any flexible tooling for VF? Looking to form castles like Elastolin

Experienced with casting concrete in silicone molds. I am looking to vacuum form some castles similar to the Elastolin castles made in Germany in the 1960s-1970s. They seem to push the process to the limit. Anyway, is there some kind of silicone or other flexible mold tooling that could be used for more complex designs for vacuum forming? I plan on using negative molds with a fairly thick plastic (1/8" or greater). I know it would work but mold life may be too short. Would like to produce 200 or so before the mold wears out. Also, anyone have success with using concrete molds?

Were those Elastolin castles really vacuum-formed? They look like castings to me; there are lots of undercuts. If you really tried to produce them with a vacuum-former, it looks like you'd need to do a lot of piecing together afterwards; it doesn't really seem worth the hassle. Why not just make rubber molds and pour them in resin?

Yes, most, but not all, were vacuum formed, but some parts are added. I had one as a kid and they are very thin. Things like the arch over the gate entrance and some tower tops. They used a multi piece mold, or cuts in a rubber mold, as you can see parting lines. German ingenuity. I have seen photos of the bottom of the castles. Too much volume for resin unless you built it up in layers, then too much time. There are some more advanced material now days, so maybe a specialty RTV mold material would hold up to the casting process and give more than a few castings. Thanks for your time though, it is a challenging project.

Hi Geoffrey - I doubt the castles were vacuum formed. VF won't give the surface detail achieved in those parts and then there is the undercuts to deal with. The original elastolin was a cast plastic using sawdust as the reinforcement. After the war, the period you mention, they moved to polystyrene which would have been injected. If the parts have a cavity then they used a countermould to reduce volume and maintain a thickness or reduce material cost. I would gravity cast or vacuum cast these in urethane or epoxy. Using silicon or urethane moulds... I'd use a countermould to minimise resin volume...Regards Peter

See https://en.wikipedia.org/wiki/Elastolin

This is not the best example, but here is one: https://www.sportscards.com/item/vin...e/302690907783

The plastic is very thin. I think they dealt with the undercuts by having multi-piece molds. The last photo is the bottom. I have seen a better example but can't find it at the moment. The detail is achieved by using a female/negative mold.

Here is another one:https://www.worthpoint.com/worthoped...tle-1918160141

Hi Geoffrey - Then they are vac formed polystyrene which makes sense if they are thin. PS is easy to vac form and will pick up detail. Elastolin was used for figures so they changed process for castles but kept the name for marketing. There's quite a drape and stretch in these castles. The tool would have been pushed up into the soft sheet or the sheet would have been draped down onto the tool.... If you do this make sure the plastic has been dried correctly "wet" plastic is the source of most issues in this sort of process. Peter

Yeah, multi piece vacuum molds with deep draws. Quite the challenge. It seems like you could spot heat with a handheld heat gun after the pull but still under vacuum to help problem areas fill. I will start with less challenging designs. If I had tooling that had a bit of flex to it it would help. Thanks for the suggestion. I have a lot of experience with silicone molds but not molds like this.

Hi - spot heating won't help. If the film has not pulled down this means there is no vacuum behind that area. This sort of mould is usually covered with 1mm holes. If there is an area that doesn't pull down, more holes are added until it does. Its really important to get the entire sheet heated evenly and quite hot. It chills when it hits the tool. That's why it has to be dry. Wet film/plastic does not heat up evenly and the outer surface may read the correct temp but the internal temp is low so does not stretch. Lots of things to learn..

eg you need to use plastic that is made for VF. "Normal" plastic has been stretched and will have a preferred direction. You need a "non-oriented" film so it stretches evenly in all directions.... 99% of commercial film is oriented due to its production process... if you put a plastic package in an oven it will shrink quite a bit maybe 75%. So you need plastic that has not been stretched in any way as you want to stretch it!! Most plastic is stretched (called orienting) so less is used for the job les material less cost....cheers Peter

https://parkinsontechnologies.com/in...ow-and-the-why

Wow, I haven't learned that in my research but sounds like good stuff, especially finding plastic that has not been stretched. There is a lot for me to learn.

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