GRBL shield - Z driver issue

Discussion about the arduino based g-code interpreter, grbl
loopingz
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Joined: Fri Jul 27, 2012 5:00 pm

GRBL shield - Z driver issue

Post by loopingz » Mon Sep 24, 2012 7:32 am

This week end I did all my connections and stuff. X and Y work flawlessly with my 19V PSU. Z by the way never really worked. When I send something like Z0 or Z10 I just hear a sound like "clac", the motor is putting some torque on one side or the other and that is it.
I did my mounting following the wiki which I have found out it is better to test the motors without load... but they were already mounted.
After this issue I freed my Z-Axis motor, to find out that it still does work. I rechecked the wiring: good from the beginning. Then I swapped Y & Z, Y motor, z shield "clac", z-motor, y shield smooth, obviously the issue is on the grbl shield.
So I tried and I put back Y and Z normal and tried to play with the Z pot, I thought maybe it has a different setting than X Y (but all are kind of centered). Full counter clockwise. Z500, slow up to the max. The motor is still not turning. I notice that the X and Y chip on the board were hot, I stopped as soon as I was done testing the pot.

Is my Z channel dead? What else can I try?
Shapeoko 1. Dual Y 1m with Name 17 (twice lower torque as the original motor). Double Xrails side to side. Acme-Z. Metalspacers.Wood 22mm waste board. Kress1050 with custom holder. Arduino GRBL + GRBL shield.

cvoinescu
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Re: GRBL shield - Z driver issue

Post by cvoinescu » Mon Sep 24, 2012 12:57 pm

It may be dead, but the fact that the motor makes any noise at all is encouraging. Does the Z motor become hard to turn by hand while the Z500 is running? If so, check the connection on the Z STEP pin.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

loopingz
Posts: 107
Joined: Fri Jul 27, 2012 5:00 pm

Re: GRBL shield - Z driver issue

Post by loopingz » Mon Sep 24, 2012 4:32 pm

Well it is like turning one step and bloking or trying turn one step and putting some torque from one side or another (depending of of the position asked).
What do you mean by checking the Z step pin? I will try to put directly the motor on the terminal blocks of the card to see if it is working better but I already did some extensive wiring check and yet to find any issue!
Shapeoko 1. Dual Y 1m with Name 17 (twice lower torque as the original motor). Double Xrails side to side. Acme-Z. Metalspacers.Wood 22mm waste board. Kress1050 with custom holder. Arduino GRBL + GRBL shield.

cvoinescu
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Re: GRBL shield - Z driver issue

Post by cvoinescu » Mon Sep 24, 2012 8:13 pm

You say that "obviously the issue is on the grbl shield". It's not that obvious. What is obvious is that it's not the Z motor, and it's something on the Z channel on the GRBLShield or on the Arduino. It could be that the Adruino output is fried, or the connection between the Arduino and the Z driver is bad. That's why I said "check the STEP pin". What you described can happen if the STEP driver input of the Z channel is disconnected. If you can, swap the Z and Y channels between the Arduino and the GRBLShield.

Substitute "parallel port" for "Arduino" if using LinuxCNC or Mach3.

Note that when processing commands, all motors are engaged; when idle, all are disengaged. So if your Z is completely dead, when you send a Z move command, the X and Y motors still engage with a "snap" noise. Are you sure your Z motor engages? A disengaged motor can be turned easily by hand; an engaged one is very hard to turn. Does that happen with your Z motor? If it does, then your driver may not be dead, and you should look at whether the control signals reach it (specifically, STEP; the motor would turn even with DIR disconnected). If it doesn't, the driver can be dead, or the ENABLE signal may not make it to it. But, IIRC, on the GRBLShield there's a single ENABLE for all drivers, so that's unlikely.

If nothing works, and this is an Inventables kit, talk to them, they will be very helpful.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

loopingz
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Re: GRBL shield - Z driver issue

Post by loopingz » Mon Sep 24, 2012 9:43 pm

Well obviously I was wrong! Even if I am not axactly sure what was wrong.
First I bought a cheap 24V 100W PSU.
I have been plugging the motor directly to the board. Same issue.
Then I thought if X and Y are working, where is the difference?
So I changed $2 from 640step by mm to 320.
Bang! Working super well both side, I have been seting the amp rating a bit lower and then I tried. 480, 600 and 640. ALL working.
So I mount back everything, check ok.
Tight motor to the screw, it works like a charm.
So my guess is that I had a contact in a terminal block that was not good or at least not good enough for the pulse frequency. Otherwise some strange bug solve by changing this parameter.

