I’m looking for some advice around prototyping a PET drink bottle, a similar form factor to a standard coke bottle. Does anyone have any experience creating a prototype that is safe to drink from, not necessarily FDA approved, just something that won’t poison me during testing.
I am working with a relatively thick wall section (1mm) which should help.
Maybe a bit more information - clear, opaque, reusable vs single-use, etc. Unless it uses a unique neck finish, do you really need to drink from it to test it? There are bio-compatible SLA resins used by the dental industry – you will likely have to find a specialist with the appropriate resin. There is also nylon SLS, shouldn’t poison you, but opaque.
I did this as a project in school. We modeled 2 halves and used a vacuum form. With very careful use of silicone glue, you can glue the 2 halves together. I have slides (yes, I am indeed that old) of 3 different designs holding water for the photoshoot.
Clear material is preferred. It will be single-use but it requires a quality feel with the final product hence the thicker wall section compared to standard bottles. We are testing a custom neck finish vs standard, the standard would remove the need for a custom preform. The use case for the bottle is quite unique, I can’t really say much but it will require a lot of testing. Dental SLA looks interesting, my only concern with 3D prints is the finish, we really need the prototype to replicate the surface of a PET bottle so I think machined/polished or cast would be preferred. I have had a quick discussion with someone about lost wax casting that seems interesting!
This sounds good, it’s something I’ve seen done in the past bonding two parts with chloroform, however, I’m sure silicone would be safer! How was the strength once assembled, could it take a bit of pressure? Do you recall the wall thickness?
It has been a few years, but I imagine I use 0.040" (1mm) sheet stock. As for pressure, you could pick the bottles up and drink from them. But obviously it didn’t take much pressure to blow out the glue. It was a butt joint on a 0.040 edge. You could integrate a lap joint into the mold design to increase glue surface area which would increase the ability to resist pressure.
Dental SLA looks interesting, my only concern with 3D prints is the finish, we really need the prototype to replicate the surface of a PET bottle so I think machined/polished or cast would be preferred.
A thin 1mm casting is very difficult to polish as polyurethane is pretty heat sensitive - same with any water-clear SLA material. An SLA model, sanded and clear coated inside and out with a polyurethane finish, or a UV clearcoat if you can find someone to do it, will likely give you the best appearance. We used to make hollow, working frangrance bottles but the wall thickness was about 3mm. We also used to make thermoformed PET (.060"it will thin out to about .040") bottles from highly finished, tooling board, CNC patterns - we glued them together very carefully with cyanoacrylate - best for presentation models not testing. Do you really need a clear model for functional testing - you may be trying to do too much with one type of model.
PM me or call me if you want to talk more about this, lots of experience in this area of model making before I sold the business. Happy to help.
Thanks Dan,
Clear would be a nice to have at this stage, I think you’re right we are trying to do a little too much. I also think for the proto, we could increase the wall thickness of the main body of the bottle to help with printing or gluing depending on the process. Thanks for the offer! the print and coating is something to investigate for sure!
I’m also going to dig a little deeper into this lost-wax technique a prototype house recommended.
SLA with a clearcoat after sanding is probably the way to go for a presentation model. No idea how safe the clearcoat is to drink out of, so you may have to have separate testing model. Maybe that’s just bare clear SLA, which may be just a rough or at very least translucent?
Yesterday I was contacted by a sales rep for contract manufacturers (Kyle Franson of https://www.buchanansalesco.com/ to give him credit) and they represent Protocam, who did prototypes of Gatorade bottles (Post-Processing and Finishing Service Provider | ProtoCAM). The photo looks great. They aren’t the only ones out there who can do this, as I’ve seen samples from others and have done some myself that have come out well using clearcoat over clear SLA, but they could be someone to reach out to.
I’m also going to dig a little deeper into this lost-wax technique a prototype house recommended
Unless you can see several examples I would be very skeptical. We broke our pick years ago trying to work this out as a technique. The problem is that the polyurethane generates heat and needs additional heat to cure - higher than the melt temp of even high temp waxes and because of that you get bad bad interior surfaces.
Utley’s in NYC makes hollow bottles all of the time for cosmetic and skincare Utleys.com
Gatoarade bottle looks great! certainly worth contacting them.
Wow really niche, great find!