Odd Y-Axis shift since Repartier Host and Slic3r update

Odd behaviour with my Orca 0.42.

It could be a coincidence that this problem has occurred twice since I updated to the latest Repatier Host with latest Slic3r, but I'd welcome any thoughts.

I printed 2 different "plated" objects yesterday - the Babylon 5 Starfury ( [www.thingiverse.com] ) and a Battlestar Galactica Cylon Raider ( [www.thingiverse.com] ).

In both cases (but at different vertical heights) the Y-Axis shifted (~1.5mm on the Raider and ~2mm on the Starfury).

I've attached a pic.

Has Y simply "slipped" or have others experienced this lately?

Any input would be welcome.

Interesting to note - I was successful in printing the nut and bolt from [www.thingiverse.com] after a failed cylon print.

I had a similar problem with my setup.

Do a search on here about 'shift' and you'll find a few suggestions. For me the solution was to go into the configuration.h portion of my firmware and dial back the 'acceleration' and 'jerk' settings.

Here's the section of code that appears to be working for me: (I started at 5k for each of X, Y and now it's set at 600.

Good luck!
//-----------------------------------------------------------------------
//// Acceleration settings
//-----------------------------------------------------------------------
// X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.
#define _ACCELERATION 1000 // Axis Normal acceleration mm/s^2
#define _RETRACT_ACCELERATION 2000 // Extruder Normal acceleration mm/s^2
// #define _MAX_XY_JERK 20.0
//#define _MAX_XY_JERK 10.0
#define _MAX_XY_JERK 10.0
#define _MAX_Z_JERK 0.4
//#define _MAX_START_SPEED_UNITS_PER_SECOND {25.0,25.0,0.2,10.0}
//#define _MAX_ACCELERATION_UNITS_PER_SQ_SECOND {5000,5000,50,5000} // X, Y, Z and E max acceleration in mm/s^2 for printing moves or retracts
//#define _MAX_ACCELERATION_UNITS_PER_SQ_SECOND {900,900,50,2500} // X, Y, Z and E max acceleration in mm/s^2 for printing moves or retracts
//#define _MAX_ACCELERATION_UNITS_PER_SQ_SECOND {700,700,50,2500} // X, Y, Z and E max acceleration in mm/s^2 for printing moves or retracts
#define _MAX_ACCELERATION_UNITS_PER_SQ_SECOND {600,600,40,2500} // X, Y, Z and E max acceleration in mm/s^2 for printing moves or retracts

Edited 1 time(s). Last edit at 09/23/2012 09:38PM by a_shorething.

I had this problem but the fix for mine was to increase the current to the X and Y motors on the electronics board. In my case I use Printrboard and each motor output has a variable pot next to each output and clockwise is more. Just a fraction of a turn should do the trick, ie 5-10 degrees of rotation. I hadn't heard about the acceleration thing so that might help although I decreased my movement speed to a low value and it was still skipping before I adjusted the motor current.
Whatever the solution is please post it when you solve the problem

Edited 1 time(s). Last edit at 09/24/2012 03:11AM by Wired1.

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Richmond, New Zealand
Thingiverse ~ YouTube

OK, forget what I said about acceleration.

I just had an 8 hour print ruined overnight by 'the shift'.

I'm thinking Sunny might be right here. I had an extruder problem and the fix was just a *bit* more current on the polulu driver pot. I have the X and Y set to about .333 volts and the Z is at about .66 volts (two motors in parallel). The E had been at .25 but that wasn't enough so I bumped it to .33 and it's been perfect.

Now I'm thinking the Y might need just a bit more.

I'll post back when I find the sweet spot.

If you go too low I think you get these issues. Too high and they run hot (the driver and the motor) and you run the risk of burning them out. Akhlut has heat sinks on his stepper motors and I always thought it was overkill since my motors never seemed to get that hot to the touch. Now I'm thinking it's because I wasn't running quite enough amperage to be able to consistently maintain the correct position, hence the shift.

I think for me it's always in the 'Y' axis (have to check my notes) so I'll just work on that one. I guess I should also check for resistance in the Y travel since that would be the main reason for having insufficient power.

Will post back with my results, but it may be a while since for me it's not every print that has problems...

Edited 1 time(s). Last edit at 09/24/2012 05:18AM by a_shorething.

I run fans on the bvack of the y and x motors as they run too hot to touch otherwise.
Made these here: [www.thingiverse.com] to solve this heat issue.

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_________________________________________________________________________________________

Richmond, New Zealand
Thingiverse ~ YouTube

Ok tested my theory last night. I had adjusted the pot on the Pololu driver for the Y axis up from .26 volts to about .36 and no Y axis shift on the next print.

This time it was on the X-axis .

Checked that and it was about .26 as well, so I'm going to bump that one to about .30 and try it again now.

Here's my thinking on why this is intermittent and why more amperage is the fix (up to a point):

I'm thinking there is just enough amperage to run the motors well during tests and small calibration runs, but when everything is going for a while, every once in a while the demand for power from the hotend, the heater bed and all of the steppers is all at MAX and if your driver board is tuned to just put out exactly what is required under typical conditions, the extra demand means the weakest link gets less than required. Hence you drop steps and the system thinks you're at the right location (signal was sent to step) but it's actually reset the relative location to less than was called for at that point (which could be positive or negative in that axis depending on what was requested at the time.).

