PVC Help

Signed-In Members Don't See This Ad
micharms

micharms

Member
Joined
Nov 8, 2004
Messages
681
Location
Port Elgin, Ontario, Canada.
I've gotten lots of good feedback before on my problems with casting bottlestopper blanks in PVC. I want to give it a try again but thought I'd slice the tubes so a screwdriver or something could be inserted to pry things open. I'd seal the slit with tape. But hears what I got to thinking - what about cutting the tube in half and sealing both sides together with tape and then do the pour? I would think that would be even better than just a slit on one side. Any opinions would be greatly appreciated.

Thanks
Michael
 
Signed-In Members Don't See This Ad
Michael,

I for one have had nothing but trouble making PVC molds for my PR castings. So, I think you should cut both sides. Should make the removal so much easier and the pipe should be able to be reused. If you cut either side, keep in mind that the final diameter of the blank will not be as large as you originally measured the pipe at. You take away the saw kerfs when you squeeze the pipe cuts back together...

I stopped using PVC and made some silicone round molds. The PR never gets stuck and they are reusable with perfect results every time...
 
micharms said:
Thanks Fred. I'm not concerned about the small loss in diameter since I've given myself lots of leeway with the pipe.

What did you use to build your molds around?

Michael
Click to expand...

Product called OOMOO silicone. Link: http://www.smooth-on.com/OOMOO=-Silicone-/c1136/index.html?catdepth=1

The 25 is more pliable than the 30. That is pretty much the only difference.

I took a piece of 1/2" PVC and turned down a piece of wood to plug one end. Centered it in the middle of a 1-1/2" PVC pipe and poured the silicone between the two of them. Makes a nice 3/4" round verticle mold.

If you have any more questions let me know.
 
Fred:
Two more questions then. Is your mold a hollow tube or did you have the plugged end of the 1/2" pipe at the top and poured enough to cover that over? Does that make sense?

The website doesn't tell you how much is in the trial size - how many molds can you make with it or did you go whole hog and buy the gallon size?

Thanks
Michael
 
micharms said:
If I'm going to cut the pipe in half, what is the safest way to do that - bandsaw?

Thanks
Michael
Click to expand...

Did mine on my table saw. One side at a time with the blade only high enough to cut the thickness of the PVC piping. I used a long clamp to hold the top of the pipe so that no body parts got close to the blade.

BE CAREFUL when you try this. The piece could roll and jam into the blade. That's why I supported it with the clamp and stayed as far from the blade as possible.
 
micharms said:
Fred:
Two more questions then. Is your mold a hollow tube or did you have the plugged end of the 1/2" pipe at the top and poured enough to cover that over? Does that make sense?

The website doesn't tell you how much is in the trial size - how many molds can you make with it or did you go whole hog and buy the gallon size?

Thanks
Michael
Click to expand...

The trial size is enough to do 2-3 molds depending on the length you are making.

My molds have one end that is sealed. It is done by making the inner pipe shorter than the surrounding pipe and then pouring silicone above the level of the inner pipe. This will make a sealed bottom. You have to plug the inner pipe tough. I will go take some pictures and post them.
 
micharms said:
Thanks Fred. That answers all my questions for now.

Michael
Click to expand...
I use 3/4 PVC pipe for all of my molds for pen blanks. I pour Alumilite mostly and at first they slid right out then after the third pour I had to use a 12 ton press to remove them. I called Alumilite and they sold me a can of silicone spray called "Stoner". I spray some on a cotton ball and swab the pipe and I have not had any more problems. I seal the bottom of the pipe with duck tape, I cut a piece of tape big enough to cover the end and go up the side about an inch then I wrap a 1/2" piece around the pipe real tight to make a complete seal. All of my casting is done in a pressure pot at 60 psi and I have only had one or two that have leaked. After curing I remove the tape, Place a wooden dowel on top of the blank and tap it with a dead blow hammer and they slide right out. I have used this method with pipe up to 2" and have had great results. I cut my pipes at 6" pour to about to about 5 1/2" and the pressure seems to condense it to about 5 1/4" .
 
Thanks Max. I'm pouring bottlestoppers right now and I'm using 1 1/2" pvc and PR. The first pour worked well - slid right out. Second not so good. Had to bang them out and of course they were filled with cracks that made them unusable. They were some nice coffee blanks and rotini blanks too!:frown: People keep talking about PR shrinkage but the stopper blanks seem to be tight to the pipe.

I wonder if just plain old silicone spray will work as a release - guess I'll try that and see since I have 2 cans of it here. I'll maybe try a small pour tomorrow and see how things work out. That means there may or may not be photos cuz maybe it didn't happen if it doesn't work out.:wink:

Michael
 
micharms said:
Thanks Max. I'm pouring bottlestoppers right now and I'm using 1 1/2" pvc and PR. The first pour worked well - slid right out. Second not so good. Had to bang them out and of course they were filled with cracks that made them unusable. They were some nice coffee blanks and rotini blanks too!:frown: People keep talking about PR shrinkage but the stopper blanks seem to be tight to the pipe.

I wonder if just plain old silicone spray will work as a release - guess I'll try that and see since I have 2 cans of it here. I'll maybe try a small pour tomorrow and see how things work out. That means there may or may not be photos cuz maybe it didn't happen if it doesn't work out.:wink:

Michael
Click to expand...

Some people have used PAM cooking spray. Don't use anything with water in it. PR and water don't get along.
 
Dry silicone will work, but are you useing SCH 120? You need to use SCH 40, the 120 distorts with the temps. and the blanks get stuck. With the SCH 40, nothing is needed to release the blanks. They slide out when cured. Also keep in mind, that when pvc or cpvc heats up, it gives off dioxins that are linked to cancer.
 
it's sch 40 but it only slipped out the first time. Subsequent casts stuck like crazy.

The cast is on hold until at least after the weekend. Unfortunately my PR had gone bad and I don't live anywhere near a store that carries it. My dear sweet wife reminded me of what an expensive loss that was. Heading for London, Ontario (just to keep things clear) on Sunday so might have to see if Michael's has a deal for me.

Thanks for all the suggestions and help.
Michael
 
micharms said:
Thanks Max. I'm pouring bottlestoppers right now and I'm using 1 1/2" pvc and PR. The first pour worked well - slid right out. Second not so good. Had to bang them out and of course they were filled with cracks that made them unusable. They were some nice coffee blanks and rotini blanks too!:frown: People keep talking about PR shrinkage but the stopper blanks seem to be tight to the pipe.

I wonder if just plain old silicone spray will work as a release - guess I'll try that and see since I have 2 cans of it here. I'll maybe try a small pour tomorrow and see how things work out. That means there may or may not be photos cuz maybe it didn't happen if it doesn't work out.:wink:

Michael
Click to expand...
The way it was explained to me is:: when the PVC is run through the extruder it has a release agent that prevents it from sticking. The first time you use it, you use up most of what was left over, :biggrin: the next time the two plastics try to bond :confused: the third time (12 ton press) I was lucky to get it out. :beat-up: FORTH TIME I had to turn the PVC off with a round nose scraper. :devil:. That's when I Called and talked to the girls at Alumilite and she said I needed "Stoner", the can cost $8.00 but I have been using it for about 6mos. (30-40 blanks) and I still have about 1/2 a can left. I was using 2" pipe and making a rod to slice pendent blanks out of.
 
I'm almost fearful to try alumilite since it sets so quickly - I'm not as young as I used to be:frown:

My biggest problem is I don't live close to anywhere that has either PR or alumilite although supposedly sometime in the future we are actually going to get a Michaels.

Oh well I guess there is lots of wood to turn to keep busy.

Michael
 
micharms said:
I'm almost fearful to try alumilite since it sets so quickly - I'm not as young as I used to be:frown:

My biggest problem is I don't live close to anywhere that has either PR or alumilite although supposedly sometime in the future we are actually going to get a Michaels.

Oh well I guess there is lots of wood to turn to keep busy.

Michael
Click to expand...
The Alumilite people are a whole lot closer to you than me but they are in the same country, so shipping is easier. If all else fails, Make your pour a little fat and turn the PVC off between centers.
 
With PR I have cast over 100 blanks in 1 pvc mold and still was able to use it. I've never had PR stick to pvc SCH 40.

As for your resin going bad...I just cast a couple blanks with some resin I've had for a year and it was fine. It turned no different than any of my other blanks.
 
DozerMite:
I know people like you have had great success with the pvc but one cast was all I got before things stuck really badly. I don't know what could be different but that was my experience.

As far as the PR going bad - it is a semisolid mass in the can. I had it stored in my workshop which is pretty cool compared to the rest of the house but it was only a partial can and was probably a year old before I initially opened it. It was my fault. I knew I was trying to keep it too long but things just got in the way of finding the time to cast and finish off the can.

Thanks for the input.
Michael
 
You must log in or register to reply here.
Back
Top Bottom