Rotocaster experts - What RPM or range for rotocasting resin?

[CJP]

I've got a rotocaster just about finished, but I'm struggling with what RPM to run it at.

What's too fast? What's too slow? Does the size of the mold factor in? It can do 20" cubed, but generally I think I'll be doing hand props.

I've got it geared for a 2:1 ratio from the outer frame to inner frame which I can reverse to 1:2, although I don't think the reversal matters.

 

[swgeek]

A lot depends on the size and complexity of your mold, also what resin you're using. Everytime I roto cast it takes a few tries to get it right. I tend to err on the slightly too fast side.

 

[Krats]

I've been experimenting with rotocasting recently and am also interested in any advice anyone might have.

 

[starbuckcylon]

I've done a lot of rotocasting and I found less resin is better otherwise it snap cures and you have a big hunk of resin inside. For something like the size of a helmet I would do 5 small pours or resin every three minutes.

 

[Zinger]

I've done a lot of rotocasting and I found less resin is better otherwise it snap cures and you have a big hunk of resin inside. For something like the size of a helmet I would do 5 small pours or resin every three minutes.

I once accidently poured a double shot (forgot to divide my shot weight by 2 before measuring part A and part B). The resin got hot enough I could feel it through the mother mold. Inside the part there was a "wave" about 1/2" thick where the resin snap cured.

That was using 57D which is designed for rotocasting and usually has a nice, gentle gel phase cure.

 

[joberg]

To sum up:

What kind of resin (low/fast cure).
Mold and details of the piece you want to mold.
Better make it in layers rather than a big pour.
Speed up rather than speed down, especially if small details. You want that resin to go, forcefully, into every nooks and crannies.
Experimentation is a +...costly sometimes, but once you get it, you'll never forget it

 

[starbuckcylon]

I use to use Smooth On 65D its made for rotocasting but its doesn't hold up well in heat. And try Smooth-On 300 and it works just fine. I think my ratio is 3:1 its better to go slower.

I also have a Wireless Endoscope and I'll use that to look in and see what the coverage looks like.

 

[Pagan]

I once accidently poured a double shot (forgot to divide my shot weight by 2 before measuring part A and part B). The resin got hot enough I could feel it through the mother mold. Inside the part there was a "wave" about 1/2" thick where the resin snap cured.

That was using 57D which is designed for rotocasting and usually has a nice, gentle gel phase cure.

I did not like the 57D, it didn't seem to flow well, I've always had great success with 65D although it does not have a very workable pot life especially if one is mixing then pouring into the mold then sealing the mold, panic, panic and more panic!

 

[13doctorwho]

I use 65D. It's kind of an art, with a lot of trial and error to get the rotation down. I actually do it by hand. There are a lot of factors to speed, like many have mentioned.