Survey of the die and mold manufacturing industry - practices in Germany, Japan, and the United States

Journal of

Materials Processing Technology

ELSEVIER

Journal o f Materials Processing Technology 59 (1996) 158-168

S u r v e y o f the d i e a n d m o l d m a n u f a c t u r i n g i n d u s t r y - Practices in Germany, Japan, and the United States P. Fallb6hmer a'*, T. Altan a, H.-K. T6nshoff b, T. Nakagawa c ~ERC for Net Shape Manufacturing, Ohio State University, Columbus, Ohio, 43210, USA b Institute of Production Engineering and Machine Tools, University of Hannover, Hannover, Germany Clnstitute of Industrial Science, University of Tokyo, Tokyo, Japan

Industrial Summary The survey of the die and mold manufacturing industry is a cooperative research project which is conducted at the Institute for Production Engineering and Machine Tools (IFW) in Germany, the Institute of Industrial Science in Japan, and the Engineering Research Center for Net Shape Manufacturing (ERC/NSM) in the United States. The surveyed companies were asked about current practices in their die/mold making operation. The data presented in this paper is an aggregate of the obtained information based on responses received from die/mold manufacturing companies: 38 in Germany, 173 in Japan, and 99 in the United States.

1. Introduction The die and mold manufacturing industry delivers tooling for die casting, forging, injection molding, and sheet metal forming applications. Dies and molds are utilized to manufacture discrete parts to "Near Net Shape" (NNS) prior to machining and grinding to assembly ready tolerances [1]. Dies and molds are composed of functional and support components. More than 60% of the production time of a die/mold are spent to manufacture the functional parts which often include sculptured surfaces. The intricate geometry and high material hardness make die and mold design and manufacturing a most demanding and difficult engineering task [2]. New technologies like CAD/CAM and 5-axis machining were introduced to the business some years ago. A survey conducted at the IFW in Germany in 1990 indicated that these technologies had failed to fulfill the original expectation in

* Corresponding author.

09244)136/96/$15.00 © 1996 Elsevier Science S.A. All rights reserved PI10924-0136 (96) 02297-2

increasing productivity [3]. But technology has improved since then. A survey of the die/mold industry in Japan, Germany, and the U.S. illustrated the state of technology in the die/mold making business today. In all of the figures discussed in this paper, the surveyed country is indicated by its flag:

~-O-~

Japan Germany

United States

P. Fallb6hmer et al. / Journal o f Materials Processing Technology 59 (1996) 158-168

2. The D i e / M o l d Market

In Germany, as well as in Japan and the United States, the automotive industry is the main customer of die/mold making companies, followed by consumer electronics and household appliances industries, Fig. 1. This diversification makes the die/mold industry less vulnerable to economic cycles. In the U.S., there is more emphasis on dies/molds for household appliances. The portion of die/mold companies that supply to the consumer electronics industry is larger in Japan and Germany. In all three countries more than 50% of the surveyed companies are involved in manufacturing injection molds, Fig. 2. Advantages of plastic materials like light weight and good formability have resulted in an increasing demand for injection molding tooling. Several companies that manufacture injection molds are also involved in manufacturing die casting dies. These two groups show some similarities such as complex die/mold geometries and deep thin pockets.

159

die/mold shops have fewer than the shops in Japan and Germany, Figure 3. The typical die/mold shop has less than 100 employees. The numbers shown in the figure represent an aggregate of the surveyed companies only. Some of the numbers, for example, employees in German die casting die shops, are not representative of the industry in its entirety.

6O%

miol

--

4o% -

~o

[],l

20% 0%

Injection Molding

Die Casting

Sheet Metal Forming

Forging

Fig. 2. Types of Dies/Molds Produced

100%

300

80% 60%

i []

40%

2o%

e~

o%

-

100

Z

Automotive

Consumer Electronics, Including Computers

Household Appliances

Die Casting Dies

Sheet Metal Forming Dies

orgm' FDiesg

Fig. 1. The Die/Mold Industries Main Customers

Fig. 3. Average Number of Employees

The number of companies that manufacture forging dies is the smallest in all cases. This may be due to the fact that (a) the forging industry is considerably smaller than the die casting or injection molding industry, and (b) a relatively small portion of forging dies is supplied by independent die and mold makers.

4. Number Of Dies/Molds Per Year

3. General Information About The Surveyed Companies

At least 60% of the die/mold manufacturing companies are independent. The remainder is either part of a larger company or has chosen not to provide this information. In terms of employees, U.S.

