Need Help! Machine out of square


Results 1 to 12 of 12

Thread: Machine out of square

  1. #1
    Member
    Join Date
    Sep 2017
    Location
    United States
    Posts
    18
    Downloads
    0
    Uploads
    0

    Default Machine out of square

    When cutting a piece out that should be square, my bottom edge is 1/16" shorter than my top edge, and instead of 90-degree angles, I have 90.121-degree angles (or 89.879-degree). It's not much, but it seems to be enough that my machine is chugging around corners and giving me very jagged edges on any rounded part. When cutting straight lines my long axis cuts smoothe, but my short one is a little jittery. Round holes come out as irregular roundish shapes.


    How do you fix the square of a plasma table? Our manufacturer keeps telling us that the machine is field serviceable and he shouldn't have to send a tech out.

    Similar Threads:
    Attached Thumbnails Attached Thumbnails Machine out of square-jagged-edges-png  


  2. #2
    Member
    Join Date
    Sep 2006
    Location
    United States
    Posts
    245
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    Do you have 2 motors on one of the axis? The problem is that one side can be further advanced than the other and the second axis will be out of square.

    Mach3 allows you to calibrate ganged rails to be square. You set up limit switches to detect when the machine is exactly square. A calibration routine moves both sides until one limit switch trips, then advances only the side that is behind. When it trips, your machine should be square.

    This will be the next upgrade for my CNC router. It cuts reasonably close, but would be better if it could be calibrated each time.

    Steve



  3. #3
    Member
    Join Date
    Sep 2017
    Location
    United States
    Posts
    18
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    I have a stepper motor on each side of the gantry.I have the software that came with the table, but I don't see how to control each motor individually, just how to control the entire axis. I jsut downloaded Mach3 to take a look at that, and most of the features seem similar between the programs, and I can't find a calibration option. Is there a tutorial somewhere?



  4. #4
    Member
    Join Date
    Sep 2006
    Location
    United States
    Posts
    245
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    The calibration program for Mach3 might be an add-on macro. Search Google for Mach3 slave axis calibration. I haven't looked seriously at adding it to my machine yet, since it stays relatively square. I measured it once and was comfortable with the error, but in the back of my mind I think I should add the feature.

    I am not sure what your picture is supposed to look like, but it seems like a 90.121 degree angle would only produce a small error. I calculate 0.002" per inch, so a 12" part would only be off by 0.024". Are you sure there is not something else going on? Maybe backlash or some other issue?

    Steve



  5. #5
    Member
    Join Date
    Sep 2017
    Location
    United States
    Posts
    18
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    I'm actually not sure there isn't another issue. This is the only thing we've found that's actually off by anything. The manufacturer told us that if the table isn't square, it will bind up and stutter like it has been. We haven't been given a technical manual for the thing or told how to check any of the mechanics, just that "it should be field serviceable" so we should be able to fix it. My problem is that I know how to run the software well enough to cut my parts, but I don't know anything about the mechanics of the hardware. I know it isn't the torch; it does the same thing with a sharpie.



  6. #6
    Gold Member LeeWay's Avatar
    Join Date
    Jun 2004
    Location
    United States
    Posts
    6618
    Downloads
    2
    Uploads
    0

    Default Re: Machine out of square

    Post up a few pictures of the machine and how it is driven.

    Lee


  7. #7
    Member
    Join Date
    Sep 2006
    Location
    United States
    Posts
    245
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    Does the machine have stepper motors or servos with position feedback?

    My machine has stepper motors. If one of the X axis motors skips a few steps, the gantry will rack and bind. It is typically not recoverable.

    If the machine has closed loop servos, then it might be possible for the motors to skip and catch back up. That might cause jagged edges, but otherwise completes cutting the part to the approximate outline.

    Steve



  8. #8
    Member
    Join Date
    Sep 2017
    Location
    United States
    Posts
    18
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square



    The machine uses stepper motors and a rack and pinion system. I've gotten it square now, according to a 3/4/5 triangle, but the problem persists. It slows down considerably around the rough corners. My kerf width is about 6 times wider than Hypertherms estimated compensation says it should be in my manual. I have bad dross with Hypertherms recommended settings.

