resin casting

[VPW]

I have tried to draw on your photo. The lines are too thick and wavy but I hope it conveys the idea. In addition to this, you can "burp" the mold to get the blocking air out. The vents will allow the resin in and can be cut after the mold is made or added with lengths of plastic rod as you make the halves. I used to glue fine plastic or brass rod to the high points of the master from the surface of the mold prior to pouring.

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[Dave Stevens (Lumberyard)]

I have cut vents into molds where air gets trapped I also used plastic and brass tubes to create vents.

what I am trying here is not having vents just to see if the mold will cast I am thinking in a vacuum it should suck any air out of the mold cavity. If it does not work I can always go back and cut vents.

so here is the progress so far

I found out without a vacuum pot like this one you have to design the molds so they will cast by using air vents as well as "burping" the mold like a baby or injecting the resin.



the first half of the mold was cast in Silicone and here it is in the vacuum pot. first I mixed the silicone and degasses it then I poured it into the mold and put that into the pot and sucked out the air bubbles. you can see the air being sucked out



looking up close



I am using a slow set silicone so it gives me lots of time to mess around with it

here is the first half after it set up clear and free of bubbles and an OOPS! the mold leaked a bit.




now I remove the clay and clean up the silicone mold half





next step is to add the sides and paint the mold with a rubber to rubber mold release if you don't do this the mold halves will stick together and you will have to cut them apart.

 

[Dave Stevens (Lumberyard)]

to cast or not to cast?

if your thinking on doing castings for say a 20 gun model it is not worth the cost and the time. To start with it is really difficult to do casting without a vacuum pot, yes it can be done and if your good enough at it you might get bubble free molds and castings. One issue is you will waste a lot of time and materials before you get results. In the end those cannons may cost you $30.00 each, the cost of the molding rubber and resins are expensive.

Other than casting there is CNC but very few model builders have a CNC lathe or the software to create the cutting files so this is pretty much out of the question.

another method is 3D printing here again very few model builders if any have high end printers or are able to create the print file. If you can create the print file you can send it to a printing service. most of these services are low quality and the high end printers are to expensive. A 3 inch long cannon can cost as much as $60.00 the print looks fantastic and the detail is perfect. This is used to print one master and thus the use of casting.

here are some examples of 3D printed carronades and you can see what the quality is. Some are from places like Shapeways others are from other services. Now I have not tried all the different materials offered so these are an average print. I am sure the more you pay the better the quality

different materials produce different results





different resolutions produce different detail quality



different material different results in detail



depending on how much your willing to pay will give you sharper prints







you get what you pay for a cheap $8.00 print looks like this





middle of the road cost for a print is usable still expensive but passable.




to cast or not to cast? pay for a high end high resolution resin print and make a silicone mold and cast the cannons

 

[VPW]

I misunderstood. I didn't understand you had vacuum.

 

[Dave Stevens (Lumberyard)]

No you did not misunderstand actually I did not have a vacuum when I started this topic but after 2 months of trying and a couple hundred bucks in materials I decided to get a vacuum pot.

Working on kit projects with model ship builder like the battle station kit and the new bomb vessel kit and more in the design stage we decided these kits have to include guns because most kit builders do not have the resources, machines and software to make their own.
it is one thing to make a gun or two and a totally different story to mass produce them.

 

[Dave Stevens (Lumberyard)]

here is a work area I am using different types of resins and different molding materials



what I am finding out if you tint clear resin you do not get a solid opaque it is somewhat translucent but I did find out if you paint the casting with a matt heat paint it gives the cannon a perfect scale looking texture. I could buy a pre tinted black resin but early tests with this gave a glossy surface and it did not look all that good.

here is a cannon for the Blandford X section model if anyone is interested in these cannons they are available.