Injection Molds

On average, Japanese companies produce the largest number of dies/molds annually, i.e. between 101 and 500. This may be due to a combination of a higher productivity and a higher number of employees per company. The majority of U.S. companies produces between 26 and 50 pieces annually. In Germany this number ranges between 50 and 100 pieces. An example for this trend can be seen in Fig. 4 which shows the numbers for companies manufacturing injection molds. An exception to this rule are forging dies. They are usually small and thus produced in larger quantities (>100 per year) in the three countries.

P. Fallb6hmer et al. /Journal of Matemals Processing Technology 59 (1996) 158-168

160

5. Weight Of The Die/Mold

As mentioned above, forging dies are manufactured in large numbers. Typically their weight is less than 500 lbs. In Japan and the U.S., some larger forging dies are produced for aerospace applications. Their range weight is 1,000-5,000 lbs. and 5,000-20,000 lbs., respectively. Regardless of the application, t h e majority of the dies/molds produced in Germany weighs less than 500 lbs. In Japan and the U.S., t h e average weight of injection molds and die casting dies ranges between 1,000-5,000 lbs. Sheet metal forming dies are heavier. Their average weight ranges between 1,000-20,000 lbs., Fig. 5.

Fig. 6 demonstrates the lead time for injection molds. Yet, the lead time for sheet metal forming dies is more evenly distributed and ranges from less than 5 to more than 30 weeks. In this aspect, no significant differences among the three countries are noticeable. 80% o

60%

o

40%

cu~

~.~ o ~

mlel

20% m

0% 1 - 5 Weeks

10 - 20 Weeks 5 -10 Weeks

60%-

40%

K= 0

|

> 30 Weeks

20 - 30 Weeks

Fig. 6. Lead Time for Injection Molds

DI

7. Die Mold Manufacturing System

20%

0% < 10

10 - 25

26 - 50

51 - 1 0 0

101 - 500

> 500

Fig. 4. Number of Injection Molds Produced per Year

.~ _-

50%

~

lO%

-

0% < 500

1000 - 5000 5 0 0 - 1000

> 20000

5000 - 20000

Die and mold manufacturing must be considered as a complete system. It includes: i) part design for NNS manufacturing, ii) production of prototypes for visualization, testing, and evaluation, iii) process modeling for optimum mold design, iv) CNC machining (if required), v) manufacturing of EDM electrodes (if required), vi) EDM (if required), vii) polishing and manual finishing, viii) dimensional control of electrodes, dies, and the NNS formed product [1]. In short, t h e information flow and processing steps can be described as follows: process planning, part and process design, NC tool path generation, machining, polishing or manual finishing, and tryout, Fig. 7. The process information collected in the survey will be presented according to this sequence.

fibs.)

Fig. 5. Weight of Dies for Sheet Metal Forming

8. Process Planning

6. Lead Time

Fig. 8 illustrates the amount of time the companies spend in the process planning step. This is, in general, less than 5% of the total lead time necessary for manufacturing dies and molds.

In general, forging dies have a lead time of less than 10 weeks. An exemption to this rule are h e a v y forging dies produced in the U.S. that take 20 to 30 weeks. The Japanese not only manufacture more dies/molds per year than their American and German counterparts, but they also require less time. Most of their die casting dies and injection molds have 5-10 weeks of lead time whereas the Germans and the Americans, in most of the cases, require 1020 weeks to manufacture these types of dies/molds.

9. Part And Process Design

To ensure the production of high quality parts a t low costs in a short period of time, the part, process, and die/mold design have to be compatible w i t h each other and should be considered simultaneously. After the design stage, manufacturing and life cycle costs of a product are fixed, allowing for little or no

P. Fallb6hmer et al. /Journal of Materials Processing Technology 59 (1996) 1.58-168

alterations in the latter stages of production. The German die/mold shops spend 10% to 15% of the processing time at the die design stage. In Japan and the U.S. the corresponding values are 15% to 22%, Fig. 9.

161

12%

[] o~ ~

m,l

4%

0%

Injection Molds

Die Casting Dies

Forging Dies

Sheet Metal Forming Dies

Fig. 8. Portion of Lead Time Used for Process Planning Prototypes | and Models

I

Part Design for I Manufacturing

1

I

Process Modelling I and Structural Analysis

Die / Mold initial Design

25%

.~ .~

20%

"~ .~

10O/o.

