Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: jimstapenell on December 30, 2012, 08:31:34 PM

Title: X & Y axis creep when spindle running - 3040 cnc router
Post by: jimstapenell on December 30, 2012, 08:31:34 PM
G'day guys,

If this post is in the wrong place, can someone please advise where I should present this problem...

I have a 3040cnc router and have recently added limit switches (all in series). The system was working fine until a couple of days ago, my Z axis started to play up - eratic movement and occasional wrong direction. Found the problem - broken wire between controller and Z stepper motor.
So, I then replaced the 4 wire conductor between the control box and the Z stepper with shielded cable and grounded the screen/shield mesh wire at the plug where it attaches to the control box. The other end of the screen/shield mesh is not connected to anything.

I now have a problem that when Mach3, the router and the PC are running - and the router spindle is running, the X and Y axis motors creep - turn slowly and the red led's on the drive control boards (controller cover removed) for the X and Y axis light up intermittently.
If I switch off the spindle motor the X and Y axis are steady and no creeping. The Z axis with the screened cable does not suffer from the creep problem. I then replaced the X & Y axis with screened cable to match the Z.... - this upgrade to the X & Y cable did not fix the problem but did reduce the creeping slightly.

I then replaced the limit switch wire with screened cable similar to the X Y & Z axis. I only had enough screened cable to do between the control box and to a corner of the table where I branch in 2 directions with normal un-screened cable to the limit switches. I will get more cable this week.... Adding this screened cable did not stop the creeping - but the amount of creep has increased to be similar to before adding the screened cable to the X and Y axis.....
OK, after testing different procedures, I found something interesting.... With the control box live, running the spindle motor there is no creeping on the X & Y axis - but when I switch on the PC and the PC configures the printer port (cable between the PC and the control box), the X and Y axis start to play up again. This is without running Mach3.....
Another interesting point, there is no creep when I unplug the limit switch cable from the control box. This is the same for the partially screened cable and no screen on the limit switch cable. Remembering that the system was running perfectly before replacing any un-screened cables with screened cables.....

I am scratching my head now - I do not know what to try next to eliminate the X and Y creep... Anyone have any ideas on what I can try next? I could try to remove all screened cables - I really do not want to do this - adding screened cables should not be a negative feature - but is should be a worthwhile upgrade...
Title: Re: X & Y axis creep when spindle running - 3040 cnc router
Post by: Hood on December 31, 2012, 03:09:55 AM
Screens should be attached at a single point and that point should be earthed.
Title: Re: X & Y axis creep when spindle running - 3040 cnc router
Post by: jimstapenell on January 02, 2013, 02:27:07 AM
G'day Hood, thanks for your reply - I checked each connector at the control box with my multimeter and all are grounded to the earth terminal which is connected to the earth pin on the mains cord socket on the control box. I just realised the spindle cable is not screened. I will do that next. Seems strange that this problem all started when I found the broken wire in the un-screened Z axis cable which I replaced with screened cable. This is when the problem started. If running screened cable on the spindle does not work, I will try to isolate the spindle cables and power supply to another box... This machine is a tiny 3040 router which I bought as a learning tool for when I complete the upgrade to CNC on my HM46 mill.... The 3040 does wood carving quite well - I do not want to do any wood machining on my HM46..... I will log on again if I find the problem or a solution on the creeping X & Y axis on the 3040
Title: Re: X & Y axis creep when spindle running - 3040 cnc router
Post by: keverett on January 04, 2013, 08:09:15 AM
For what it's worth, this is what I found in my machine when getting creep in the Z direction.  I was using probotix electronics and the stepper drivers were the side step variety.  I would get creep in the Z azis with no command input.  I found out that the wall wart that I was running my BOB with was providing only half wave rectification and basically pulsed DC.  When I switched out this wal wart to a fully rectifiec supply, all my problems disappeared.  I don't know what your setup is, but if you've got a half wave wall wart somewhere in the mix, you might have problems.  Just a thought.