Help! Injection molding question

[andrew.scharhag]

Hi all!
I'm having difficulty with an injection molding project. Maybe this group can make some recommendations? I have a design (3d files) and am looking for a manufacturing company that can do injection molding of a light foam material. Having chatted with Xometry, Hubs, and Protolabs, I have not yet found a company that is able to manufacture via injection molding at the weight desired. The best they can offer is .9 grams/cm^3. I'm hoping for about half that to make the project viable. Any recommendations on manufacturing companies?

More background: I published a paper airplane book 10+ years ago called AFS Paper Airplanes and I'm looking to build a toy based on the designs made of lightweight foam. I think this should be possible with the right tooling and injection molding material. It has been difficult to find a company that can do this. The material I am looking for would be the same as the material in the hobby lobby "little gliderz".

Thanks so much for any advice!

Andrew

 

[Inq]

Are you sure you have your units right? 0.9 grams/cm^3 is just slightly less dense than water. IOW... that is very heavy for an airplane model. Solid ABS plastic is only just slightly denser at (1.0-1.05 g/cu-cm). The newer LW-PLA that a lot of hobbyist planes are being printed from is about half that (0.5 g/cu-cm).

Injection molding isn't really needed if you're wanting that light of weight. It is usually needed for complex shapes using far higher density and viscous media. Simply using the 2-part urethane foams that can be cast into complex shapes without injection molding. Just getting the volume right and the mold closed will cause the constrained expanding foam to fill all intricate shapes. The density can also be adjusted by the foam itself and many vary from a low of about 2 to 16 lbs/cu-ft. (0.03 g/cu-cm to 0.25 g/cu-cm). The 2 lb is not very good structurally and is best as a core filler while toward the other end it approaches wood in strength.

 

[andrew.scharhag]

Hi Inq,
Thank you for the advice very much!!
I still have not had luck finding a company that can manufacture a mold for this lightweight foam injection. my searches have not been helpful since I think I am not using the right terminology and it commonly takes a few conversations to determine that the company is NOT able to make a mold for this type of use. Do you happen to know any companies I might reach out to that could create a complex mold for an injection of the required lightweight foam? Or have any other advice?

 

[Inq]

I don't think I can help you on companies. I have more of the DIY mentality. I have considered making molds and selling airplanes based on the urethane methodology I referenced above. However, I would just make the molds as well. Thus... I've never even looked to companies that do that kind of work. The type of planes I would be interested in doing would not be high volume. They'd be more like the cottage industry of designers that made balsa plane designs and sell kits with plans. Most of these are sold in the hundreds/year... not thousands, millions/year. Although I haven't done it, it's pretty strait forward to make molds with silicon. Searches on YT and Amazon will show the techniques and materials.

 

[andrew.scharhag]

Thanks for the info Inq!