Does anyone on these boards have experience with thermoforming? I usually deal with injection and compression molding but I have a good idea that would require thermoforming.
Unfortunately I have no support from my overseas development staff & no in-house knowledge of it either.
What I need to know is what are the typical materials used, their limitations, and durability. The end product would have to withstand some serious punishment.
I’d prefer not to disclose to everybody what it is that I’m working on 
but if anyone can help I would really appreciate it.
I am just posting this before I start researching. It might turn out that I’m wasting my time & I’d much rather know that sooner than later!
…the trick with thermoforming is mainaining good material thickness as material is drawn into the mold…be as generous as you can be with draft angle and radius…undercuts can be designed in without plugs or sliders as long as the part can pivot around this detail as it is demolded…often air is blown into the mold before a vacuum is pulled to prestretch the material…the mold needs to be evenly heated to prevent chill marks from forming…we typically use an acrylic/abs coextruded sheet from .05-.25" thick…this material can be very brittle when stretched thin…fiberglas can be sprayed onto the backside of the parts if needed…the acrylic surface needs no finishing and provides a very durable surface…it can also be polished to remove surface scratches and sanded smooth along the trimmed edges…one of the negatives with thermoforming is scrap material…10-15% of you material cost is a loss.
Hmmmm. Well, thanks for the reply.
I don’t think this idea is going to work if the end product is even the least bit brittle.
Anybody else?
…Bueller?
Hey Robin,
I’ve worked with thermo-formed ABS for a number of years. In the eighties we manufactured monocoque motorcycle fairings and sidecar bodies from .375" ABS and they we not in the least brittle. I’ve intentionally laid enough of them down during testing to know that from first hand observation.
The brittleness that mrd is observing is probably a function of its coextrusion with Acylic. Blowing Fiberglass Reinforced Plastic (FRP) onto the back of a vacuum-formed part is actually a method of increasing the production rate of FRP more than a thermo-forming method (the thermo-formed part serves as the ‘gelcoat’ and mold for the FRP / production rates increase because the part does not have a ‘demold’ time because there is essentially no mold).
Thermoforming is a great process especially in low volume situations, but it does have some hidden costs; tooling fixtures are required to trim the parts after forming being a notable one. “Assists” and other techniques may be required to help move the hot material into the mold prior to application of vacuum. A number of materials are suitable for forming. Trimmed material can be returned to the vendor for recycle (provided it hasn’t had FRP blown onto the back of it).
Without giving up the actual product, let’s generalize for talking purposes: how big is the item you are proposing?; what is the enviroment it will live in (household, recreational vehicle, medical, marine, etc.)?; how much should (or can) the part cost?
I tried posting this last night, but the forum server seemed to have been down…
I’m not sure if this info. is what you’re looking for, but I’ve used thermoforming for one-off private stuff (mostly costuming, and an engineering competition, for a model airplane, which did fairly well)
I used pretty thin stuff (think it might have been 1/16th sheets) because I could more easily form it, so I can’t speak for the thicker stuff, which is probably more durable.
I didn’t notice much brittleness, in fact you could deform most of the peices fairly far before they’d crack, impact could put holes in them (as I learned when I mis-aimed a hammer while cramping connectors for the costume-peice, a chest-plate that was designed to look like cartoonish armor as featured in the online game World of Warcraft).
The nose-piece on my airplane project was thermoformed, and withstood a few, um, less than successful landings with the 10-pound plummeting prototype behind it.
For aestetics, even heating and slow, even vaccum pressure is a MUST (though I assume professional machines will not have the same problems with that as a kit-bashed thermoformer and hand-made molds) or you get strech marks.
Overall, I was satisfied with the performance of the 1/16th in. ABS sheeting, it was fairly durable, able to stand up to consistant use, and when put to use in a non-cosmetic application it stood up to some fairly hard abuse before it broke (well, I think 3 or 4 crash-landings is about the maximum life of ANY plastic part you’re throwing airborn…), it also had good enough aestetics for costuming, OK paintability (scuff and prime and good to go), many shades availible when I was buying the sheets, and the ease of use was great for my use.
I’m not sure how much of my experiance applys to what you’re doing, but I hope I helped.
edit: oh and don’t underestimate the time/tooling costs for demolding, not sure how it is for your existing methods, but depending on shape, you can get some annoyingly intricate and large flanges.