Tube Casting Problem

[PTownSubbie]

Alright, I cast some blanks in some tubes the other night. I poured, post cured and popped them out no problem. It was great.

I poured another set yesterday. I followed the same process but today they won't come out for anything. I have pounded the s*#& out of them but they won't budge.

I am using SCH-40 pipe.

Any ideas how to get these out without turning them out?

Can you perform multiple casts from the same pipe or do you coat them with something or how do you clean out any leftover stuck to the walls after a cast?

Does SCH-40 work as good as ABS pipe?

Thanks!!

 

[Druid]

You may want to try a release agent the next time, I've used butchers wax succesfully. But then again, I no longer use any type of pipe for pouring anymore.

 

[dalemcginnis]

I've used PVC without any type of coating and have always been able to get them out. Sometimes easier than others but never so hard I thought I was going to have to cut the pipe off. Usually I just slip a dowel in the space at the top of the tube and bang it on my concrete floor like I do when I'm trying to disassemble a pen.

 

[RHunter]

Fred,

I had the exact same problem. I use Schedule-40 PVC to cast blanks in (why make square just to turn around and make 'em round?)

The first set in the mold slid right out. The second set stuck like no one's business! I had to destroy the PVC by hammer and chisel to get the blank out. Not a good idea in hindsight. I must have nicked the PR Blank inside 'cause the first time I hit that spot with a skew -BAM! Big time catch, big gouge, chunks everywhere...

Solution? I use PAM (well the Food Lion version with flour). Spray the inside of the PVC liberally- yes it might drip out. Yes it will make "roots" on the outside of the blank (so what- you turn that part off anyway). Finally yes, the blank will be "greasy" once it comes out of the blank- and it will slide right out onto the floor if you are not careful- again, so what, wipe it down with DNOH or Acetone.

-Doug

 

[snyiper]

I would think of using Johnsons paste wax and put it on a shotgun swab and run it in and out the mold till it has a film I bet this will make things slide. Now bear in mind I have never cast anything but I do plan to and this is one of the things I was contemplating. I want to use the pvc as well. Another idea was to split the pvc with a saw (table saw or dremal works great) put together with a couple hose clamps and push on the end before pouring when cured, loosen the clamps and push her out. If you are worried about slight leaking I am sure a strip of painters tape on the inside of the seam would do nicely. Just my thoughts for what its worth...

 

[KenV]

I do bedding of firearms and use either a mould release or pam to get them apart more easily. sometimes a trip to the freezer for differential changes of dimensions are needed to free up a catch.

Pam is a vegetable wax in a food safe solvent. Cheap and available

 

[PTownSubbie]

Thanks for the feedback. I was hesitant in using PAM because I thought it might contaminate the casting but if nobody has had any problems then I might give it a go.

I will also try to freeze the blanks to see if I can free them tonight.

 

[Tim'sTurnings]

I would try the post cure again. I presume you are using a toaster oven? I had that same problem and I re-cooked the thing and the PR shrunk enough to come out.

 

[PR_Princess]

Fred, I tried casting in PVC, but gave it up. The first few pours per mold were OK. But I found that the PR would eventually etch or corrode the smooth surface of the PVC. If you poured into a mold that had been so etched - you were done. No way was it coming out. As always, YMMV!!

 

[PTownSubbie]

I would try the post cure again. I presume you are using a toaster oven? I had that same problem and I re-cooked the thing and the PR shrunk enough to come out.

I will try the post cure one more time. I can see some seperation between the cast and the tube but it is not all the way around the pour.

Wish me luck!!

 

[PTownSubbie]

Well, I must have something that I am doing differently than others. I tried the pam with high hopes....... I guess you can tell from my tone that it didn't work. They still stuck like nothing was there.

Those that use pam cooking spray, do you cast under pressure? I am wondering if that is causing the amount of shrinkage that normally is seen from PR from happening because as it shrinks, it is filled by non cured resin?

Is that even possible? BTW, with these castings I was using 60psi to ensure all voids were filled.

To the drawing board. I am going to design my own silicone casting tubes. A couple of different sizes of PVC and I should be able to get a good mold. I will keep you all posted.

 

[RHunter]

Fred,

I do cast under pressure, about 70psi in the HF PP. I let it cure in the pot 24hrs, I cast after the kids go to bed, and don't get back until the next night.

