Quality Pen
Member
I read a couple guides and tried a search but what I came across was pretty ambiguous. Basically, I am trying to figure out how many blanks you can make with a gallon of Clear Polyester Casting Resin.
Thanks.
Thanks.
How many pen blanks can 1 Gallon of PR make?
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Ed McDonnell
Member
One really big blank or.....
I cast rods that are good for one pen any kit (or any type custom I make) using about 1.5 oz of resin. Divide 128 by 1.5 subtract some wastage / spillage and lets call it 75.
I cast tube on blanks using about an ounce per two tube blank set. Less spillage and wastage, call it 100.
That's my experience. Really neat people with more efficient modls might get more. Sloppy people casting blocks with a lot of waste built in might get less.
By the way, tell all the IAP members you know to vote in the Russ Fairfield Contest.
http://www.penturners.org/forum/f228/vote-russ-119646/
Ed
Ed
I cast rods that are good for one pen any kit (or any type custom I make) using about 1.5 oz of resin. Divide 128 by 1.5 subtract some wastage / spillage and lets call it 75.
I cast tube on blanks using about an ounce per two tube blank set. Less spillage and wastage, call it 100.
That's my experience. Really neat people with more efficient modls might get more. Sloppy people casting blocks with a lot of waste built in might get less.
By the way, tell all the IAP members you know to vote in the Russ Fairfield Contest.
http://www.penturners.org/forum/f228/vote-russ-119646/
Ed
Ed
PSNCO
Member
If you're casting blocks about 40-45.
If you're casting in pvc pipe about 60-65.
If you're casting your first couple of gallons.....much much less. (Unless luck is on your side.)
I figured my 3x5 block mold contains 8.5oz and gives me 3 blanks
A 3/4" pvc pipe for a 5.5" blank is about 1.9 ounces
If you're casting in pvc pipe about 60-65.
If you're casting your first couple of gallons.....much much less. (Unless luck is on your side.)
I figured my 3x5 block mold contains 8.5oz and gives me 3 blanks
A 3/4" pvc pipe for a 5.5" blank is about 1.9 ounces
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PenMan1
Member
My goal is to get 250 blanks per five gallon bucket of PR. That works out to 50 blanks per gallon or 2.5 ounces per 7/8 x7/8x5 inch blank.
Sometimes I get more (due to embedded casting), sometimes less because of mistakes. But 50 blanks per gallon is a pretty close number.
Sometimes I get more (due to embedded casting), sometimes less because of mistakes. But 50 blanks per gallon is a pretty close number.
its_virgil
Member
divide 128 by the # of ounces in each blank. The answer will depend on the size of your blanks.
Do a good turn daily!
Don
Do a good turn daily!
Don
Quality Pen
Member
Oh sorry, I should add that it would be round pen blanks in PVC pipe. It seems like this method gives the least waste, no?
its_virgil
Member
Still depends on the pipe diameter and length of your mold. Fill one of your pvc pipe molds with water then pour into a measuring cup. Note the # of ounces then divide that number into 128 ( the # of ounces per gallon.
Do a good turn daily!
Don
Do a good turn daily!
Don
its_virgil
Member
(inner diameter of your pvc pipe) divided by (2)= radius of blank
(radius) x (radius) x (3.14159) x (pvc pipe mold length) = cubic inches in the blank
(cubic inches in blank) divided by (1.80469)= fluid ounces in blank
(128) divided by (fluid ounces in blank) = number of blanks per gallon
(radius) x (radius) x (3.14159) x (pvc pipe mold length) = cubic inches in the blank
(cubic inches in blank) divided by (1.80469)= fluid ounces in blank
(128) divided by (fluid ounces in blank) = number of blanks per gallon
Pjohnson
Member
I get 17 out of a quart - that would be 68 for a gallon.
Most of my blanks are 3/4 pvc 5 1/4" blanks.
Most of my blanks are 3/4 pvc 5 1/4" blanks.
BSea
Member
My experience is around 60 to 65, so I agree with these 2 posts. One thing that comes into play is how many blanks you pour at a time, and how many colors. More colors = more waste. More blanks you pour at a time = less waste.
firewhatfire
Member
PSNCO
Member
That would be what my wife said. It was easier to have her fill each different sized tube with water and then dump water from the filled tube into a measuring cup with fractional ounces listed. Then I marked the 5.5" tube "1.9oz", the 8.5" tube "2.5oz", etc.
She yelled at me that I was taking all the fun out of pouring by inserting math into everything.
its_virgil
Member
Someone else who napped during geometry in HS. What will we ever use this stuff for? Who would have thought it would be to calculate the number of pen blanks in a gallon of PR? :biggrin:
Don
Don
ronfinch
Member
So far......none! It's been sitting on the shelf for a very long time, having too much fun with Alumilite.
robutacion
Member
While this is also my goal, there can be a lot of variants, and those have to do more with size of the objects I put into the molds before I pour the resin. This obviously is not applicable if you are doing only all resin blanks.
These is no doubt that, round vertical molds use a fair amount less of resin, if the tubes are the minimum sizes require to make regular size pens however, the "saver molds" are beyond any doubt the molds that allow most blanks cast per litre.
I also account for 10% wastage at least, this can be the result of over filled molds, resin staying in the containers use to mix, spillage, oops and more oops. Blanks that didn't turn out any good and are put in the bin, don't count, obviously...!:wink::biggrin:
Cheers
George
Wood Butcher
Local Chapter Leader
May be easier to work from volume; there are 231 cubic inches in a U.S. gallon.
WB
WB
Also there is thin wall and thick wall pvc water pipe. Schedule 40 or 80?
PenMan1
Member
ROTFLMAO!
