So I was planning on milling some 25mm thick hdpe and since slotting is less than awesome when it gets deep I thought I could try tape+superglue (and machine the entire piece). But I cant find any reflections about the size and material limits (how small can you go) of this technique.
So anyone care to share their experience about surface area and different materials?
NYCNC video of them machining a large aluminum part using the tape method:
If the tape has a good grip on the HDPE I think yo should be good.
I’ve milled some 400x300x15mm sheets of aluminium using this method. It’s incredible. The larger the piece the better it works.
Caught me at just the right time. Below is the smallest HDPE piece I have done with tape + superglue
The stackup:
25mm HPDE block (faced down to 20mm on the first operation)
2 layers of 3M #2093 ScotchBlue tape with Lepage Superglue (think that is a Canadian thing) in between
MDF wasteboard
This worked pretty well with an aggressive 2D adaptive toolpath with 5mm stepdown. I carefully arranged the toolpath such that the outside was removed last (cut out the inner sections first) to keep maximum tape surface contact as long as possible. With the toolpath strategy I had I doubt if I could go smaller without being alot more gentle as the HDPE piece was starting to vibrate visibly as the last bits were removed.
I almost exclusively use tape/CA glue for holding material, my concern would be the ability of tape to stick to HDPE, as it’s pretty slick. However in my experience of doing full depth cuts with wood using that method, there are limits. For example, I was cutting a project where the inside was cut out, then cut around the outside, leaving a 3/8" strip between (making a box in layers to be laminated together). The tape was not able to hold that securely and it let go from the wasteboard on the very last pass. I started using tabs in addition to the tape when cutting projects that I’m unsure will hold well.
Agreed. It’s all about tape surface area. If you can start with large stock and remove a small piece from it that definitely works better compared to starting with smaller stock.
well that held my piece very well… sooooo how do I get it loose? 
I didn’t use the wasteboard, the tapes stickiness vs mdf didn’t seem too reliable so I use a aluminium board.
No but srsly, put it in the oven? dunk it in acetone? just trying to work a knife in at the edge seems futile.
Edit; nvm putting it on the stove worked perfectly
the hdpe to the aluminium plate by way of tape+superglue… couldn’t get a knife in to jimmy it loose.
but as i said, I just put it on the stove and in softened up the tape glue perfectly so it came loose easily.
I guess I need to get better at applying my tape!
WARNING WARNING WARNING
My local hardware started to stock a cheaper version of the 3M Blue Tape called “BASIC”
I bought a roll without thinking about it. Went to use it and it was paper thin but I went ahead. Had my work-piece cut loose after about 3.5 hours of cutting and is gouged beyond repair. Completely lost. This stuff is crap for hold-down! May be ok for painting but absolutely stay away from it for CNC!
I use blue tape hold-down most of the time. The one time where I had lots of issues was cutting delicate Christmas ornaments. The finished pieces end up with blue-tinted adhesive in all the little crevices and are almost impossible to clean.
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