524,397 active members*
2,842 visitors online*
Register for free
Login
Page 1 of 4 123
Results 1 to 20 of 63
  1. #1
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Rough Finish on 45 Degree wall

    So i once thought that some of my rough finishes on angles might be do to my linear rails needing replaced on my Hurco Mill.(https://www.cnczone.com/forums/dynom...-software.html) But have recently replaced them. And now iam making an aluminum part that is octagon shape with 45 degree walls. All the walls that are inline with X or Y axis have a nice finish but the walls that are 45* have a rough finish, see pics.You can easily feel High and Low spots with finger. The walls are .425" tall and iam using a new carbide .5" variable-helix endmill.
    Could this be my settings setup in the Trajectory Planner Screen?
    Here is Gcode.

    Code:
    %
    O1001 (ENCODERMOUNTPLATEOP1C)
    (T5 D=0.5 CR=0.005 - ZMIN=-0.425 - BULLNOSE END MILL)
    N1 G90 G94 G17 G49 G40 G80
    N2 G20
    N3 G53 G00 Z0.
    
    (2D CONTOURFINISH)
    N4 T5 M06
    N5 S2500 M03
    N6 G54
    N7 M08
    N8 G00 X0.05 Y-2.919
    N9 G00 G43 Z1. H05
    N10 G00 Z0.2
    N11 G01 Z0.0394 F5.
    N12 G01 Z-0.425
    N13 G01 G41 X0.325 Y-2.869 D05 F20.
    N14 G03 X0. Y-2.544 I-0.325 J0.
    N15 G01 X-1.0538
    N16 G01 X-2.544 Y-1.0538
    N17 G01 Y1.0538
    N18 G01 X-1.0538 Y2.544
    N19 G01 X1.0538
    N20 G01 X2.544 Y1.0538
    N21 G01 Y-1.0538
    N22 G01 X1.0538 Y-2.544
    N23 G01 X0.
    N24 G03 X-0.325 Y-2.869 I0. J-0.325
    N25 G01 G40 X-0.05 Y-2.919
    N26 G00 Z1.
    
    N27 M09
    N28 M09
    N29 M05
    N30 G53 G00 Z0.
    N31 G49
    N32 G53 G00 X11. Y0.
    N33 M30
    %
    Troy
    Attached Thumbnails Attached Thumbnails Right45.jpg   RightYaxis.jpg   Left45.jpg   LeftYaxis.jpg  


  2. #2
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    I notice this as well. Not that bad, but I do get slightly better finish in X and Y moves then on interpolated moves. Im guessing its most likely to be minor oscillations in the servo tuning. Might be worth trying to same test with less P/I gain or more D gain. Another thing that could be working against you is servo deadband. I found turning deadband off made noticeable improvement in surface finish on interpolated moves. I hear a tiny amount of dithering without deadband so now I get my M3 and M5 programs to turn servo deadband on only while stopped.

    Could possibly be a rough thrust bearings or maybe even ball screw. My Y axis thrust bearing has very slight rumble in it. I wonder if this could be causing the problem on my end. Hasn't been enough of a problem for me to dig into it yet.

  3. #3
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Re: Rough Finish on 45 Degree wall

    I had 0 for my Deadband except for X axis it had a Deadband range of 1, dont remember doing that. Made it 0 like Y and Z but still no change in finish. P and D are both 0 with I at .003.

    Dont think its my ballscrews(could be wrong) as they are double nut with .0002 backlash at most. I also checked end play of ball screw when i replaced rails and got 0. Would think if it was mechanical like this that there would be similar(not exact) finish on surfaces inline with axis also, especially in harder materials??

    Is your drives +/- 10V analog? Mine is still DMM-Tech's Step/Dir. I have plans to try the analog again now that the lathe is working in analog mode.

    Troy

  4. #4
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Yes im using +/- 10v analog torque mode. This is with the original Fadal DC servos with feedback to Kflop only, no tach feedback to servo drives. Since your using the DMM servos and have lots of options, might be interesting to try and come up with a good tune in both torque mode and velocity mode and try cutting in both modes and compare your results. I wonder if velocity mode may do a little better here?

    Curious to see what Tom has to say about this and possible ways to improve it.

  5. #5
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Re: Rough Finish on 45 Degree wall

    Ive never been truly satisfied with DMM-Tech drive in Step/Dir. Could never get it as smooth as it should be. Its really noticeable when doing high speed toolpaths with short moves. The drives in this mode are always "tunning" themselves as they state, and seems like it is fighting Kflop. I can smooth it out some by changing my Trajectory Screen settings per gcode.

    Can you share your tunnings and filter settings you are using? I used your settings from your 4th axis on my lathe and it worked well.

    Thanks,
    Troy

  6. #6
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Here are my settings for X axis. Y and Z are pretty much same.

    ch0->InputMode=ENCODER_MODE;
    ch0->OutputMode=DAC_SERVO_MODE;
    ch0->Vel=1020000;
    ch0->Accel=3500000;
    ch0->Jerk=200000000;
    ch0->P=2;
    ch0->I=0.025;
    ch0->D=0;
    ch0->FFAccel=0;
    ch0->FFVel=0;
    ch0->MaxI=500;
    ch0->MaxErr=300;
    ch0->MaxOutput=1000;
    ch0->DeadBandGain=0;
    ch0->DeadBandRange=2;
    ch0->InputChan0=0;
    ch0->InputChan1=0;
    ch0->OutputChan0=0;
    ch0->OutputChan1=1;
    ch0->MasterAxis=-1;
    ch0->LimitSwitchOptions=0x10;
    ch0->SoftLimitPos=2377440; // set limit +19.5 inches
    ch0->SoftLimitNeg=-2377440; // set limit -19.5 inches
    ch0->InputGain0=-1;
    ch0->InputGain1=1;
    ch0->InputOffset0=0;
    ch0->InputOffset1=0;
    ch0->OutputGain=-1;
    ch0->OutputOffset=0;
    ch0->SlaveGain=1;
    ch0->BacklashMode=BACKLASH_LINEAR;
    ch0->BacklashAmount=36; // 48 for 0.0003" 12.192 COUNTS PER TENTH
    ch0->BacklashRate=2000;
    ch0->invDistPerCycle=1;
    ch0->Lead=0;
    ch0->MaxFollowingError=5000;
    ch0->StepperAmplitude=20;

    //Pole zero 45, 180
    ch0->iir[0].B0=14.849600;
    ch0->iir[0].B1=-28.946699;
    ch0->iir[0].B2=14.106600;
    ch0->iir[0].A1=1.804700;
    ch0->iir[0].A2=-0.814233;

    ch0->iir[1].B0=1.000000;
    ch0->iir[1].B1=0.000000;
    ch0->iir[1].B2=0.000000;
    ch0->iir[1].A1=0.000000;
    ch0->iir[1].A2=0.000000;

    // Low pass 500
    ch0->iir[2].B0=0.123861;
    ch0->iir[2].B1=0.123861;
    ch0->iir[2].B2=0.000000;
    ch0->iir[2].A1=0.752278;
    ch0->iir[2].A2=0.000000;

    I didnt come up with the pole zero settings. But they seem to work very well. I bought the machine used and previous owner had started the retrofit and had motor tuning pretty much done.

    I have a DMM servo on my 4th axis (+/- 10V analog setup) and tried all sorts of tuning but never got great results either. Just for kicks I tried running torque mode and adding that pole zero filter, with no idea of what it does or what values I should use, and it worked awesome. And seemed to work for you too. Strange there isn't more people using this, and more discussion about it.

  7. #7
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Also one more thing to note with the DMM drives. Using analog torque mode bypasses all the DMM tuning, so you have full control with Kflop. No fighting with each other. I had much better results with my 4th axis in torque mode.