~

s%

0%

N

Injection Molds

÷ Data for - CMM

Die / Mold Detail Design

~

Forging Dies

Sheet

Metal Forming Dies

9.

EDM i Electrodes Inspection

EDM E ectrooes

Die Casting Dies

Portion of Lead Time Used for Die/Mold Fig. Design

I

Data for CMM

Cavities / Cores

[

i,

Data for CMM

Cavities / Cores [ Inspection EDM

Cavities / Cores

I Polishing i ( Manual, Mechanical, Electro-Chemical )

¢

Drawings are the most popular medium to transfer part data from customer to manufacturer, Fig. 10. In Japan, the use of CAD data appears to be far less popular than drawings. In Germany and the U.S., the use of CAD data catches up with the popularity of drawings. Eighty-six percent of the Japanese shops still use drawings for data transfer but only 37% are present in the second largest group w h i c h represents the transfer of CAD files with surface models. To provide a prototype of a functional part is more common than CAD files with solid models.

] Cavities / Cores I "I Inspection i

k

Die / Mold [ Assembly

80%

~e

4o%

I

Die/Mold Try out

~

I~1

r,

out L PartsTry Inspection

60%

e~

20%

I Inspected

Parts

#

}

0%

tmqe

- [

Drawings

II

CAD CAD Protoype Surfaces Wire Frame of Curves Functional

CAD

t-

Solid

Part

Fig. 7. Information Flow and Processing Steps in Die/Mold Manufacturing

Fig. 10. Methods Used for Part Design Data Transfer

P. Fallb6hmer et al. / Journal of Materials Processing Technology $9 (1996) 1S8-168

162

If an electronic medium is used to transfer data, IGES is the interface format that is preferred by most companies, followed by the DXF format, Fig. 11. VDA-FS, which was established by the German auto industry, has not found many users in Japan and the U.S. The 'Others' group includes cases where the die/mold manufacturer owns the same CAD system the customer does. This eliminates the necessity of using interface formats. Since the 'Others' group is very small it is evident that the case of 'same system' is rather rare. More than 60% of t h e companies have problems with data transfer. On the other hand, the q u a l i t y - o f the obtained computer files is considered 'acceptable' or 'very good' by the majority of the die/mold companies. 100%

~.

It-#7

80% 60%

'~

40% 20%

0% IGES

DXF

Others

VDA-FS

Fig. 11. Formats for Transfer of Electronic Data

Regarding the type of CAD model the die/mold shops use, the most popular CAD systems tend to be those working with surface models, wire frame models are in close second. Solid models are becoming increasingly popular. However, it appears that the industry will need more time before t h e popularity of solid models reaches that of surface and wire frame models, Fig. 12.

10. Part Design For Manufacturing

Under optimal conditions the part designer should consider the producibility of the product, equipment and tooling requirements, and material properties. But in reality, more than 60% of the die/mold companies are required to modify the customer's part design for manufacturing purposes. Their complaint is that customers often do not have the manufacturing experience or do not care about design for manufacturing as long as they get the die/mold on time. The result is lengthy communications between customer and die/mold maker.

80% ,~Iwl o

60% 4O%

b~

,~

20% 0%

Surface Model

Wire Frame/ Curve Model

Solid Model

Fig. 12. CAD Models Used in Die/Mold Shops The integration of die/mold design know-how into the computer models used for part design would be beneficial. Another alternative seems to be a significant trend. In this case, the molder (or caster, forger, stamper) receives the functional specifications from the designer or original equipment manufacturer (OEM) and takes responsibility for the design and production of t h e assembly ready part or even of the subassembly. If the part or die/mold design has to be modified in order to comply with manufacturing process restrictions, the companies rely on the experience of their die/mold makers rather than handbooks or FEM simulations, Fig. 13. Only 10% of the companies support their decision about die design modifications with FEM simulations. This indicates that it is necessary to make the existing codes for process modeling more user friendly. In addition, die/mold design engineers need exposure to and training in the use of process modeling techniques.

