I am trying to cast small helical gears from a gearbox we use.  I am using the Easy Composites Starter kit.  Frst timer

I have tried using FAST CAST Polyurethane Casting Resin, with mixed results, though still testing.  My question is, the originals appear to be a form of nylon.  Is there different materials available to cast with other than FAST CAST, that have properties that are closer to nylon.  Also is there other materials that are easier to pour or are closer to water.

Best Regards

Carltonm

Hi Carltonm,

When you say you're getting 'mixed results' using the Fast-Cast, can you elabourate on what these mixed results are? - Generally, casting using Fast-Cast is very reliable and problem free so if you're not getting good results then that's unusual. Maybe something is not being done as it should or maybe you're expecting too much of the system.

As far a PU casting resins (or in fact any casting resin) go the Fast-Cast is a pretty low viscosity. You won't find something much more 'water-like' in terms of its viscosity but I would be suprised if it's the viscosity of the resin that's causing the problem.

There do exist a wide range of PU casting resins with different properties, including 'simulate' resins which come close to emulating the behaviour of other plastics (like Nylon) although many of these are designed for mixing and pouring in a vacuum using a rapid prototyping 'Vacuum Casting' machine and so are considered by us to be a little too niche to justify stocking.

Let me know what problem you're having exactly with the Fast-Cast and I'll see if I can help some more.

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Dear Matt

Thanks for coming back to me. 

The main problem I have had is small air bubbles at the bottom of the molded gears, the gears are very small.  However over the last day or so we have experimented with pouring the resin and altering the actual mould and we think we have cracked this problem.  We are filling the mould using a syringe and large needle placed at the bottom of the mould and this appears to be giving repeated results, by filling the mould from the bottom.

It would be helpful if you can recommend a nylon type material we can try or are there other casting resin's materials. I have seen some materials on You tube filmed in the USA but want to try and source here in the UK.  We are concerned as we have to machine the end surface to ensure a dimension and also drill a hole through the Polyurethane material.

I have attached a couple of photographs to show you what we are trying to replicate.  The dark gears are the originals and the white are our first attempts though as I say we are seeing better results now.  The small gear is around 5mm in diameter.

Let me know if you can recommend and supply a nylon type material and also is there a way we can colour the casting resin?

Best Regards

Carlton

Hi Carlton,

Sorry for the delay in getting back to you. I see, given the tiny scale you're working at, why you might be getting some issues. The amount of surface compared to the volume is so significant that the resin is tempted to miniscus around the detail. Filling with a syring from the bottom is obviously helping with that.

I'm afraid I don't know of any manufacturers or other suppliers who have a Nylon simulate designed for use outside of a vacuum casting machine; all the simulates I know of are intended for mixing and pouring under vacuum.

Your question about pigmenting is easier though, you can so this using polyurethane colour pigment paste. We have a full range of colours on our website.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales