Cutting thick carbon fibre sheet

[carbongr]

I have to cut many bars of a 10mm thick carbon fibre sheet, each 1m long. The sheet is made by unidirectional fabric and high temp epoxy resin, cured in the oven.
I have tried with the band saw but the saw, (which is probably one of the best for hard metals) was ruined after just one cut.
Coolant is not an option.
Is there another way or machine i should use to do the job with high accuracy?

 

[Compositepro]

You have to use an abrasive blade for cutting composites. Without coolant you will be limited in cutting speed due to heat generation. Even high temp epoxy will soften when it gets hot enough. It will then gum-up the blade a create more heat. The fibers must be supported by hard ,rigid resin to get cut cleanly.

Can you not use pure water for coolant? If not, a compressed air jet will help, or even air from a Vortec cooler. There are grit edge band saw blades available. They will work as long as the cut is kept cool enough. If the blade gums-up once it may not be useable anymore.

 

[QuentinNZ]

You could try water cutting with a high pressure jet. Should be able to work with 10mm thickness. The cut will also have a much higher accuracy than using a band saw.

 

[carbongr]

Thank you Compositepro for the answer. I would rather avoid coolant due to the potential corrosion. Either way i do not think i will have durability and accuracy with a band saw. Compressed air didn't work either, and unfortunately, i can not find grid edge saw blades for my band saw (Metabo).

Anyway, i will try water jet (as QuentinNZ recommended - thanks) or laser cutting. Which solution do you believe is the best for this case? Anything to worry/take care with laser cutting?

 

[RPstress]

Waterjet works well. If you want high accuracy the waterjet cutter must take account of the spread of the jet. This sometimes means using a five axis machine rather than three and more material has to be removed in the cut. Some process development (optimisation of things like head distance from the laminate, pressure and feed speeds) may be needed to avoid delaminations, especially if the panels/bars aren't flat. Also, feed speed affects the surface finish markedly.

Most tools for cutting carbon need to be diamond grit or polycrystalline diamond (PCD) coated. Water jets typically have a garnet or other hard cutting powder in the jet.

Cannot speak much for laser/EB cutting. For metals, laser typically leaves a small HAZ which often needs removing.

 

[rerig]

I got this Boeing Document at a Training Class many Moons ago.
I don't think it is proprietary as it was used in a Vendors' Training Class.
If someone feels otherwise please feel free to flag and remove it.

Rerig

 

[Ludilord]

Use a diamond blade on a table saw

 

[spudpeeler]

I'm surprised no one has suggested using a tile saw for these cuts. In this particular situation the 1 meter length might cause some difficulty but provided that can be managed a low-cost tile saw provides an excellent quality of cut at the fastest possible feed rates without overheating the blade or composite and without rapidly wearing out.

 

[MandrelMan]

Cutting and triming carbon fiber parts can be done with diamond coat carbide and ceramic cutting tools. Carbides are less expensive but have a thermal "footprint" that is transfered to the carbon over cutting time, thus causing degradation of resin structure. Ceramic cutting tools do not have the thermal transfer, but are brittle, so only slow feed rates are recomended regardless of cutting RPM.

 

[sailorguy]

Does your material have to stay on site? A shop that machines large quantities of stone or glass will have saws and/or waterjets that are designed for cutting ceramics and related materials (some "engineered stone" for countertops is nothing more than quartz bonded with filled polyester). For large quantities a CNC saw would work better but there is no reason a manual saw won't work.

The saws use large quantities of coolant water so materials stay cool. When you keep the matrix cool, composites act pretty much like ceramics. The water on a stone saw is normally recycled, so it normally somewhat alkaline from stone dust. Waterjets require clean water, so their water source isn't normally recycled. It normally comes from the municipal water supply so it is quite clean.

A saw will leave a finish that is very smooth (quite often when they are fabricating a granite counterop they can simply polish the sawn edge). If the saw is set up and operated properly it will give you cuts that are dead on. I don't recall the feedrates they use on a saw, but I would be surprised if they were less than 300mm per minute. They move right along. Kerf is normally about 1/8".

Waterjet feedrates vary big time depending on the operating pressure, but will be much slower than a saw. The edges are fairly straight and smooth, but it depends on various factors. The edge won't be even comparable to the smoothness of a saw cut, however. Kerf is typically around 0.006".

Because of the housing slump, many stone shops are hurting for work, so they would likely to be anxious to talk to you. Larger shops are more likely to have the CNC equipment, so you might call Home Depot of Lowes and see who makes their custom granite countertops. Or if you don't need huge quantities keep your local stone or glass shop in business.