"tube in" mold idea

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jkeith

jkeith

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I made some molds out of HDPE and had some left over material so I had this idea of making a tube in mold. I turned some small removable inserts and fit them into a couple of removable blocks and also put a small bolt to apply some pressure. I guess the only real way to tell is to try casting something but I was curious if anyone has tried this before? Do you think it will work?
 

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I don't see why that wouldn't work ... just don't spill any casting resin on the screw !
 
Very similar to this one http://www.penturners.org/forum/showthread.php?t=150389 but with a screw I suppose. From a practical standpoint, I'm not sure the pressure from the screw is really needed. Just got my molds in from that kickstarter campaign and the silicone definitely holds plenty tight on its own. Now, for a do it yourself kinda person that wouldn't buy already made molds, I can see it being a cool option.
 
mckenziedrums said:
Very similar to this one http://www.penturners.org/forum/showthread.php?t=150389 but with a screw I suppose. From a practical standpoint, I'm not sure the pressure from the screw is really needed. Just got my molds in from that kickstarter campaign and the silicone definitely holds plenty tight on its own. Now, for a do it yourself kinda person that wouldn't buy already made molds, I can see it being a cool option.
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I was on the fence about the screw at first but ended up using it since the inserts were not pliable like silicone. There is really nothing to hold it in other than pressure from the outside. The blocks are pretty solid in the mold so maybe it was needed but I didn't want to chance it. It's really just finger tight to keep it from shifting


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"Has this been done before?"

Yes, it has. It comes down to the individual: DO I want to spend the extra time to cast around the tube and stop the ends up; Or is it more time efficient to cast solid and drill.

If you are selling the blanks, you will need to charge more for your extra time involved.

For me, things like this depend upon the situation and there are times that it is beneficial to cast around the tube and there are other times it is not.

If you are set up for that, go for it. There are cast blanks on some sites in which they were cast that way, and in general I think they are somewhat higher priced. The problem with pre-cast with tubes is that they cannot be used except for specific pens,- where as solid blanks can be drilled for any pen.
 
This should work just fine for you. When I first began casting I was doing something very similar but with left over pieces of resin instead of a screw. The only issue I see is using more resin than needed. It's not a problem but it cuts into profits if your selling blanks and trying to get as much out of your resin as possible. It also adds to your turning time having to remove the extra resin. That's why I switched to round vertical casting. They come out round without having to knock off those corners and I get a lot more blanks out of a can of resin. Just something to think about down the road. Good luck
 
Actually the screw Idea is a viable one if you are using hard plastic for the inserts. This was my idea for tube in castings,

tubein.jpg


The inserts are a self lubricating nylon so the resin does not stick, but they are hard and more often than not, the resin will seep in, especially when put into a PP. If you don't put them in a PP, air will leak out of one end and create bubbles at the seem.

Alumilite doesn't adhere well to the inside of the tube, so it usually pushes right out - but LD does stick to the brass and the last one I did, I wasn't sure if I could get it out without destroying the blank. It finally came out (and this was with a mold release) but I will wait for my KS purchase as mentioned above before I cast another.

As long as your cones are formed even, the screw idea should help seal up those joints without the need for soft silicone like the others.
 
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Just wanted to give an update. I was able to cast a label blank that is part of a Christmas present for my brother in law. The mold worked well. I will probably make smaller inserts since there is a lot of unused resin on the ends. Since its all made from HDPE it pops right out with no need for a release agent. Also, the screw is really not necessary and actually caused the first attempt to fail as I tightened it (finger tight) and it must have expanded the tube slightly. When I released the mold the tube went back to normal size and the cured resin stayed in place and created a small void. The second attempt I simply slid the end with the insert in place without using the screw at all. The sides of the mold holds everything tight under pressure and it came out perfect.

Honestly, if you do a lot of "tube in" casting its probably easier to just buy pre-made molds, but since I am an avid DIY'er, I am happy with it. Plus, I can use it on pretty much any size tube/kit. Let me know what you think, or if you have any questions.
 

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