CASTING PROCESS AND MATERIALS:
What type of casting does APC do?
Plaster and sand. Our castings are produced using a plaster mold casting process, which simulates a production die casting for prototyping eventual die castings. Castings may also be used for a low volume production process.
What materials do you cast?
Aluminum, magnesium and zinc.
How long does the process take?
Typically 3 to 5 weeks from order placement to first part in your hand. This time includes construction of tooling, sampling, and first article inspection.
How does the plaster mold casting process work?
First, we construct a positive tool similar to the eventual casting, only larger to allow for material shrinkage during solidification. After the establishment of parting lines (the same parting lines used by the die casting process), slurry plaster is poured onto the tooling halves, allowed to solidify, extracted, dried, rejoined and molten material is introduced. After solidification of the cast metal, the plaster is broken off. The result is a simulation of a die cast part.
Are the plaster molds reusable?
The plaster is used one time only. It cannot be reused or recycled.
At what rate can they be produced?
A single cavity tool can produce approximately 9 parts per day. This means that a 2-cavity tool can produce 18 parts per day, a 3-cavity tool 27 per day, etc.
How is the tooling constructed?
From your dimensional data, we machine a negative the same way one would machine a die-casting die. After locating the negative halves on a ground aluminum tooling plate, we pour aluminum or iron-filled epoxy into them. This produces a rigid tool that offers dimensional integrity.
How long do the tools last?
The plaster is non-abrasive, which allows the tooling to last almost indefinitely. In low volume production situations, we have tools on the floor that are more than 20 years old.
PLASTER MOLD CASTING VS. OTHER CASTING PROCESSES:
Is this similar to the Investment Casting Process?
No. Our methods are actually more similar to "sand casting," although it's quite a different product.
How do plaster cast parts differ from sand cast parts?
The plaster cast process allows the casting of thin walls (.040" in aluminum and magnesium and .025" in zinc). The parts have a very smooth surface finish: 90 RMS for plaster cast parts versus 250 to 500 RMS for sand cast parts. The process allows the casting of complex shapes, providing greater dimensional accuracy that most closely approximates the die cast part.
Can you core holes like you can with die casting?
Yes. But depending on casting size, location, hole size and positional tolerance, they can often be introduced to the part more effectively via secondary operations.
What about drill points?
Yes, bearing in mind that cast drill points will carry cast tolerances. You may or may not want these to be the only guide to hole location.
Can you provide secondary operations?
Yes, we can supply the parts with secondary machining and finishing operations. However, we like to quote them separately. This gives you the option of handling these operations yourself or contracting them out to a vendor of your choice. If the latter is the case, we can "drop ship" for you.