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IndustryArena Forum > CNCzone Club House > Machinist Hangout > Rapidly dulling end mills?
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  1. #13

    Join Date
    May 2019
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    8

    Re: Rapidly dulling end mills?

    Quote Originally Posted by wmgeorge View Post
    Its all about Chip Load. Look at GWizard from CNC Cookbook. You can download a free trial and then decide if its worth the cost. Use 2 or 1 flute mills for wood, same as aluminum.

    You need to increase the feed rate. Did you even bother reading what was posted?

    GW Wizard says: .25 Inch dia 2 flute end mill. .375 Deep Cut 10676 Rpm and 92 ipm feed rate at least.
    My most recent settings:
    0.125 inch dia 2 flute end mill, 0.04 Deep cut, 9000 RPM, 79 ipm.
    The mill starts to veer off course if cut depth is 0.08 inch or higher. The depth of 0.375 inch is actually not cutting by CNC, and breaking bit in manual operation.

  2. #14
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    Jun 2010
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    3755

    Re: Rapidly dulling end mills?

    Sounds as though the cutter is doing more rubbing than cutting. The friction will cause heating and then abrasion of the cutter edge.
    Sometimes you find that the machine you have is not meant for the job. Sometimes you find you are using a cutter meant for steel rather than softer materials. The shape of the edge changes a lot between those materials. A 'steel' cutter will be rather poor on timber.

    Cheers
    Roger

  3. #15
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    Sep 2005
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    1475

    Re: Rapidly dulling end mills?

    Quote Originally Posted by trurle View Post
    My most recent settings:
    0.125 inch dia 2 flute end mill, 0.04 Deep cut, 9000 RPM, 79 ipm.
    The mill starts to veer off course if cut depth is 0.08 inch or higher. The depth of 0.375 inch is actually not cutting by CNC, and breaking bit in manual operation.
    The .125 or 1/8 inch bit is bending and veering or since your running a X-Carve the whole machine is twisting? Try the .250 as suggested in my post and those settings. I have bits I have used on MDF and never have an issue, I don't buy the $100 ones, nor the cheapest usually around $20 or so for .250. You are trying to cut, correct? I cut an 8 hour job with one bit in MDF using a Hitachi router motor I think was rated at 1 + Hp on 120 volts.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router

  4. #16
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    Re: Rapidly dulling end mills?

    The mill starts to veer off course if cut depth is 0.08 inch or higher.
    Very sad. What this means is that the spindle is too flexible, or too weak, to be able to make any serious cuts.
    There is no way this should be happening with any well-made machine. This means you have a lot of work to do to stiffen the whole machine - or you need to start with a new machine. Or just make very light cuts at all times - and forget about cutting metal.
    Sorry about this, but that's how it is.

    Cheers
    Roger

  5. #17

    Join Date
    May 2019
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    8

    Re: Rapidly dulling end mills?

    Quote Originally Posted by wmgeorge View Post
    The .125 or 1/8 inch bit is bending and veering or since your running a X-Carve the whole machine is twisting? Try the .250 as suggested in my post and those settings. I have bits I have used on MDF and never have an issue, I don't buy the $100 ones, nor the cheapest usually around $20 or so for .250. You are trying to cut, correct? I cut an 8 hour job with one bit in MDF using a Hitachi router motor I think was rated at 1 + Hp on 120 volts.
    The problems with veering off always start at X-axis, which had only 1 belt-driving stepper as opposed to 2 steppers on Y axis and screw-driving stepper on Z axis. Therefore, likely the problem with depth of cut is under-performing stepper. May be because i try to run 120V AC machine at 100V AC outlet.
    Regarding bits, i actually try to use bits in the range $1 - $5 per 1/4 inch bit (this is direct buy from China - likely corresponds to $20 per bit in US retail). The last batch is completely destroyed by now, and need to buy a new one.

  6. #18
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    Re: Rapidly dulling end mills?

    Not sure about the underperforming stepper idea. Usually, when a stepper starts to lose steps or get pushed around, the whole axis stutters to a stop.

    You can test this. Halve the axis speed and acceleration and see if the problem persists. Then up them by (say) 50% and test again.

    Cheers
    Roger

  7. #19

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    May 2019
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    Re: Rapidly dulling end mills?

    Quote Originally Posted by RCaffin View Post
    Not sure about the underperforming stepper idea. Usually, when a stepper starts to lose steps or get pushed around, the whole axis stutters to a stop.

    You can test this. Halve the axis speed and acceleration and see if the problem persists. Then up them by (say) 50% and test again.

    Cheers
    Roger
    Tested. Problem is speed-related. To be exact, in last batch i have tried to cut a round corner 60 mm radius at 2mm deep and 3000 mm/min. After making about 60 degrees curve into X axis (of required 90), end mill repeatedly cut the jagged diagonal instead of remaining part of curve, with severe vibrations (at which point i press abort button).

  8. #20

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    May 2019
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    8

    Re: Rapidly dulling end mills?

    Finally it turned out to be a debris accumulation problem.
    The problem was resolved by vacuum-cleaning the surface of workpiece after each pass. Successfully cut planned 2 pieces of furniture (72 meters of cut line total) with no visible degradation of bit.
    Final cut setting:
    1/8 inch, 2 flutes HSS bit. 3000mm/min, depth of cut 1mm, spindle speed 9000 RPM.
    Temperature rise is 8-12 C per minute. With stops for vacuum cleaning, the collet nut do not get hotter than 48C.

  9. #21
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    Re: Rapidly dulling end mills?

    You could phrase that as too much rubbing in the dust!

    You can solve a lot of that with a continuous air blast aimed at the cutter. It will cool the cutter and clear out the swarf. Then you could probably run continuous. Downside is that you need a compressor. Plenty of us use an air blast.


    Cheers
    Roger

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