Hey Brady how to hold these down?

[knight_toolworks]

this is a sheet of acrylic 24"x24" 1/8" thick the parts are about 2x3" cut through at 1ips with a 1/8" bit. I made a small vac table for such things 24" x24"with a 1/2" ultralight mdf top and powered with one fien vac. but it can't hold them in place when they are cut out. what would be the best way to do it? to add both vacs to the job? or use a top with cutouts for the pieces?


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[beacon14]

This looks like a job for a Gast pump and a custom vacuum mask using the Allstar sheet mask. Mask the whole area, mill away all except a thin perimeter just inside the perimeter of each part, rout holes under each part to connect to plenum. Not sure if you can cut these all through on one pass the last few may need two passes to keep them from shifting.

How did I do Brady?

[carlcnc]

Steve
Are you cutting this plex with the protective paper in place?
If so then you use a spray adhesive[3m 77} on the paper back and glue to a sacrificial board,I use 1/8 masonite. vac it down,cut, and remove the paper back asap.
works great for me

CArl

[knight_toolworks]

if I was to do more then 4 sheets I would invest in making a vac puck for them. but the things they go to are not selling great so I may not make any more for my customer.
gluing them down like you recommend is a good idea. I have tried leaving the paper intact by not cut though through it but it is hard to do.

[scottcox]

Thanks for that tip, Carl.

I never thought of doing it that way.

-Scott

[rbarrow]

subcontract this out to someone with a laser...you would probably end up paying less to have it laser cut than it would cost you in time/materials to setup on the bot and the quality will be 1000 times better (polished sides).

Just a thought.

[knight_toolworks]

but could a laser do countersunk holes? the edges are not seen so thats not n issue. but right now it would be money out of my pocket. but if I do more and they can coutersink the holes it may be the way to go.

[Brady Watson]

Steve,
You should have no problem holding these down using a 'BradyVac II' setup. 1st, take a sheet of 24X24X0.75" - anything - and mill a grid in the back of it. Make it about 3/8" deep. Then, using the vectors for your parts, offset them .125" to the inside, and then do an area clear .125" deep, leaving a .75" circle raised in the center of each area clear. This will keep your parts from drooping in the center. Then, drill a hole somewhere in that pocket to puncture the vac gid below - feeding each little 'pod' that you created with the area clear. You'll need a 2.27" hole drilled in your table thru to the bottom of the support board to plug in the Fein. Then, toolpath your parts as necessary & cut to your heart's content. Those babies aren't going anywhere. No gasketing needed.

-B

[Brady Watson]

Like this:


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[knight_toolworks]

here is a vac table I made for such jobs. it bypasses all of the piping and is 24"x24" so I take it you want me to replace the ultralight top with a solid one and make the grid below right? should I hook up both vacs or just one?



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[knight_toolworks]

got it. I made this little guy to make it easy to replace tops it has internal support so I can use thinner material.

[Brady Watson]

...you can do that too - although you/'ll probably want to make it out of something a bit more robust. I made mine out of corian because I had some laying around & it is non-porous...and epoxies together well. After you make a good plenum. you can make removable masks that are made out of 1/4" MDF, luan, plastic etc that slip right into the plenum and interchange patterns as needed for repeat jobs. I must have at least 30 interchangable masks that I use for repeat jobs.

At the very least, run duct tape around the entire MDF plenum you made...or you'll probably lose 2 or 3" of Hg.

-B

[knight_toolworks]

good idea. the mdf is sealed with yellow glue but it is easy to replace with something stronger. it has ribs inside to support it from sag though.

[Brady Watson]

Good. The ribs should be the same height as the surrounding perimeter. I used the bot to plane them all the same height, taking off as little material as I could. Just don't put BBQ sauce on these ribs & you'll probably be OK


-B

[knight_toolworks]

here is the inside all leveled.

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[Brady Watson]

Steve,
Keep in mind that you'll want open air getting to the bottom of your parts like the BV II shows. If you attempt to cut your parts pulling thru a hole-less bleeder, then it will not work well.

-B

[knight_toolworks]

I plan on removing the bleeder board and replace it with solid material for this job.

[knight_toolworks]

this method worked great. the only loose ones were the ones that came loose when I did a fast cleanup. that popped them free of the paper back. I will use this method for other things for sure.