deep drawing

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

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Design and Development of Sheet Metal Draw Component Using CAE Technology

Y. N. Dhulugade1, P. N. Gore

2

1PG Student, Mechanical Dept. DKTE Societys Textile and Engineering institute, Ichalkaranji. India. 1

Senior Engineer Design & Development, Dies and fixtures, Adventtooltech Pvt. Ltd. Pune, India. 2Associate Professor, Dept. of Mechanical Engineering, DKTE Societys Textile and Engineering institute, Ichalkaranji. India

Abstract Achieving high standard quality products in almost no time with great economy in industry demands

for a technology that helps exceed the engineering

requirement of products. This paper highlights development

of draw component and the changes made in product design due to manufacturing and assembly reasons considering the

design intent; and also the advantages of using various CAE

softwares used in designing draw tools. It helps reducing the

complete product development cycle as compared to what

happens with conventional methods. Lesser effort and ease

to model the complete setup and important features with

different design parameters, improved the product

development without compromising quality. Thorough

attempt is aimed for design sheet metal draw die using the

latest technology to make it time and cost effective, identifying

the problem areas through analysis results and Based on the

analysis prepare the query report and suggest revisions/

modifications in the product design. Finally, work out the best

die design to produce defect-free components based on the

inputs received. Thus using the CAE software one can design

economical die because the design changes, modifications and

challenges can be observed and solved in the initial phase of

the design only. Otherwise without these efforts the die design

and the processing could end up as a costly and complicated

assignment.

Keywords- Design Intent, economy, FEM simulation,

Product Design, sheet metal draw die.

I. INTRODUCTION

The sheet metal deep drawn technology is one of the

most challenging processes in manufacturing. Drawing

operation is the process forming a flat piece of material into

a hollow shape by means of punch which causes the blank

to flow into the die cavity (refer figure 1). The depth of the

draw may be shallow, moderate or deep, various

geometries and sizes are made by drawing operation, two

extreme examples being bottle caps and automobile panels.

Typical defects that occur due to incorrect flow of material

into the die during the stamping process are wrinkling

caused by excessive compression, tearing or splitting

caused by excessive tension, and spring back caused by

elastic recovery of the material. [6, 7]

Fig.1(a) Schematic illustration of the deep drawing process on a

circular sheet-metal blank. (b) Variables in deep drawing of a

cylindrical cup [10].

II. WHAT IS THE PROBLEM?

Tool development for form component is very costly

process and it will take lot of time if we go conventionally.

So we can use latest technology such as crash analysis

during the design phase so that problem areas in forming

can be easily pointed out through analysis results which

will make our work, time and cost effective. And based on

analysis report tool designer can suggest revisions/

modifications in the product design which will help tool

designer to design a tool which will produce defect free

components based on the inputs received. Without these

efforts the die design and the processing could end up as

costly and complicated assignment. [1, 5]

As shown in fig. 2, draw Component may face

challenges such as, Wrinkling, Tearing, Thinning, Spring-

back.

Fig.2 Draw component challenges



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While the die designer attempts to design a draw die, the

process for drawing entails the use of hydraulic press since

the rate of deformation has to be controlled throughout the

operation of draw. The draw die should be built to tackle

the problem of wrinkling especially prominent at the top

corners; tearing along the sides of the corner and the

bottom area; while thinning is associated along the corner

edges prone to uneven flow. And the problem of spring

back may occur due to elastic recovery of material. The

rejection amounts to a loss of man hours of the hydraulic

press, skilled labor, special material (DD or EDD quality

for draw) and other resources directly or indirectly

associated with the process.

A. Necking Failures

Necking failures such as shown in Figure 3 are preceded

by localized thinning that may not be visible in the part. [6]

Fig.3 Necking failure of component

B. Material Quality Issues

When drawing operations fail, often the material is

immediately blamed. The logic is that if the vendor can

supply some material that will run it should be possible to

do so consistently. Material formability properties do vary

from lot-to-lot, and even within the same coil.

Proper deep drawing material should be selected while

going for good quality products and error free deep

drawing operation. [6]

1. Why The Problem Is So Important

Stamping industry applies CAD techniques both in the

process planning and die design already for many years.

After determining process sequences and process

parameters the forming dies are designed using

sophisticated CAD systems. However still we dont have any evidence whether the designed tool will provide the

right component and as it is die goes for tri-out and

automatically it consumes time and cost and it will effects

on the final cost of the die.

If the die tri-out goes well and component received

matching to the requirements, the die will go for

production, on the other hand if die tri-out fails and

component showing some splitting and wrinkles, die set

needs to be reworked. It means firstly rework the die

construction by changing the die parameters such as draw

radii drawing clearance etc. even if the problem not solved

we have to think for new die design and process planning.

In some of the cases the development team goes to the

product design stage to modify the product parameters so

more we go back the design and development costs are

increasing indirectly. [5]

2. Conventional Practices for die design and development

As shown in following schematic (diagram 4) in

previous days the method used for process planning and die

designing will becoming costly due to some reasons.

Initially the process planning is done when the final

product design received from the product designer and after

that tool is designed, die construction is made and finally

tool is shifted for tri-out this is what conventional method

of die design for a particular product. If everything goes

well and if the drawn parts matching to the required part

then the die is sent to production. On the other hand if tri-

out fails and part showing undesirable results then

development team goes for die reworking and if problem

not solved after die rework, new die design or new process

planning is required, in some cases product design is also

changed and in all this activities the lead time go on

increasing as well as cost and time. All this happens

because problem observed at the last stage of the

development. [5]



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Schematic diag.4

3. Solution for the problem:

Decreasing the lead time for product development along

with the cost and time is the real challenge to the industry

but it can be achieved with the latest CAE techniques such

as simulation. The schematic diagram for process planning

and die design using these techniques is shown below in

schematic diag. 5

Efficient use of simulation techniques from the earliest

stage of product development to give feedback from each

step to make the necessary corrections and improvement

when it takes the least cost, with this approach stamping

defects can be minimized or eliminated before die

construction and try-out. If any correction or redesign is

needed it can be done immediately, in very short time, thus

it lead to a much smoother die try-out and to shorter lead

times with less development costs. [5]

Schematic diag.5

4. Areas To Check

The areas where a necking failure or fracture is occur on

a stamping can be predicted with analysis during the

development and die tryout period for new stampings [6].

Once the areas found to thin leading to failure are

identified, regular checks should be made, this permits

corrective action to be taken before a necking failure

becomes visible. Causal factors for a pronounced increase

in thinning include:

1. Excessive blank holder force.

2. Material problems such as a lack of draw ability.

3. Material too thin.

4. Scored die surfaces.

5. Die Tryout Procedure

A skilled die tri-out technician will optimize the metal

flow by making a series of trial parts and reworking the

blank holder as needed. In some cases, it is necessary to

increase punch radii with the approval of the product

designer. [6]

6. Benefit of Minor Product Changes

Minor product changes are often highly beneficial to

reduce or eliminate the occurrence of fractures. The corner

is the usual location of a fracture in a rectangular drawn

shell.



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Fig.6 rectangular drawn shell having a corner fracture

Refer fig. 6 typical fracture caused by the metal flow at

the corners locking due to circumferential compression is

shown.

Fig.7 Rectangular box draw with large outboard tab. The tab may

severely restrict metal movement into the draw cavity and result in a

fracture. [6]

6. Effect of various parameters on drawing process observed by CAE techniques

A. Blank holding force:

Drawing process is greatly influenced by blank holding

force. It is seen that deep drawn part quality is affected

significantly by flow of metal into die cavity. The force

exerted by blank holder on the sheet provides restraining

force which controls the metal flow. Excessive flow may

lead to wrinkles, while insufficient flow can result in

tearing. Curve shows (Fig.8) that larger blank holding force

requires more forming load. [11]

Fig.8

B. Drawing force:

As the drawing process progresses the force increase and

reaches to peak and begins to drop until it reaches the

fracture point. It is observed from the curve (Fig.9) that the

fracture point is not at the maximum load condition but it is

after that. The maximum principle stresses occur at fracture

rather than at point of maximum load, material fails after

the maximum load due to its ductile properties. [11]

Fig.9

C. Effect of clearance between punch and die:

As shown in the curve (Fig.10) it is clear that large value

of clearance between punch and die would require effective

forming load more to form the component. Required

effective forming load decreases as the clearance between

punch and die decreased. [8, 11]



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Fig.10

I. Simulation Validity:

Different blank holder forces selected for evaluating the

effect of BHF, on the other hand parameters such as

drawing speed, blank dimensions etc. are kept constant.

Refer fig.11, if we apply 350 KN BHF the wrinkling is

more & risk of crack is less, on the other hand if we

increase the BHF to 800KN the crack area is visible,

thinning and tearing is also increased at this BHF.

Fig.11 Simulation of drawn component at different BHFs

According to the results of these simulations a wrinkle

has been observed at 350 KN BHF, increase in thinning

and fracture has been observed at 800KN. It also shows

that wall thickness of component becomes thinner from the

edges. Finally 600 KN BHF is selected which gives

desirable results.