Anyway, my frustration is away, I am glad the most expensive part is perfectly working now.

I tried a "air" hello world. It seems to be ok!
Shapeoko 1. Dual Y 1m with Name 17 (twice lower torque as the original motor). Double Xrails side to side. Acme-Z. Metalspacers.Wood 22mm waste board. Kress1050 with custom holder. Arduino GRBL + GRBL shield.

AndrewR
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Re: GRBL shield - Z driver issue

Post by AndrewR » Mon Sep 24, 2012 10:24 pm

loopingz wrote:Well obviously I was wrong! Even if I am not axactly sure what was wrong.
...
So my guess is that I had a contact in a terminal block that was not good or at least not good enough for the pulse frequency. Otherwise some strange bug solve by changing this parameter.
...
It wasn't a connection issue. The Arduino was sending the steps to the motor too quickly for the motor to keep up. All stepper motors are speed limited with a finite voltage. You should change your $5 (seek rate) setting (and $4 - feed rate) to a lower setting which gets your z-axis working, then adjust your $0, $1, & $2 settings to get the correct movement distances. i.e. when you command 100mm in each axis, they each move 100.0mm. Once your machine is scaled right, then you can start ramping up $5 until you find the speed limit for Z. I've found that one of the limits with GRBL is that it has a single speed setting for all three axes. Being that only the Z-axis is screw driven on the ShapeOko, that will be the limiting axis. The X & Y axes have the capacity to move MUCH faster with the belt system. Fortunately, if you're milling, you'll never need those fast speeds.
- Andrew

ShapeOko #0080

cvoinescu
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Re: GRBL shield - Z driver issue

Post by cvoinescu » Mon Sep 24, 2012 10:55 pm

I subscribe to AndrewR's explanation -- seems very likely. I also agree with his comment about the single speed limit in GRBL, which can be important when doing things other than milling.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

loopingz
Posts: 107
Joined: Fri Jul 27, 2012 5:00 pm

Re: GRBL shield - Z driver issue

Post by loopingz » Tue Sep 25, 2012 7:34 am

Well that was my first thought but why was I able to go back to the initial settings and then maintain that under load?
Shapeoko 1. Dual Y 1m with Name 17 (twice lower torque as the original motor). Double Xrails side to side. Acme-Z. Metalspacers.Wood 22mm waste board. Kress1050 with custom holder. Arduino GRBL + GRBL shield.

cvoinescu
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Re: GRBL shield - Z driver issue

Post by cvoinescu » Tue Sep 25, 2012 10:24 am

Yes, that's weird. Are all the settings your original settings, nothing changed? If so, well, I don't know. Glad it works now!
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

jc21
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Joined: Wed Sep 26, 2012 3:39 pm

Re: GRBL shield - Z driver issue

Post by jc21 » Wed Sep 26, 2012 4:04 pm

I'm having the same problem but with the X axis!! its not a mechanical problem, all the motors are working fine. I'm using 3 nema 17 sanyo denki 200steps.

My settings are.

$0 = 87.49 (steps/mm x)
$1 = 87.49 (steps/mm y)
$2 = 320.00 (steps/mm z)
$3 = 30 (microseconds step pulse)
$4 = 500.00 (mm/min default feed rate)
$5 = 500.00 (mm/min default seek rate)
$6 = 0.10 (mm/arc segment)
$7 = 0 (step port invert mask. binary = 0)
$8 = 50.00 (acceleration in mm/sec^2)
$9 = 0.05 (cornering junction deviation in mm)

When i lowered 4 and 5 to 500 started to work better. BUT! it doesn't work as fast as the Y Axis and sometimes instead of going forwards goes backwards. (manually)

UPDATE! when i send manually to move 10 step, the green light from Z and Y Axis lights 10 times, X axis only once and then a sound.

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