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First Plug and Mold - Please provide any advice.

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Old 04-29-2017, 04:24 AM
  #26  
manks7477
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Pulled the first part from the mold, it came out ok, but not good enough to use on the model. I am ok with that as this was a learning tool for me this time around. I think now that I have made a couple of molds and understand how to do it better I will restart the process, make a new, better plug and mold - it will be a bit more complex - and I will use that to make the parts.

Overall good start for me here. I am enjoying this part of building.

Quick question - after I use a mold, what do I need to do to prep it again to make a second part?

Thanks!
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Old 04-29-2017, 08:34 AM
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GREG DOE
 
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For storage just wax the mold. I have molds that are 30 plus years old. If you are unhappy with the surface of your mold it can be sanded with several grades of sandpaper, finishing up with 1500, or 2000 grit, and then buffed out.
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Old 04-29-2017, 08:43 AM
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manks7477
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Originally Posted by GREG DOE View Post
For storage just wax the mold. I have molds that are 30 plus years old. If you are unhappy with the surface of your mold it can be sanded with several grades of sandpaper, finishing up with 1500, or 2000 grit, and then buffed out.
Are you talking about 8 - 10 coats of wax or just one or two?
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Old 04-29-2017, 08:45 AM
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It depends, if you had any spots that stuck to the point that the mold surface was damaged you do the complete routine. I would recommend to do that anyway, in time you will know what is necessary but for now I would stick to the routine every time. I would wax a minimum 2-3 coats the second time.

It is generally better to be too cautious than to take any chances.

Congratulations!
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Old 04-29-2017, 12:38 PM
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One application of wax is sufficient for storage. Actually as the mold ages it improves in how well it will release a part. Later, when you plan to lay-up another part, wax the mold. When working in polyester, in an aged mold, I have success with just wax for a release agent. When working in epoxy I always use wax, and PVA. Here's another couple of suggestions: use compressed air to pop your parts out of the mold, and if necessary use soft thin strips of material to wedge into the edges of the mold. They make wedges for just this purpose that can be bought from fiberglass supply houses, but you can use thin strips of aircraft plywood, with a bevel on the edge. Sometimes just getting a wedge in the edge of the mold provides an opening to inject a blast of air. As has already been mentioned, there are hundreds of tips on how to make glass parts, and in many cases there are more then one way to accomplish the same task. For example it has been discussed whether to spray, or brush the PVA in the mold. I prefer to spray, but someone else posted that they prefer to brush. Another trick I like to do, is warm my mold in the oven for about 5 minutes (lowest temp setting) before spraying the PVA, which makes it dry quicker, before it can run. In the end ask question, try different ideas, and decide what works for you. Good luck.
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Old 05-03-2017, 06:04 AM
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Pulled my second part yesterday - from a new mold. This part turned out better, made a couple of mistakes,but nothing that can't be fixed with some bondo and sandpaper. This was a very basic part but still getting it to release was a challenge - need to improve on that!

Going to start 2 more plugs, since I will only need one part per plug, I may try to skip the Mold step and just go right from the plug to part. Will take some sanding and work, but I think it will be ok, if not, then we go to the mold process.
Fun stuff!
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Old 07-21-2017, 07:53 AM
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Hi!
Did you use a special black or Grey thick epoxy (metall filled) when first making
the female mold?
You should!
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Old 07-24-2017, 06:17 AM
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Surface coat has already been sufficiently covered here. Metal filled resin would be of no value.
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Old 08-08-2017, 06:23 PM
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The purpose of the surface coat is to avoid air bubbles in the mold surface and such, if you are an experienced guy like Pylonracr it does not matter but as a first time it might make it easier to get a good result using a dedicated surface coat (mold epoxy), I use mold epoxy if I make a mold - it's basically a very thick non dripping epoxy that equal gelcoat (polyester version). The mold epoxy I use is simply a dark brown (black) colored very thick gel-like epoxy, it's quite expensive as an epoxy tool coat though. The aluminum filled mold epoxy have a slightly different characteristics that you don't need to worry about if you are not an experienced composite fabricator that knows exactly what you want. Mold epoxy can also be made by yourself using different additives to suit your preferences.

Last edited by ibuild; 08-08-2017 at 06:41 PM.
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Old 08-09-2017, 06:55 AM
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Originally Posted by ibuild View Post
The purpose of the surface coat is to avoid air bubbles in the mold surface and such, if you are an experienced guy like Pylonracr it does not matter but as a first time it might make it easier to get a good result using a dedicated surface coat (mold epoxy), I use mold epoxy if I make a mold - it's basically a very thick non dripping epoxy that equal gelcoat (polyester version). The mold epoxy I use is simply a dark brown (black) colored very thick gel-like epoxy, it's quite expensive as an epoxy tool coat though. The aluminum filled mold epoxy have a slightly different characteristics that you don't need to worry about if you are not an experienced composite fabricator that knows exactly what you want. Mold epoxy can also be made by yourself using different additives to suit your preferences.

Correct.
Surface coat does one more thing though. It provides a smooth surface that (as opposed to the weave of the fabric showing through on the finished mold surface.) In post 7 I gave my method. The same laminating resin I use for the mold and final component thickened with microballoons or colloidal silica and graphite powder. Not terribly expensive and it works very well.

Good Luck

Scott
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Old 11-14-2018, 07:43 AM
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Originally Posted by GREG DOE View Post
For storage just wax the mold. I have molds that are 30 plus years old. If you are unhappy with the surface of your mold it can be sanded with several grades of sandpaper, finishing up with 1500, or 2000 grit, and then buffed out.
I agree, waxing makes them last forever.
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