Shifting in x axis

[Owen M Collins]

I have a persistent (as in happens in different prints at different points) shift in my x axis. I am using polulus for my xyz. I guess it could be overheating and losing steps. I have attached a picture, the ends should have a circular hole on them. But the shifting has messed that up.

I will check the temp of the driver while printing, any other thoughts on what it could be?

(Cupcake with stepper extruder)

Thanks
Owen

[whosawhatsis]

Could be too-high current (overheating), too-low current (truncated torque curve), increased idler friction (it's worth "down-grading" to the old style bearing idler). Might also just be too much mass for the motor's torque at that voltage.

The motors included with the cupcake have a TERRIBLE torque curve when run at 12V. They're rated for 14V, and a current-limiting driver like the Pololu should have about 2.5X the motor's rated torque). I HIGHLY recommend replacing at least the X motor (the stationary one that doesn't need to be small and light, but DOES need the spare torque to whip the entire Y axis back and forth) with a larger, higher-torque, lower-impedance stepper. I replaced both motors on my cupcake with different 400-step models, and it performs amazingly.

Here are the motors I'm using:

X: https://www.sparkfun.com/products/10846

Y: http://www.ebay.com/itm/NANOTEC-0-95A-Phasemotor-Stepper-Motor-ST4209S1006-KFUT-/300658203431

Note, these are 400-step motors, while most are only 200-step. You'll get better detail (I originally tried them because I got my quality so high that the X/Y resolution was the limiting factor) and lower noise, but you'll have to modify your machine profile to make them work.

Sent from my mobile

(Please excuse my brevity and typos)

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Attachments:

- photo.JPG

[Owen M Collins]

For idler, are you talking in the extruder or the pulleys in the XY?  I am running a MG that is doing great.  I want to get this thing tuned enough o finish printing the XY lowrider replacement. Then I hope it will be easier to move the XY since it will be on bearings, instead of plastic bushings. 

I will check the current setting on the driver.

Thank you for the detailed response.

O.

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[Whosawhatsis]

I was referring to the X axis idler pulley. The lowrider is a good choice, and you may want to just reduce your speed until you get that installed.

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[Joheinz]

Could I as well use both Sparkfun motors for the X and Y axis? I am
just in the process of upgrading various parts for my cupcake and
would like to save some on P&P as I order from Germany.

Markus


2012/10/16 whosawhatsis <whosaw...@gmail.com>:

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[whosawhatsis]

No. That motor is too long to fit the Y axis.

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[Owen M Collins]

Thanks, Would the fact that my idler pulley is laser cut plywood rather than printer or manufactured change what you think? I haven't adjusted or check the tension in months so Maybe I should look at that as well.

O.

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[whosawhatsis]

Oh, you have a really old one. The laser cut ones do have the bearing, though you can probably reduce the friction sightly by replacing the laser cut parts with the printed version, though it won't be as big a difference as if you were using the manufactured pulley without a bearing like mine came with.

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