Z Axis Plunging during cut


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    Default Z Axis Plunging during cut

    I have a CNCRP 5x10 with CNCRP spindle. I am having problems running larger bits. I set Z zero to the machine bed. Once it starts under load, it's almost like it pulls the spindle down further and further. I am running the Amana 46199-K (1/2" D, 2"CH) compression bit. I never have this problem when I am running 1/4" bits. It's really frustrating, especially since it just went through my spoil board and took out two my threaded inserts!!! Any thoughts?

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    Default Re: Z Axis Plunging during cut

    I actually figured it out. To my surprise, the torque of the cutting is putting so much down force on the bit that it is actually pulling it out of the collet. I am not really sure how to remedy that, as my collet is a relatively new ER20 1/2". Any suggestions??? I suppose the easiest thing is to just take smaller bites.



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    Default Re: Z Axis Plunging during cut

    Tighten the nut more.
    With a 1/2" compression bit, I can cut 1" deep at 800ipm with no issues. (With a 15HP spindle).

    If the bit is coming out of the collet, it's just not tight enough. It's that simple.

    Gerry

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    Default Re: Z Axis Plunging during cut

    Hi,
    good quality collets are required also.

    You might be tempted to think 'how can one collet be good when another seemingly identical one is not?'

    The angle of the taper is critical. The clamping force of the nut forces the collet deeper into the taper and the collet closes on the shank of the
    tool. If there is the slightest difference between the angle of the internal taper and the taper of the collet then the transmission of the clamping
    force (nut tension) to clamping force on the tool is much reduced.

    I have a set of Jones & Shipman collets for my ER25 and I use Rego-Fix collets in my ER16 high speed spindle. They work well. I have used cheap Chinese
    ER32 collets but had the same problems as you.....the tool pulling out....even with the nut clamped to 200 ft.lb....as tight as I could get it.

    Next issue is the shank of the tool. It should be spotlessly clean and oil free. I use a methylated spirits soaked rag to wipe the shank before I fit the tool.
    If the shank of the tool has a Weldon flat then it will almost certainly pull out.

    Craig



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    Default Re: Z Axis Plunging during cut

    Quote Originally Posted by ger21 View Post
    Tighten the nut more.
    With a 1/2" compression bit, I can cut 1" deep at 800ipm with no issues. (With a 15HP spindle).

    If the bit is coming out of the collet, it's just not tight enough. It's that simple.
    Is it a 2 flute or 3 flute compression bit? RPM's? I'm cutting 37 & 55 mm thick birch with a 3 flute, 1/2" compression in 3 and 4 passes respectively. 315ipm I'm going too slow, arn't i?



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Z Axis Plunging during cut

Z Axis Plunging during cut