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IndustryArena Forum > Material Technology > Composites, Exotic Metals etc > Carbon fibre threading improvements?
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  1. #1
    Join Date
    Nov 2022
    Posts
    2

    Carbon fibre threading improvements?

    hi all, We make many carbon fibre components, some with around 80 tapped holes blind and through in a range of sizes. these are currently thread milled with ticn-coated treadmills.
    This works well but is very very time consuming keep adjusting cutter comp to size them.
    ~Also puts all the pressure on the machinist to keep adjusting cutter comp as you know one digit wrong and the part is scrap. One of our ops is around 30 mins to run the whole thread milling program, then adjust and re-run, hours of work...

    Are there any taps out there for rigid tapping in carbon fibre that produce a good thread and not de-laminate the top few layers of carbon.
    We have tried with many different taps but find they always slightly de-laminate the top skin, on safety critical areas in our industry this is not acceptable.


    any help or experience would be great

  2. #2
    Join Date
    Mar 2008
    Posts
    683

    Re: Carbon fibre threading improvements?

    Countersink the first few layers with a diamond abrasive countersink first. Then try to run a tap. But it seems to me the nature of laminated carbon will not lend itself to using regular taps since it will just delam the fibers rather then cut them.

  3. #3
    Join Date
    Jun 2015
    Posts
    4131

    Re: Carbon fibre threading improvements?

    always slightly de-laminate the top skin

    just delam the fibers rather then cut them.
    hy k-turner warenb's idea about the countersink seems nice; even so, a countersink could lead to same delamination; carefull with not visible delamination

    is one thing to plunge a countersink/tap, and another to interpolate the chamfer/thread, thus there is a balance between cutting forces and time

    to make that tap work with less delamination, it has to be more sharp, have longer entrance ( conical zone ) and less calibration teeth ( cilindrical zone ); you could take a tap and grind it so to have a single helix, thus it's cutting force will be as low as possible, but you may not be able to guide it if there is overhang

    to make your process work, you simply need to find a tool that has cutting force as close as your actual method of intepolation you will have to test many taps

    Also puts all the pressure on the machinist to keep adjusting cutter comp as you know one digit wrong and the part is scrap
    i suggest :
    ... checking the consistency of the process, and mapping things as needed, so to identify & eliminate time waste
    ... avoid error related to inputs, by using a macro that checks offset deviation, and an incremental aproach for final finishes, that simply increases the toolpath radius, without requiring the operator to always modify ++++ then ---- at a new part; if process is stable, is possible to bound it's corections, and speed up or at least partially replace operator's actions

    such actions can ease the operator, and works as long as deviations follow a previsible pattern; there may be burs, lack of thread rigidity

    some with around 80 tapped holes blind and through in a range of sizes

    One of our ops is around 30 mins to run the whole thread milling program, then adjust and re-run, hours of work...
    at 1st glance, time seems fine

    you can boost feed by adding one more tooth, thus instead of experimenting with taps, simply use denser threadmills, at least for orughing

    consider also finish with different tool / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  4. #4
    Join Date
    Jul 2018
    Posts
    6248

    Re: Carbon fibre threading improvements?

    Hi KT - Do you have design input to the parts? If so consider using a CF veil or glass veil on the top layers. This will produce a layer that has less chance of delaming. Veils come in 25gsm thru to 100gsm and can be very useful for this sort of thing.... Peter

  5. #5
    Join Date
    Mar 2008
    Posts
    683

    Re: Carbon fibre threading improvements?

    This gives me an idea. I have a whole box of form metric mills. I'll get some scrap and see how it works.

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