Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: Backlash Compensation

  1. #1
    Join Date
    Jan 2004
    Posts
    693

    Default Backlash Compensation

    Is there any provisions for backlash compensation in the SB control software?

  2. #2
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,940

    Default

    No there isn't. It really isn't a good idea either and falls under the category of, "You can't fix hardware problems with software." But that doesn't stop people from trying.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  3. #3
    Join Date
    Jan 2004
    Posts
    693

    Default

    I did a bunch of reading on it last night. What I was able to figure out from a few forums is to get your machine right. Then try and pick up a few more thousands by backlash compensation. But you think is not a great solution either way? It seems to be pretty widely used and accepted. I'm with you though...seem kind of like a giant band-aid. I was just thinking if I could dial it in it might help pick up .003-.005" in tolerance. Just something to play with if it were available. Thanks as always for your hard earned insight.
    Erik

  4. #4
    Join Date
    Jan 2004
    Posts
    693

  5. #5
    Join Date
    Jan 2008
    Location
    Hobby-Tronics, Chiloquin Oregon
    Posts
    1,244

    Default

    "backlash compensation" - I don't think so! There are some great posts on here discussing keeping things properly tuned and replacing worn parts (IE pinions etc). I had an instance awhile back with some china end mills that were not cutting to my liking and what I discovered was a lot of 'bit flex'. Symptoms were similar to what I would expect from backlash but turned out it was in the bit itself. My machine is over 10 years old and I cut mostly cheap HD ply, so it gets a lot of long run use. The replaceable parts are cheap, quick to change, make my machine a good wood working tool. Russ
    AKA: Da Train Guy

  6. #6
    Join Date
    Jan 2004
    Posts
    693

    Default

    Thank you for the feedback guys.

  7. #7
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,940

    Default

    A Shopbot is 'reasonably' tight and backlash free when you measure .003-.007" of play in any one axis. I'd recommend getting a good dial indicator set up and measure everything including gantry AND table deflection when you press down on them with moderate force. There comes a point where you can't get a bolt together machine any tighter and you just have to do the best you can or look at other options. The gearboxes themselves will show .004- 006* in many cases when new.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  8. #8
    Join Date
    Apr 2013
    Location
    Kennebunkport, Maine
    Posts
    4,096

    Default

    Slightly off topic....Brady...5 yr old Desktop....Any time frame to replace anti-backlash nut on Z-axis, and spring for spindle support?
    What are indications of the need to replace?
    LIKE the one piece older Desktops with welded frame, and machined Y-rail area...vs. the new bolted together for my applications.
    Sorry for the off topic....and appreciate any info/threads Brady(Thanks in advance).
    scott
    Scott Plaisted
    2013 Desktop/spindle/VCP 9
    Maine

  9. #9
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,940

    Default

    Scott, What kind of play have you measured on your machine?

    I don't have a lot of good things to say about plastic lead nuts when real ballscrew/nut combos can be had for dirt... They are fine if you don't cut over 2 IPS in most cases on these machines.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  10. #10
    Join Date
    Apr 2013
    Location
    Kennebunkport, Maine
    Posts
    4,096

    Default

    OK,OK......THIS week I'll buy a dial indicator set Brady
    Still pretty tight on second passes, BUT Z seems to drop a hair on every RR(5 RR's will eliminate a light pencil mark on wood).
    Was just wondering if those years of cutting buttons at low Z had stretched the spring.
    I'll get some hard numbers when indicator(and steel plate?) come in.
    Sorry I asked the question without any numbers Brady
    scott
    Scott Plaisted
    2013 Desktop/spindle/VCP 9
    Maine

Posting Permissions

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