides (front, rear and/or vertical) and the turret, such as box tools.


2/15

A form tool turns one or more diameters hile feeding into the or!. "efore the use

of form tools, diameters ere turned by multiple slide and turret operations, and

thus too! more or! to ma!e the part. $or example, a form tool can turn many

diameters and in addition can also cut off the part in a single operation and eliminate

the need to index the turret. $or single-spindle machines, bypassing the need to index

the turret can dramatically increase hourly part production rates. n long-running obs

it is common to use a roughing tool on a different slide or turret station to remove the

bul! of the material to reduce ear on the form tool.

There are different types of form tools. &nsert form tools are the most common for

short- to medium-range obs (*+ to +,+++ pcs). ircular form tools are usually for

longer obs, since the tool ear can be ground off the tool tip many times as the

tool is rotated in its holder. There is also a s!iving tool that can be used for light

finishing cuts.

A drabac! hen using form tools is that the feed into the or! is usually slo,

+.+++* to +.++ per revolution depending on the idth of the tool. 0ide form tools

create more heat and usually are problematic for chatter. 1eat and chatter reduces

tool life. Also, form tools ider than.*times the smaller diameter of the part being turned have a greater ris! of the part

brea!ing off. 0hen turning longer lengths, a support from the turret can be used to

increase turning length from .* times to * times the smallest diameter of the part

being turned, and this also can help reduce chatter. #espite the drabac!s, the

elimination of extra operations often ma!es using form tools the most efficient option.

THEOR OF FORM TOOL!

"UR"OSE OF FORMING TOOLS!

A form tool is defined as a cutting tool having one or more cutting edges ith ell

defined profile or contour that is reproduced as the desired form on the or! piece

surface. $orm tools utili'ed for turning applications are classified according to type of

cross section. The classification is shon in the tree diagram of $igure


3/15

$lat or bloc!ed tools are further classified according to the setting of tool ith respect to

the or!piece, vi'. radial -fed tools and tangential -fed tools. $urther, form tools are alsoclassified ith respect to orientation of tools ith respect to the or!piece axis.

#ARIOUS T"ES OF FORMING TOOLS!

F$at Form Too$!2traight and flat form tools have a s%uare or rectangular cross-section

ith the form being along the side or end. These tools are similar in appearance to

the turning tools. These are usually set centrally so that they ill cut their contour

hich is identical to the desired contoured of the or! piece. A typical example of 3-

notch tool is shon in $igure. This type of tool is suitable for ma!ing deep straight-

sided form grooves. The cutting is restricted type due to the mixed chip flo.

"ecause of the existence of the good surface finish, this type of tool must be operated

at very lo cutting speed.


4/15

$igure shos a typical flat form tool ithout ra!e angle. &t is necessary to compute x to be machined in the tool in

order that the depth BC is correct profile. This distance x is to be planned by a fly cutter or planning tool and is

measured normal to the clearance face. The amount of x is less than actual depth of form AB produced on the

or!piece because of the clearance angle α. $rom the geometry of the figure

x 4 AB cos (α) . . . (5.)

$igure 5.6 shos a flat form tool ith ra!e angle. The edge angle is given by

(7+ 8 γ 8 α) . 9sing geometry of the figure, the depth x to be ground or machined can be determined in the

folloing manner :

H = r sin ( γ s ), l s = r cos ( γ ) and l = R− h

Therefore, L = L − L = R, − h

,− r cos ( γ)

s

= ( R − r sin ( γ s )) − r cos ( γ)

;o, x 4 L, cos (α


5/15

Circ%$ar Form Too$

The circular form tool is circular in shape. &t has depth x or proection of distance x

produced all around the diameter in the form of annular grooves. The outside diameter of

circular form tool is determined in accordance ith the height of profile to be turned. The

graphical method is recommended for this purpose. ircular form tool is shon in $igure.

&'(GRA"HICAL METHOD OF DETERMINING

"ROFILE OF FORM TOOL

'(') "ro*i$e o* F$at Form Too$


6/15

The graphical method profile of flat form tool is

shon in $igure 5.*. The graphical method is

described as follos :

(a) #ra profile of the or!piece in loer left corner.

(b) =roect basic points on the axis I - I vi'. >, >, 6> etc. andform point O as a centre. #ra circles corresponding toradius r , r , r 6 passes through >, >, 6>respectively.

(c ) Assign proper value of ?, γ. $ind outer diameter and centre of flat

through point form tool.

d)Through point , , 6, dra a line parallel to the flan!.

e)To construct the cross-section of the tool perpendicular to the

flan! (set N - N ), dra line LL (perpendicular to flan!).

f)$rom the line LL, e lay off the lengths l and l , since the

dimensions of the tool profile measured along the or!piece are

e%ual to the corresponding axial dimensions of the or!piece.

g)At lengths l , and l dra lines parallel to LL and obtain point of

intersection as @, @, and 6@, hich on oining gives profile of

form tool.


7/15


8/15

affected by ear strain as a result of friction beteen the or!

piece and the tool. The bottom die is exposed to pressure and is

subected to mainly sliding friction (ear). The face of the upper die

and the surface of the loer die should have as high a friction co-

efficient as possible, hilst the lateral area of the upper die

should have a lo friction co-efficient so that the sheet does not

move during the cutting operation.

The situation in 0ee, 0raing o,erations is similar. 1ere, the

upper die is exposed mainly to pressure and only to a lo level of

bending load, the loer die is exposed mainly to friction and to a

lesser degree to pressure. As in the cutting operation, care must

be ta!en to ensure that the sheet does not flo at the upper die

area. The friction co- efficient should therefore be as high as

possible at the rounding of the upper die but lo at the rounding

of the draing ring.

&n *orar0 e/tr%sion operations, compressive and temperature

stresses occur at the upper die and compressive, tensile, friction

and thermal stresses at the loer die. Thermal load also develops

in cold extrusion operations as a result of the inner friction during

material flo.

The situation in the case of re1erse e/tr%sion is similar, although

the upper die is additionally affected by bending and friction

stresses.

The types of stress listed, also occur in varying degrees in other

processes such as extrusion, *orging, pressure casting and shell

casting. The high operating temperatures are particularly liable to

cause stresses hich are generally mas!ed in forging o,erations b+

a00itiona$ s.oc2 stress


9/15


10/15

TOOL DAMAGE AND 3EAR :

The types of damage shon in $ig., occur as a result of the types of stress

previously described. These may render the tool unfit for use and include:

.0ear

.Bechanical crac! formation

6.Thermal crac! formation

C.=lastic deformation.

CAUSES OF DAMAGE AND THEIR MECHANISMS2ince ear is the most important type of damage, it ma!es sense to

investigate its causes in more detail.

There is no one material characteristic hich provides a conclusive

indication in itself, as to the level of ear resistance of that material. This is

because in the vast maority of cases, a number of causes interact and combineto cause ear in the tribo-technical systems in industrial practice,


11/15

These include:

-Adhesion

-Abrasion

-2urface brea!-up and

-Tribo-chemical reaction

0ear inhibiting coatings are fre%uently e%uated ith hard coatings. This may

be true in the case of abrasive ear, in hich there is a correlation in many

cases beteen surface hardness and ear resistance. 1oever, this does not

apply to other types of ear or to a combination of stresses, since factors

other than hardness, such as surface design, toughness etc. are also important.

The most important ear mechanisms and means of reducing ear, are

therefore discussed briefly in the folloing-


12/15

A0.esi1e ear! ccurs hen bonding forces in the area of the atomic

lattice ta!e effect beteen to metallic materials. The prere%uisite for this is

that the lattices of the bodies concerned, are structurally similar and that

they approach one another until there is only a short distance beteen

them. $urthermore, the more the lattice structures of the materials

concerned differ the loer is their susceptibility to adhesive ear.

Abrasi1e ear! ccurs hen the harder of the to bodies involved in the

ear process, has pronounced roughness bea!s, hich tear particles of

material from the surface of the softer body. Baterials hich are resistant

to abrasive ear, have outstanding hardness in comparison ith the

abrading material. 0hen there is s%r*ace brea20on4 the crystal and the

structural condition is damaged irreversibly as a result of alternating stresses

and hich depend on the duration and level of stress involved. 2urface

brea!don is reduced hen the strength of a material is high, hereas

stress pea!s and notch effects result in an increase.

Tribo-c.emica$ reactions! Occur hen the ear processes ta!e place only


13/15

in the outermost boundary layer of the bodies involved. This boundary or

interfacial layer can be formed by reactions beteen the material and the

surrounding medium. onse%uently, the ear characteristics of the base

material itself have no influence on this process. &t is not possible to specify

any particular material behavior in order to avoid the tribo-chemical

reaction, since the formation and characteristics of the outer boundary layer

are determined to an e%ual degree by the material and by the surrounding

medium. onse%uently, the lubricant is the primary determining factor. The

various types of damage sustained by tools, are illustrated in $ig by the

example of a forging die. &n 5+ D of all cases in hich tools become unfit

for use, ear is the underlying cause. Bechanical crac!ing occurs in * D

of all cases.

&n contrast, plastic deformation and thermal crac!ing very rarely mar! the

end of tool life. These results cannot be transferred directly to other

forming operations but ear ill be the most common type of ear there

too, since shoc! and temperature stress are generally loer in these

operations than in forging.


14/15

5ASE MATERIAL AND 5OUNDAR LAER!

Re6%irements to be met b+ *orming too$s!

#ue to the types of stress listed, there are a number of specialre%uirements hich must be met by the base material and the boundary layer

of tools. These are shon in $ig. The focus in the folloing is on the

re%uirements to be met by the ear and strength characteristics.

Ee%uirements to be met by the base material and the subsurface layer:


15/15

Too$ materia$s *or e/tr%sion too$s

Re*erences—

)'.nitc.ac.in/dept/me/agadeesha/Tool...#esign/1

A=TFE5.pdf.. https://en. i2i,e0ia.org/ i2i/$ile: Form-too$.pg

6.$undamentals of Tool #esign "y A2TBF.

C.$undamentals of metal cutting and tools by

Eanganath.

.

S%bmitte0 5+- Gro%, 7

8Sc.no )7)))9:)7 -)7)))9:77;

G%i0e0 5+- Dr' M'< "ra0.an Sir'
https://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpghttps://en.wikipedia.org/wiki/File:Form-tool.jpg

form tool design procedures

Documents