Rotational casting question

burlrice
New Member

Posts: 7

Rotational casting question Mar 7, 2015 16:17:58 GMT -5

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Post by burlrice on Mar 7, 2015 16:17:58 GMT -5

I have a project I am trying to rotocast. I was wondering if there is a magic number I should be shooting for, as far as wall thickness goes?

I want the total wall thickness to be between .100" and .125". I am using RC-3. I realize Slow Set 7 is advertised on the store's site as suitable for rotational casting, but I am making large scale model railroad kits, and I am concerned about the temperature resistance of Slow Set 7 for an application that could potentially be outside for several hours at a time.

I have tried casting in several layers, and tried thickening with micro balloons, but I am still getting some unevenness in my castings:

burlrice
New Member

Posts: 7

Rotational casting question Mar 8, 2015 8:03:40 GMT -5

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Post by burlrice on Mar 8, 2015 8:03:40 GMT -5

After reading that again, I don’t think I worded it very well. What I’m trying to figure out is the optimal layer thickness, per pour.

I calculated the volume of resin I need (12 fluid ounces) from the desired shell thickness (.100”) and now I’m trying to determine how many layers I should pour it in.

mike
Moderator

Posts: 295

Rotational casting question Mar 10, 2015 11:36:46 GMT -5

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Post by mike on Mar 10, 2015 11:36:46 GMT -5

Ideally one pour ... correct? So like with any part, there is a learning curve. When rotational casting a hollow part you have even more variables. Amount of resin, shape of mold, thickness you desire, temperature of mold, rotation speed of inside vs outside frame, frame speed, surface area, and so much more.

If you pour too much resin all at one time in the mold, the resin can gel quickly in a big lump due to the heat it generates. A good starting point for inside to outside ratio for the frames is 3 inside rotations for every 1 rotation of the outside frame. Trying to keep the mold fairly centered is in the frame is recommended.

I would start with 2 coats and warming the mold. I'd also use approx. 50% microballoons to build some viscosity and allow it to flow and stick to the wall. As soon as the first coat gels, start mixing the second.

Mike

burlrice New Member Posts: 7	Rotational casting question Mar 10, 2015 14:41:53 GMT -5 Quote Select Post Deselect Post Link to Post Back to Top Post by burlrice on Mar 10, 2015 14:41:53 GMT -5 Thanks. I'll give that a try. How warm should the mold be?

carol - Alumilite Corp Global Moderator Posts: 411	Rotational casting question Mar 11, 2015 8:07:02 GMT -5 Quote Select Post Deselect Post Link to Post Back to Top Post by carol - Alumilite Corp on Mar 11, 2015 8:07:02 GMT -5 Burl, The mold should be warmed around 120-130 F, just so it is good and warm to the touch! Best, Carol

burlrice New Member Posts: 7	Rotational casting question Mar 11, 2015 9:51:47 GMT -5 Quote Select Post Deselect Post Link to Post Back to Top Post by burlrice on Mar 11, 2015 9:51:47 GMT -5 Thanks Carol. I tried making the other changes Mike pointed out, and I got a good casting out of it last night:

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Rotational casting question

Post by burlrice on Mar 7, 2015 16:17:58 GMT -5

Post by burlrice on Mar 8, 2015 8:03:40 GMT -5

Post by mike on Mar 10, 2015 11:36:46 GMT -5

Post by burlrice on Mar 10, 2015 14:41:53 GMT -5

Post by carol - Alumilite Corp on Mar 11, 2015 8:07:02 GMT -5

Post by burlrice on Mar 11, 2015 9:51:47 GMT -5

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