Straight talk about rapid prototyping

When you try to find learn about rapid prototyping it is easy to get a whole pile of conflicting information. This is due in part to the fact that the technology has advanced rather quickly. So if you find article that has been hanging around on the web for a few years, you might get accidentally led down the wrong path. I don’t know it all, but I have ordered hundreds of rapid prototypes over the years. So, here is my one-page summary to help de-mystify the process.

WHO can use this process?

If you are looking to prototype a part that will eventually made by injection molding, the rapid prototypes are usually the way to go (but I have prototyped die castings and even sheet metal designs). If you have a 3D CAD file that you can output into *.stl format, you are a perfect candidate for the process.

WHAT do I get?

You get a part that looks pretty much like the CAD file you have created. It is plastic and has many of the properties that you might expect from a molded part, but it is not as strong. All rapid prototypes are made in layers which leaves vertical walls with a series of fine grooves, not unlike a record (remember those big round things we used to play music on?). The same limit gives curved surfaces a staircase effect. But, if you are careful about sanding and painting, you can buff the surface into perfection and make the part look, more or less, like a production part.

WHEN should I get a prototype?

I usually do not get a prototype until it is time to prove in the final CAD; I have checked and double checked the fits and tolerances, I’ve confirmed that the part is suitably designed for manufacturing, I’ve sourced all of my standard components to make sure that they will properly interface with this part, etc. However, there are some exceptions to this rule. If I am working on something very ergonomic, such as a joystick control, I might get an early prototype to see how it feels in my hand. This gives me quick feedback before I spend time figuring out all the details of fitting in the electronics and routing my wires through a handle that might have to change.

WHERE can I get one?

At the time I started my hunt for suppliers, there was no consistent and reliable source here in the lower mainland. I have since built a relationship with a great US supplier and I do a high volume of business with them and they have given me no reason to look elsewhere. Google rapid prototype and you will find many suppliers ready to quote. I do know a great FDM guy who is local (more on FDM below), write me if you are interested.

WHY should I spend this money?

An SLA prototype may be expensive but it is bound to be less expensive than a mistake on an injection mold. So it is cheap insurance, and having the prototype will let you pre-sell your idea while you are waiting for tooling to complete.

There are several processes associated with the term rapid prototyping, the terms you will hear most often are SLA, SLS, and FDM. Years ago SLAs were weak and only offered a visual representation of your part, SLS parts were stronger but finished poorly and FDMs were quite strong but had poor detail. Today, the inherent pros and cons are still similar but the lines have blurred significantly. In general, SLAs look quite good and have adequate strength to prove in most projects.

The subject is deeper than I can cover here. I have not even touched on the terms Hi-res, ABS-like, water clear, etc. But I wanted this to remain simple. If you are confused by your rapid prototype quote, or want a second opinion, drop me a line, you can get to my contact info through my web link below. You can also post general questions in this forum.

Happy prototyping!

Brad Madu
www.sourcedesigngroup.com