11. NC Tool Path Generation

Machining of sculptured surfaces in dies or molds has been done by copy milling for many years. This strategy has become less popular since unfavorable engagement conditions of the milling cutter result in tool deflection and machining inaccuracies. In addition, copy milling is a time consuming operation. Nowadays, accurate and time effective machining of dies and molds, with sculptured surfaces, is almost impossible without the use of CAM systems. Although the performance of the available systems has been constantly improved in the last few years, the use of CAD/CAM still requires considerable skill and time, especially for machining complex geometries. The Japanese and the Americans spend up to 22% of the total processing time for NC programming, Fig. 14. NC programrning seems to be

P. Fallb6hmer et al. / journal of Materlals Processing Technology 59 (1996) 158-168

less of a problem for German companies. They spend approximately 7% of the time for NC programming regardless of the application.

100% "

60%

~e

40%

40%

[]m

"~ 20./0 0%

re

CAM

O

System

20%

0"/°

m[o-1--

!!1

6O%

o

- -

i:!i

80% o e~

m

80%

163

Digitizing

Copy

Milling

External NC Programming Service

Fig. 15. Methods for Tool Path Generation Experience

Handbooks

Process Modeling (FEM, etc.)

mFi-l

60%

Dm

Fig. 13. Guidelines for Design Modifications 25%

20% b- e~

[] ~

-m ~

15%

20%

10%

0%

• Injection Molds

5%.

Die Casting

Forging Dies

Dies

0%

Injection Molds

Die Casting Dies

Forging Dies

Forming Dies

Sheet Metal

Forming Dies

Fig. 14. Portion of Total Lead Time Used for NC Programming By far the majority of companies uses a CAM system to generate tool paths. In Germany manual programming takes second place. Reverse engineering is the second most used method in Japan and the U.S. A prototype part is digitized and the tool paths are generated based on the digitized data, Fig. 15.

12. M a c h i n i n g

The die/mold makers in the three surveyed countries take different approaches to machining of dies and molds. In Germany and the U.S., most of the processing time is spent in machining in order to keep the effort for polishing and manual finishing as low as possible. Contrary to this approach, the Japanese spend as much time for polishing/manual finishing as they do for machining, Fig. 16. In Germany and the U.S. machining of forging dies requires up to 60% of the processing time. But the effort for manual finishing is low due to lower surface finish requirements compared to other applications.

Sheet Metal

Fig. 16a. Portion of Total Lead Time Used for Machining Though the surface finish is not as critical as in injection molding, dies for sheet metal forming take only 40% of the processing time for machining but around 20% for polishing/manual finishing. Convex surfaces on the punch and slightly curved surfaces in the die allow the use of automated polishing equipment. Higher scallops are left after machining that can be more effectively removed by polishing. The numbers for injection molds and die casting dies lie in-between these figures. Surface requirements for injection molds are higher than for forging and stamping dies, but complex geometries impede the application of automated polishing. n~

~

D~

20%. •~

o

10%" O%

Fig. 16b. Polishing

Injection Molds

Die Casting Dies

Forging Dies

Sheet Metal

Forming Dies

Portion of Total Lead Time used for

164

P. FallbOhmer et al. / Journal of Materials Processing Technology 59 (1996) 158-168

Most of the surveyed companies own the necessary equipment to manufacture dies and molds. Milling, grinding, and electrical discharge machining (EDM) equipment is present in almost all of the shops. A newer process called electro-chemical machining (ECM) which is a slow, hard to control process with environmental problems caused by the electrolyte, is hardly used at all. In Japan it seems to be quite common to have parts of the machining work done by contractors. Sixtyfour percent of the Japanese die/mold shops, 29% of the German die/mold makers, and 26% of the American die/mold makers seek help from outside sources. The focus of the die/mold companies is on the finishing part of the operation where dimensional and form accuracy are determined. For roughing operations, more than 40% percent of the Japanese companies seek help from outside their facilities. This might explain the short lead times in this country since the die/mold is bought already roughed and in a heat treated state. In the U.S., where contract work is not quite that common, the polishing is sometimes performed by outside companies. In Germany, roughing and polishing are more likely to be provided by outside sources, Fig. 17.

.~

40% ~ - ~ I

.,~

30% ~

E

[] ~ - ~ - -

o,,--'"

20 Yo

10% ~ 0%'

_ .

[]

,--,

.

.

.

.

_ .

