stepper only goes one direction

I have a Chinese CNC machine and for some reason the stepper motor only goes one direction. I push +Z or -Z on the pendant and it will only move one way.

I swapped the Z and X axis at the control board and then the X moves fine (using Z commands) but the Z still only moves one way (using X commands).

I know the stepper is physically capable of moving backwards because I swapped the X and Z cannon plugs where they connect to the motors and the Z would work really jerky and weird (not smooth at all) both directions. It obviously didn't like being hooked up that way but at least it worked.

I swapped the motor direction on the pendant (software) and that didn't fix it either.

Also, twice today I somehow managed to get it to work. Not sure what I did. It was either a connection thing or it was something in the controller software, possibly having to do with the Z axis limits?

Any idea what's wrong or how to troubleshoot further? Do you think it's hardware (like bad connections to the motor, driver, board, etc) or software (like the controller settings).

Thanks so much folks!

[if it helps the Chinese stepper motor is a "FL86STH118A-22" and the controller/board is a "RZNC-05"]

Any ideas here guys?

Quote:

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Originally Posted by HalfRhoVSquared

I have a Chinese CNC machine and for some reason the stepper motor only goes one direction. I push +Z or -Z on the pendant and it will only move one way.

I swapped the Z and X axis at the control board and then the X moves fine (using Z commands) but the Z still only moves one way (using X commands).

I know the stepper is physically capable of moving backwards because I swapped the X and Z cannon plugs where they connect to the motors and the Z would work really jerky and weird (not smooth at all) both directions. It obviously didn't like being hooked up that way but at least it worked.

I swapped the motor direction on the pendant (software) and that didn't fix it either.

Also, twice today I somehow managed to get it to work. Not sure what I did. It was either a connection thing or it was something in the controller software, possibly having to do with the Z axis limits?

Any idea what's wrong or how to troubleshoot further? Do you think it's hardware (like bad connections to the motor, driver, board, etc) or software (like the controller settings).

Thanks so much folks!

[if it helps the Chinese stepper motor is a "FL86STH118A-22" and the controller/board is a "RZNC-05"]

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This also could be a noise issue, try isolating the wiring from the driver to the Z from any other cables or electronics (especially the power cable to your cutting head).

Cory
CNCRouterParts

I'll try that. At this stage I'll try anything... so frustrating...

Well now it's acting strange. Sometimes it works OK but will only go in "step" mode, not "continuous" mode from the control pendant. Then it will go really slow and sound funny. And then it will go back to only moving in one direction.

Still sound like noise? Or possibly a bad wire connection?

I'm not impressed at all with the electrical wiring on this Chinese router. The rest of the router seems stout but they use too small of wires with lousy connections.

Your swap test indicates that whatever's going on, it isn't the fault of the software, controller or breakout board. That leaves the motor, plus its wiring and cable. Double-check to make sure the wiring is correct and well-attached. Assuming a 4-wire motor, there should be two phases with continuity between them. (a six-wire motor works basically the same way, but there's a center tap which can be connected so as to give you the choice of parallel or series operation). A stepper motor works by energizing one phase at a time, pushing the armature from one position or "step" to the next one, that's typically 1.8 degrees apart. When the motor changes direction, the phases change their pattern of energizing the internal electromagnets and push the other way. It sounds like one of those phases isn't operating correctly, so you're only getting half the control you need. A faulty cable can cause that, as can mis-wiring, a bad motor, bad grounding or electrical interference.

Andrew Werby
www.computersculpture.com

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Originally Posted by awerby

Your swap test indicates that whatever's going on, it isn't the fault of the software, controller or breakout board. That leaves the motor, plus its wiring and cable. Double-check to make sure the wiring is correct and well-attached. Assuming a 4-wire motor, there should be two phases with continuity between them. (a six-wire motor works basically the same way, but there's a center tap which can be connected so as to give you the choice of parallel or series operation). A stepper motor works by energizing one phase at a time, pushing the armature from one position or "step" to the next one, that's typically 1.8 degrees apart. When the motor changes direction, the phases change their pattern of energizing the internal electromagnets and push the other way. It sounds like one of those phases isn't operating correctly, so you're only getting half the control you need. A faulty cable can cause that, as can mis-wiring, a bad motor, bad grounding or electrical interference.

Andrew Werby
ComputerSculpture.com ? Home Page for Discount Hardware & Software

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Well put Andrew

Cory
CRP

Intermittent operation is almost always a loose connection somewhere. Check the connector and the wire connection to the motor. Also, verify that the Z axis is not somehow binding. Beyond that, could also be a noise issue. On many of the Chinese machines, it's almost standard operating procedure to tear them down and rebuild them as soon as you get them.

Ok guys, thanks for the suggestions. I suspected it might be a bad wire but now I'll go through very carefully and confirm. I have some new connectors ordered so plan to swap those out for ones of better quality and size.

Ok, I replaced one of the connectors that I suspected was bad but it didn't fix the problem. So here's the symptoms...

1. When I start testing with things cold (after I haven't used it in a while) the Z axis seems to work properly when attached to the X and Y ports on the board. But when attached to the Z port it only works right in "STEP" and "DISTANCE" mode but stutters and sounds bad and barely moves in "CONTINUOUS" mode when I hold down the button (moves both up and down but barely).

2. After I work with things for a while and things warm up (or whatever...something else may be happening to trigger it) now the Z axis will only go down no matter which port on the board it's plugged into.

Weird.

Does this bring any other clues as to what may be wrong?

Hey mate I had a similar problem with a 6040 cnc router.i found it was ****ty motor cabling,how I found this was testing the z axis up and down it behaved in a weird way,it would work then stall then only go one direction and make all kinds of noises. I ended up finding a sweet spot in x and y on the table where the cable carrier was bending the cables and problem solved it worked perfectly then I moved it back and it started again,after finding this I replaced all the cables and its been sweet eversince. so my advise is try the z axis in all different places on the table,try rattaling the cable carrier and see what happens also I could hear a noise it would change in sound when I moved the cable carrier around hope this may help. Danny

Well it use to only have problems on the Z axis and only after I used it a while. Now it has problems on every axis, even when cold. I think it's the controller since it's affecting every axis and is really irregular. It only seems to get worse the more I use it.

Anyone else using this DSP RZNC-0501 controller effectively?

I would suggest the likely culprit is the direction line going to the driver. Put a voltmeter on it and see if it toggles as you command the axis forward and reverse.

Ok, I'm happy to report back that I made major improvement... it was the darn acceleration settings. This is a bit embarrassing but the controller is a new English version of an older metric unit and the metric settings were still programmed in there so it was accelerating about 25.4x as fast as it should!

(I guess if it could happen to NASA getting to Mars...)

Dropped the linear and curve acceleration values down and now it seems to work exactly as it should. Very smooth 800 ipm rapids with nice accel and decel at all ends of travel.

Sheesh- what a relief!

Now onto getting it running with my laptop, ESS, & BOB so I can run it off Mach3 as well as the pendant.

As another update <hope the room isn't empty>... things running smoother but still having some uncommanded Z-axis down movements, especially around the home position. I think I have a lead though after talking to a UK guru on this controller. I'm cutting the resolution from the driver down by half to see if that helps. Having too high of resolution apparently may be causing the Z-axis to get confused (highly technical term I know) during certain instances and since the Z-axis is vertical the weight causes the stepper to choose the easiest direction which is down.

Hopefully this fixes things for good. <cross fingers>