Scratchbuilder Posted February 8, 2013 Share Posted February 8, 2013 Hi all, thinking that any vac-form models should be made into female moulds to ensure crisp details, but what are the females made of? I'm sure metal powder-filled resin is ideal, but how does one ensure that the basically very adhesive epoxy doesn't stick to your valuable master? Can we trust silicon release sprays? Or is the trick to make a silicon mould, then a resin copy to potentially sacrifice if the epoxy resin sticks to the masters? The alternative is something like Hydrocal/Kristocal K, the hard dental plaster, which is not by nature so sticky. I've done a lot of vac-forming but never into female moulds. Cheers, Martin Link to comment Share on other sites More sharing options...
heloman1 Posted February 8, 2013 Share Posted February 8, 2013 Hi Martin. I've left an answer to your other post re the vacformed kit. May I suggest a trip to the resin supplier get as much technical info as you can, they will have tech data sheets and they should also have a 'resin work manual'. They after all want to sell you as much of thier product as they can so wil want top support you. You could try the 'Smooth On' site in the US there products are aimed at the hobby market, lots of on-line support/info. If memeory serves me they should supply a silicone based aerosol release agent. Colin @ ROTORcraft Link to comment Share on other sites More sharing options...
Scratchbuilder Posted February 8, 2013 Author Share Posted February 8, 2013 Colin, PM coming if I get any sense out of this bloomin forum. It is so slow lately. And thanks, Martin Link to comment Share on other sites More sharing options...
Pin Posted February 8, 2013 Share Posted February 8, 2013 This article (sorry - in Russian but with a lot of good pictures) recommends .... shoe wax as a separator: http://scalemodels.ru/articles/4684-termovakuumnaja-formovka-na-primere-fonarja.html Written by Musa Zekoreyev - a man behind Prop-n-Jet Link to comment Share on other sites More sharing options...
Scratchbuilder Posted February 8, 2013 Author Share Posted February 8, 2013 Thanks, Pin. I'll have a look later. Martin Link to comment Share on other sites More sharing options...
Radleigh Posted February 8, 2013 Share Posted February 8, 2013 This article (sorry - in Russian but with a lot of good pictures) recommends .... shoe wax as a separator: http://scalemodels.ru/articles/4684-termovakuumnaja-formovka-na-primere-fonarja.html Written by Musa Zekoreyev - a man behind Prop-n-Jet If you open it up in Google Chrome it'll translate Link to comment Share on other sites More sharing options...
Pin Posted February 8, 2013 Share Posted February 8, 2013 If you ask me being a native Russian speaker I will translate too Link to comment Share on other sites More sharing options...
Scratchbuilder Posted February 8, 2013 Author Share Posted February 8, 2013 Well! Do our combined talents know no limits? Martin Link to comment Share on other sites More sharing options...
Scratchbuilder Posted February 8, 2013 Author Share Posted February 8, 2013 Well, I got through the odd translation very well and these things are always useful. Many thanks for the link, Pin. Martin Link to comment Share on other sites More sharing options...
Cheshiretaurus Posted November 11, 2013 Share Posted November 11, 2013 I made some vac formed spats and other parts for my cherokee conversion trick was to cast a copy of your master to avoid damaging the origional. The following is from several posts extracted the cherokee thread so apologies if bits dont read right I made an RTV mould of the spats and made resin casts to make the vac mould from. I CA’ed the casts to a plastic card backing along with another cast cut out for a second set of main wheel spats then started spraying PVA mould release in a very light layer at a time and leaving it for 10 to 15 mins between layers, I think they got 5 or 6 maybe 7 layers in total this forms a barrier only a few microns thick. The mould release needs to be dusted on lightly at first as it tends to bead and form blobs if too much goes on at once. After a few layers the tendency to bead reduces . Don’t use your expensive airbrush for this, I used a cheap £7 mini spray gun from ebay. I had also made a couple of wooden frames to fit round the cast from 12x4mm batons and glued together with white PVA glue. Sewing pins were gently tapped in at strategic points for the air evacuation points on the mould. The frames were fitted and dammed with plasticine. A mix of 50% aluminium powder and 50% resin was then prepared, this becomes a thick mud so a little acetone was added to thin it into a pourable mix. This was then poured into the frames leaving an air chamber above the resin, given 15 mins to gel then the pins were removed. I gave them about an hour to set then gently prised the plasticard along with the cast masters away, took a little force at times but they both cleanly released, leaving a negative impression of my parts for a female mould. I’ll leave them for a couple of days to set hard before I try to make use of them. Taped the moulds to my vacuum tool and sealed up all other gaps. Toaster at the ready and go. Just really test and practice pieces at moment, spats are formed from 0.5mm card and seemed to come out ok but I think next time I make a vacuum mould I'll make smaller air holes, the pip marks left are quite pronounced but these can be sanded so ill stick with this mould and try using 0.75mm card, (1mm card will be too thick and wont leave room for wheels). I've now run out of 0.5mm card so need to order some more today along with some 0.75mm and have another go. As for the windscreen, Ive made a few from 0.5mm PET-G, I'll regard it as a partial success as last time I tried to mould a canopy it just stuck to the resin mould leaving marks on the canopy, I had used less aluminium powder to make that mould but this time I used more I think I've solved that bit. I'm going to make a new master & mould for the windscreen as this one has too many imperfections and no defining line for the edge of the screen making it hard to see where to cut it. for the side windows I need to make a master, this was created in a similar way that the resin windows would have been done. A piece of acetate was taped over the windows but instead of resin I pushed RTV putty into the apertures. Once set the left & right were stuck to a flat surface and the space between the two filled in with more RTV putty to create a smooth mound with the windows at the top suitable for vacforming. A wooden casting frame was put around and dammed, and a negative cast made from resin. Now I can make as many RTV moulds of the windows as I want in case I trash them while making the vacuum mould. The vac mould was made in the same way as the previous ones this time I used acupuncture needles as suggested by Carlos, one in each corner of the each window, 16 needles. I found grouping the all together with a bit of blutac helped to keep them neat and upright while working and not falling in the way. Pulled several copies this morning from it some better than others but I think I've got a set of usable ones from it going to give them a test fit soon then, hope this helps Mark Link to comment Share on other sites More sharing options...
Scratchbuilder Posted November 11, 2013 Author Share Posted November 11, 2013 Mark, a very good post. many thanks. I am so busy currently that my vac-formed models are on the back burner in deference to paying work. And my son, with the vac-former has got a job! Cheers, Martin Link to comment Share on other sites More sharing options...
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