Roughing

~

'

~

SemiFinishing

emir'/'/'1] Finishing

Polishing

Fig. 17. Work Done by Outside Contractors

Tooling for sheet metal forming purposes consisting of slightly curved, large surfaces, is mainly rough and finish machined by milling or a combination of milling and grinding. Forging dies are rough and finish machined by milling or a combination of milling and EDM. In Germany, where extensive research has been conducted in milling forging dies, EDM is only used for polishing. The finishing part is done by milling or grinding. In the U.S. and Japan, EDM is more often applied in rough and fInish machining of forging dies. Die casting dies are also rough and finish machined by milling and milling-EDM. In the U.S.,

the sequence milling-EDM takes first place and 'EDM only' is also popular. The manufacturing processes used for machining injection molds are quite similar to the processes used for machining die casting dies. Obviously, miUing and electrical discharge machining (EDM) are the most important machining methods in die/mold manufacturing and will be discussed further.

13. Milling With the introduction of high speed machining (HSM) the application of the milling process in die/mold production is expanding. HSM offers the possibility to cut down on lead time by diminishing the effort for finishing and polishing operations. The technology is rather new and a lack of process knowledge and appropriate cutting tools h a v e impeded a broad application of HSM thus far. Forty-four percent of the German companies h a v e experience with this technology and 59% are considering making investments in HSM. In Japan and the U.S., approximately 30% have experience with HSM. The majority of the companies considers HSM as an attractive technology for the future (96% in Japan, 72% in the U.S.). The surveyed companies were asked about the milling equipment they use. Although vertical machining centers have disadvantages concerning chip disposal, they are the less expensive choice and, therefore, more popular than horizontal machining centers. Observations made in an earlier survey [3] indicated that copy milling was the most popular machining method. The present survey revealed that CNC 3-axis machining is more common now. CNC 4-axis milling offers the possibility to tilt the milling cutter to improve the cutting conditions. It is in use by 35% of the German companies. CNC 5-axis machining exceptionally offers advantages when machining convex surfaces on punches and cores. It is still not widely accepted in Japan and the U.S., Fig. 18. Though brazed cutting inserts offer a higher accuracy during machining, they need regrinding when they are worn. Thus, indexable tools are preferred over tools with brazed inserts, Fig. 19. In regard to cutting tools, the most important improvement die/mold producers expect, is a longer tool life. The majority of the die/mold shops is unsatisfied with the life they obtain from presently available cutting tool materials, Fig. 20. This

P. FallbgJhmer et al. / Journal of Materials Processing Technology 59 (1996) 158-168

information illustrates that the costs of cutting tools do not have the highest priority. Therefore, tool materials that offer longer life, at a reasonably higher cost, would be desirable.

method for electrode manufacturing is milling. Machining of copper with wire EDM is often done by German and Japanese companies. For g r a p h i t e electrodes grinding is a popular alternative in t h e U.S. 10o%

t~

s0%

12% o

o 0,

~ o

[..

60%

8%

40010

,~ b-,

4%

20%

0% Horizontal

Vertical

Solid

Brazed Insert

Indexable

Fig. 19. Milling Tools in Die/Mold Making

80%

14. E D M e~

Electrical discharge machining (EDM) plays a major role in die/mold cavity machining. The performance of this process is independent of t h e workpiece hardness. More than 90% of the surveyed companies use EDM machines mainly for finishing operations in already hardened material, Fig. 21. Plunge type EDM machines are used for complicated geometries such as deep thin cavities. Wire EDM is applied in manufacturing of progressive dies, blanking dies, extrusion dies, and drawing dies. An entirely new market has developed around hole EDM machines that drill holes with diameters of less than 25 m m in hardened material. Some major disadvantages of the EDM process are (a) low material removal rate, which limits t h e application of EDM to finishing operations, and (b) environmental concerns due to the use of environmentally hazardous materials in t h e dielectric fluid. A replacement of conventional dielectric fluids by water-based dielectric fluids has been partly successful. Fifty-three percent of American companies, 45% of Japanese companies, and 38% of German companies have experience w i t h this type of dielectric fluid. In terms of electrode material, the Japanese and the German tool and die makers prefer to use copper. In the U.S. graphite is more common, Fig. 22. Concerning the electrode material, no apparent differences could be noticed between roughing and finishing operations. All of the surveyed German companies machine the EDM electrodes themselves whereas 5% of Japanese and 24% of American die/mold shops subcontract this activity. The preferred machining

[

Dm

0%

Double Column/ Gantry

Fig. 18. Equipment for 5-Axis Machining

165

o

60%

~

4o"/o

Dm

m o

20% o%

Longer Life

Lower Price

Process Reliability

Better Tolerances

Fig. 20. Desired Improvements in Cutting Tools

lOO%

e

m~

.........

