Jack Posted December 21, 2008 Share Posted December 21, 2008 Folks - can someone educate me on resins and moulds :??? If I wanted to create a mould so that I could for instance produce resin mortar rounds... Where would one start, what is the process of fabricating master moulds and what resin would be best used? Would it be best to have a company make the moulds etc etc? Yours most grateful. Jack. Quote Link to comment Share on other sites More sharing options...
No Signals Posted December 21, 2008 Share Posted December 21, 2008 A lot would depend upon how complex a shape the final items were. I would class (my visualisation of) mortar rounds as a 'second stage' item. First stage being something completely symmetrical such as an artillery round. The fins would be the (quite literally) 'sticking point'. The item has be capable of being released from the mould and so tapers would have to be built in to the mould to allow for this. Using an original round to make the mould would require some adding of material to the fins to give them this slope if it were not there already. Modelling wax could be used for this. There are a whole load of grp product suppliers so check your Yellow Pages or do a Google search for ones in your area. As well as supplying suitable matting, resins, release agent, instruction sheets etc etc for the master mould they will also be able to supply an inert filler powder for mixing with the filler resin to do just the job you want. Personally I dont like working with GRP as I always found I got it everywhere and it irritates like mad (memories of making umpteen canoes over the years). An alternative to GRP for the master would be to use latex or plaster but neither of these would have long term durability if you were thinking of doing a lot of them. If only doing a small batch then I would look in to those options. The process of moulding is not difficult or complex, just messy. You are correct in thinking that you have to get the master mould right but despite them being a projectile it is not rocket science:) Quote Link to comment Share on other sites More sharing options...
ArtistsRifles Posted December 21, 2008 Share Posted December 21, 2008 (edited) Folks - can someone educate me on resins and moulds :??? If I wanted to create a mould so that I could for instance produce resin mortar rounds... Where would one start, what is the process of fabricating master moulds and what resin would be best used? Would it be best to have a company make the moulds etc etc? Yours most grateful. Jack. How good an engineer are you (serious question)? And what acess do you have to: 1) Either an original round, or drawings there of, to use as a master?? 2) A lathe or similar machine tool to turn the shape in wood?? The process is fairly simple - from the orginal or the drawings turn up a wooden mater core - possibly in two peices for the charge and the tail section. Forget moulding the fins, these can be fabricated from sheet metal later on. Once you have the master core mark the centre line around it, cover it in release agent, then build up the fibreglass matting to make one half of the pattern. Needs to be about 4 or 5mm thick so it's rigid. Repeat for the other side making sure you have a nice wide lip on each half for clamping and alignment. Once the fibreglass has cured place the two halves together with the master in place and drill two holles through the lip either side and use some bolts the same size as the hole to act as alignment guides and initial clamps. Drill another couple of holes though the top surface of one half to act as pouring and air vents. Split the mould, remove the master, coat the inside faces with release agent, clamp back together and pour in the resin to be used to make the actual projectile replica making sure all the air is expelled from the mould. Once the resin is cured, split the mould and remove the part, clean up the surface and fabricate tail fins from sheet steel or ally then fit them to the moulding. That basically is it...... Probably take you a few days to get the mould right then you can turn out replica mortar rounds as fast as the resin will cure (no prizes for guessing what mug had to spend 6 months in a pattern shop as part of his apprenticeship...) Edited December 21, 2008 by ArtistsRifles Quote Link to comment Share on other sites More sharing options...
Espressodude Posted December 21, 2008 Share Posted December 21, 2008 Neil: Must have been a while since apprenticeship, otherwise you would have brought up using a SHRINK RULER for measurements....even though the resin probably doesn't shrink much. Quote Link to comment Share on other sites More sharing options...
6 X 6 Posted December 21, 2008 Share Posted December 21, 2008 As well as the excellent advice in the previous posts there's quite a lot of helpful information on YouTube. This link is a starting point and will take you into an area where you might want to dig around. http://uk.youtube.com/watch?v=_s3crDAOlX8 Quote Link to comment Share on other sites More sharing options...
ArtistsRifles Posted December 21, 2008 Share Posted December 21, 2008 Neil: Must have been a while since apprenticeship, otherwise you would have brought up using a SHRINK RULER for measurements....even though the resin probably doesn't shrink much. Yeah - you could say that - I qualified waaaaaaay back in 1976 :-) Most of what I did in the practical way was for metal casting - the resin moulding stuff was considered too expensive to let appretices play with!! Quote Link to comment Share on other sites More sharing options...
