Separation from Tube

[vtgaryw]

This has been covered before (in fact, I had started a thread about 4 years ago regarding this happening with PR), but I just cast 4 bottle caps onto tubes. Royal Palm, cast at 50 psi for 24 hours. Two of the blanks showed some separation at one end between the tube and the resin. One I was able to fill with a little think CA and save, the other one not so much.

I know you can't put too much pressure on the bushings, but I was wondering if there are any other tricks? The smoother the tube (e.g., powder coated) the more prone it seems to be. Is there a resin less susceptible to this? The ends were perfectly square, used TBC bushings when turning, but not when finishing.

Thanks,

-gary

 

[jttheclockman]

I know with epoxy resin the cure time is a lot longer than resins such as silmar or Alumilite. Did this seperation happen before you stated doing any turning or squaring or while one of those operations was being done?? I never used that resin but have used Liquid Diamonds and so far I am very happy with it. Use it and will use it on things that are delicate and many nooks and crannies in when casting on a tube. Maybe you did not allow enough cure time. Just a guess.

 

[vtgaryw]

Definitely once I started turning it, most likely while finishing it (not the turning, although it's hard to tell until you start getting a clear enough surface to see.)

I had let them cure 72 hours post pressure pot.

Does anyone coat over the tubes before casting? The worst one was a powder coated tube as opposed to ones I spray painted, but I don't want to jump to conclusions on a small sample size.



-gary

 

[Kenny Durrant]

I've had hit and miss with separating. I've read here that some people wait 3 days to a week before trying to turn epoxy. I cast inside and the temp is always around 74 degrees so I'm sure that adds to the cure time as well. If the separation occurs during demolding it could be flexing while coming out or trapped air expanding because the resin is soft. I also coated the tubes with Elmers glue in the past and that helped a lot with the problem.

 

[vtgaryw]

I've had hit and miss with separating. I've read here that some people wait 3 days to a week before trying to turn epoxy. I cast inside and the temp is always around 74 degrees so I'm sure that adds to the cure time as well. If the separation occurs during demolding it could be flexing while coming out or trapped air expanding because the resin is soft. I also coated the tubes with Elmers glue in the past and that helped a lot with the problem.

Does the Elmer's dry clear and even enough?

gary

 

[Gregory Hardy]

The only time I have had this happen (once - one of the few times when I learned the easy way), I was turning "too vigorously," and I am certain that it was heat. I also am using Liquid Diamonds. Good luck with your solution.

 

[jttheclockman]

I do not know the answer but maybe oils from your hands have an ill effect on adhesion. just throwing it out there.

 

[Kenny Durrant]

At first I used the White Elmers and it worked fine except on black and other dark colors. Now I use the clear and it does well with all colors. If you use a soft fine brush you shouldn't have trouble seeing any glue streaks. There could be several different reasons why so I'd suggest being careful and giving everything extra time. Like make sure the resin is set before taking it out of the pot and demolding. Try giving the blanks a week to fully harden before turning. I warm the resin and molds before pouring. I heat the molds with the tubes inserted in them to help make sure there's no moisture. Make sure your hands are clean and don't handle the molds and or plugs that have mold release on them then handle the tubes. It might not be one big issue but a few small ones.

 

[JohnU]

Unfortunately there's no way of knowing exactly what lead to your issue with so many variables... type and age of resin, objects cast, time for curing, tool sharpness, aggressiveness of turning, heat generated, etc. I've had these issues with different blanks over the years. One thing I have found to help was not trimming the blank ends to the tube before turning. Try turning the blank down with the blank ends longer than the tube, so the end of your bushings are against the resin and not the end of the brass tube. Then after you get it turned down close to size, sand the ends down to the tube. I usually leave a 1/4" of resin at the ends when doing this. Sometimes the barrel trimmers can also be too rough and cause separation. Good luck !

 

[vtgaryw]

Unfortunately there's no way of knowing exactly what lead to your issue with so many variables... type and age of resin, objects cast, time for curing, tool sharpness, aggressiveness of turning, heat generated, etc. I've had these issues with different blanks over the years. One thing I have found to help was not trimming the blank ends to the tube before turning. Try turning the blank down with the blank ends longer than the tube, so the end of your bushings are against the resin and not the end of the brass tube. Then after you get it turned down close to size, sand the ends down to the tube. I usually leave a 1/4" of resin at the ends when doing this. Sometimes the barrel trimmers can also be too rough and cause separation. Good luck !

I use a jig on my disc sander to square the ends, and when you look at the ends, there's no apparent separation afterwards. Even trying to get it to suck a little thin CA in doesn't appear to do much. I might try leaving extra resin at the ends.

It seems that the smoother the tube, the more prone it is to the problem. I might try a clear coat, just anything to give the resin a little something more to bite into.

Gary