Building a vacuum table.

[Jerry]

That was very instructive Don. I have been waiting until the heat is such that there is a much larger sag in the plastic in the frame before taking it out of the oven. My results are as you describe in your last sentence.

I had a question about joining the corners of the frame but edited it out when I looked back and saw that they were cut from a single sheet of plywood. Any special type of material? Whenever I try cutting something that thin with ordinary plywood, I frequently will get chips out of the top layer in places.

Looks like it is time to dig out the saber saw. Your frames are much thinner that what I have been using. It is snowing and everything is shut down for the day so this looks like a good project.

I enjoyed the video, thanks for doing it.

Jerry

[dfbowers]

Hey Jerry. I know what you mean about cutting plywood. Try going with plywood with one finished side and cut it with a fine tooth saw. Or.. you can cover the surface of the wood with masking tape. That helps minimize splintering too.
Don..

[golfnut]

Don, inspirational as ever. Never seen it done before - moving pictures are worth a million words. Legend

Steve

[Jerry]

Don,

How do they ship those 48"X 96" sheets referenced in your link? Will they cut them to smaller size or just roll it up into a tube? I like the price compared to what I have been paying for smaller sized sheets from Micro-Mark.

Jerry

[joop]

Yeah, prices are unbelievable... the only distributor I found in The Netherlands for ABS sheets is farnell. They charge 4 times the price.

Anyone know a firm in Europe who sells 1.5mm ABS sheets for a good price?

[dfbowers]

Don,

How do they ship those 48"X 96" sheets referenced in your link? Will they cut them to smaller size or just roll it up into a tube? I like the price compared to what I have been paying for smaller sized sheets from Micro-Mark.

Jerry

They roll it up in a tube - about 48" x 12". I was originally buying 6 sheets - 16" X 16" from Micro Mark as well, and thats' OK of you don't want to make more than 6 coils. U.S. Plastics sells the same thing for 1/3 the cost, but shipping is still a killer. I can get 18 sheets from U.S. Plastics for the same cost.

[Jerry]

They roll it up in a tube - about 48" x 12". I was originally buying 6 sheets - 16" X 16" from Micro Mark as well, and thats' OK of you don't want to make more than 6 coils. U.S. Plastics sells the same thing for 1/3 the cost, but shipping is still a killer. I can get 18 sheets from U.S. Plastics for the same cost.

Thanks for posting all of this good information. You certainly set a high standard for all of us to follow.

Jerry

[dfbowers]

Here are a few tricks that I have learned and hopefully this will help keep builders from unnecessarily wasting material.

1. Drill an air hole in the center of your pattern - It will help the vacuum to draw air out of some of those tough places!

2. Place your pattern on a group of coins. It helps the system remove air quickly.

3. Removing your pattern - Do not try to pry the pattern out of plasitic. Just tap the edges of the plastic on a table top and the pattern will work itself free and drop out.

4. Build a simple jig for aligning a pilot hole for drilling the ears on your completed coil. Nothing is more annoying than a crooked hole.. and that is what I get without a jig .
The jig is just a block of wood with cuts made on a table top saw against a rip fence. Note: It is virtually impossible to drill a long, straight hole through the block of wood. It
is far better to cut a groove to assist in drilling a long hole. Then fill the cut with epoxy or glue in thin strips of plywood.

Hopefully someone can learn from my mistakes!!


Don..

[golfnut]

Here are a few tricks that I have learned and hopefully this will help keep builders from unnecessarily wasting material.

1. Drill an air hole in the center of your pattern - It will help the vacuum to draw air out of some of those tough places!

2. Place your pattern on a group of coins. It helps the system remove air quickly.

3. Removing your pattern - Do not try to pry the pattern out of plasitic. Just tap the edges of the plastic on a table top and the pattern will work itself free and drop out.

4. Build a simple jig for aligning a pilot hole for drilling the ears on your completed coil. Nothing is more annoying than a crooked hole.. and that is what I get without a jig .
The jig is just a block of wood with cuts made on a table top saw against a rip fence. Note: It is virtually impossible to drill a long, straight hole through the block of wood. It
is far better to cut a groove to assist in drilling a long hole. Then fill the cut with epoxy or glue in thin strips of plywood.

Hopefully someone can learn from my mistakes!!


Don..

Top posting right there.
S

[ApBerg]

Don, again great info !

[Jerry]

Here are a few tricks that I have learned and hopefully this will help keep builders from unnecessarily wasting material.

1. Drill an air hole in the center of your pattern - It will help the vacuum to draw air out of some of those tough places!

2. Place your pattern on a group of coins. It helps the system remove air quickly.

3. Removing your pattern - Do not try to pry the pattern out of plasitic. Just tap the edges of the plastic on a table top and the pattern will work itself free and drop out.

4. Build a simple jig for aligning a pilot hole for drilling the ears on your completed coil. Nothing is more annoying than a crooked hole.. and that is what I get without a jig .
The jig is just a block of wood with cuts made on a table top saw against a rip fence. Note: It is virtually impossible to drill a long, straight hole through the block of wood. It
is far better to cut a groove to assist in drilling a long hole. Then fill the cut with epoxy or glue in thin strips of plywood.

Hopefully someone can learn from my mistakes!!


Don..

Another trick I use is to varnish the pattern several times, giving a light sanding in between coats so the final finish is very smooth. I apply liberal coat of wax just before vacuum forming. It pretty much falls out of the shell.

I like the tip on the penny spacers will try that next time.

Jerry

[golfnut]

I have been looking at buying a coil cover and using it upside down.

So the coil sits in it and use that as shell. Pot it from above, coat inside with graphite/carbon paint as usual.

Cheaper than buying the pc abs.

http://www.staffsmetaldetectors.co.u...oil_covers.htm

Any thoughts?

S

[Qiaozhi]

I have been looking at buying a coil cover and using it upside down.

So the coil sits in it and use that as shell. Pot it from above, coat inside with graphite/carbon paint as usual.

Cheaper than buying the pc abs.

http://www.staffsmetaldetectors.co.u...oil_covers.htm

Any thoughts?

S

In ITMD, Chapter 10, we describe a simple method of constructing a coil using a commercial coil shell and either 5mm 3-ply, or MDF, for the top of the shell. This method allows the ears to be easily constructed out of offcuts from the 3-ply. However, you might have to be somewhat creative if you wanted to fill it with epoxy.

[dfbowers]

And now, for your viewing pleasure and entertainment.. What happens when vacuum forming goes really really bad.

[ApBerg]

No...no...is not bad....its a piece of art... you can put it on the wall ! , just give it nice blue eyes an a smilie red mouth ..