Casting material

[hombre4]

Hi All, The casting resin I am using has been shrinking quite a bit. Question: What is everyone using and where are you getting it?


Thanks....Archie

 

[bkersten]

I get mine from Moore's and Michales - Cast n Craft PR. Not sure how much you mean it shrinks. Mine do at the ends a little but not enough to
make a change in the length of the tube &, nor from around the tube to cause it to brake hold and slide out.

 

[PTownSubbie]

Most people use Silmar 41. I use Silmar 40 because I can get it locally.

Most people buy from US Composites. I think a gallon with shipping runs somewhere close to $50.

Do a search through this forum. There are more specifics on where they purchase.

I would also check with local boat repair shops and see if they carry clear casting resin. That is how I found my Silmar 40 supplier. Those phone calls save me almost $15/gallon because I don't have to pay shipping and I am supporting a local small business owner!

 

[its_virgil]

Everyone is using either polyester resin or alumilite. Polyresin shrinks. alumilite does not. Both have their place in the casting realm. What is the problem with the shrinkage you are having? It must be with the length of the cast since I can't think of a reason shrinkage in diameter or cross section would present a problem....most of it gets turned away and ends on the floor.
Do a good turn daily!
Don

I did not comment on where to get products because others helped you out with that.

Hi All, The casting resin I am using has been shrinking quite a bit. Question: What is everyone using and where are you getting it?


Thanks....Archie

 

[bruce119]

Hi All, The casting resin I am using has been shrinking quite a bit. Question: What is everyone using and where are you getting it?


Thanks....Archie

Are you using pressure and a silicone or flexible mold. If so most likely the mold is being squeezed and it gives the appearance the resin is shrinking this happen to me and I thought for about a year that the resin was shrinking but it was the mold. Now PR does shrink a little but not a lot.

Need more info on what you are using and your process. Just about everything effects PR casting.

Good luck

 

[hombre4]

Thanks to all for your response. I am using Castin'craft Clear liquid plastic casting resin for Michaels. I am using the resin savor molds and a pressure pot with 60 lbs. of pressure. When hardened the tubes are protruding from both ends. I am able to use them (Sierra) because the pen kits are somewhat forgiving, but I do need to find my problem and stop the shrinking. All kits may not be as forgiving.

Thanks...Archie

 

[jttheclockman]

Thanks to all for your response. I am using Castin'craft Clear liquid plastic casting resin for Michaels. I am using the resin savor molds and a pressure pot with 60 lbs. of pressure. When hardened the tubes are protruding from both ends. I am able to use them (Sierra) because the pen kits are somewhat forgiving, but I do need to find my problem and stop the shrinking. All kits may not be as forgiving.

Thanks...Archie

Wow 60 lbs of pressure with resin saver molds??? Are these Charlie's molds??? I hjave to say that is way too high of pressure even if you were not using the molds. If I were a betting man I would say what is happening is the pressure is pushing the resin more toward the center of the tube because the mold is expanding. The ends are digging into the edges of the mold.

I am sure Charlie could shed some more light on this if these are his molds.

 

[bruce119]

Thanks to all for your response. I am using Castin'craft Clear liquid plastic casting resin for Michaels. I am using the resin savor molds and a pressure pot with 60 lbs. of pressure. When hardened the tubes are protruding from both ends. I am able to use them (Sierra) because the pen kits are somewhat forgiving, but I do need to find my problem and stop the shrinking. All kits may not be as forgiving.

Thanks...Archie

I have very good experience with this very problem and mentioned it several times on the forum. YOU CAN NOT USE PRESSURE WITH A RESIN SAVER MOLD at more then 10 psi. I am working on a modification so you can use these molds with pressure. I have destroyed at least 3 molds before I figured it out. Now you have cut deep into your mold and soon you will tear out your plug. As I said the resin is not shrinking your mold is. What is (I believe) happening is when pressure is applied air is squeezed I know this from SCUBA now 60 psi is a lot. I use 60psi when I do my shredded money. So what is happening to your mold there is a LOT of air in the mold little tiny air bubbles then when you pressurize it the mold shrinks and squeezes the resin sets and you think the resin shrunk the mold returns to it's original shape after the pressure is relieved. Now look closely at your plugs in the mold grab them and move them a little you will see just how deep you cut them.

