CNC 6040 Router Z-Axis Problem

**robert4wd** · 17th June 2013, 06:20 PM

Hi All

I have a CNC router which has worked reliably for about 12 months. Its a Chinese one I brough off eBay. I think it was advertised as a "6040" machine. I think it has NEMA23 stepping motors as the measure 2.3" square.

The other day I made a programming error and ran the z-axis against the bottom stop which physically locked the lead screw. Unfortunately did not notice for some time that the motor continued to try and turn the lead screw. Since I did this I have a problem with the z-axis. If I zero it and start a program it seems to loose its zero position. To see what is happening I have set the z axis to go up and down 20mm 50 times from zero and then return to zero. The carriage returns to a different position each time I do this between 11 and 34mm below the original zero.

Obviously I have either damaged the motor or the driver board. I have taken the stepping motor off and when I turn it by hand I cannot feel any roughness or problem. Similarly the lead screw feels fine and turns freely.

Do I replace the motor the driver board or both and see if it improves? Could I have damaged the 4 wires between the motor and the driver? Physically they look fine, they were not crushed or anything. Should I swap it with the x-axis motor and see if it makes any difference. Would I run the risk of damaging the x-axis motor is the driver board is faulty?

I am not sure what to do next. Any suggestions would be welcome. Thanks in advance for your help.

Regards Robert

**Bob Willson** · 17th June 2013, 08:13 PM

Before you do anything too drastic, I would try tightening the screws on the motor shaft. It is possible that the shaft could be slipping a bit.

**robert4wd** · 17th June 2013, 09:29 PM

Hi Bob

just went and checked the coupling is tight and I cannot make it slip. Thanks for the suggestion.

Regards
Robert

**dj_pnevans** · 17th June 2013, 09:38 PM

Change the motor over with your X or Y and see what happens. David

**Bob Willson** · 18th June 2013, 12:40 AM

When you turn on the machine and the motors lock, does the motor lock properly?
What sort of setup do you have on your Z axis?

**robert4wd** · 6th July 2013, 05:15 PM

Hi All

I had sometime to play a bit with much success, here is what I have done

1) When I turn the power on all three axes lock and I cannot turn them
2) The set-up on the z-axis is Steps per 320, Velocity 799.8, Acceleration 37, Step Pulse 15, Dir Pulse 10. I have used these settings for some time successfully before the present problem
3) I have swapped the z and x axis motors - the z-axis still loses zero
4) I have swapped the z and x axis driver boards ( the control box has three separate driver boards, a power supply and a break out board) - the z -axis still looses zero
5) I have complete disassembled and reassembled the z axis and can find no problems
6) I tried another piece of program that had worked previously - it too loses z zero this time by 9.5mm

Should I try a new parallel board in the computer or a new break out board in the controller box?
Could it be the control box power supply? With a DC volt meter the supply looks ok.
Could it be the cable connecting the controller board and the stepping motor?
Any other suggestion?

Thanks in advance for you help

Regards
Robert

**Bob Willson** · 6th July 2013, 06:47 PM

Try dropping the velocity to 200 and see what happens then.

**robert4wd** · 10th July 2013, 07:53 PM

Hi All

Tried lowering the velocity to 200 and reran the test. The z-axis still lost it zero. Any further advice? Thanks

Regards
Robert

**SawDustSniffer** · 10th July 2013, 09:09 PM

i had random movements of the zaxis , it would come down touch the surface then reverse on contact ,
basically random movements , not really loosing zaxis zero , but might be the same problem

broken wires in the chain carriers , my z went first , followed soon by the y axis ( china 6545 )

the wire they used was too stiff , and snapped with movement

i used the small 4 core wire , off the shelf from Jaycar ( their only 4 core ) and have ran it for over 200 hours since , also changed the plugs over to "molex" 4 pin hard drive plugs at the same time

??? clutching at straws ??? build up of friction on the rails / screws , ive been using "Lanon " in a spray can every 8 hours , it the oil off a sheep's back

**Bob Willson** · 11th July 2013, 09:17 AM

Good thought sawdust. It could well be that.

**GRS** · 11th July 2013, 09:25 AM

I have the same problem with my home made machine, ran for 3 years with no issue then Z started losing zero

I have had a new driver board , Z axis , Stepper motor and still have the same issue , is it possible that a broken or frayed wire in the harness could be the culpret

I'm no good at electrics or anything brainy so I am stumped

Cheers Gary

**robert4wd** · 11th July 2013, 01:34 PM

Hi All

Thank you for the suggestion, its worth a try. I will get some wires and connectors on the weekend are replace the wiring to the stepping motors. I have looked at the Jaycar web site, Is this the right type of wire?

4 Core Screened Professional Microphone Cable
Super flexible black matt finish PVC low noise cable with tinned copper screening.
High quality mic cable for Public Announcement, stage or semi professional use.
- 11/0.20 x 4 core +112/0.12
- Colour: red, white, yellow & Black.
- Outer dia: 6.2mm.
- Roll length 100 Metres
- Sold per metre

Thanks again
Regards
Robert

**Bob Willson** · 11th July 2013, 08:24 PM

Yes

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