Machining Carbon Fibre
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  1. #1
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    Default Machining Carbon Fibre

    Using catia, I need to make some 17mm holes. I am interpolating out from an existing 11mm hole.

    Always getting entry and exit delamination.

    Tool I have is a 14mm slot drill, 3 fluted, carbide.


    Tried the following;

    Climb & Conventional

    3 Degree ramp

    Flood coolant, minimal coolant, dry

    Changed feeds and speeds:
    1600S 120F
    1600S 240F
    6000S 900F
    6000S 600F

    Tried slotting a 14mm hole straight through first to reduce material

    Tried slotting a 14mm hole then using side of cutter instead of ramping

    Any ideas?

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    Tool is a slot drill, what is that? Looks like an end mill or T slot cutter. Sounds like it is your tool to me.

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    Search for compression router bit (or compression endmills), buy a few of them for cutting laminates. The compression section should be roughly centered on the thickness of the laminate.

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    Quote Originally Posted by DavidScott View Post
    Tool is a slot drill, what is that? Looks like an end mill or T slot cutter. Sounds like it is your tool to me.
    Another name for a 2 flute endmill.

    A down cut bit or a sacrificial topper to support the CF are probably the easy solutions but I've had good luck pecking 3mm holes on size with just a regular carbide endmill so I wouldn't toss out the idea of a flat bottom drill and just going on size either.

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    Thanks for the replies,

    We dont have any time to get tooling in, all tooling has to be qualified prior to use which is a lengthy process.

    I have to use the 14mm slot, Nominal hole is 17mm +/0 0.15 so only option is to interpolate it

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    I'm wondering about diamond cut router bits used to machine fiberglass laminate. Still cheap and very available. Kind of the cheap alternative to a vacuum brazed diamond grit router.

    A two flute end mill shouldn't be "qualified" for this task as it's not a very good tool for the job. Sounds like you need a magic wand for when you can't get the proper tools.

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    Quote Originally Posted by Madocks View Post
    We dont have any time to get tooling in, all tooling has to be qualified prior to use which is a lengthy process.
    Well, I think we found the problem.

    If your company's managerial process controls are so draconian that you can't get the proper tools for the job without a massive procurement process, you will intrinsically limit your capabilities. Argue for a variance in the process so you can get the proper tools on hand, or advocate for the creation of a prototype/R&D path that allows you to rapidly procure tooling for experimentation/problem solving before the beancounters throw handcuffs on the process with their byzantine bullshit. Once you have a working process, then the procurement folks can go to town.

    In the meantime, try interpolating with a very lite cleanup pass to minimize the stresses that cause delimitation. It might take 2-4 passes.

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    Quote Originally Posted by gkoenig View Post
    In the meantime, try interpolating with a very lite cleanup pass to minimize the stresses that cause delimitation. It might take 2-4 passes.
    And immediately change out tools when they start to dull (and they'll do that quickly on CF). The dull tool will put more stress into the cut, increasing the "lift" effect of the tool profile as it moves through the laminate.

    Please don't tell me only one specific tool has been "qualified" for the job...

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    The last time I ran CF we tried DLC coated tools from Niagara and they weren't worth the extra cost. Supposedly they've changed the coating process to make it better but at the time I got the best life out of regular coated 4flute 5/16 endmills on 1/4 and 1/8" plate. The 2 flutes had a bad habit of suddenly lifting the weave while the 4 flutes would burr and be replaced long before that.

    IIRC I was running that 5/16 at 5000 rpm and 20ipm (500mm) per minute.

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    Quote Originally Posted by Madocks View Post
    Thanks for the replies,

    We dont have any time to get tooling in, all tooling has to be qualified prior to use which is a lengthy process.

    I have to use the 14mm slot, Nominal hole is 17mm +/0 0.15 so only option is to interpolate it
    How did the tooling for the job get qualified when it doesn't work?

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