    Attached Thumbnails Attached Thumbnails Machine out of square-20171003_155610-jpg   Machine out of square-20171003_155617-jpg   Machine out of square-20171003_155511-jpg   Machine out of square-20171003_155549-jpg  



  9. #9
    Member
    Join Date
    Sep 2006
    Location
    United States
    Posts
    245
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    My best guess after seeing the pictures is that the wavy edges are due to backlash compensation. I never got backlash compensation in Mach3 to work properly on my router and eventually just turned it off. Again, this is just a guess. It seems like you either have some serious mechanical backlash, or the software is trying to adjust for backlash and making it worse. Can you try turning off backlash compensation?

    A machine that is out of square would produce ovals instead of circles, but the edges should still be smooth unless something else is going on.

    Steve



  10. #10
    Member
    Join Date
    Sep 2017
    Location
    United States
    Posts
    18
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    The only mention of backlash I can find in any of my documentation reads: "DRIVE SYSTEM – Zero-Backlash drive system is powered by heavy-duty NEMA 34 drive motors."



  11. #11
    Member
    Join Date
    Jul 2005
    Location
    USA
    Posts
    2415
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    . Get a 90 deg large square or measure and find a piece of metal sheet that is the same length from corner to corner lay yhe long edge along the left side of the gantry rail . Jog your axis so the torch is at the far left of the sheet. now jog just the cross axis . It helps to have an insert that will hold a pointer , scriber tool or pencil in place of the torch. Run the torch back and forth and see how far out you actually are from square. Now turn off the motors and see if the gantry springs in either direction. If it is not square when the motors are freewheeling then loosen the bolts on the carriages and tap the gantry nice and square using the square sheet edges. you will need to loosen both side of the gantry so you can twist the cross structure. Once you know the gantry bean is sqaure to the left rail and you adjust the other carriage to run smooth than its down to keep ing the motors in sync. The gantry structure needs to start out sqaure to the lef rail and then the right rail needs to be exactly parallel to the other one . You can use the gantry to act as a gap gauge at both ends.

    Another way to get a perfect 90 deg triangle. Get a large sheet of cardboard that is factory edge on one edge. Measure down that side and mark mark 4 ft .Get a straight edge and lay it at 90 degs to the bottom of the 4 ft long side. Mark the srtaiht edge at exactly 3ff Measure with a tape measue from the top of the 4 ft side down at an angle until it you can move the tap and the staight edge to innersect at the 3ft and 5ft mark on the tape. Its a perfect 3/4/5 triangle and the 3 ft length will be exactly 90 deg to the 4 ft side. The objective is to get a large traingle you canuse to sqaure your gantry to the rails and have it run square and true

    Once the gantry is perfectly square then you need to sync the motors. You use dual homing switches and it will auto -square itself every time it homes. While you can tune each axis slighlty different in MACH (motor tuning) its seldom necessary if the motors and mechanics are the same on each side. Biggest issue is always loose mechanics causing backlash. turn on you motors so they lock and go to each motor and try hard to move the mechanics back and forth. It should have virtually no slop. If it does you need to hunt down what is slipping and either tighten down the set screws or take the pulley.or gear off the shaft and use Loktite Cylindrical locking fluid. NOT regular thread locker.

    The alighnment of your table is like the alignment of your car. It needs to be correct and checked from time to time. You should not have jerky movement on an axis. Put your hand on the Z while someone jogs first one axis then the other. Jog the Z up and down. It should move smoothly.



  12. #12
    Member
    Join Date
    Sep 2017
    Location
    United States
    Posts
    18
    Downloads
    0
    Uploads
    0

    Default Re: Machine out of square

    We've gotten it square, and we've already tightened the set screws on everything. It moves smoothly between commands, and there isn't really any slop when you just push things around. It will execute a G02 command smoothly, at full feedrate along the entire curve. A G02 curve cuts with no jagged edges. The same curve recreated with G01 commands cuts like the pictures shown, and it doesn't maintain the same feedrate along the entire curve. It's like its stopping for half a moment between each line of code before continuing on to the next line, or jerking from one to the next like a sitcom teenager learning to drive. I don't remember this being the case a few months ago, before this started. But maybe they all do that and I never noticed thanks to safety shades?

    "Though many systems aim to simply minimize backlash, we use a gearbox that offers zero backlash. That means that our gearbox has been perfectly designed and manufactured to ensure that no thermal expansion or retraction interferes with the system." From the maufacturer's site.

    Last edited by Fyresparxx; 10-04-2017 at 12:10 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
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Machine out of square

Machine out of square