[edwinshap]

Hello, I am a rocketry enthusiast and a friend of mine found out that I have access to both a CNC router table and a CNC 4D.

I need to cut a piece of 0.04" carbon fiber laminated in west systems 105/207 (regular laminating resin) into hopefully 6 fins. The piece is about 6"x6" but he only wants 5.5"x5.5" to be milled for use since the edges lose thickness and strength.

The way i currently have it set up, the blank will have about 1/8" or 3/16" between.

I'm unsure on how best to go about cutting this. It's too small to use a regular saw, and I do not have access to extremely strong thin cutting tools, so I thought that the CNC router table would be the best option. The cutter can spin at upto ~21k RPM (i think), and I have a lot of cutting bits to choose from. I need the cutting bit to be no more than 1/8" to make sure that no fin loses material due to an overly large bit.

Is what i hope to do possible or should i attempt it with a different tool/machine?

[txcncman]

Several ways to do this.

I might suggest sandwiching it between 2 pieces of aluminum and standing it on edge and using a jeweler's saw, 0.050 wide.

[edwinshap]

what thickness of aluminum do you recommend? And is there any special parts i should buy for the jeweler's saw (like blade wise?)

Thanks

[txcncman]

The thickness of the aluminum depends on how much support you are able to provide. If you are able to clamp the sandwich against a 6" angle plate, then the aluminum can be relatively thin, say 1/8". If you are going to stand the sandwich up in a vise and only grip on about 2" of the bottom, then at least one piece of the aluminum needs to be relatively thin, say 3/8".

A wooddruff keyway cutter could be used in place of a saw since a jewelers saw will need an arbor. Example: 3/4X1/32 HSS KEYSEATNARROW CUTTER KEO :: Narrow Width High Speed Steel Keyseat Cutters | Travers Tool

Examples of jewelers saws: http://travers.com/skulist.asp?RequestData=CA_Search&navPath=All+Prod ucts%2F%2F%2F%2FUserSearch%3Dslotting+saw%2F%2F%2F %2FCutting%3A+H.S.S.+%26+Solid+Carbide&q=block+id+ 50102+and+class+level3+id+30228&minPrice=$5.80

[edwinshap]

Thanks, i'll give it a shot and let you know how it turns out.


Another question, my friend sent me a CF tube which is about 0.125" thick, and i need to make square edges, and i can take off upto 0.5". Would it be smarter to use a metal lathe or the 4D CNC that i will manually operate to lower the cutting bit onto the material?

[txcncman]

When cutting any composites, rigidity of the work holding is extremely important. Hardness, sharpness, and wear resistance of the cutting tool is important also. In your case, to make just a few cuts, wear resistance will not be as critical as it would be in a production setting. I would recommend the smallest diameter cutting tool that is reasonable to reduce cutting tool pressure against the material, but large enough to remain rigid and avoid tool deflection. Probably a 1/8" carbide end mill would work best in this case. Cutting on a lathe would require very precise setting of the tool tip on the center line. Holding the part as close to the cutting is important also to maintain rigidity.

When I have worked with carbon fiber before, I have been able to clean up any frayed cutting with 400 grit sandpaper on a hard sanding block.

[ckelloug]

I'd suggest finding a diamond bit if you have to do more than a few of these. I've seen the much thicker 1/8 thick carbon fiber take teeth of a bandsaw blade.

[TDA]

We've have had very good luck cutting carbon fiber with diamond cut router bits. They are made for cutting composites (FR4) and are quite inexpensive. Standard sizes range from .0315" to .250".

[Ryan_in_AZ]

Yeah, go to Precice Bits and get some diamond cut bits. Perfect for carbon. Don't breathe the dust though.