  8. #8
    Junior Member
    Join Date
    May 2006
    Posts
    3384

    Re: Rough Finish on 45 Degree wall

    Hi Troy,

    I'd suggest capturing data while making that cut so we can analyze how well the servo is doing.

    The attached program should capture 10,000 data points with a sample rate of 540us/sample (~5 seconds worth). You must have a C:\Temp directory. The file will be KFLOPdata.txt

    Assign it to an MCode (Execute without any wait and some unused Thread).

    Then place the MCode into the GCode just before the diagonal cut - between N15 and N16. Then if you send me the data I will plot and analyze it.

    Please also post what your axes resolutions are.

    Any guess at how much deviation there is causing the ridged pattern? Any way to measure it?
    TK
    http://dynomotion.com

  9. #9
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    After cutting, rotate your part 45 degrees so its inline with the X axis, then run a tenths indicator over it to see how much variation you have.

  10. #10
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Re: Rough Finish on 45 Degree wall

    Hi Tom,
    Sorry late responding.Getting things ready to test Granite Devices drive with my 4th axis Fanuc servo.(They give 3 weeks to try it out.)

    Attached is Data file, current test Gcode and screen shot of my current Trajectory Planner Screen.

    I used a .0001" indicator with a .08" diameter probe tip on the 45* and was getting .0006" to .0008" high and low spots.If i had a smaller tip probe there would most likely be more than .0008". When i checked the 0* there was not even a .0001" tenth of movement.

    Thanks much again,
    Troy

  11. #11
    Junior Member
    Join Date
    May 2006
    Posts
    3384

    Re: Rough Finish on 45 Degree wall

    Hi Troy,

    Never a rush from our end

    Here is the data plotted:

    Attachment 441254

    Attachment 441256

    Attachment 441258

    Not sure what to say. The servo errors seem to be only several encoder counts so I wouldn't expect it ever to be better than that. The servo errors seem to be ~ 4X better than what you are measuring so even if they were zero I wouldn't expect much improvement. However there does seem to be a repeating pattern every ~ 0.2seconds. Maybe lead screw pitch/wobble or something. And I would expect the servo to correct errors that persist for ~0.1 seconds.

    What is your lead screw pitch and feed rate again?
    TK
    http://dynomotion.com

  12. #12
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Interesting stuff guys. If you look at the fact that the error is adding and subtracting, the total error is much closer to measured. For example at 3.35 seconds X is leading by 0.0003", then at 3.45 seconds its laging by 0.0002", that would be 0.0005 total variation which you would definitely see in the finish. Not sure how the exact total amount of error works out considering its at a 45 degree angle, its probably much more complicated then this.

    Seems odd to me that both axes have the exact same repeating pattern, its even the exact same shape of waveform. This makes me think its in the servo or drive. Looks like your feeding at 20 IPM at 45 degrees, this works out to 14.1 IPM per axis, over 2 seconds this would be 0.47", and there are just under 5 cycles so looks like its repeating every 0.100". No way your ball screws are this fine. My guess is that you have 10mm pitch ballscrews (approximately 0.400"), and you have 4 pole servo motors, and this is a pattern created going from pole to pole of the servo motors.

  13. #13
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Troy, try doing the same test again, but do it in 4 different depths, and offset the Y axis 0.025" for each depth. I bet every offset will give you a different pattern, and one will give a very good finish. This will confirm my pole theory, or eliminate it so you can go back to looking at mechanical issues.

  14. #14
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Re: Rough Finish on 45 Degree wall

    Screws are 10mm pitch.
    That is interesting murray, checking with indicator the pattern is about every .100".
    Do you mean different Z depths?
    Also, there has always been a different tone of the servo on my Z axis. So the other day when i was doing a spiral bore and Z was feeding about 10IPM, i placed my finger on the servo coupling(dont try this at home) and was feeling a pulse of motor maybe every second. Shouldn't it be smooth all the time?

