waterjet cutter backing material for cutting cfrp

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#1

Hey guys,
I’m working with a waterjet cutter an we’re trying to get through two layers of 20oz/12k 2x2 CF that is infused. It’s an abrasive waterjet, and he’s not only having trouble with delamination during piece maneuvers (which we expected), but even along a normal cut path we’re getting delamination and bursting on the reverse/exit surface - again, even along straight paths. He’s solved the problem a bit by using an aluminum plate as a backing material and using double sided tape to bond the cf panel to it, but that’ is obviously not going to work for production as the 0.25" aluminum gets consumed in 1:1 rate as the cf.

Anyone have any ideas concerning a suitable backing material for the CF? What do people normally use when they’re cutting cf on waterjet machine?

Thanks,
Chetan

#2

Try to back with plywood or mdf , I had a project once at a water jet company, and that is what we did and it worked really good. Of course, you are going to have to pay for the wood as well.

#3

Definitely considering 1/4" plywood or MDF. Did you use double sided tape along the entire part face to bond it or did you just screw the sheet down on all four corners?

#4

In our case, we didn’t use any double sided tape, we didn’t cut hundredths of the same part, so we carefully hold the workpieces with a stick, to push down. The company had a steal stock piece, used like a paper weight. So simple and effective.

#5

I have lots of plate water jet cut over the years. All of it epoxy pre preg carbon or epoxy pre preg fibreglass.

The back side blows out (delaminates) at the starting point but it is ok from there on. We just made sure to start away from the actual part and then cut continuously without stopping.

#6

Another idea about the delamination issue. Are your infused parts tempered?
I remember a non tempered infused plate (room temperature cured) of mine which delaminated during water jet cuting and was only 2 layers of 200gsm twill weave. After that, we use to tempere the plates, no problems anymore. I hope this helps. Let us now, please.

#7

The parts are infused with the schedule being 2x plies of 20oz 12k 2x2. We use an RT curing epoxy but we do take it up to 95F/36C for 10 hours so it should be cured enough, I think.

We are looking to do high volume production of this thing so we do need a mounting solution that will allow us to get the machine going and then walk away so holding the parts down by hand isn’t really an option unfortunately.

We picked up a piece of quarter inch (6.35mm) plywood and are going to affix a large sheet of the infused material to that pat with a screw in each corner but not tape between the actual faces. Hopefully that will quell some of the vibration.

I know that you need lead ins because the back side will burst outwards during a pierce, but we are actually getting not just a delamination along edges, but actual full separation of both plies from each other in some areas :/. The machine is using an 80 grit abrasive so I’m guessing that might have something to do with it too.

Thanks for the help so far. I will let you guys know how the new cut goes with the plywood. If you guys have any more suggestions I’d love to hear them.