RAPID TOOLING & PROTOTYPING   

RAPID TOOLING REPORT

RAPID TOOLING REPORT

PROPOSAL FOR IN-HOUSE PROTOTYPING SYSTEM

PROPOSAL FOR INTEGRATED IN-HOUSE PROTOTYPE TOOLING SOLUTIONS

DATE:  1/11/98
TO:  Jerry Yablans
FROM:  Phil Orenstein
RE:  Rapid Tooling Report

CONTENTS:

1. Nickel Shell Tooling
2. RapidTool by DTM
3. Spray Metal Tooling
4. "Direct AIM" tooling by 3D Systems
5. Cast Kirksite tooling
6. Investment cast mold inserts

This memo is a report on the recent Rapid Prototyping and Tooling conference sponsored by the Society of Manufacturing Engineers which Andreas Piteras and I attended, as well as the results of my cumulative ongoing research. I have outlined below the specific applications that I believe are most worthwhile for us to pursue in order to help achieve our overall objectives of reducing cost and shortening the mold fabrication time. 

As I have explained previously, sophisticated mold and die shops are already adding these new rapid tooling technologies to their bag of tricks along with the customary CNC and EDM capabilities. As the conference clearly pointed out, rapid tooling is not a panacea or a substitute for CNC. The CNC is the foundation of the mold shop. However, in the case of certain complex cores, cavities and inserts that are difficult or even impossible to machine on a CNC, rapid tooling techniques will be a valuable addition. One case in point is the Kid's Shampoo Tray mold which I have recently brought to your attention in another memo. Machining the core side was a snap because it was all positive male geometry. However the deep recesses and compound inner surfaces of the female cavity, made it impossible to machine entirely on the CNC. Nickel shell tooling would have been the best alternative, I believe. Instead of going through the difficulty of machining it the usual way, I would simply machine the cavity as a male positive in Ren Shape and then create the female negative nickel shell from the surface to produce the tool. The machining time and cost compared to machining an aluminum cavity could conceivably be 1/10th!! (i.e., 2 days machining time compared to 2 1/2 + weeks for 3 men to completely machine the Kid's cavity!)

The conference was a realistic appraisal of the pros and cons of the various RP systems and rapid tooling processes without any hype from the OEM's. It covered everything from the most popular RP systems currently available to industry applications and actual case studies. It was an honest evaluation and actual experiences with the various systems from end users. This will give us the necessary food for thought to make objective decisions on how these new technologies can help us. 

I have briefly outlined 6 Rapid Tooling processes which I believe would be worthwhile for us to look into and discuss, although there are numerous new processes emerging continuously. As the conference pointed out, there is a lot of hype and undocumented claims. Keeping that in mind, we should proceed objectively with sufficient investigation.


1. Nickel Shell Tooling

Although it was only touched upon briefly at the conference, it was reported to be a successful and promising process. I believe that this is the most favorable rapid tooling process for us to pursue. Two companies, that I know of, are already specializing in this tooling process to create complete molds: Cemcom Corp. and Weber Mfg. Ltd. (see attached article). Cemcom is developing this process to be marketable to mold shops. Briefly, the process involves creating an RP model of the part from 3D CAD data with the parting lines, shutoffs and gates built in. Next a nickel shell is electroformed on the surface. Then, the core and cavity shells are backed with a thermally conductive ceramic material and water lines (copper tubing) are cast into the mold frame. They claim that these tools are capable of 10,000 to 50,000 parts. The advantages of the process are that the nickel shell picks up all the detail of the model perfectly, its hardness is comparable to tool steel and it dissipates heat just as quickly. The process can use alternatives to RP models such as CNC machined models. The conference pointed out that one weakness of all the current RP systems are their inherent inaccuracy for large parts. According to industry benchmarks, the system which gives the most accuracy and best surface finish is the SLA (Stereolithography). Its accuracy is +/- .002 inch/inch. That means a 10" part could be off by as much as .020" which is unacceptable for our molds. It would be most advantageous for us to CNC machine Ren Shape models which would give us the accuracy we require. I recommend that we seriously look into this process. We can try it out by sending a Ren Shape cut model to one of the above companies to produce a mold insert for evaluation. If it works out, then we can investigate implementing the nickel electroforming and ceramic casting processes in-house.


