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IndustryArena Forum > MetalWorking Machines > Haas Machines > Haas Mills > Poor finish on a Mini Mill SS
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  1. #1
    Join Date
    Jun 2010
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    60

    Question Poor finish on a Mini Mill SS

    I've been running a part on a VF2. 12K spindle. HSM activated

    I've had to move it to a MiniMill SS. 10K spindle HSM activated

    Part is 6061 T6 Aluminium.

    The was had an excellent finish coming off of the VF2
    Now on the Mini Mill running at 80% feed(to compensate for the lack of 2000 rpm) the finish is unacceptable.








    It isn't chatter. It happens in XY as well as Z. For lack of a better way to describe it. The machine seems to be shuddering for a short distance after a direction change. Like it has to step left and right to find the correct direction.

    In the first photo you can see the shudder mark as the toolpath comes off of the straight edge onto the sweeping radius. If you look at the sweeping radius above the step it is perfect. It was like that all the way around until the path below the step was cut and the cutters flutes put the marks all the way up. The waves are ±2.5mm crest to crest.
    The next photos you can see the up down movement in Z. Feed rates range from 5000mm/min - 2500mm/min. These were just fine on the VF2.

    I have an idea that the machine has backlash and the previous owner tried to eliminate it electronically and not physically.
    Another possibility is parameter or setting variations. Can someone point me in the direction on which ones to look for.
    3rd possibility is the machine is not 100% level. I saw the setting up, and I'm a fussy barstard. The technician kept telling me "that's within tolerance". Not my tolerance!
    Or it is rocking on the feet. It does not feel like it is moving as far as I can tell.

    Slowing the feeds down does reduce the shudder but does not eliminate the problem.

    Any ideas?

  2. #2
    Join Date
    Aug 2014
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    889

    Re: Poor finish on a Mini Mill SS

    Terrible finish is right.It almost looks like your tool isn't sitting properly in the spindle taper and is loose. You can see the bad results in Z much more than any other. I think its mechanical.

  3. #3
    Join Date
    Jun 2010
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    60

    Re: Poor finish on a Mini Mill SS

    Quote Originally Posted by G59 View Post
    Terrible finish is right.It almost looks like your tool isn't sitting properly in the spindle taper and is loose. You can see the bad results in Z much more than any other. I think its mechanical.
    Definitely isn't the tool and/or holder. Happens with multiple tools. And only at specific places with the same tool. Direction change.
    Spoke to the technician and he said check the "minimum radius setting" I only found setting 85 "MAX CORNER ROUNDING" - set to 0.001.
    setting 191 is also set to "FINISH"

    Frustrating!!!

  4. #4
    Join Date
    Apr 2005
    Posts
    713

    Re: Poor finish on a Mini Mill SS

    I would first try setting max corner rounding to 0.025 and setting 191 to medium. Those are the default settings (atleast on my '07 VF-2ss). I doubt that is the problem but it's free and quick to try.

  5. #5
    Join Date
    Jul 2005
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    12177

    Re: Poor finish on a Mini Mill SS

    The machine seems to be shuddering for a short distance after a direction change.

    Good diagnosis; the MiniMills, Super or otherwise are simply not as rigid as a VF2. I have both machines and run the same parts on them and to get an almost comparable surface finish on the Super the feed has to be reduced to about 60% of that used on the VF2. Note I didn't say 'same' I said 'comparable. You can tweak the settings for corner rounding and use HSM but you will never get the same performance out of the SMM.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  6. #6
    Join Date
    Mar 2010
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    1852

    Re: Poor finish on a Mini Mill SS

    The difference SMM and a VF-1 or VF-2 is not just the machining envelope. It is the difference between machine that weight 7,500 lbs and one that can easily be moved around with a small pallet jack. That changes everything.
    Two Haas VF-2's, Haas HA5C, Haas HRT-9, Hardinge CHNC 1, Bother HS-300 Wire EDM, BobCAD V23, BobCAD V28

  7. #7
    Join Date
    Feb 2011
    Posts
    605

    Re: Poor finish on a Mini Mill SS

    Sure, but what he's talking about seem to be an actual problem.
    PM-45 CNC conversion built/run/sold.

  8. #8
    Join Date
    Nov 2013
    Posts
    5

    Re: Poor finish on a Mini Mill SS

    Check X and Y Coupling...

  9. #9
    Join Date
    Nov 2005
    Posts
    56

    Re: Poor finish on a Mini Mill SS

    I have always found the Haas poor when using high feed rates. It will also suffer if it isn't level.

    If it's juddering it could be the high feed milling it will try and cut corners to maintain feed rate but can be modified by using a G187

  10. #10
    Join Date
    Jun 2010
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    60

    Re: Poor finish on a Mini Mill SS

    Quote Originally Posted by Geof View Post
    The machine seems to be shuddering for a short distance after a direction change.

    Good diagnosis; the MiniMills, Super or otherwise are simply not as rigid as a VF2. I have both machines and run the same parts on them and to get an almost comparable surface finish on the Super the feed has to be reduced to about 60% of that used on the VF2. Note I didn't say 'same' I said 'comparable. You can tweak the settings for corner rounding and use HSM but you will never get the same performance out of the SMM.