I KNEW the old math professor WOULDN'T "let it go" with just fill the tube with water and measure it, when a PERFECTLY GOOD volume equation opportunity presented itself:biggrin:
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its_virgil
Member
Always looking for those "teachable" moments Andy. Maybe it is time to dig out the Ideal Gas Laws and investigate just how much those pressure pots actually do compress air bubbles...
Do a good turn daily!
Don
Do a good turn daily!
Don
Quality Pen
Member
Do these matter? which is preferable? Thanks
steve worcester
Member
Every manufacturer will post the volume for the mix, you have to divide that (cubic inches) by the volume of your mold. I would also add a waste factor. Like when you mix up too much product to fill a mold.
BSea
Member
I use schedule 40 thats 3/4". That's the thick stuff. Blanks come out slightly thicker than 3/4.
Krudwig
Member
Can u use 3/4 cpvc the hot water PVC pipe ? If so does anyone know what size the rod would be?
Sylvanite
Member
PV=nRT
Ed McDonnell
Member
But you need to add the factors for increased solubility at increased pressure and how much was already in solution.....
Ed
Cmiles1985
Member
Pipe is measured as inside diameter, so no, the PIPE type does not matter for casting volume. If it's 3/4", it's 3/4". Tubing is a different story. It is measured as outside diameter.
Cmiles1985
Member
Having mentioned the ideal gas law, how truly effective is pressure at only 40 psig? Would it help if the pressure pot were cooled with dry ice or liquid argon (assuming some of us may have access to that). With PR/Alumilite, would a vacuum help to actually remove the air rather than compress it? What does the vacuum do to the quality of the polymerization mechanism?
Sorry my inner chemist is coming out!
Sorry my inner chemist is coming out!
Mason Kuettel
Member
That would be in "unit 9." I will be teaching that to my 9th grade geometry students in about 2 weeks, may just have to bring this topic into my classroom and let them try some casting (probably not PR!).
Quality Pen
Member
Good thing I still have that spectrophotometer and gas chromatograph lying around! I should be casting PR blanks in no time now!
its_virgil
Member
Personally, I think that pressure for casting polyester resin works more to keep air in solution than it does to reduce the bubble size.I t is similar to carbonization...pressure keeps the carbon dioxide dissolved in the solution and when the cap is removed the bubbles start to "fizz". The pressure just does not allow air in solution to escape and form bubbles. I know others will disagree.
Boyle's Law: At constant temperature, as the pressure on a gas increases its volume decreases at the same rate. If the pressure is increased by a factor of two then the volume decreases by a factor of 1/2. Double one and the other is cut in half. Triple one and the other is cut by 1/3. You get the idea.
According to my calculations if I place a polyester resin casting in a pressure pot at twice the normal air pressure (approx 30 psi) then the volume decreases by one half if the temperature remains constant. One would think the "size" would be cut in half but the actual size is only reduced by about 20%. The radius of the bubble used in my calculations decreased from 2 units to 1.6 units.
Granted, the bubbles in our castings are very small and a 20% reduction in size would appear to be a helpful. Another pressure doubling would reduce the size by anther 20%.
As the polyester resin cures heat is produced and the constant temperature of Boyle's law is out the door. Charles's law states as the temperature increases a gas at a constant volume will increase in pressure. Our little bubbles are not at a constant volume so I must assume the volume will increase from the temperature rise in the curing process. I will also assume that the bubbles will either float to the surface or burst as they get larger.
I am no science person so if my logic is incorrect please correct me. I know my calculations in Boyle's law are correct as long as the temp is constant. Confusing isn't it? Have fun thinking about this.
Do a good turn daily!
Don
Boyle's Law: At constant temperature, as the pressure on a gas increases its volume decreases at the same rate. If the pressure is increased by a factor of two then the volume decreases by a factor of 1/2. Double one and the other is cut in half. Triple one and the other is cut by 1/3. You get the idea.
According to my calculations if I place a polyester resin casting in a pressure pot at twice the normal air pressure (approx 30 psi) then the volume decreases by one half if the temperature remains constant. One would think the "size" would be cut in half but the actual size is only reduced by about 20%. The radius of the bubble used in my calculations decreased from 2 units to 1.6 units.
Granted, the bubbles in our castings are very small and a 20% reduction in size would appear to be a helpful. Another pressure doubling would reduce the size by anther 20%.
As the polyester resin cures heat is produced and the constant temperature of Boyle's law is out the door. Charles's law states as the temperature increases a gas at a constant volume will increase in pressure. Our little bubbles are not at a constant volume so I must assume the volume will increase from the temperature rise in the curing process. I will also assume that the bubbles will either float to the surface or burst as they get larger.
I am no science person so if my logic is incorrect please correct me. I know my calculations in Boyle's law are correct as long as the temp is constant. Confusing isn't it? Have fun thinking about this.
Do a good turn daily!
Don
Cmiles1985
Member
Nice... I didn't think about solubility of gas in the liquid resin. With heat being the vehicle of the polymerization reaction, I guess a small pressure increase wouldn't do much. It's all fun and interesting to me given my chemistry background and the fact that I'm building a pres/vac pot.
BSea
Member
Math is great, but real world works for me. I poured 72 blanks today. And that was just over a gallon of resin. Most were 2 color pours, so I got a little more than the 65 blanks I would normally expect.
Edit: One thing to consider about the bubbles. The blanks don't get very hot until after the resin has set up. It's still tacky, but I doubt bubbles would be able to expand at that point.
Edit: One thing to consider about the bubbles. The blanks don't get very hot until after the resin has set up. It's still tacky, but I doubt bubbles would be able to expand at that point.
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kirkfranks
Member
Don,
You made my head hurt. Now where is my Maple Burl blank?
You made my head hurt. Now where is my Maple Burl blank?