What do you think?

Will post results of the latest test...

EDIT: 9:31pm on the 25th.

Didn't get any 'Y' shift in the past two tries, but even after I bumped the setting on the X driver from .26 to .36 it still shifted. I'm at .41 volts right now and it hasn't shifted yet. The X and Y motors are noticeably warmer to the touch (several hours into the print) but not HOT. The heat sinks on the driver boards are too hot to touch at this point though.

This is definitely having an effect since the Y shift is apparently gone. We'll see about the X shift.

Harbi, any luck with this technique?

Edited 2 time(s). Last edit at 09/25/2012 09:36PM by a_shorething.

How hot are your stepper driver chips getting?

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Hey Matt,

How's it going?

Was that question for me or for the OP?

If it's for me, the heat sinks on the stepper drivers are too hot to keep my finger on, but I haven't actually taken a temp.

I can say that the overnight print came out with no shift (yay!) with the X and Y both up in the .36-.41 volts range. I know that's only one print, but this particular part (part of the intrinsically awesome lathe posted on Thingiverse) had shifted on me 4 out of 4 tries prior to this, so I think it's progress.

Do you monitor your driver chip temps? Is there a temp that I should use as a max if I can get some kind of reading on it?

Edited 1 time(s). Last edit at 09/26/2012 12:09PM by a_shorething.

Mike,

Pretty good. Well, I had a similar incident not that long ago where my X-axis was shifting on every print. Drove me nuts. finally threw a fan onto the RAMPS/Pololus and no issues since then.

I don't monitor the chip temps, but it would be a good idea. Pretty easily done with an arduino, some resistors/thermistors and and an LCD.

PS - you headed to MF this weekend?

a_shorething Wrote:
-------------------------------------------------------
> Hey Matt,
>
> How's it going?
>
> Was that question for me or for the OP?
>
> If it's for me, the heat sinks on the stepper
> drivers are too hot to keep my finger on, but I
> haven't actually taken a temp.
>
> I can say that the overnight print came out with
> no shift (yay!) with the X and Y both up in the
> .36-.41 volts range. I know that's only one
> print, but this particular part (part of the
> intrinsically awesome lathe posted on Thingiverse)
> had shifted on me 4 out of 4 tries prior to this,
> so I think it's progress.
>
> Do you monitor your driver chip temps? Is there a
> temp that I should use as a max if I can get some
> kind of reading on it?

---

- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Matt,

So you're saying the RAMPS/drivers were generating heat and when you started cooling it the problem cleared up?

I don't have any fans on any of my system yet, but I think the drivers are running too hot now. Problem is, any cooler and I think it causes a similar skipping of steps.

Seems like I need to add some fans.

and for the last question. I don't know what MF is, so I don't think so.

Maker faire!

Yeah, try cooling down the Pololus with a small fan.

Edited 1 time(s). Last edit at 09/26/2012 03:07PM by akhlut.

---

- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Hmm... Steppers produce the most current when not moving, what Power supply voltage are you running?

Its normal for steppper motors to run at 40 to 70 degrees C, the issue isn't the motors and highly unlikely with the pidely drivers driveing these steppers that they will have any issues, the issue is the Chips/Controllers, they are what needs cooled, simply mount a fan on them, or rig up someway to put heat sinks on them and if you really want to get crazy mount a peltier cooler on them with a fan... it's endless, but focusing on motor voltage and thinking it's the motors problems isn't correct, the motors can take a hell of a lot more heat than that little driver chip can. I suggest boosting your power supply voltage to around 13.5, little higher, little lower, whatever... and mounting a fan blowing over the chips.

I also suggest lapping your lead screws on the Z [www.youtube.com] , you can use a drill or whatever, but use some WD-40 and the Metal Maroon Scotch-brite to do it, do it as much as you can, you aren't going to hurt it, then do the same with all your linear rails (drill rod) You will be suprised at how much easier your machine seems to move.

Is everything (x,y,x) square with each other? Did you leave your Z axis mounts on the bottom lose (also the ones on the cross brace under the center of Y) and move z all the way down before tightening? etc..

I can confirm that dialing up the power on the X and Y solves the symptoms.

I won't try to say that this is the cure, because I'm too new at this to make that claim, but dialing up the power on both of them just slightly (.10 volts difference) did the trick.

I've done several prints since then including the one that was shifting every time and every one has been perfect.

What is your Power Supply voltage at, and do you have an auxiliary capacitor on it?

Sorry, didn't know if you were talking to me or the OP. Sorry for the hijack Harbi, I hope this discussion helps your situation.

My PS is a PC power supply that can handle 17Amps of draw. It doesn't have the auxiliary cap to bump the voltage, but it's putting out 11.9vdc. The voltage doesn't seem to drop at all under full load with the extruder and heated bed cranking so I didn't put the extra load on the 5vdc line.

Do you think that increasing the voltage will change anything for this setup?