Welcome to Our Community

Some features disabled for guests. Register Today.

Sign Up

Large Z dive when CNC pocketing

Discussion in 'CAM' started by sergiomajluf, Apr 4, 2021.

Tags:
  1. sergiomajluf

    sergiomajluf Well-Known
    Builder

    Joined:
    Jun 2, 2020
    Messages:
    44
    Likes Received:
    36
    Hi everybody

    I'm getting weird hops in the z axis when doing pocket operations.

    For example, a 30mm deep pocket, with 3mm cut per path should generate 10 "layers", am I right? I'm getting only 4 layers, three 3mm deep, and then a fourth, 300mm deep.

    upload_2021-4-4_10-16-0.png

    Or a 6.73 deep cut ("base-pivotes" toolpath), with DoC of 2mm creates a first Z pass of -0.73, then correctly a -2.7mm pass and then incorrectly -6.7

    (on a side note, is it possible to make the first pass deeper so I can appropriately use a compression bit?)

    When doing shallow pockets it is not as noticeable, but it is still there. Have attached workspace for reference. All three toolpaths show the same behavior.
     

    Attached Files:

    #1 sergiomajluf, Apr 4, 2021
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Aug 6, 2013
    Messages:
    3,279
    Likes Received:
    1,836
    smells like a classic floating point inequality Peter
     
    #2 David the swarfer, Apr 4, 2021
    Peter Van Der Walt likes this.
  3. sharmstr

    sharmstr OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 23, 2018
    Messages:
    2,035
    Likes Received:
    1,431
    Peter will be able to answer this. But yes, I see the issues. However, if I select your 30mm pocket and add a new operation, it correctly gives me 10 cut layers. So maybe your toolpath got corrupted.

    G0 Z0
    G1 F400 Z-3.0000
    G1 F1200 X-35.4546 Y29.1279 Z-3.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-3.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-3.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-3.0000 S1000
    G1 F400 Z-6.0000
    G1 F1200 X-35.4546 Y29.1279 Z-6.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-6.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-6.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-6.0000 S1000
    G1 F400 Z-9.0000
    G1 F1200 X-35.4546 Y29.1279 Z-9.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-9.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-9.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-9.0000 S1000
    G1 F400 Z-12.0000
    G1 F1200 X-35.4546 Y29.1279 Z-12.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-12.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-12.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-12.0000 S1000
    G1 F400 Z-15.0000
    G1 F1200 X-35.4546 Y29.1279 Z-15.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-15.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-15.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-15.0000 S1000
    G1 F400 Z-18.0000
    G1 F1200 X-35.4546 Y29.1279 Z-18.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-18.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-18.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-18.0000 S1000
    G1 F400 Z-21.0000
    G1 F1200 X-35.4546 Y29.1279 Z-21.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-21.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-21.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-21.0000 S1000
    G1 F400 Z-24.0000
    G1 F1200 X-35.4546 Y29.1279 Z-24.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-24.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-24.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-24.0000 S1000
    G1 F400 Z-27.0000
    G1 F1200 X-35.4546 Y29.1279 Z-27.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-27.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-27.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-27.0000 S1000
    G1 F400 Z-30.0000
    G1 F1200 X-35.4546 Y29.1279 Z-30.0000 S1000
    G1 F1200 X-35.4546 Y27.3201 Z-30.0000 S1000
    G1 F1200 X28.2123 Y27.3201 Z-30.0000 S1000
    G1 F1200 X28.2123 Y29.1279 Z-30.0000 S1000
     
    #3 sharmstr, Apr 4, 2021
    Peter Van Der Walt likes this.
  4. sharmstr

    sharmstr OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 23, 2018
    Messages:
    2,035
    Likes Received:
    1,431
    Forgot to say that you can set your first cut depth by entering a value in "Cut Depth Start" box. So, if you want to start at 6 and your cut per pass depth is 3 then set it to 3.
     
    #4 sharmstr, Apr 4, 2021
    Peter Van Der Walt likes this.
  5. sergiomajluf

    sergiomajluf Well-Known
    Builder

    Joined:
    Jun 2, 2020
    Messages:
    44
    Likes Received:
    36
    Thanks sharmstr. I started fresh and got a correct pocket toolpath for the 30mm. Then added a second toolpath for other geometry, always with whole numbers, and got the same error (don't know if whole vs decimal makes a difference then).

    I can still cnc the piece by trying to create new files for each operation still, but hopefully this apparent bug will be catched by the allmighty Peter :)

    happy easter sunday guys!
     
    #5 sergiomajluf, Apr 4, 2021
    sharmstr and Peter Van Der Walt like this.
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,002
    Likes Received:
    4,113
    Post the workspace exports so we can go bug hunting next week
     
    #6 Peter Van Der Walt, Apr 4, 2021
  7. sergiomajluf

    sergiomajluf Well-Known
    Builder

    Joined:
    Jun 2, 2020
    Messages:
    44
    Likes Received:
    36
    Attached to first post. Thanks!
     
    #7 sergiomajluf, Apr 4, 2021
    Peter Van Der Walt likes this.
  8. sharmstr

    sharmstr OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 23, 2018
    Messages:
    2,035
    Likes Received:
    1,431
    I just tried to recreate your issue and cant. Clearly there's an issue with the workspace you posted, but any and all new toolpaths generate correctly even with 11.19 cut depth. Peter might need more info (exact steps, video, etc) in order to find the issue. I dunno.
     
    #8 sharmstr, Apr 4, 2021
    Peter Van Der Walt likes this.
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,002
    Likes Received:
    4,113
    Quick, not-at-work-bugfix pushed, give it a test (force a refresh with ctrl+F5/shift+F5) and let me know if that broke something else in turn, didn't do a lot of testing.
     
    #9 Peter Van Der Walt, Apr 4, 2021
  10. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,002
    Likes Received:
    4,113
    Changing the geometry to unmerged on a pocket revealed a bug. I just cannot remember why the stepdown routine differed between merged and unmerged - was there a reason - or just forgot to update one of them at some point lol. Fixed bug with Z on pockets · OpenBuilds/OpenBuilds-CAM@f86c7cc anyway if it broke something else, his sample workspace works now with both merged geometry and without.
     
    #10 Peter Van Der Walt, Apr 4, 2021
    sergiomajluf and sharmstr like this.
  11. sergiomajluf

    sergiomajluf Well-Known
    Builder

    Joined:
    Jun 2, 2020
    Messages:
    44
    Likes Received:
    36
    Can confirm it works OK.
    THANKS!
     
    #11 sergiomajluf, Apr 5, 2021
    sharmstr and Peter Van Der Walt like this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Accept Learn More...
    Dismiss Notice