Making plastic parts

I don't know how cheap epoxy out of a tube is, but I do know I used to use it and it worked for me.

I also made my molds from silicon bathroom caulk and that worked, too.

It depends on how accurate you need the parts to be, the cheaper materials are more prone to shrinkage and the mold durability. I have used Dow Corning RTV for molds and melted styrene crystals in the oven in them for small parts where the shrinkage factor is not noticeable. Works fine for things like mirrors and other small parts. Sam

i've been searching around for the cheapest way to make plastic parts from molds. I've looked at alumilite/alumalite. The stuff is expensive. What is the cheapest way to make plastic parts from a mold?

They don't have to be exceptionally strong or tough or anything, just cheap.

Is epoxy any cheaper or some other kind of resin perhaps? Have you rocket, railroad or scale model guys found anything economical.

Wow! Great post George. Thanks!

vac-forming

Polyester casting resin is cheaper than urethane, though it does not make as finely detailed parts.

Also, you can make molds from Plaster of Paris, which is cheap compared to RTV mold materials.

However, with plaster molds they are rigid and fragile, so you absolutely cannot undercut mold angles. >

Thanks so very much for your post, George.

I've been curious about Alumilite since I picked up a brochure a fair while ago. Your informative, insightful info is greatly appreciated.

Dwayne

TAP plastics has a "quick cast" resin (2 part white polyurethane) - seems pretty similar to what PML uses for the Cirrus Dart nosecone.

(They also have a rubbery urethane "mold maker" resin.)

-dave w

Click on 'mold making'. Haven't tried it myself yet but it's on the big list.

Ted Novak TRA#5512

zalz> Hi,

Try the mold making materials and resin from Micro-Mark. These are the most forgiving for starters. After you get the hang of it try some of the resins and mold materials such as Quantum Silicones especially QSIL 40 RTV.

For what it's worth, I make all my molds and castings at "Moldin' Oldies" using 2-part silicone RTV and 2-part polyurethane resin from a company called Smooth-On.

The 2-part materials all mix 1:1, so it's extremely easy to measure them out. There is no vacuum de-gassing required. There is no bubbling. Shrinkage is virtually non-existant. Both the molds and castings reproduce even tiny details. The RTV material becomes fully cured and ready for use in about 6 hours. The castings resin flows like water and starts to set in 3 minutes, is fully cured in 10 minutes and rigid in less than

30 minutes. They have a starter package that gives you everything you need, including a detailed instruction book for around $25-$30. If you ever want to try making your own molds or castings, this is the set I'd recommend. Mike

zalzon wrote in news: snipped-for-privacy@4ax.com:

Get a Micromark catalog,they have a section with supplies for mold-making and casting in resin and low-melt point metals. How-to materials,too,IIRC.

I wrote, about Alumilite mix ratios:

About the only drawback is that you have to mix it up just right. I like to use just a hair more of the clear part ?A? than the part ?B?. I usually make small mixes, where I count out the drops from the bottles. So I like to use 1 drop of ?A? for every 10 drops of ?B?.

So I like to use 11 drops of "A" for every 10 drops of "B".