    Troy

  15. #15
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Yeah do 4 different depths. For example start with a piece of stock at least 0.550 above your vise and do your test 0.125 deep. Then shift Y -0.025 negative and Z -0.125 and do it again. When your done you have 4 faces to compare. This small shift in Y will cause a phase shift in the Y axis error in Toms graph. At some point, the waves should be close to on top of each other and you should have very little position error between the two. If they overlap, the cycling will just result in micro small variations in feedrate then, and not actually create any error in the cut.

    Really looks to me that this is what your seeing. If it is, its disappointing to see this from the DMM drives. You think the drive manufacturer would have this figured out, and output would be perfectly smooth.

  16. #16
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Re: Rough Finish on 45 Degree wall

    So i did the different depths and offset in Y. I started at .525" deep and came up from there each time and moved Y in the plus direction each time.
    You can see the pattern moving to the left but finish is the same. Attached is 4 plots, one for each depth. Think the final test would be with drives in Analog mode.
    Troy
    Attached Files Attached Files

  17. #17
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Can you post a picture of the block? Curious what it looks like. I was really thinking you would see some cuts with a better finish then others.

  18. #18
    Junior Member
    Join Date
    Dec 2007
    Posts
    553

    Re: Rough Finish on 45 Degree wall

    Hi murry,
    Attached is X axis only and 2 of XY 45*.
    Attached Thumbnails Attached Thumbnails Xaxis.jpg   XYaxis1.jpg   XYaxis2.jpg  

  19. #19
    Registered
    Join Date
    May 2012
    Posts
    495

    Re: Rough Finish on 45 Degree wall

    Hmmm, doesn't look to be a whole lot of difference, bottom one could possibly be a little smoother but might just be picture. Do they all look similar on the dial? They all seem to have some micro variations in the finish, but the larger 0.0005-0.0008 wave you were getting may be reduced. Doesn't look like you have any repeating mechanical patterns which is good.

    Interesting fact... If you feed a half inch endmill 0.004 per flute on a finish pass, you can clearly see each tooth on the machined part if you look close. The height difference on the part from flute to flute is theoretically 0.000013" high. A hundredth of a thou. So unfortunately the bar is set pretty darn high to get absolutely perfect looking interpolated cuts.

    You might still have room for improvement. Will be interesting to see if analog mode is any better/worse, and how different tuning affects it.

  20. #20
    Member
    Join Date
    Jan 2005
    Posts
    11232

    Re: Rough Finish on 45 Degree wall

    Quote Originally Posted by Need TECH Help! View Post
    Hi murry,
    Attached is X axis only and 2 of XY 45*.
    What are the servo motors and encoder PPR

    It looks like a normal finish of a low count ( PPR ) encoder machine, The difference between the actual and command position is known as lag, following error or position error, add in the jerk factor and you get what you are seeing in your finish
    Mactec54

Page 1 of 4 123

Similar Threads

  1. Only MeshCam has option to rough and finish?
    By estes53 in forum Uncategorised CAM Discussion
    Replies: 5
    Last Post: 07-18-2015, 04:46 AM
  2. VMC Side wall surface finish, Newbie question
    By BlueTwo in forum Uncategorised MetalWorking Machines
    Replies: 10
    Last Post: 10-07-2011, 10:06 AM
  3. Problems with rough finish
    By 44-henry in forum Tormach Personal CNC Mill
    Replies: 11
    Last Post: 06-02-2009, 06:43 PM
  4. How to rough/finish threadmill in MCX?
    By John_B in forum Mastercam
    Replies: 4
    Last Post: 07-27-2008, 04:25 PM
  5. Very rough finish when turning 6061-T6 ... why?
    By cnczoner in forum Uncategorised MetalWorking Machines
    Replies: 18
    Last Post: 03-16-2008, 11:24 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •