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Author Topic: Anyone using Galil in stepper mode?  (Read 2217 times)

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Anyone using Galil in stepper mode?
« on: December 17, 2011, 10:58:15 AM »
  I am getting ready to return from Afghanistan and finish up my machine build.  I had been experimenting with position mode and torque mode (DMC-4080), with poor results.  However, that was because I had crippled the Galil by releasing the precious smoke. Galil is fixed now.   I would prefer position mode, as it enhances my servo-drives' ability to handle the load.

That being said, is anyone here using position mode (stepper mode)?

What kind of performance are you getting from the galil with regard to stepper mode?


« Last Edit: December 17, 2011, 11:00:34 AM by rforney »
Re: Anyone using Galil in stepper mode?
« Reply #1 on: December 17, 2011, 02:57:40 PM »
If you have servo's and Galil  why would you want to run in stepper mode?
Using encoder feedback with the PID loop is far superior, IMO.
Re: Anyone using Galil in stepper mode?
« Reply #2 on: February 10, 2012, 09:52:05 PM »
Well, here goes:

In stepper mode (Position mode for yaskawa), my drives can utilize real-time adaptive tuning.  I have spent over 100 hrs trying to tune my servos in torque mode.  I was able to achieve 2000 ipm, with small following error.  However, when trying to change accel rates in Mach, my tuning setup went to poo.  I am not saying that the Controller is to blame, here.  I wish I had 20 years of experience tuning these things, but I dont.  I am at the point where I just want my machine to run; I want my life back.

That being said, I am running in stepper mode right now.  I can accelerate at 90 ips sq (as opposed to 50 ips sq in torque mode).  As I do a lot of 3d carving, Accel/decell is the where I make my money.  My machine was not built to cut big rectangles all day, my code involves a lot of direction reversals in the y and Z axis (think sowing machine).  In stepper mode, the servos never become unstable, and I can accelerate to my hearts content.  There is quite the graceful hum to the machine when the gantry is moving at 2000ipm this way.

There are some bugs involved with stepper mode in the galil plugin, though.  I cannot home to an index, it appears.  I also cannot home the Z axis, as the plugin sets the decelleration to an astronomical level.  The servo drives fault out.  I think it is because I am running a big machine, but I am not sure.  I spoke to galil today regarding the homing sequence, and was told that when it goes to find the index, decel rates are not critical.  The servo will reverse to hold the servo on the index once it finds it.  Decell rates are important for the $3 limit switch setups, though.

Another issue I am looking into is the constant velocity mode.  I am tring to push 200,000 lines of code through this thing in less than 30 minutes.  I think that is around 110 lines per second.  It appears to be slowing down a lot through the small G1 segments.  Not sure if this is a buffer thing.  On my old machine (geckos, DC Servos, parallel port), it just fudges through the curves, never slowing down.  The results are satisfactory on the old machine, though.  I need to figure out how to make the new one flow through these multi-segment moves.

Video is here.  http://youtu.be/tD-tDLEe4v0 

In summary, position mode is recommended by yaskawa, and many machine tool manufacturers.  If is not really "stepper mode"; more like "digital mode" (in contrast to analog).  Stepper mode is just what galil calls it.