If we compare the experimental results with the

simulation results it showed the validity of simulation to

predict where the damaged zones will appear in the part

during deformation and it is an accurate simulation

technology to achieve precise prediction of quality defects

in initial phase of design only so need for costly

experiments will be eliminated. In this way great time and

cost can be saved. [3, 4]

A. Benefits of simulation:

It is used as try-out tool to shorten production die try-out

and thus to reduce the die cost and lead time. It is used as

production tool to provide production stamping conditions.

It is used as guide to use simulation output to drive

consistency among die engineering &construction etc.

Stamping simulation may be used as learning tool to

explore and gain new knowledge and application guidance

for new forming techniques. [5]

III. CASE STUDY- DESIGN AND DEVELOPMENT OF OIL PAN

A. What is oil Pan:

An oil pan is a component that typically seals the bottom

side of four-stroke (Refer fig.12), internal combustion

engines in automotive and other similar applications. Its

main purpose is to form the bottommost part of the

crankcase and to contain the engine oil before and after it

has been circulated through the engine. During normal

engine operation, an oil pump will draw oil from the pan

and circulate it through the engine, where it is used to

lubricate all the various components. After the oil has

passed through the engine, it is allowed to return to the oil

pan.

Fig.12. Oil pan assembly.



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B. Methodology:

Analysis for the given configuration of the component under `draw (Method CAE analysis using Auto-Form).

Evaluate the `design intent of the features on the component.

Document the query report and discuss with the concerned Product designer for his comments/

explanation/ views.

Based upon the analysis, suggest revisions/ modifications in the product design for ease of `flow of the sheet-metal material in the die cavity.

Determination of blank size.

Calculate ejection force required.

Material selection for die and other auxiliary items for the process of stamping.

Selection of configuration for the die set.

Press machine selection based on the type of press, tonnage required.

Detailed Design for the Draw Die.

Manufacturing of the die as per the 3D data.

Assembly of various components of the die together to make it ready for tri-out.

Take the tri-out on suitable no of components, note down problems occurred during the tryouts.

Do inspection of suitable no of components and see whether they are matching with cad data received

(CMM- Inspection).

C. Oil Pan Simulation:

While the die is being considered for design, the blank

development is inferred from the Draw Analysis using

software depicting crash- as in Hyper-Form or Auto-Form

where nature and extent of deformation resulting in the

formed component is analyzed. This method of finding the

blank development is deployed using the software interface

and later fine-tuned during trials and experimentation. For

the study we have used Auto-form software for simulation

purpose. Auto-form can address these issues very well as it

gives various forming plots and thickness plots at different

loading conditions Refer fig.13.

Fig13. Oil Pan simulation at different loading conditions

D. Design Intent of oil pan

The oil pan should contain sufficient amount of oil that can be used for lubrication purpose of the engine.

Design should be such that it will provide lubrication oil to all engine parts that require the lubrication.

Drain plug should be provided to change the oil and located at lowest point.

During drainage of used oil, all the oil should collect at one point so that it will be easy to remove it out.

There should not be any oil leakages in the oil pan after fitment.

The shape of the oil pan should be such that it will not foul with the other parts below the engine.

Design Iteration 1:

During development stage initially one simple design is

made taking the reference from same oil pan designs and

keeping in mind the functions of oil pan. After studying the

component data decision is made to make the forming tool

for the component. But the side walls of the oil pan are

having the straight walls having 90 deg. Angle with the

horizontal plane. As far as sheet metal forming is

concerned it is not possible to press such component

without any draft angle for good effect. So tool designer

has requested to product designer to change the design on

the basis of analysis results received. The holes provided

on the oil pan for assembly purpose are less and it can lead

to leakages, so no of holes are added and emboss is

provided to avoid any leakages (Refer fig.14).



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Fig.14

Design Iteration 2:

As shown in fig.15. some draft angle is given as shown

and emboss added and as mentioned earlier the oil should

be collect at one point after it is used for lubrication

purpose so taper is given to front side of the oil pan as

shown so that all the oil is collected at one corner and it

will be drained out from drain plug easily.

Fig.15

Design Iteration 3:

Some design changes were done in the lower side of the

engine assembly so automatically the shape of the oil pan is

changed and is made as shown in fig.16, the depth of first

chamber is decreased and depth of second chamber is

increased so that it will not affect the volume of the oil. But

in this design the depth of second chamber is very deep and

is not possible to form the components with this depth. To

give technical support to this statement we have done

simulation of the same design and in that we see due to

extra deep material gets cracks due to thinning and some

wrinkles are also observed. So design is changed.