80%

o e~

~,

60Olo

~

4o%

~

2o°/°

-

-

D

!

o%

Roughing

Finishing

Polishing

Fig. 21. Processes where EDM is Used

80% m to

c~ e~ "~

m

60%

Dm-

40%

F-,

20°/° 0%

Graphite

Copper

Fig. 22. Electrode Materials for Finishing

Others

166

P. FallbOhmer et al / Journal of Materials Processing Technology 59 (1996) 158-168

15. Polishing Die/mold polishing can be divided into two major groups, mechanical polishing and electrical polishing. EDM and electro-chemical machining (ECM) belong to the latter. Around 70% of the shops in the U.S. and Japan do polishing by hand while in Germany 66% of the companies have automated polishing equipment, Fig. 23. ECM plays a minor role in Japan and the U.S. and is circumvented by German die/mold makers. If automated polishing equipment is used, EDM is the favorite method. Mechanical polishing methods such as robot assisted polishing and abrasive flow polishing is second choice, Fig. 24. The German and the American companies emphasize polishing with EDM, the Japanese companies prefer mechanical polishing. Since mechanical polishing methods offer h i g h e r material removal rates than electrical polishing methods, the Japanese companies spend less time finish machining their dies/molds and remove t h e remaining material with polishing equipment.

80% 60°Jo~

m~

__

stresses. Therefore, the die/mold material is usually heat treated. In addition, nitriding, PVD and CVD coatings are examples for treatments t h a t protect the die surface and extend the die life. The heat treatment usually takes place before semi-finishing, finishing, or polishing. The die/mold shops attempt to avoid rough machining in hardened material. Although, this would save time and eliminate the interruption of t h e processing flow for heat treatment, Fig. 25. In German companies the heat treatment never takes place before roughing. Fig. 26 shows that more than 60% of the German companies coat some of their dies/molds compared to 27% in Japan and 20% in the U.S. The most common method of surface treatment is texturing, in a most likely effect to satisfy the requirements of the customer regarding part appearance.

4O%

m~

! o~

-~m

0%

.

.

.

0%

Before

-

-

:

•

Before

Roughing

Finishing Before Semi-

After

Polishing

Before Polishing

Finishing Fig. 25. Heat Treatment in Die/Mold Making

,

Automated

.

1

No Heat Treatment

--

~

Manual

.

20%~

-

4°%~UK/,'~,---~'-

.

30%

Combination of Automated and Manual Polishing

Fig. 23. Methods of Die/Mold Polishing

mpe~ ~" 60% 80% "~ 40% ,~

p...?::..q

t -m

rnl

20% 0%

0o/oLW

I

Texturing

m

Sand

, Coating

None

Blasting EDM Machine

Abrasive

Robot

Flow Assisted Polishing (ExtrudeHone) Fig. 24. Use of Polishing Equipment

Milling Machine Assisted

16. HeatTreatmentAnd Coatings The life of a d i e / m o l d is mainly determined by its resistance to wear processes which can be of different nature depending on the application. H o t forging dies and die casting dies suffer abrasive wear and thermal fatigue. Stamping dies and cold forging dies must withstand abrasive wear and h i g h

Fig. 26. Surface Treatment in Die/Mold Making

17. QualityControl The complexity and high expenses of dies/molds require quality control throughout the manufacturing process, starting with CAD data and continuing on until the final tryout stage. It is almost impossible to manually measure the accuracy of machined sculptured surfaces, CMM equipment is needed for this purpose. The measurements taken by the CMM are cross checked against the original geometry represented by the CAD model. Off-line

P. FallbOhmer et al. / Journal o f Materials Processing Technology 59 (1996) 158-168

CMM programming can already be done in the design stage. The Japanese companies have a reputation for high quality of their engineering products. T h e y prefer to support their quality control w i t h electronic measurement equipment. In Japan, t h e number of companies using off-line CMM programming is almost as high as the number of companies that measure some or all of t h e i r dies/molds manually, 47% and 53% respectively. Compared to these figures, 78% of German companies and 74% of U.S. companies perform, some or all, measurements manually, Fig. 27.

