Problem- Losing steps?

[zimba43]

My gantry type router has been doing pretty well over the last 2 years but now for some strange reason it's misbehaving. This is what happens, when setting up for a sign I do a practice run first just to make sure and then rout the sign. Sometimes it will cut a perfect sign on the practice run then on a decent piece of hardwood one of the motors makes a strange noise and it will cut one letter on top of the other as if loosing steps.
Just for the record the setup is as original, nothing has been changed.
Any suggestions would be gratefully received.
Zimba.

[robe_uk]

Hi
Hard to say without more details of the machine, drive type etc. But sounds like something is binding, a bearing or ballnut, try taking off the motor from the suspect drive and turn the drive by hand to see if it smooth or any signs of 'notchieness', if its a bearing or something starting to go that is intermittent it may be hard to pin point.

Good luck
Rob

[ger21]

I'll agree with the binding assessment. Check all the moving parts, especially the screws if screw driven. Clean and lubricate, too.

[hemsworthlad]

Originally Posted by zimba43 then on a decent piece of hardwood one of the motors makes a strange noise Any suggestions would be gratefully received. Zimba.

Use Softwood.!!. . .

Sorry couldn't resist. .Lol

First have you installed any other software lately or updated any software, by this I mean any software at all not just CNC related. If so remove and try again or a bit extreme but better still reinstall the whole system with just the bare bones system and your control software. (only if new software or updates installed)

Second check very carefully all motor and signal wires for lose connections, trapped or partly broken(including PP cable). After 2 years and strange motor noise's there's a good chance a wire is corroded or wire is frayed cocking signals up. . . . If ok move to next stage.

Check the axis are moving freely without motors attached and not sticking or jammed with crap or sticking ballscrew etc.? Check motor bearings while off.

Does this strange noise come from the same motor all the time.? Is this also attached to the axis which would move the letter over to the next position.?

If so try swapping motor with other axis and see if the problem moves to that axis. . If yes then chances are your motors on it's way out. . . . If No then next stage.!

If you have access to another PC try hooking this up using the same settings etc (or xml if mach3) this will be the easist quickist way to eliminate parallel port completely and will also help to partly eliminate control software ( It could still be a dodgy xml )

If after all or any of the above doesn't work then it pritty much leaves only the BOB, drivers and PSU.
Try swapping drivers from axis to axis see if any changes, if ok swap the axis at the BOB and reset axis outputs in the control software to these outputs.

Working back this way eliminates components individualy, If all these checkout then your only left with the PSU.!
PSU could be going down and giving less power but i'd be surprised if this was the case, I would expect drives tripping and stalls more than missed steps.

Personaly this would be my line of attack. Check very very carefully the wiring/cables, then check again.!!. . then sticking axis, then swap motors axis, then reinstall of software, then change of PC, then swap drivers, then swap BOB, then panick. .!!

hope this helps.

[zimba43]

cheers:Hemsworthlad,
happy xmas and thanks for the great reply, and one in terms which I understand. It seems I have a fair bit of work to do so I'll let you know in due course what happens. Just shows what a great site this is.
Zimba.

[hemsworthlad]

Your welcome, let me know how it goes. If you suspect electrical troubles Drives, BOB etc then let me know I have spare so may be able to help if you need any to try for elimination purpose's. PM me if needed.

[DonFrambach]

I had a problem similar to this with my ShopBot several years ago that was solved by tightening one of the set screws (and adding LocTite) on the stepper's shaft coupler.

My first thought was that the router was losing steps. ShopBot technical support told me to check that first. Hope your problem has an easy fix too.

Don

[cheetahcnc]

I experienced a similar situation on my x (gantry) axis. It was one linear bearing, intermittently binding from dust, causing that axis to "lose" steps. I have since wrote a "warm up" program, which follows a "lube cycle". The lube cycle oscillates each axis a few inches individually at about 20 IPM so I can oil (grease caused my initial problem) the linear bearings. Then the remainder of the program runs the machine to its limits (61"x100") a few times, y, x, y, x in a rectangle in traverse 900 IPM speed. Then all three axes simultaniously in an opposed triangle criss-cross a few times. If the machine is cold (40F) it takes a few cycles to repeatedly return to the home position perfectly, after the complete cycle, at traverse speed. Then I start. Though it does not cut at 900 IPM, starting and stopping at that speed exaggerates any skipping step problems I might have through the program, which could take hours to find out.