View Full Version : Need Help! PRO4824 Build - Strange Slaved Motor Behavior

02-15-2014, 09:08 PM
Hi All
Been lurking here a bit since building a PRO4824 the last couple of months.

I have encountered a problem that has me baffled!

When I run a program or jog the router on slow speeds the slaved axis on the gantry stops moving throwing the gantry askew and alignment until the gantry is homed against my switches. Another words the slaved motor on the left front side is motionless with the master motor keeps moving in step. The problem is random but more often than not. I have a few other minor kinks but this one make the router unreliable/unusable at present!

I have some familiarity with Mach3, Metal Mills, CNC, etc. The router is a new one to me, particularly the slaved axis setup.

Currently I'm simply trying to do some holes and circular cuts in some mdf and at random the slaved motor stops moving, I sent Ahren at CNC RP an email that didn't really give me any direction other than to advise the motors work in tandem it must be the gcode. However it can occur while simply trying to jog at slow speeds but never at higher speeds. I have listed the technical information below and can supply more if anyone might know what to check further.

Nema23/G540 from CNCRP
MACH3 setup as follows
Motor Velocity 400im/Acceleration 20im for Y/A Gantry Axis. Steps 1736
I have dropped both motors off the rack and can roll the gantry forward and back with one finger no binding anywhere along V-Con Rails. I have checked for pulley slippage. Binding of the V-Con bearings, meshing of the motor to the rack. The bolt tension on the motor gear to the rack from relatively loose to very tight and everything in between. Frame squareness, loose parts.

As for the Gcode I"m using a 1/4" 2-Flute up spiral bit 350im rapid speed/ 40im Cutting Feedrate.

I'm running out of things I can think of checking, I'm even questioning the rated size of the motors from CNCRP for the gantry.

02-15-2014, 11:49 PM

I don't recall your original inquiry with us, but if the problem happens when jogging, it is not related to G-Code. I would guess that the issue is related to your G540 or parallel port, and is probably related to pulse width. There are a number of G540s that have a CPLD issue on some drivers that requires a longer pulse width than normal:

What is wrong with my system? (http://cnczone.com/forums/gecko_drives/86339-wrong_system.html)

You can try setting Mach to Sherline 1/2 Pulse mode to see if this fixes the issue. If not, feel free to give us a call on Monday and we can look into other solutions -- we'll need to know what operating system you are running on and if it is 32 or 64 bit.

Best regards,

CNCRouterParts (http://www.cncrouterparts.com)

02-16-2014, 01:45 PM
In regards to the previous inquiries to CNC I spoke to you and Cory via. phone & emails on this and primarily a proximity switch problem that has since been rectified.

I did swap out the G540 this morning and can say the problem has appeared to have abated. I have run a geode 10 minute program 4 times and the machine appears to be zeroed after the program runs each time. The problem has been sporadic so I can't say it is gone for good.

In regards to another issue of my ignorance most likely the safe limits don't appear to be working correctly either. I have attached some photos of my setup and errors for you to double check. When I jog to the Y+ or X+ side of the switches the safe limit is detected the machine stops and I can then jog in the negative direction. When I jog negative on the X or Y Axis the limit switches are tripped and I have to override the limits to jog off them. The Z-Axis does not have proximity switches so I'm not totally understanding how mach3 knows what the safe limit range is for it to work correctly for the z-axis.
After looking at the attached photos let me know if you or anyone else here can see what the problem could be. The Y is the 24" Movement, The X is the 48" Movement.

02-16-2014, 03:40 PM
In your last pic, the axis haven't been homed (Ref'd). The softlimits are referenced from the Home position. For the Z axis, wherever it is when you click Ref All is where it considers zero for the softlimits. If you're not homing with the Ref buttons, that your softlimit location can be different every time you use Mach3.

02-16-2014, 03:51 PM
Since I don't have a switch on Z I haven't always "Ref All Home" with the Z Axis at its home position. Would this cause the X or Y to trip the limits in the negative direction only when jogging up to the negative switches only. Seems a little strange as the Y and X are watching the switches at all times and do protect excess movement in the positive directions but not the negative directions.

02-17-2014, 12:04 PM
On a side question. Can someone advise if the Zero Touch Input and the Z-Home switch can share the same input on the Gecko G540. I'm thinking they can but checking before I attempt it.

02-17-2014, 12:10 PM
Since I don't have a switch on Z I haven't always "Ref All Home" with the Z Axis at its home position. Would this cause the X or Y to trip the limits in the negative direction only when jogging up to the negative switches only.

The Z axis should have no effect on the X and Y axis.

As for sharing an input, it should be OK as long as the Z home is not also a limit, and the active low setting is the same for both the touch plate and switch.