60%

40% o

20% 0%

Manual

CMM,

Online

CMM, Off-Line

Surface Profilometer

Programming Programming

Fig. 27. Measuring Methods in Quality Control The emphasis on quality by the Japanese die/mold makers is illustrated by the number of dimensions that have to be controlled. This becomes most obvious in dies for sheet metal forming, Fig. 28. To check sculptured surfaces requires t h e measurement of a high number of data points to assure dimensional and form accuracy. 60%

~ o

40%

o

~

E3I

20%

< 10

10-20

21-30

31-40

>40

Fig. 28. Number of Controlled Dimensions in Sheet Metal Forming Dies

18. Summary And Conclusions Dies and molds are mainly used by t h e automotive, household, and consumer electronics industry. Injection molds have the largest market share among the different types of dies/molds t h a t are manufactured.

167

Most of the die/mold shops are independent enterprises with less than 100 employees. The Japanese companies produce more dies and molds in a shorter time period than German and American companies. Drawings are still the most common media for data transfer between customer and die/mold shop but the popularity of CAD data is growing. If an electronic medium is used for data transfer, IGES format is preferred in most cases. The majority of companies works with CAD surface models. Most companies are required to change the p a r t design for manufacturing purposes. To improve efficiency and quality in die/mold manufacturing, the dialog between customer and die/mold maker has to be intensified. The customer needs to consider the manufacturing aspects in the design stage of t h e part. Forging dies, die casting dies, and injection molds are mainly machined by milling, EDM, or a combination of both. Dies for sheet metal forming processes are mainly machined by milling and grinding. An outward trend from conventional machining methods towards new technologies can be seen. The copy milling strategy is being replaced by CNC 3-axis machining and is expected to be abandoned by most die/mold makers. A quite different approach in machining dies/molds can be recognized. While German and American companies emphasize roughing and finishing to keep the effort for polishing as low as possible, Japanese companies emphasize polishing and spend less time for roughing and finishing. German die/mold makers have the leading edge in multi-axis machining. The use of EDM as a method to perform finishing and polishing operations will decrease with further development of the high speed milling technology. As opposed to Japan and Germany with this trend apparent, EDM is still heavily applied in the United States. Manual polishing still is the most used method to achieve the required surface finish, especially in Japan and the U.S. Regarding automated polishing, the Japanese companies focus on mechanical machining methods whereas the Germans and t h e Americans prefer electrical machining methods (EDM). Japanese and German tool makers acquire outside contractors to do machining work, more so than t h e i r American colleagues. Focusing on the field of expertise can save time and enhance the quality of the product. The next several years will demonstrate whether contract work will become a typical phenomenon in the die/mold industry.

P. Fallb6hmer et al. / Journal of Materials Processing Technology 59 (1996) 158-168

168

In all three countries the die/mold makers consider tool path generation with CAM-systems and high speed machining of hardened materials as the most important technologies for the future, followed by CAD related issues, Fig. 29.

in the survey for their time and effort and for providing the authors with most valuable responses to the survey questionnaires. The details of the survey are available in a two part report prepared by the ERC for Net Shape Manufacturing [4].

References Tool Path

High Speed

Generation with CAM System

of Hardened

Machining

CAD Data Transfer

CAD Systems

Materials

Fig. 29. The Most Important Technologies in Die/Mold Making in the Near Future CAD/CAM systems are expected to be more reliable and more user friendly. The CAD/CAM system suppliers are certainly attempting to respond to this requirement. The high speed milling technology is expected to bring another boost in manufacturing efficiency. It remains to be determined how far the expectations can be fulfilled.

Acknowledgements The authors would like to thank the Japanese, German and American companies that participated

[1] Altan, T., Lilly, B.W., Kruth, J.P., K6nig, W., T6nshoff,H.K., van Luttervelt, C.A., Khairy, A.B., 1993, "Advanced Techniques for Die and Mold Manufacturing", Annals of the CIRP, Vol. 42/2/1993, pp. 707-716 [2] K6nig, M., 1992, "New Technologies in Milling (High Speed Milling, 3- and Multi-Axis Machining, Working of Hardened Parts)", 7th Int. Conf. of Tool, Die and Mold Industry, ISTA, Bergamo, Italy, May 1992 [3] Gehring, V., Becker, M., Camacho, J.H., 1990, "Entwicklungstendenzen im Werkzeug und Formenbau', VDI-Z, Vol. 132, No. 8, pp. 12 16, August 1990, in German [4] Fallb6hmer, P., Akgerman, N., Altan, T., 1995, Survey of the Die and Mold Manufacturing Industry, Vol. I+II, ERC/NSM