cold forging process and product development - case study

Process and Product Development

Valve Tappet Cold forging Process

Abdullah Ansari

INDEX• Introduction

• Nature of Problem

• Existing Blank & Forging Die Analysis

• Cold Forging Standard

• Existing D2/d2 & l/d Ratios

• Corrective Actions

• Recalculations,  Results Of Recalculations

• Trials & Decisions

• Previous Process & Revised Process

• Results with Revised Tooling & Conlusion

• Support During Development

INTRODUCTION

The problem of head offsetting while cold forging of item R 708‐13 is observedin since new product development.

To avoid the same several corrective actions [short method] were initiated suchas using flat ejector etc. but effectiveness of the actions taken was not 100%satisfactory. The results were not consistent.

After all above it is concluded to analyze and re‐design of cold forging tooling &process.

While analyzing the same whatever the calculations, observations and theactions taken by undersigned are recorded here, which will be one guide line toattend this kind of problems in future.

A. T. ANASRI              Date : 22.08.2000

Nature of Problem 

( Tappet R 708‐13 )While cold forging 1st stage Head Diameter of Tappet getting more offsets & not getting controlled after 

several adjustments.

Existing Blank & Forging Die analysis • .Size of Cold forging blank: Total Length            = 85mmOuter diameter ( d ) = 12.5mm• .Size of cold forged part:Head diameter ( D )  = 30mmHead thickness          = 5.5mmTotal length               = 61mmOD of stem               = 12.8 & 12.6mm• .Size of Cold forging Die:Length of die                                    =  90mmLength of blank outside the die  ( l ) =  30mm

( From flat face ) 

Cold forging standard

Cold forging standard states that:D2/d2 and  l/d should not exceed 3. Where 2 is ideal.

In our caseD = 30mmd  = 12.5mml  = 30mm

D2/d2 = 302/12.52 = 5.76l/d = 30/12.5 = 2.40 By above calculations it is noticed that value D2/d2 is 

exceeding the standard and l/d is almost in range. So we may conclude that above exceeding value is 

affecting to forged head diameter offsetting.

In light of Cold Forging Standard Existing D2/d2& l/d ratios

What to do now ???

Corrective action planned : 

–Recalculate the die design as per coldforging standard. And manufacture thecold forging die as per new calculateddimensions.

Recalculations as per Cold forging standard

D2/d2 = 2 ( as per standard )Hence D2/12.52 = 2D2 = 2 x 12.52

D = 17.67mm.‘l’ of ‘D’ will be 17.67x17.67x l x /4 = 12.5x12.5x30x /4

l = 15.01mm

What Recalculations Indicating!!!

Recalculations indicating that the forging is not possible in one operation& it will need double operation. For second operation stepped blank willbe required, while first operation stepped blank will be produced.

For preparing stepped blank separate die isrequired

Trials .

For trials stepped blank is prepared by machining. While trials forming punch is used. 

Trials are taken with stepped blank on 22.08.2000Results found satisfactory in all aspects.Head offsetting is very low & will not create anydefect while head turning.

Dimensions are found consistent.Trials are successful.

Way Forward.

Based on successful  trials, die designed for first operation for preparing the stepped blank (cold forging 1st operation).

# PREVIOUS PROCESS

Fig. Shows the 

blank ready for 

forging of R708‐

13 tappet. 

85

12.5

1 ‐ PREVIOUS PROCESS

Fig. Shows the 

forging drawing of 

R708‐13 tappet. 

Previously this was 

created in single 

setting.

30 12.8

5

40

12.6

# REVISED PROCESS

Fig. Shows the 

blank ready for 

producing 

stepped blank 

for forging  of     

R708‐13 tappet. 

85

12.5

1 ‐ REVISED PROCESS 

Fig. Shows the 

stepped blank

ready for finish 

forging of R708‐13 

tappet. 

12.6 12.5

40

17.7

15

30 12.8

5

40

12.6

2 ‐ REVISED PROCESS

Fig. Shows the finish 

forging  of R708‐13 

tappet. 

Now it is created in 

second stage from 

stepped blank.

Die drawing for stepped Blank

Results with revised tooling.

Implemented the new tooling & monitored for 1000nos forcold forging 1st & 2nd operation.

No problem while preparing stepped blank. I.e. 1stoperation.

No problem of head forming while 2nd operation.Improved consistency in dimensions while cold forging 2nd stage.

Setting time for cold forging is  reduced.Minimizes rejection at cold forging drastically . Hence reduction in wastage. 

FINAL CONCLUSION.

The newly designed tooling is OK & Proven

for production.

05.11.2000

Mr. V RamgopalMr. M. GANAPATHY

For Giving A Opportunity To Work On Such A Special Task.

Mr. S.C.SALVI & Mr. P.S.KULKARNI Team members

Acknowledgements

Thank You

abdullahta@gmail.com