ferrettkitt Posted December 22, 2008 Share Posted December 22, 2008 How good an engineer are you (serious question)? And what acess do you have to: 1) Either an original round, or drawings there of, to use as a master?? 2) A lathe or similar machine tool to turn the shape in wood?? The process is fairly simple - from the orginal or the drawings turn up a wooden mater core - possibly in two peices for the charge and the tail section. Forget moulding the fins, these can be fabricated from sheet metal later on. Once you have the master core mark the centre line around it, cover it in release agent, then build up the fibreglass matting to make one half of the pattern. Needs to be about 4 or 5mm thick so it's rigid. Repeat for the other side making sure you have a nice wide lip on each half for clamping and alignment. Once the fibreglass has cured place the two halves together with the master in place and drill two holles through the lip either side and use some bolts the same size as the hole to act as alignment guides and initial clamps. Drill another couple of holes though the top surface of one half to act as pouring and air vents. Split the mould, remove the master, coat the inside faces with release agent, clamp back together and pour in the resin to be used to make the actual projectile replica making sure all the air is expelled from the mould. Once the resin is cured, split the mould and remove the part, clean up the surface and fabricate tail fins from sheet steel or ally then fit them to the moulding. That basically is it...... Probably take you a few days to get the mould right then you can turn out replica mortar rounds as fast as the resin will cure (no prizes for guessing what mug had to spend 6 months in a pattern shop as part of his apprenticeship...) Hi Neil, What would you use as a releasing agent? Andy Quote Link to comment Share on other sites More sharing options...
Timinder Posted December 22, 2008 Share Posted December 22, 2008 You can buy commercial release agent, which you spray/wipe/paint onto the polished mould surface. I would be wary of filling an entire mortar round sized shape with resin, some types get extremely hot as they cure in those kinds of concentration. I would be more inclined to fill with a smaller quantity, plug the holes and rotate the mould to coat all of the mould in resin, then once cured fill it with expanding foam (or plaser for more realistic weight). Quote Link to comment Share on other sites More sharing options...
Jack Posted December 22, 2008 Author Share Posted December 22, 2008 Wonderful advice - thank you very much chaps. . I would be more inclined to fill with a smaller quantity, plug the holes and rotate the mould to coat all of the mould in resin, then once cured fill it with expanding foam (or plaser for more realistic weight). Timinder - would that be strong enough to handle being erm, handled? Quote Link to comment Share on other sites More sharing options...
ArtistsRifles Posted December 22, 2008 Share Posted December 22, 2008 Hi Neil, What would you use as a releasing agent? Andy Back then it was a form of bees wax(aka honey wax IIRC......) Would have to try and find my old apprentice log books, not an easy task in this place..... Seem to recall having to "polish" the moulding surface everytime..... As a thought though - having just seen a craft prgram my daughter is addicted to - what about a latex mould??? Looks like you just coat the master object with several coats of this stuff them peel it off and you can then take a number of mouldings from this - would that work in this instance??? Quote Link to comment Share on other sites More sharing options...
No Signals Posted December 22, 2008 Share Posted December 22, 2008 As a thought though - having just seen a craft prgram my daughter is addicted to - what about a latex mould???Looks like you just coat the master object with several coats of this stuff them peel it off and you can then take a number of mouldings from this - would that work in this instance??? As I said in my first post latex and plaster are both viable options if you are not going to be doing huge numbers. In case the point hasnt been clear enough the outer surface of the original which you are going to be making your master mould from needs to be as perfect as possible. All small irregularities will show up on the copies and in some cases combined will hinder/stop the copy from releasing from the mould. IMHO casting in the fins in the long run would be preferable than having to fab up and attach them. Just one process to do and they are finished. Quote Link to comment Share on other sites More sharing options...
LeeEnfield Posted December 22, 2008 Share Posted December 22, 2008 Just a thought on this subject,..........does this run foul of the VCRA ?? I know the making of REPLICA guns etc does,......or eise they need to be painted PINK..............not wishing to pee on anyones parade,.....as I said, just a thought. Andy Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted December 22, 2008 Share Posted December 22, 2008 Just a thought on this subject,..........does this run foul of the VCRA ??I know the making of REPLICA guns etc does,......or eise they need to be painted PINK..............not wishing to pee on anyones parade,.....as I said, just a thought. Andy No, they are not firearms... Ordnance is not part of the VCR Act Quote Link to comment Share on other sites More sharing options...
No Signals Posted December 22, 2008 Share Posted December 22, 2008 No, they are not firearms... Ordnance is not part of the VCR Act Ok then, so how about we knock up a couple of dozen accurate replica Blue Steel stand off weapons and leave them lying around. How long before they become covered? Quote Link to comment Share on other sites More sharing options...
Stormin Posted December 22, 2008 Share Posted December 22, 2008 Ok then, so how about we knock up a couple of dozen accurate replica Blue Steel stand off weapons and leave them lying around. How long before they become covered? Not the sort of object you'll be carrying into a bank to do a job though are they? Quote Link to comment Share on other sites More sharing options...
84KB11 Posted December 22, 2008 Share Posted December 22, 2008 My choice would be a silicone or vinamould rubber. http://www.flints.co.uk/acatalog/Silicone_Rubber_Mastermould.html Most compounds are self releasing, making removal of the resin easier. Make a fairly thin rubber form around the original, then support this form in a sand box when casting to prevent distortion/streching when full of liquid resin. Quote Link to comment Share on other sites More sharing options...
Tony B Posted December 23, 2008 Share Posted December 23, 2008 Refering to another thread, what's the idea? Going into Xmas Decorations? :-D The Flint lot are very nice to deal with, I've got stencil Mylar and other stuff of them, quick delivery and good prices. Quote Link to comment Share on other sites More sharing options...
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