Machining Carbon Fiber with PCD endmill
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    Default Machining Carbon Fiber with PCD endmill

    Hey guys,
    It's been quite a while since I last worked with carbon fiber. Last time, I used carbide, it was a simple feature in only 1 or 2 pcs. This time around, I need to mill a face roughly 2"x2", average depth of 1/16", in 50x pcs, and decided to go with PCD for tool life. My thought was to run this dry with a shop vac as to not contaminate my coolant, and have the shop vac outside, the hose is long enough. Thoughts on this? If this ventilation is "good enough" for this run, what would you suggest for speeds and feeds, keeping in mind it'll be dry? I appreciate any input on this.

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    I run all of my composites with flood coolant... I checked with my accountant, and it is cheaper to replace coolant that to replace lungs. In production, we have an elaborate filtration system for the coolant. For small volume, I just dump my sump and vacuum out the sludge.

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    Quote Originally Posted by G00 Proto View Post
    I checked with my accountant, and it is cheaper to replace coolant that to replace lungs. In production, we have an elaborate filtration system for the coolant. For small volume, I just dump my sump and vacuum out the sludge.
    I don't disagree with that, but this is a one-off job, likely won't see carbon fiber again for a long while. The cost associated with replacing coolant, or otherwise draining tank etc, and an elaborate filtration system, is not something that I nor the customer will want to front for a 1-off job with only a few hours involved otherwise. If this were a job that would be recurring or higher qtny, absolutely, it'd be worthwhile.

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    I usually run with coolant but make a dam out of filter paper around the part to help remove the particles from the coolant. Works well.

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    Get a good HEPA filter for the vac, a "drywall" rated bag, and sure, have the vac outside. When the job is done junk the bag, wash down the vac barrel housing with water, and ensure the HEPA filter is still clean and not contaminated (replace if in doubt).

    This should get you pretty close to "safe" CF machining, in addition wearing a good fitting 3M or similar respirator won't hurt.

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    Carbon Fibre is nasty. You shouldn't "blow it off" as a non health issue.

    At the very least add water to the vacuum stream and when you empty the tank be sure to dump it on land used to produce crops used in making ethanol fuel, their home driveway would be optimum.

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    What sfpm do you guys run?

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    Quote Originally Posted by pianoman8t8 View Post
    What sfpm do you guys run?
    With a PCD tool that's sharp, and with a matrix material that's not gummy (and prone to buildup on the tool edges) run fast - likely your machine can't go faster than any limit. For FPT, try .004" to start, test by cutting inside the final profile and look for fiber tearout from the part. If clean edges, increase feed or keep as-is.

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    This particular feature is just milling a face to an angle. There will be no interior wall, so my thought was to first go around perimeter of face via climb milling, with about 1/3 of cutter width engaged radially, to help curb fraying/delamination outward around edge, if that makes sense.

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    Sure, why not. If you do this sort of work again you may want to find a "downcut" tool to help with pullout risk, but usually PCD tools are low (or no) helix and don't create a lot of delam.

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    The cutters I ordered are straight flute, so hopefully they'll work decent enough.

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    Quote Originally Posted by Milland View Post
    With a PCD tool that's sharp, and with a matrix material that's not gummy (and prone to buildup on the tool edges) run fast - likely your machine can't go faster than any limit. .
    It will be hard to get too much speed here. Think insane numbers.
    Problem being can the slides keep up a reasonable cut so that you are cutting and not melting.
    People will tear up this type tooling in such because of machine feed limits (around both inside and out corners matter) and then blame the SFM.
    For some strange reason people put in high or max federates and think the control can do this when profiling or turning a 90 degree corner.
    Bob

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    The machine limit is 8k rpm, and approx 700-800ipm. Sharp SV2412 mill.


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