Now what to do.... You have to change the way you think to use these molds. I love the resin savers. What I do now is cast without pressure you can do good casting if you casting something like a label something flat. You did not say what you are casting. I preheat the resin with hot tap water that is the PR in a cup in a pan of hot water about 100f then I also preheat the mold to about 150f. I was using ultra sonic and I have stopped that I have not had a failure in the last 200-300 blanks I made. Use less MEKP when you heat it 3-4 drops per once.

Now there are time when you need pressure. I am facing that problem rite now myself and have to figure a way to use the RS mold with pressure. I came up with 2 ideas first and best is to fill the tube with something and just leave enough space on the ends to fit the plugs into so they don't push into the tube. A potato would probably be the easiest pushed into the tube and cut so it is receded about 1/4" inside the tube. I thought about modeling clay but it melts and liquefies at about 100f so that is not good. another thing I tried and it worked OK is to make a like washer. I used thin styrene cut it round so it will fit into the mold now punch a hole into it the the size of inside diameter the tube. That way it sets against the end of the tube keeping it form cutting into the mold.

I have other ideas but it would require redesigning the mold to use under pressure. I can and will make my own molds when I have time I just don't yet. Basically the same style mold just a little bigger with more room and you could work with it more easily.

Well I said enough and too much but hopefully I helped solve some of the mystery and helped someone.

Bruce

 

[jttheclockman]

Bruce, why not just cut a piece of dowel amd insert in the tube. You maybe able to make it a smidge longer than you need so you strtetch the plugs out ever so slightly.

 

[bruce119]

Bruce, why not just cut a piece of dowel amid insert in the tube. You maybe able to make it a smidge longer than you need so you strtetch the plugs out ever so slightly.

Yes I have done that or similar. Only problem when you stick something inside the tube and then go under pressure chances are good that PR is going to leak past the plugs. So you have to think about that you wouldn't want the tube to fill or even 1/2 fill with PR and have a dowel in there too. I know just drill it out. Well I had this very thing happen tube 1/2 full of PR tried to drill it out and you can't keep the drill on center it wants to cut into the tube. Best to keep the resin out of the tube so think something that plugs the tube firmly except for the last 1/4" if/when resin leaks by you can easily clean it up from the ends wit a X-acto knife.

Hope that makes sense.

.

 

[soligen]

I havent cast on tubes yet, but thinking about it. Would a drop of CA at the plug/tube joint seal things up to prevent the PR leaking in? Dowels just seem handy as once cut to length they can be re-used.

 

[jttheclockman]

don't use ca

 

[bruce119]

I havent cast on tubes yet, but thinking about it. Would a drop of CA at the plug/tube joint seal things up to prevent the PR leaking in? Dowels just seem handy as once cut to length they can be re-used.

As was said don't use CA it will ruin your mold. What would work and is something I have done is take a rubber cork now grind shape it so it fits tight in the tube make 2 of them one for each end now push one in a 1/4 deep into the tube take a wooden dowel that will slip into the tube cut it to length so that when the other plug is pushed in it will be in 1/4" and can not be pushed in farther due to the enclosed dowel. Now put your blank into the mold that will prevent the mold's plug from being pushed in by the pressure when casting under pressure. Also if/when the mold's plug leaks it will only seep in to the plug you previously installed. Then you only have a little bit of resin to clean up afterward. The rubber cork you shaped can easily be pushed out and reused.

That was a fairly detailed description of what I have tried and had some success.

.

 

[jttheclockman]

Bruce, I am not following what you are trying to. I lost you somewher. I cast all the time and use silicon corks. This was my old method. I am trying the new resin saver molds but I am finding out they will not be good for all my casting because i need to leave some overhang of material and turn it away later.

With the rubber corks there is a very tight seal. very rarely does resin get by and this is due to worn cork or I did not seat well.

 

[bruce119]

Bruce, I am not following what you are trying to. I lost you somewher. I cast all the time and use silicon corks. This was my old method. I am trying the new resin saver molds but I am finding out they will not be good for all my casting because i need to leave some overhang of material and turn it away later.

With the rubber corks there is a very tight seal. very rarely does resin get by and this is due to worn cork or I did not seat well.

I too am having trouble with the resin savers. There a great concept but no good when it comes to pressure casting. I know I wrote a lot but I am using rubber corks sanding them down a bit so I cam push them into the tubes they serve 2 purposes they seal the tube and keep the mold's plug out where they belong keeping the pressure from forcing them in. And then you will have the overhang just as if you did not use pressure. I think the resin saver molds could be engineered just a little different for pressure casting a little more room that would mean more resin and make the plug with a taper that mite seal them a little better. I got a few more ideas and plan on making some of my own molds but just can't find the time.

.