So we’re trouble with blue tape + superglue CNC workholding. I think this may be an issue with the material we are using as a “spoilboard”, which in our case is slightly dirty plywood. If your team uses this method for workholding, what do you use as the sacrificial layer, and if they don’t, what is a superior alternative?
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Clean and flat MDF works great.
Hi, my team uses the painters tape + superglue method of workholding as well. We use an aluminum spoiler plate.
Face your spoilboard to get a clean surface!
My kids prefer double stick tape, but I use blue+CA at home.
Another thought is to put some CA or other wood finish on your spoilboard after surfacing. Give it a quick scrub with a sanding block after it dries. That will harden up your surface.
Drilling first and putting screws in the holes is always a good idea…
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We generally use some large flat pieces of aluminum (when cutting aluminum). I’ve found that we get better cuts when the spoilboard is the same/similar material to the part.
Proper prep also makes a huge difference. We clean both surfaces with rubbing alcohol (allowing the alcohol to fully evaporate) before putting the painters tape on. Making sure to not overlap the tape as you want the glue surfaces to be as flat as possible. We found this 12" wide roll of “tape” that makes it a lot easier. We’ll also generally stand on the 2 pieces after gluing for a minute to clamp them together as the glue sets.
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Smooth and clean material is the key here. You don’t want voids/dips in your material, and you definitely don’t want the material dirty. I’m not sure just how dirty we’re talking about here, but imagine spreading something like small amount of salt or literal dirt onto a flat surface, and then trying to apply masking tape. All the granules will cling to the tape, and the tape itself will be unable to adhere to the flat surface in those areas.
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That’s interesting. How thick? Do you face it after every operation? Is it “permanently” attached to the machine?
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We use Polycarbonate with double sided tape, and 1" thick HDPE sheet when we screw the workpiece down, typically using drywall screws.
I believe we use either .25 or .375 thick aluminum plate. It’s not necessary to face it down after every part, we face it down at the beginning of the season and maybe 1-2 more times as needed, but take great caution not to cut into if we can avoid it. It is permanently attached to the router table.
As others have mentioned, we also wipe down both the spoilerplate and stock material (acetone in our case) before applying the tape.
We actually just resurfaced a spoilerplate for one of our Omios, I’ll see if I can get a close up picture of our setup on Tuesday at our next meeting.
Here’s a close up picture of a part + spoilerplate from the 2022 season:
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Very cool. How do you remove the residue from the blue tape + any super glue that gets through the tape?
Have you ever tried double-sided tape? It’s quick, easy, and holds well. We use Shurtape DF 545, but other high-strength double-sided tape may work just as well. You don’t need to use a lot of it. A few strips strategically placed to hold the main sheet and enough of the cut-out parts to keep them in place while cutting is fine. A spoilboard would have to be more than a little dirty for the Shurtape to not hold to it.
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Hmm that’s interesting I’ve tried VHB but it’s no where rigid enough to use for machining. I’ll give that a shot. Does it leave a residue? How hard is it to remiove?
Yeah we’ve tried that. We found the superglue we use litterally is able to pass through it which leads to nice holding force but makes clean removal not possible. Ymmv tho
No residue that I have seen. It takes a little effort to peel it off after use, but nothing to make you hate doing it or want to find another hold-down method. The harder part can be removing the sheet from the spoilboard if you didn’t think the tape would hold and taped up the whole surface.
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We use a layer of cardboard-y stuff (I don’t know what it is but it looks like cardboard but much tougher) that gets cut like a hot knife and butter but it doesn’t flex or crack while being worked over, then we will drill screws into the edges of whatever we are cutting to mount it to the bottom.
Our CNC is really big (like, maybe 4’x4’ cutting space?) and it has a slot to insert the bottom material into so that mounts it to the machine itself so it doesn’t wiggle around, but in my fairly limited experience on a CNC machine, screws are the best way to mount stuff because they aren’t as prone to moving around. For smaller parts we have 3d printed brackets with threaded holes to drill into the bottom board.
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