Navigator #5, June 1999

Rapid Prototyping Notes: Investment Casting for Prototypes

With the advancements in rapid prototyping, investment casting becomes the leading technology for producing high-quality castings quickly and inexpensively. Investment casting, also know as the “lost wax” process, consists of taking an expendable pattern (usually wax), attaching the pattern to a tree which acts as its sprue and repeatedly dipping the pattern into a stucco light slurry. Between the dippings, the ceramic shell is allowed to dry.

The end result is a thick ceramic shell surrounding the pattern and its sprue. The next step is to melt or to flash out the remaining pattern. Once the pattern is removed, the hollow ceramic shell is now filled with molten metal. After an appropriate cooling time (which is usually fairly quick), the ceramic shell is broken off, and the metal casting is the processed normally. A major advantage to investment casting is that the process is not limited to either ferrous of nonferrous materials; both can be used. The big breakthroughs have occurred on the three fronts: the waxes from the Actua, SLA QuickCast patterns and longer life epoxy tools from SLA patterns for production wax patterns.

Waxes from the Actua

The Actua is the ideal wax prototype machine. Using an .STL file, the part to be cast can be programmed for the current shrink and orientation. The envelope size of the Actua is 10" x 8" in the X and Y and 8" in the Z axis. Bigger parts can be made in multiple pieces and then glued together.

SLA QuickCast Patterns

The SLA QuickCast is a build style that leaves a hollowed out honeycombed structure as the pattern. This hollowed pattern allows the resin to flash out at temperatures about 1600°F (870°C) without expanding and cracking the ceramic shell. This requires special handling, but the results and benefits can be great.

Epoxy Wax Injection

Many times when multiple metal prototypes are needed, the expendable patterns can become quite expensive. A more practical approach may be to make epoxy wax injection molds from an SLA master pattern. This procedure usually reduces the cost and can still provide multiple metal castings in three to four weeks. Vista Technologies creates prototype castings on a regular basis. If you have any questions, please contact us.

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Rapid Manufacturing Notes:
Resin with a Twist

At Vista, we continue to search for new avenues to expand our prototype offerings. Recently, we were introduced to a new epoxy resin, DSM 8110. Twist may be a slight exaggeration, but bend, flex and snap are not! Manufacturers boast about its flexibility and its high impact strength. We were curious, we tested it, we agreed! We were so impressed with this resin, we made the decision to dedicate one of out 250's (10-inch cube envelope) to the sole production of the DSM parts, It has proven to be an excellent addition, with the customers choosing to use this option when flexibility is desired in the part being prototyped. A solid, very durable (Shore D 77 Hardness) part is the result when the wall thickness reaches a point where flexing is not possible. We are able to keep the pricing of the DSM 8110 parts the same as our standard resin. Please feel free to call for a product data sheet and/or a visit from Brian or Dan to show you some samples in person.

One's Good, Two's Better

Vista Technologies has been so impressed with the performance , quality and output of the SLA/5000 that we have brought in a second SLA/5000. This increase in capacity helps to assure that you will continue to receive quick turnaround for your products along with the additional backup in case of machine problems. With the addition of this second SLA/5000, we now have five SLA machines to take on the biggest projects and still give you the turnaround required. In addition to the newest SLA machine, Vista is pleased to announce the availability of the Actua 2100 for you wax modeling needs. In cooperation with Casting Technologies of Crystal, MN, the Actua 2100 is ready to serve your needs for less expensive concept models or for fast turnaround on waxes for prototype investment castings. Please see the accompanying article on investment casting.



Just a reminder to ask us

Vista's sales representatives have been very active in trade shows and conferences. We would like you input about future shows you would like to see us at. Or, one step better, set up a time for Dan or Brian (above) to give a free in-house presentation that focuses on your needs and projects. Just ask.

Dave and Dan participated in the North American 3D System User's Conference in Orlando, Florida, last month. The conference was from Sunday to Thursday. The main topic of discussion for the future of stereolithography was the resins. This is where most of the R&D is going. Some goals that the users gave to the resin manufacturers were to make resins that have higher heat tolerencesing and tunable resins. Tunable resin is a resin that can heave different properties outside of the machine based on how long and deeply it was exposed to the laser. If anything develops, Vista will be sure to keep you updated.

Somewhere over the rainbow...
You can find a fast and cost effective way to add color to your SLA masters. Vista has developed a way to tint a variety of colors into your protopype. This is a secondary operation, but is performed the same day the parts come off the machine. It does not affect the tolerance integrety of the part. Ask your sales representative to see samples of a slightly transparent red, yellow, blue, black, and purple colors.

Quick Quip "Well done is better than well said" -Benjamin Franklin