Vacuum Holddown

[waltie]

Anybody have the Cascade 7.5 HP vacuum holddown system on their shopbot?

[bjw]

Yes. What would you like to know about it?

[waltie]

Can I e-mail you with my questions ?

[bjw]

Sure, click on my name for e-mail info.

[Guest (Unregistered Guest)]

Does anybody use a vacuum to hold down pourous foam? I would think it would be tough to hold down due to the pourous nature of the foam. Any ideas on how to secure down foam?

[billp]

If you seal the back of it first, you have a much better chance. This could be done by using standard coatings,such as a primer or latex paint. And you might even try even using a vinyl paint mask.
Of course a lot of this also has to do with your plans for cutting into the foam as well. If you are going to V carve, it would be a lot easier than if you were going to "hog out" main sections of your piece.

[Mayo]

I regularly use 3M spray glue (Super 77) to hold down insulation foam (white, blue, and pink). A light spray on the foam is all that I have needed for most large pieces. After spraying the foam, I position it on my table, then press it down firmly with my hands to bond it to the table.

If I'm cutting anything less than about 12" square, I spray a little heavier. On small pieces, I occasionally have to use a 4" wide putty knife or wallpaper scraper to gently lift the foam from the table.

[billp]

Mayo,
Doesn't the 3M stuff have solvents in it? I've avoided trying that because the few times I've sprayed anything with a solvent it turns the foam into something similar to pink or blue pizza topping...(NOT a very attractive sight I might add....)

[bleeth]

Bill: By keeping enough distance between the spray and the foam it will be set up enough by the time it hits the foam that degradation is minimal. I've laminated fabric to foam that way in my previous life as a wallpaper installer. You can throw spray grade contact with a cheap siphon pot as long as it's well atomized (and ventilated)

[zeykr]

Bill,

Take a look at this thread. R/C foamy plane builders use spray adhesive on foam quite a bit. Says the older 3M 77 did not have the acetone in it and lists some possibilites on getting old formula or alternatives.

http://www.rcgroups.com/forums/showthread.php?t=287705&highlight=old3m+super+77 (http://www.rcgroups.com/forums/showthread.php?t=287705&highlight=old3m%2Bsuper%2B 77)

You can purchase "classic" 3m 77 here:

http://www.artsuppliesonline.com/catalog.cfm?cata_id=6100