I pull out of the pot, extract the blank, then post cure in the toaster oven for about an hour (140-150F).

Now for my mold, I use an end cap, so I get a bottom "knuckle" that is actually a larger diameter than the pvc tube, so I can grip this with a pair of channel lock pliers, but I haven't need to yet.

I'm at a loss as to why you are still having a sticking problem. :frown:

I spray enough PAM in the tube to almost pour out if you invert the mold... Now I do use PAM with flour (and there are some here that dust their molds with Baby Powder to act as a mold release...maybe that is what is working for me and the PAM is just the transfer agent?

Best of luck!

-Doug

 

[NewLondon88]

Now I do use PAM with flour (and there are some here that dust their molds with Baby Powder to act as a mold release...maybe that is what is working for me and the PAM is just the transfer agent?

No, the Pam is still acting as the release. The powder is used to break the
surface tension so you don't end up with air bubbles on the walls of the
mold.

 

[PTownSubbie]

Well, I haven't given up yet on the PVC because the thought of creating a negative to make a mold is not on the priority list right now.

I went by my supplier of resin and picked up an actual mold release spray. I am going to give it another shot. Maybe I will get to it over the long weekend.

I am just very very frustrated right now to know others can make it work but I can't.

Anyway, Doug if I can't make it work with this mold release I will try PAM with flour. Our method seems to be the same. The only difference is that I started using a new resin pigment. I wonder if that could be causing any differences. I guess I need to cast two test runs. One with the old pigment and one with the new pigment. I just can't see the pigment being the cause......

 

[NewLondon88]

Fred.. you are using fresh PVC for these, right? Once that surface has any texture
to it, it is done as a mold. (ref. Dawn's post)

 

[PTownSubbie]

Yeah. Brand new off the shelf.

I keep scratching my head. Seems like it should work fine but then again....Nothing should be hard right? Wait, I think it is nothing is easy....

 

[thewishman]

I had a friend cast some in PVC. Used the arbor press (that I assemble my pens with) with a spacer and it popped out. It took some effort, but a ton of pressure makes a difference.

 

[RAdams]

I think it is the PR you use, my Brother from another Mother...

That stuff gets hotter than Silmar41, and i think that is causing the resin to fuse to the sides of the pipe. Either that, or it doesn't shrink as much. I have been using the same handfull of PVC for molds since i started with pvc weeks ago. And i have a BIG stack of blanks made right now (about 100 i guess) I did notice that two of them were extremely difficult to get out, but then i also noticed that these two specific pieces of pvc were wrapped in electrical tape. When i first cast in pvc, i thought the process was going to split the pipe, so i wrapped a couple in tape, but it doesnt so i will remove the tape and i am sure those two molds will work fine next time.

The blanks do form a little scab on the bottom covering the blank and the bottom of the pipe, but a good smack with a hammer breaks the blank free, and with a little sweet talking with a drift and hammer, they come right out. I use the flat end of a chisel and be careful not to booger up the walls of the molds. In fact, I think i am gonna go mix a batch right now Just for fun!

 

[RAdams]

Arbor press? got pics?

I had a friend cast some in PVC. Used the arbor press (that I assemble my pens with) with a spacer and it popped out. It took some effort, but a ton of pressure makes a difference.

 

[Glass Scratcher]

Aren't you using the S40? It does accerate to a higher temp than S41. Stoner's or Ease Release, or molding Wax #9, even buffing in some high carnuba content car wax, on a shotgun buff should work. You may need multiple coats of wax buffed on.

 

[edman2]

Arbor press? got pics?

Here is one. It is the smaller one (I have one). Some like the larger one because the throat is taller. More pressure than you need but it does work. I use mine all the time.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=3552

 

[PTownSubbie]

Aren't you using the S40? It does accerate to a higher temp than S41. Stoner's or Ease Release, or molding Wax #9, even buffing in some high carnuba content car wax, on a shotgun buff should work. You may need multiple coats of wax buffed on.

That's the direction I am going to try next. I bought some Smooth-On mold release and need to get some more PVC pipe. I destroyed all of mine with the last pour.

 

[Jgrden]

Air

See that little bubble of air? How do I keep this from happening?

