Re: [Emc-users] Stepper problem
Ian, Do a test with a G1 at max speed. You should get the same results as a G0. If you have a Gecko drive you can tune the low range for smooth operation with the trim pot. Is your drive a micro step drive? or are you running whole steps? John On 9 Feb 2008 at 18:51, [EMAIL PROTECTED] wrote: Hi, I am confused by an odd stepper problem which I can't understand. The stepper affected is the one driving my rotary axis and the problem is that it won't go fast enough... To explain - if I issue a G1 command in MDI, I am limited to a F20 speed as, beyond that, the stepper gets very jittery and loses steps (at F40 it gives up altogether). However, if I issue a G0 command, the stepper whirls away happily at 3 or 4 times the speed and doesn't seem to lose steps at all (i.e. I can send it one way and then the other and it returns to where it started.). So, what is the difference between a G1 command and a G0 command and how can I get the G1 speed to increase reliably up to almost the G0 speed? I'm running the latest version of EMC2 on Ubuntu (unless I've missed a service release in the last 2 weeks ). -- Best wishes, Ian Ian W. Wright Sheffield UK - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Stepper problem
Thanks Brian (and others). I now have more speed and I now know much more about how TRAJ works I think, however, I still have one little problem which probably didn't occur at the low speed and which I don't seem able to get rid of. When the motor starts to move, it does two or three steps and then hesitates or even does a step backwards before setting off again up to speed. The same happens on the ramp down as well - the motor hesitates a couple of steps from the stop position. I have tried decreasing the Acceleration settings in the TRAJ, both MAX_ACCELERATION and MAX_ANGULAR_ACCELERATION DEFAULT_ANGULAR_ACCELERATION and I also reduced the MAX_ACCELERATION in the axis section where there is also a STEPGEN_MAX_ACCELERATION which I don't really understand but reduced anyway. I had the linear axes ACCELERATION set to around 4 - 4.5 and they were happy at that - this is the same motor and I have reduced the MAX_ACCELERATION(s) to 0.5 without being able to clear the problem. Any more advice would be most welcome - thanks.. Incidentally, I now have the rotary axis running quite happily (apart from the initial dither) at 400 which is much better than my previous limit of 20!!! -- Best wishes, Ian Ian W. Wright Sheffield UK The difference between theory and practice is much smaller in theory than in practice... -- [EMAIL PROTECTED] -- http://www.fastmail.fm - I mean, what is it about a decent email service? - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Stepper problem
I wonder if this is the same problem Fred is having? I have never used steppers so I am clueless (well okay, more than normal). On Sat, 2008-02-09 at 15:05 -0800, [EMAIL PROTECTED] wrote: Hi, I am confused by an odd stepper problem which I can't understand. The stepper affected is the one driving my rotary axis and the problem is that it won't go fast enough... To explain - if I issue a G1 command in MDI, I am limited to a F20 speed as, beyond that, the stepper gets very jittery and loses steps (at F40 it gives up altogether). However, if I issue a G0 command, the stepper whirls away happily at 3 or 4 times the speed and doesn't seem to lose steps at all (i.e. I can send it one way and then the other and it returns to where it started.). So, what is the difference between a G1 command and a G0 command and how can I get the G1 speed to increase reliably up to almost the G0 speed? I'm running the latest version of EMC2 on Ubuntu (unless I've missed a service release in the last 2 weeks ). -- Best wishes, Ian Ian W. Wright Sheffield UK The difference between theory and practice is much smaller in theory than in practice... -- [EMAIL PROTECTED] -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending) - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Stepper problem
On Saturday 09 February 2008 15:05, [EMAIL PROTECTED] wrote: Hi, I am confused by an odd stepper problem which I can't understand. The stepper affected is the one driving my rotary axis and the problem is that it won't go fast enough its not the stepper but the trajectory planning for the rotary axis in G1 in the [TRAJ] section of the .ini file set MAX_VELOCITY and MAX_ACCELERATION higher than the rotary axis then to bring the jog speed sliders in the GUI back down to working range add these MAX_LINEAR_VELOCITY = .4 DEFAULT_LINEAR_VELOCITY = .2 MAX_ANGULAR_VELOCITY = 30 DEFAULT_ANGULAR_VELOCITY = 15 in G0 it ignores the [TRAJ] section and uses individual the axis settings at least I think that's how it works Brian - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Stepper problem
On Sat, Feb 09, 2008 at 03:05:48PM -0800, [EMAIL PROTECTED] wrote: So, what is the difference between a G1 command and a G0 command and how can I get the G1 speed to increase reliably up to almost the G0 speed? There is no difference except the velocity. Steppers sometimes work badly at an intermediate speed due to resonance. For G0 I think you are accelerating quickly through this bad spot so you don't notice it. Some stepper drivers have mid-band resonance compensation which might help. Also I think someone on the list has reported that adding mass to the screws on his bridgeport helped. Maybe you can add or remove some mass to try to move the resonant speed? - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
