Roto-Casting Question

[13doctorwho]

I am relatively new to roto-casting and I'm having a small problem. I am roto-casting in multiple layers, but I'm getting some delamination between the layers. I'm using Smooth-on smooth cast 65D. I checked the tutorial on the smooth on site, but they are doing one thick coat instead of multiple thin coats. Should I just do one thick coat? If I do multiple coats do I do the coats one right after the other? Does each coat need to be fully cured before the next one? Any help would be greatly appreciated. Thank you.

 

[smurf]

I do mine in thin layers because when i use too much it makes a mess when it starts to thicken. Do all the layers quickly after the last one. I do mine a couple minutes after it turns completely white. If it cures all the way it will not bond to the last layer. I tried another layer the next day once and it could be peeled right out after it hardened. It didn't bond at all. I also use the 65D. Hope that helps.

Jeff

 

[Sinned]

I haven't done any rotocasting (would love to...making a machine is on my list of summer projects), but definitely agree with smurf, you don't want the layers to fully cure, or you'll see the delamination. I do a lot of slush casting with 65D, and once it's cured, that's it. If I find out later that I have a spot which is too thin, it's difficult to correct. I've had mild success with sanding an area, and then adding more resin, but of course that's not possible on a hollow cast.

 

[cunningham]

You do not wait until the previous layer cures before proceeding to the next. Wait until it isn't runny and turns white and you are ready for the next coat. A fresh layer of 65D will not stick permanently to a fully cured layer and that is why yo are getting delamination. Also, doing this is a hot environment quickly speeds up the cure time as well, so take that into consideration.

 

[13doctorwho]

Thank you all for your replies! The advice is very helpful. I thought it might be the time between coats.

 

[ILL GREEN]

If you are using a two-part closed mold, I recommend laying up or slush cast the first layer. Then when the resin is in a paste kind of state, Pour in a couple more ounces of resin and seal up the mold to be rotocasted.

Be sure to read the instructions of your resin. If its a 2 minute cure, be sure to pour the next batch at a minute and a half. As Cunningham stated, weather can play a role in the curing process so experiment.