Holddown for small letters

[rcnewcomb]

We use vacuum hold down for most of our work, but we have a project coming this summer where we'll be cutting smaller letters (1") out of sign foam. We expect that our vac setup will not be appropriate for this job. I looked at this post (http://www.talkshopbot.com/forum/messages/312/28498.html?1238694087) about foam glue for the edges but wasn't sure how to keep small letters from going up the dust chute.

Do you recommend tabs, onion skin, spray glue, ...?

I have time to practice and experiment but would prefer to minimize the expense of experimenting.

[Gary Campbell]

Randall...
We cut that size letters but first doing an inside, then outside profile of the letters with a .010 clearance using a 3/16 O flute. Do a full depth cut to within .020 of the bottom. (onionskin)

We then follow that up with an eighth inch, full depth, .010 into the spoilboard, cutting the inside holes first and then the outside profiles.

If the sheet is small we lay visqueene over the previously cut letters to keep the vac up. The trick is to select the vectors in the order you wish them to cut, rather than a sweep or box select.

Gary

[bleeth]

Randall: Since sign foam breaks down into pretty fine dust could you put a grid over your dust hose opening so the small pieces that did get picked up didn't disappear? I have this issue with cutting small letter centers out of acrylic and aluminum and haven't come up with a good solution yet. I suppose one could do all but last pass cutting with the dust vac on and then have it off to cut the skin or bidges away.

[carlcnc]

Randall

put "medium tack" application tape on back of sign foam,
then use water-based contact or '77 spray glue to attach to a piece of masonite or some other smooth sacrificial material ,vac it down. cut as desired,they will all stay put. although you may get brown dust from the masonite,
Carl

[dubliner]

Randall, a few of us were at Joe crumleys shop seeing how small we could get the letters. We cut down into the foam, leaving .2 in or so, then sliced the piece on a bandsaw and the letters were released, we got them down to about 1/2 in size and apx .15/.25 thick.

[john_l]

We do it similar to the statement above.. We profile cut the small letters to within .010" of the bottom of sheet (onion skin), the seperate sections of the legend with a rectangle profile cut around the small letters to the full depth.
Then we take these sections and either band saw or sand the bottom onion skin off. It usually leaves perfect little letters and if there is any imperfections... it is isolated to the extreme back edge where the oninon skin was. .

[joe]

I find the bandsaw is an excellent way to relieve small letters from HDU. I've rendered sizes down to 1/8" with a 1/16" bit. To the best of my knowledge there isn't a tape or vacuum which will do as well.

Notice, I've run a piece of 1/8" pvc half way through the blade to keep small letters from getting lost. This blade is a crude skip tooth. Any bandsaw blade will work.

Cut your letters much deeper than you need. That way you have lots of controll when setting up your fence. I usually double stick my fences on. A 1"X2" pine board is used ub this case.


5988


5989
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Joe Crumley
www.normansignco.com (http://www.normansignco.com)

[kartracer63]

Joe,

Great post. I would have never thought of that. I'm glad to see another post from you. They're always educational, and it's been a while.

Eric Erickson

[shoeshine]

Joe; that is beautiful. Thanks for the insight. so many times I get caught up in using the bot I forget my other tools.

Dave; It is an odd method but it has worked for me in the past when I have tiny letters/shapes in alum, brass, or other metals.

I got a cutoff piece of aluminum toolplate from a metal shop a while back. I think I gave them $20 for a 18" x 42" piece. I screw that plate down to my spoilboard. I then use a thin application of polyacrylite glue (superglue) to glue the material to be cut to the toolplate. I cut just through the material (-.01") then I flood the the thing with acetone. dissolves the glue and my shapes pop off.

Not exactly a "green" method but for occasional projects where I have tiny (last time I was cutting copper shim stock with a think and tinker 1/32" bit to be used in a micro-controller) it works.

Chris

[navigator7]

It's been a great thread.
When Joe makes sawdust it comes off and flies around like dollars!
;-)
When I was a machinist, small, thin parts were secured by floating in low melting point bismuth alloy.
When the machine work was completed, you heated up the square clump of metal and grasped the part with tweezers and voila!

This got me to brainstorming....What about using heat to deactivate an adhesive???

Thermal Release Tape?
Revalpha?
http://www.semicorp.com/brochures/Revalpha%20Info%20Ver%20B.pdf

5991
Heat Release Tape is a unique thermal release tape that behaves like normal adhesive tape at room temperature but can be easily peeled off by simply heating when you want to remove the tape.

I sent these boys off an e-mail. They probably sell this stuff by the train car load....but we will see.

Semiconductor Equipment Corporation
5154 Goldman Ave.
Moorpark, CA 93020

[joewino]

Hey, it's good to see old man Crumley back. We missed you Joe.

BTW - great idea. Glad you thought of it. I have some letters that need to be cut right now - I'll use your suggestion.

[navigator7]

Well....the company above replied to me e-mail with a pdf...which is a pia since I can't copy and paste.
The product has merit....but I still don't know the price.
Revalpha product # 3196 is the product that caught my eye. This product is double sided.
It can be applied by hand roller, press, spatula, squeeze roller or.......air press...or vacuum!!
A wood sandwich!
I haven't determined yet if the product works with wood. It's specific use if for the high tech electronics industry holding down thin metal, wafer chips, and whatever else they stuff in puters.
I specifically asked about wood but you know saleswomen.
It requires the least amount of heat of the four products but all four products have nearly the same adhesion spec.
The specs show 3.7 Newtons over 20 mm.
4.45 Newton equals 1 pound. So just shy of a pound of adhesion ability over a square cm or about a half inch. Seems like a lot to me.
Once heated to 90ºC or 194ºf, it loses nearly all it adhesion qualities in about 10-15 seconds and is all but nothing after one minute. It releases itself easily and doesn't stain or leave smudges. It peels off 180º like pulling off vinyl.
Infra red heat seems best. Over heating or not separating the parts in a timely fashion is not a good thing.
I guess the trick is it only works on items that can withstand car engine type heat for a minute.
If anybody wants the pdf, e-mail me.
Curios information me thinks.

[knight_toolworks]

the problem with cutting aluminum is heat. I found double sided tape and spray adhesive came loose easily. I cut some .09 copper the parts were real small and heat would pop them off.
this time I glued them down with some good epoxy cut them out hit them with a propane torch and they came off with no effort nice and clean.