Fishoey Posted July 15, 2011 Report Share Posted July 15, 2011 Hello All- I was wondering if anyone out there has used an Alumilite blank to pour a resin double sided mold for injection? Some back history on my project... I poured an RTV mold to cast a piece of Alumilite. Once the Alumilite hardened I carved it into a worm I am designing. I tried Alumilite because my previous attempt with carving a dal stick left me with a muted finish on my poured worms (in RTV), due to the porous nature of wood. Alumilite worked well for carving, and seemed to a slightly smoother finish than wood, even with sanding. Note, I did seal the finished carving with spray on acrylic. Next, I made a double sided mold using RTV to cast my prototype. I recently purchased a hand injector and was able to shoot about 5 good worms in about 3hrs (yes that is correct... 3hrs). The RTV mold was unpredictable -for me- and I'm sure it has something to do with the design, even though it is pretty straight forward. My goal... I would like to use my Alumilite prototype and attempt to cast a two piece resin mold (clear preferably). -Will the Alumilite adhere to the resign? Can it be coated with petroleum jelly (or another solution) to prevent sticking? -Does anyone recommend a resin? Are some better than others? (I purchased some at a hobby supply store for finishing table tops. I have not used it yet) Any tips would be greatly appreciated! As always... Thank you for your replies and suggestions!!! Fishoey Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted July 15, 2011 Report Share Posted July 15, 2011 By setting a hard master in a hard mold material, you are definitely risking your master, so make sure you know how to recreate your master, should things not go to plan. Some people use petroleum jelly, but I did not have much success with it. I use a floor wax, the kind used for polishing floor tiles, where I live, it is readily available and very cheap. It is more substantial than PJ. After applying, I flash over with a flame torch to smooth out the coating. I am hoping others will jump in and maybe give you more confidence in PJ or offer up a better release agent. The big problem is locking the master in the mold cast by setting too deep. Even if the master comes out easy from the first half, it will probably get stuck in the second half. Even if the master is not locked in, it is not going to just fall out, it is going to need persuasion. So you must plan how you intend to remove the master, maybe a brass or steel rod in the nose, where you are going to pour. If you have any thin, delicate parts, they are likely going to break while removing the master. In this case it may be more efficient to build the master as separate parts and soft glue them together. You may have to dress the mold at the joints, but not a big deal. With wooden masters, I find it best to give a coat of epoxy. This self levels, gives a very smooth surface and hides the wood away from the wet mold material. The best material for masters in a resin mold are soft plastic. All the problems go away. It may be better to try and work out what is going wrong with the RTV mold that you already have. For example: maybe you are clamping to heavily and the vents are closing. I found that the best way to clamp the mold is between two plywood plates, cut to the size of the mold. This spreads the load from the clamps evenly. If you cannot find the problem, it may be best to post up a picture of the mold and the failed cast. Maybe someone here will recognise your problem. Of course, if it is a secret project, then this is not an option. Dave Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted July 15, 2011 Report Share Posted July 15, 2011 By setting a hard master in a hard mold material, you are definitely risking your master, so make sure you know how to recreate your master, should things not go to plan. Some people use petroleum jelly, but I did not have much success with it. I use a floor wax, the kind used for polishing floor tiles, where I live, it is readily available and very cheap. It is more substantial than PJ. After applying, I flash over with a flame torch to smooth out the coating. I am hoping others will jump in and maybe give you more confidence in PJ or offer up a better release agent. The big problem is locking the master in the mold cast by setting too deep. Even if the master comes out easy from the first half, it will probably get stuck in the second half. Even if the master is not locked in, it is not going to just fall out, it is going to need persuasion. So you must plan how you intend to remove the master, maybe a brass or steel rod in the nose, where you are going to pour. If you have any thin, delicate parts, they are likely going to break while removing the master. In this case it may be more efficient to build the master as separate parts and soft glue them together. You may have to dress the mold at the joints, but not a big deal. With wooden masters, I find it best to give a coat of epoxy. This self levels, gives a very smooth surface and hides the wood away from the wet mold material. The best material for masters in a resin mold are soft plastic. All the problems go away. It may be better to try and work out what is going wrong with the RTV mold that you already have. For example: maybe you are clamping to heavily and the vents are closing. I found that the best way to clamp the mold is between two plywood plates, cut to the size of the mold. This spreads the load from the clamps evenly. If you cannot find the problem, it may be best to post up a picture of the mold and the failed cast. Maybe someone here will recognise your problem. Of course, if it is a secret project, then this is not an option. Dave I second this. Alumilite sticks to everything, so a mold release would be required for sure. RTV sticks to nothing but Silicone, so unless you are pooring silicone, no mold release is required. Dave has set out the best plan. Quote Link to comment Share on other sites More sharing options...
Fishoey Posted July 16, 2011 Author Report Share Posted July 16, 2011 I second this. Alumilite sticks to everything, so a mold release would be required for sure. RTV sticks to nothing but Silicone, so unless you are pooring silicone, no mold release is required. Dave has set out the best plan. Thanks Dave and Anglinarcher! @Dave. I appreciate the input. I think I may try coating the RTV mold cavity with the release agent and pouring more RTV to make a tough durable RTV master. I do like the idea about the floor wax. It make perfect sense. There is another material I thought about and it is called liquid metal. There are a couple of types, one melts at 95oF and the other at 150oF (I believe). I definitely don't want the 95o melting, however the 150o might work great. I'll pour it in the RTV mold and cast a master. I might be able to grind it down and smooth it out with heat -not sure, this is theory I'm working with -. I'll set it in clay and pour the first resin and then the second half of the mold. If I have problems with it coming out, I'll heat it under water. Thanks again for the advice. I'll try the epoxy trick on wood (and then add the wax) to save from using the Alumilite. p.s. The worm is on covert ops at this point and time. I'll let you know and post pictures if it changes. =) Quote Link to comment Share on other sites More sharing options...
