Ok - so I'm starting to think about modelling up tank proxies in CAD with a view to getting them 3D printed at shapeways and home casting them, just for kicks really.

I'm still just feeling my way through the CAD software and it's going ok, slow, but ok.

What I have less experience of is casting - specifically what the limits are of home casting, if any and what impact this would have on the level of detailing I can expect to be able to reproduce.

So I've been looking at some of the FW super heavy tanks as examples of good quality, complex and detailed models. And I'd like an opinion on the methods used to cast them.

Stuff like this:





I'm really looking at places like the tank tracks and the deep undercuts on the sponsons. Would you just take a mould line horizontally along the side of the sponsons and about half way up the barrels at the back and would the flexibility of the silcon handle the rest or am I looking at something that will have been made using a multi part mould? I can see that the searchlights and stuff have been modelled in such a way that they reduce undercuts but figuring out how you'd get those tank tracks out of a mould is giving me a headache...

Anyway - I'm just looking for some knowledge/advice from those of you who have more experience. I'm sure I'd figure it out the hard way by burying masters in blocks of rubber but I'd rather avoid that if possible!!

it depends if you want to cast in resin or metal really, you can get away with quite a soft silicone for resin and for smallish (chimera/rhino sized) models which will enable you to bend the mould and peel out anything with big undercuts

if you want to make bigger stuff, you'd probably need a firmer silicone to avoid distortion, you can get pretty fantastic results with metal, although the mould needs to be much more complicated with lots of tiny vents cut in at strategic locations

Resin will reproduce detail really really well, especially if you use pressure gear, although clever feed channels and vents can mitigate this. Resin is comparatively fragile, so may snap if you have large undercuts, it's also prone to bubbles forming, and it's a one-shot deal so if you have a miscast item, you either work out how to make an objective marker from it, or bin it, with metal it can be melted down and re-used

edit: looking at that model, however if you used RTV101 high temp silicone and cast it in metal, you'd rip chunks out of the mould after a dozen pulls or so as the undercuts would be a pain.....

I use filmsil for resin and it's okay for metal too up to around 240 celsius, it's super soft and flexible, you can almost turn moulds inside out which really helps with undercuts...

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If you want to learn more about casting in silicone with resin's and such, resin addict is the place for you.

http://www.resinaddict.com/forum/index.php

Thanks guys, it sounds like you can get away with quite a lot then, depending on the materials you use and how long you want the mould to last?

I'll definitely check out resin addict - thanks blind.

on the above model, you could do a 3-part mould to avoid the track undercuts, if using metal and hard silicone that would help mitigate the undercuts

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Army Forge List Co-ordinator