2. RapidTool by DTM

This is a rapid prototyping process, Selective Laser Sintering (SLS Sinterstation) by DTM Corp., which produces direct metal tooling from 3D CAD data supplied to the system (see attached article). A raw part is built in the SLS by laser sintered metal particles coated with a resin binder. The resin is burned out and copper is infused into the part in a furnace. The finished part has a hardness claimed to be comparable to aluminum or tool steel and can deliver 100,000 parts. The reported dimensional accuracy is within +/-.010" for parts smaller than 5". The accuracy is greater for smaller parts. This process would help us in the area of small mold inserts. We use hundreds of small aluminum inserts for our molds with complex geometries. These are very labor intensive to machine and we've typically subcontracted them out. For example, the numerous small eye-pencil and mascara inserts for the Revlon Vision Wall cabinets, the inserts for the Almay dispensers which took many weeks just to machine the deep ribs, the multi-cavity P20 steel pusher molds which was a machining nightmare taking over 2 months to complete, and so forth. The SLS system and furnace required for this process are commercially available and the entire process after the CAD model and RP part is generated is relatively fast and does not require highly skilled labor. There have been some inconsistent results and mixed reports from users, some positive, some negative. At the conference I had the opportunity to talk with a leading tooling engineer from Lucent Technologies. He had some very positive results from the RapidTool process. Their mold inserts tested very accurately and he highly recommended this process. We can evaluate this process by having some actual inserts produced on an SLS Sinterstation by DTM or a service bureau before making an expensive investment. There are other similar sintered metal processes evolving which we should pursue until we find the one that fills our needs.


3. Spray Metal Tooling

While this tooling process has experienced a lot of interest in the last few years with claims that it is capable of producing 1000's of parts, it was evaluated at the conference as being only effective for smaller prototype quantities. (It should be noted, for the sake of correct terminology, that production tooling capable of 1000's of parts for us is called prototype tooling in other industries) The process involves a thermal metal spray coating on the part model to produce core and cavity shells which are backed with metal filled epoxy, ceramic or low melt alloy. Cooling lines are cast into the mold frame. The advantages are that it is a relatively straightforward and inexpensive process, good for large parts which reproduces the surface accurately with no shrinkage. However the life of a spray metal tool is short, breaking down after several hundred parts. It develops small cracks in the surface due to the constant heating and cooling. However, there are experimental ways to extend the tool life by lowering the heat, playing with the cycle time, pressure, cooling lines etc. 


4. "Direct AIM" tooling by 3D Systems

This process produces direct tooling from 3D CAD data supplied to an SLA system (Stereolithography). The RP model is a core and cavity shell built with the SLA hard Epoxy tooling resin. It is then backfilled over inserted cooling lines with low melt alloy to draw out the heat quickly. It achieves a very fine surface finish that requires little benchwork and is extremely accurate for producing small tools, but larger tools may present a problem with regard to dimensional accuracy. It is a very fast process to produce a limited quantity of small (e.g.: 2" x 3" or smaller) injection molded parts. I have not heard of any documented reports of these tools delivering anything more than a couple of hundred parts, but there are claims from users (Tupperware) that these tools may be capable of up to 1000 parts.


5. Cast Kirksite tooling

This process was not discussed at the conference, but I have explored it in the past considering its potential to be a cost effective tooling solution. About a year ago, when I got a quote of $9000 from a mold shop for a complete Kirksite tool against quotes of $35,000 to 45,000 for traditional cut aluminum tools, I realized the value in this process. Typically it starts with a part model from which a double reverse-geometry casting process is performed to produce plaster patterns against which the kirksite core and cavity is cast at a foundry. This produces durable core and cavity inserts capturing complex geometries capable of 1000's of parts. However accuracy and surface finish may be an issue with large parts due to the Kirksite shrinkage and double casting process and some post-process finishing may be required. As a workable way around this issue, it would be worth the effort to look into a machinable plaster that can withstand the heat of the casting process. This way we can machine the positive male geometry for casting the Kirksite directly without any intermediary steps making the process much more accurate and cost effective. It would definitely be a useful solution for the complex female cavities which I discussed above. This is a proven process that will not require any capital expense that we should look into as a solution for our complex cores and cavities and inserts.


6. Investment cast mold inserts

This process was not covered at the conference, however I think that it is worth mentioning for our consideration. The process involves creating an RP model in investment casting wax from 3D CAD data and then it goes through the typical investment casting foundry process to produce the metal casting. This could also be a useful procedure to produce the small complex mold inserts that I discussed above. The Stratasys FDM 1600 can generate RP models in investment casting wax. They can then be cast in tool steel at a foundry and thereupon be ready to be used as mold inserts. This would be a relatively rapid process with no extra capital expense on our part. The drawbacks could be the rough surface finish and inaccuracy and slow build time of the FDM 1600. There are faster and more accurate Stratasys FDM systems on the market today and this process has been used to create tooling inserts, but there is no documentation that I have available on accuracy, shrinkage, warping etc. Also DTM has an investment casting grade polymer available for their SLS Sinterstation which they claim has yielded impressive results in producing fine, detailed accurate castings. However, here too, I have not heard of any documented reports.


I have presented what I think are the most workable rapid tooling solutions on the market today. Interest is growing daily and more techniques and procedures become available as companies scramble to cut product development costs and time to market. I think that I have presented a number of valid options that we can try experimentally at first with little or no capital expense. Thank you for the opportunity to be working on this exciting project.