Fig.16

Design iteration 4:

In this iteration(Fig.17), the depth of second chamber is

decreased and depth of first chamber is increased

somewhat, Due to Engine block assembly is fouling with

the oil pan hump shape is given as shown to center of oil

pan. But such revert draw is not possible and design is

changed again.

Fig.17

Design iteration 5:

In this design depth of second chamber is decreased so

that it will be possible to form the component and depth of

first chamber is increased somewhat. The sharp corners

provided in the earlier designs are given fillets so that there

should not be any problem of cracking of material at the

corners. After such changes the design is finalized and

approved (Fig.18). [1, 2]



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Fig.18

E. Blank Development using CAE Techniques:

Blank is developed from available cad data using

forming suite software. Initially the component is imported

into the software. Then the software will create meshing

using available skin.then the tipping direction is given to

the software, tipping direction is the direction in which

forming has to be done. Then give input of material used

for forming and its thickness. Finally the software will give

the developed blank data and forming area along with scrap

layout (Refer fig.19). [3]

Fig.19 Blank development using CAE software

F. Tool Design for oil pan:

Forming tool is designed for oil pan considering draw

depth of oil pan the decision is made to make two dies for

drawing and one die for restrike and flanging. Oil pan

quantity required is only 100 no. of batch so decision is

made to not go for blanking tool and trimming and holes

are going to made on five axis laser cut machine Following

fig.20 will show the process sheet for oil pan development.

Fig.20 Process sheet for oil pan development



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G. Experimentation:

The experimentation will be carried out over a suitable

press machine (Refer photographs 21)based on the tonnage

requirement for the subject component and requisite raw

material identical with the specifications on the drawing of

the Die/ Component will be provided for the trials. The

parameters such as blank size, blank holding pressure, die

block radius, drawing speed (rate of deformation) etc. are

varied looking towards the problems like wrinkling,

thinning, tearing etc. these parameters will be changed one

at a time and also in combination of two or three. The

simulation and analysis software provides sufficient

information regarding above problems. The component will

be tried out for a batch quantity for checking the

consistency of the draw operation over the given lot.

Record the necessary parameters on the machine while a

satisfactory lot of the desired component quality is

produced.

Fig. 21. Oil Pan-Tool tri-out photographs

H. Validation

The components received as a consequence of the above

trial are referred to as the sample pieces exhibiting the test

results. The die validation process would be said as

complete while the sample component received from the

Die over the test run matches the requirements specified

over the drawing by using the CMM, following figures 22

will show some of the snaps of the CMM report.

Fig22. Cmm report

IV. CONCLUSION

The problem areas such as wrinkling, thinning, spring

back are the biggest challenges to the industry now a days

but these problems can be tackled and sorted out in the

initial phases of the design by using simulation techniques.

While designing new product for a particular

requirement, the product designer and tool designer should

have good communication between them and each of them

should share their thoughts and queries in front of

development team and final product should validate all the

functional and manufacturing requirements.

Decreasing the lead time for product development along

with the cost and time is the real challenge to the industry.

It can be achieved with latest CAE techniques such as

simulation, efficient use of simulation method at the

earliest stages of design can help to make necessary

corrections and improvement when it takes least cost.

Defects can be minimized or eliminated before try-out. So

that lead time along with time and cost can be minimized.



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A. Future scope

Study can be done on increasing fatigue life of oil pan

by modifying the oil pan structure & increasing frequency

of natural vibration modes to a specified level.it can be

done by developing a finite element model of existing pan

and verifying it against experimental modal analysis

results.

Heavy steel oil pans can be replaced with thermoplastic

polymer material as it provides high strength to weight

ratio, long flow distances, short injection times and reliable

molding of thin walled sections. Unlike with steel or

aluminum, plastic oil pan can be molded with integrated

valves or cooling channels.

FEA simulation can be significantly used in plastic

injection molded oil pans for positioning of ribs at edge of

oil pan and to significantly improve the overall stiffness of

the critical flat sections, yet with minimum height of

design. FEA can also be used to simulate impact of wall

thickness, number of gates and their positioning, weld line

formation, warp age behavior and to optimize respective

processing parameters.

Acknowledgement

Authors would like to take this opportunity to express

sincere and whole hearted thanks to Mr. Shailesh

Bhadade from Icon Technologies, Pune for giving the

opportunity to work with the development of oil pan

through-out the process. We would also thankful to Dr. V.

R. Naik, Head, Department of Mechanical Engineering,

DKTES, Textile & Engineering Institute, Ichalkaranji for

continuous encouragement during this work. We are

extremely thankful to Prof. Dr. P.V.KADOLE, Principal

of DKTES, Textile & Engineering Institute, Ichalkaranji

for his help provided during this work.

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