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Author Topic: Z zero (plane) moves upwards with every Z dir movement  (Read 2904 times)

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #30 on: April 10, 2018, 04:53:54 AM »
Okay, I will. I'll have time on Wednesday afternoon (gmt+1)

Offline RICH

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #31 on: April 10, 2018, 05:59:15 AM »
I usualy don't even reply to any problems when someone is using a TB*********x controller as they
are know to be problematic. I am making an exception here.

 Your problem is accleration and understand  that it s directly related to your complete system
and how they are all interelated. Also understand that the demands for doing 3d work as compared to
doing 2D work is is greater. Based on what you have posted here is what you need to do.

1. Create a new xml file, maybe call it TESTING
2. Set the drives for 1/8 microstepping. So find the new value for the steps per unit for each axis.
    You can use the axis calibration of Mach to find the steps per unit instead of calculating them.
    The resolution for an axis is 1/ steps per unit     in theory but prsacticaly may be less.
     Your drives have automatic idle current reduction and if there is an option to not use it don't use it.
     Don't know a recomended value for pulse width for that drive, consult you manual.
     - turn off  backlash comp
      
3. Tune EACH axis this way:
    - start with low velocity setting say 10 and double the velocity until the motor skips.  Then reduce the
       max velocity found when it skipped to a value 30%  to 40% less. Suggest setting start accleration
      value of 1 for a max velocity value of 10 to 100, and increase the accel as you test ie; accel 2 for max value  of
      of 100 - 500, 3 for value of 500 to 1000. ( 1000mm/min = 39.4 inches per min )
 
      After you find where the motor skipped  and have the max velocity set, do similar for the accel
      but the increase value, may be small increases ie; like 0.5 . Do this until the axis skips.
      
      Note the following:
      -You want a the highest velocity and acceleration for your system which is accurate and reliable.
        You need head room on the settings to allow for machining forces, axis change in forces to move
         the axis, etc. Reliability is more important than speed and high acceleration is desirable.

       - a motor spec would help as that gives basic ball park info for motor tuning and just how much power
         motor can deliver, but, yo would still do the above tuning

        - Mach3 is not your problem.
        
         - The problem in 3D is the motor must have the ability to accel and decell the axis for small moves.
            You can have no problems doing 2D work, but the motors may be inadequate  for 3D work.
             Minimize the torque to just move the axis ( refinement of the machines axis components),
             and provide appropriate gcode for YOUR machine.

          - steppers can skip and you would not know it but will see the affects when doing 3Dwork.
             The loss of position can be repeatable or random, usualy random so you get into a guessing
             game of what is wrong.

          - Backlash when applied properly works quite well but has no place adn can be problematic.
            
          - as Gerry replied that the driver test may be adequate, franlky, i would comment that the
            HZ value is probably  floating more or dropping even lower when your actualy running a
            program.
            
4. After you have configuration correct for YOUR machine. Test for skipping. Use a short length
    gcode file form CAM. Make sure the code generated  is appropriate for your machines capabilites.

Please don't reply back (to me) and give another "guess" or even question other parts of the system until you have
done the above.

RICH
« Last Edit: April 10, 2018, 06:05:35 AM by RICH »
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #32 on: April 11, 2018, 10:43:09 AM »
Well, I did what you told me to, but I don't understand what you say about the xml file or what should I do with  it.
So I did everything you told me to do and what I could, but the problem still persist.


My settings are on all axes: 2400mm/min velocity and 50mm/sec/sec acceleration, although it didn't skip on 150 and even on 200.
I use 4mm pitch  leadscrew and here are the motors details:
Step Angle (1,8°)   Motor Length (56mm)
Rate Current (2.8A)   Phase Resistance (0.9Ω)   Phase Inductance (2.5mH)   Holding Torque (1.26N.m)   Lead Wire (NO.: 4)
Rotor Inertia (280 g.cm)
Motor Weight (0.68 KG)
I use a 36V5A PSU inverter for the motors. I measured the voltage it produces and it's more than 35.5V all the time. I measured the current that the motors draw and it is never more than 2.9-3A even when all the axes are jogging at full speed.

Offline RICH

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #33 on: April 11, 2018, 08:02:33 PM »
You can copy a current xml file and rename it to say test.xml if you wish.
You use the test.xml file to play with settings and still have the original xml file with current settings should you wish to go back to where you started.

So you went through all the testing and found that 2400mm/min velocity is a reliable max velocity to use?
Then did you test for max acceleration at that setting? If you did then why are you setting it at a value of 50?
Then did you try running some code to see if it skips?


RICH
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #34 on: April 11, 2018, 11:49:08 PM »
Yes, 2400 is very reliable velocity.
I set lower acceleration because I didn't trust the higher settings to be fully okay.
When I ran a code it still went off position.

Offline RICH

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #35 on: April 12, 2018, 06:29:15 AM »
At what velocity did each axis start skipping for each axis?
At what accel did each axis     "                     "    ?


RICH
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #36 on: April 12, 2018, 06:40:40 AM »
They do it all the time, except maybe when it's so slow that I cannot comprehend.

Or do you mean in the motor tuning?
The x managed 3500-4000, the y and z managed 5000-6000 velocity, and they all worked up to 350-400 acceleration.

Offline RICH

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #37 on: April 12, 2018, 07:44:31 AM »
Post your the xml file you are using. The file name should be unique, so change the file name to something like  da98.xml
before posting it.

RICH
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #38 on: April 12, 2018, 09:42:44 AM »
Okay, I will, thanks :)