 

[PTownSubbie]

View attachment 20045See that little bubble of air? How do I keep this from happening?

Sit with your cast while it is curing. Have a piece of small diameter material (wire) and when the bubbles form, use the wire to remove them from the surface. This will move them off of the label.

Another tip is to put the label on the tube and let it sit for at least 24 hours. This has a tendancy to work out any air from under the label.

 

[Glass Scratcher]

That's the direction I am going to try next. I bought some Smooth-On mold release and need to get some more PVC pipe. I destroyed all of mine with the last pour.

You also may want to try like someone else mentioned, cut the pipe in half down the length, and tape it together with some duct tape or even blue painters tape, after curing , pull the tape and pop apart with the edge of a screwdriver.

You should still use the mold release though.

 

[NewLondon88]

I know that if you turn the resin before it is fully cured (not just hardened) it can
twist, causing some separation between the tube and label. That can cause an air
bubble in a part that looked fine before you started. I'd probably leave the blank
for a few days after casting to make sure.

Some casters also paint the label with un-catalyzed resin before they pour.

 

[PTownSubbie]

You also may want to try like someone else mentioned, cut the pipe in half down the length, and tape it together with some duct tape or even blue painters tape, after curing , pull the tape and pop apart with the edge of a screwdriver.

You should still use the mold release though.

The problem is I use pressure with these molds due to added objects and I don't want any air bubbles.

I have tried tape on the bottom but it leaked all over the pot.

 

[NewLondon88]

The problem is I use pressure with these molds due to added objects and I don't want any air bubbles.

Try warming the resin in a bath. Put your container of resin in a pan of
warm water. That thins out the resin so the bubbles rise to the surface
much easier.

There's a TON of good information in Don Ward's post about this.

http://www.penturners.org/forum/showthread.php?t=48807

 

[Glass Scratcher]

The problem is I use pressure with these molds due to added objects and I don't want any air bubbles.

I have tried tape on the bottom but it leaked all over the pot.

Sounds like a job for Oomoo.

 

[ed4copies]

I think it is the PR you use, my Brother from another Mother...

That stuff gets hotter than Silmar41, and i think that is causing the resin to fuse to the sides of the pipe. Either that, or it doesn't shrink as much. I have been using the same handfull of PVC for molds since i started with pvc weeks ago. And i have a BIG stack of blanks made right now (about 100 i guess) I did notice that two of them were extremely difficult to get out, but then i also noticed that these two specific pieces of pvc were wrapped in electrical tape. When i first cast in pvc, i thought the process was going to split the pipe, so i wrapped a couple in tape, but it doesnt so i will remove the tape and i am sure those two molds will work fine next time.

The blanks do form a little scab on the bottom covering the blank and the bottom of the pipe, but a good smack with a hammer breaks the blank free, and with a little sweet talking with a drift and hammer, they come right out. I use the flat end of a chisel and be careful not to booger up the walls of the molds. In fact, I think i am gonna go mix a batch right now Just for fun!

Remember you did all of this, when some of the blanks have hairline cracks in the finished pen. Or when they shatter while you are turning them.

DAMHIKT!!!

This is why we abandoned PVC.

 

[RAdams]

I do have a couple of blanks that i am worried about. They will probably explode when i try to turn them which will be exciting no doubt! I think the rest of them will be good though. I haven't had any problems yet.

 

[ed4copies]

I DO wish you luck, but I was perplexed for a while--NOW it seems so obvious!!

 

[PTownSubbie]

Try warming the resin in a bath. Put your container of resin in a pan of
warm water. That thins out the resin so the bubbles rise to the surface
much easier.

There's a TON of good information in Don Ward's post about this.

http://www.penturners.org/forum/showthread.php?t=48807

Since Don has posted about his no bubble casting, I haven't used my pot with the exception of stabilization and these special blanks.

I did a pour tonight with no pressure. We will see if I can get all the voids filled.

 

[follow3]

Fred, I tried casting in PVC, but gave it up. The first few pours per mold were OK. But I found that the PR would eventually etch or corrode the smooth surface of the PVC. If you poured into a mold that had been so etched - you were done. No way was it coming out. As always, YMMV!!

Hey Dawn,

What do you use for molds now?

Thanks,
Steve