What do people usually do to keep material down when flamps alone wont do it?
I am having trouble keeping thin material down on the spoil board. Specifically, I am cutting out a 2’ x 4’ sheet of hard board into shapes. the sides are clamped down but the material still flexes up and down resulting in bad cuts and destroyed parts.
You can try a downflute bit. It pushes the material down instead of trying to pick it up.
Double sided tape, spray glue, tape looped back on itself, vacuum table.
Double sided tape works. When I was cutting thin acrylic I used blue painter’s tape and superglue. Put tape on your part, and tape on the spoil board. Run a bead of superglue on the tape and stick it to the other piece of tape. Hold it down until the glue sets, or use an accelerator. The tape will hold the parts down while you’re cutting, but will pull off fairly easily with a putty knife. Got the idea from a guy on youtube cutting aluminum parts on a mill.
thats an interesting idea. I will check out double sided tape and also might try the super glue tape idea.
I have added small drill holes near the patterns to be cut out, then do an initial gcode file generation of just the holes, once they are drilled, put small screws in (moving the router with gcode commands so I don’t lose registration), and then cut the pattern using the original file. I make sure the screws will clear (i.e lift 5mm between cuts). I leave full depth holding tabs on thin mdf - they can easily be cut with a knife.
The spider on my grapevine covered dome was done this way (attached)
A vacume table woukd be awesome but i just dont have it in me to take on another project like that right now lol.
I used some spray adhesive, but I must not have used the right stuff, because it just left a bunch of gunk on my spoilboard.
I drill holes and put screws in where I’m cutting stuff out, similar to what CamOnt said, but I don’t use a gcode file. Their way is probably faster.
I just watched this yesterday.
Thinking hard of going the vacuum plate route. My concern is the plate im looking at is smaller than the actual work piece. I’m fairly confident that there would be plenty of vacuum to hold the part even still.
If you have exposed holes you just mask them off with tape. I just wonder as you cut and then expose holes how does it hold up.
So far a few screws has done all I need, but a vacuum table would be cool for really thin stuff. My table is already hollow I could just add the vacuum and let the machine drill it’s own holes.
You can also mask off the unused holes with paper, doesn’t have to be taped on, the suction will hold it in place. I was thinking the same thing about using the table, but I don’t have enough support inside mine, the hardboard will buckle.
The one I’m looking at is appx 20" long and 8.5" wide. It uses the foam/rubber inserts to “block” off the unused portions. I’m thinking though that with that much surface area on a larger board, it would still be plenty. As in the video Berry linked, he lifted that large board with what looked to be no more than a 10x10" vacuum plate.
Plus I could move it around the main table as needed since I wont be permantly mounting the vac plate. >>> Yes, I am talking myself into it 
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These look really useful http://www.ebay.com/itm/2-SIDED-VACUUM-CLAMPS-PODS-Vacuum-Table-CNC-Machining-/280708685096?hash=item415b8a9d28:m:mhdcZWKES9x7qRhn2ffWxAw
I may have to bite
These are incredibly strong, i used some similar a few years back at a shop i worked in. The downside was the venturi they had to make the vacuum made a loud high pitched noise. A vacuum pump would be much quieter.
Pretty sure you need a pretty beefy air compressor for the ones Brian linked to. Little pancake compressors won’t cut it.