    You certainly know how to spoil a party :-(

    If I had have known this was going to be an issue, we would have passed on the machine. Why do Haas even sell this machine if it cannot do what they say it can?

    Thank you for all the answers so far.

    The technician has just replaced the drive amplifiers and we are about to test

  11. #11
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    Jun 2010
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    60

    Re: Poor finish on a Mini Mill SS

    As per advice on a different forum, I did the spiral test today. Interesting and a little confusing results.

    Programmed a Ø250mm spiral in to out, 5mm step over. Feed 2500mm/min Spindle on but no tool.

    Ran the program and definitely had shudder. More prominent at North-South Y-axis direction change. Roughly 45° to 60° spread. It fades in and out so it is hard to pin point when it starts and stops. It can be felt touching the machine bed as it moves.

    Took of the front slide cover to check the Y-axis coupling. It is practically brand new and perfect condition.

    Ran the program again with the coupling exposed. The shudder is visually apparent when the Y slows down and changes direction. But it seems to happen in a wave pattern. It doesn't happen every lap. On for 2-3 laps, off for 2-3.
    I tried to take a video of the coupling and shudder, but the frame rate of my Samsung S5 is lacking to show it. I will try to get a slomo capable camera and take a video.

  12. #12
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    Jun 2010
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    60

    Re: Poor finish on a Mini Mill SS

    Did I scare everybody away with my last post?

  13. #13
    Join Date
    Jan 2005
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    15362

    Re: Poor finish on a Mini Mill SS

    Aquatic

    Running the Super MiniMill at 2500mm/min, is only for dreamers, if you can do that cutting at half that speed, I will be surprised,(Roughing would be ok at that speed) the MiniMill is better for finishing at high speed, than the Super Min-Mill, the Super Mini has a 10mm Pitch ballscrew, the MiniMill has a 6mm Pitch Ballscrew, they both have the same Encoders

    So the MiniMill has a higher Resolution,per/rev so a smoother cutting machine, not as fast in rapids, but does a better job over all

    The machine Resolution (low Encoder Count Per Rev) & control is where your problem is for high speed machining
    Mactec54

  14. #14
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    Jun 2010
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    60

    Angry Re: Poor finish on a Mini Mill SS

    Hey mac

    I only ran the test @ F2500.

    I'm beginning to believe we were conned into buying this machine.
    The technician/broker knew what I wanted to cut and said the machine would do it.
    And when the truth came out he said we were pushing it beyond its limits.
    I still say the we are not exceeding the limits and the machine should be able to do it. It can't even give a good finish @500mm/min

    Anyone want a Super Minimill 2 $60 000 Australian. You may want to take it slow though.




    Quote Originally Posted by mactec54 View Post
    Aquatic

    Running the Super MiniMill at 2500mm/min, is only for dreamers, if you can do that cutting at half that speed, I will be surprised,(Roughing would be ok at that speed) the MiniMill is better for finishing at high speed, than the Super Min-Mill, the Super Mini has a 10mm Pitch ballscrew, the MiniMill has a 6mm Pitch Ballscrew, they both have the same Encoders

    So the MiniMill has a higher Resolution,per/rev so a smoother cutting machine, not as fast in rapids, but does a better job over all

    The machine Resolution (low Encoder Count Per Rev) & control is where your problem is for high speed machining

  15. #15
    Join Date
    Aug 2014
    Posts
    889
    Quote Originally Posted by Aquatic View Post
    Hey mac

    I only ran the test @ F2500.

    I'm beginning to believe we were conned into buying this machine.
    The technician/broker knew what I wanted to cut and said the machine would do it.
    And when the truth came out he said we were pushing it beyond its limits.
    I still say the we are not exceeding the limits and the machine should be able to do it. It can't even give a good finish @500mm/min

    Anyone want a Super Minimill 2 $60 000 Australian. You may want to take it slow though.

    For 60grand, I would expect way better than what your getting

  16. #16
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    Re: Poor finish on a Mini Mill SS

    Quote Originally Posted by G59 View Post
    For 60grand, I would expect way better than what your getting

    eg fecking zactly

  17. #17
    Join Date
    Nov 2005
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    164

    Re: Poor finish on a Mini Mill SS

    That floor finish looks like some of our parts when the drawbar went bad. Have they tested that?

  18. #18
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    Re: Poor finish on a Mini Mill SS

    Quote Originally Posted by JMFabrications View Post
    That floor finish looks like some of our parts when the drawbar went bad. Have they tested that?
    Yes. Perfect

  19. #19
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    Jul 2005
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    12177

    Re: Poor finish on a Mini Mill SS

    Question for you:

    The floor toolpaths that show the tight little swirls, are they trochoidial paths? (I don't think my spelling is correct.)
    An open mind is a virtue...so long as all the common sense has not leaked out.

  20. #20
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    Jun 2010
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    60

    Re: Poor finish on a Mini Mill SS

    Quote Originally Posted by Geof View Post
    Question for you:

    The floor toolpaths that show the tight little swirls, are they trochoidial paths? (I don't think my spelling is correct.)


    No. Straight lines.
    Coming from the right on the right hand side. straight - 20° left - straight - 110° left - straight

    And even adding a small radius at the junctions doesn't make a difference.

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