inconsistent step/mm of Y axis

shaolin30

<p style="font-family: Arial, Helvetica, Verdana, Tahoma, sans-serif; font-size: 15px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; margin-top: 0px; margin-right: 0px; margin-left: 0px; line-height: 1.5rem; border: none; color: rgb(51, 51, 51); margin-bottom: 10px !important; background-image: none !important; background-position: initial !important; background-size: initial !important; background-repeat: initial !important; background-attachment: initial !important; background-origin: initial !important; background-clip: initial !important; box-shadow: none !important;">Hi, do you have any idea why my Y axis doing this?</p><p style="margin-top: 0px; margin-right: 0px; margin-left: 0px; line-height: 1.5rem; border: none; margin-bottom: 10px !important; background-image: none !important; background-position: initial !important; background-size: initial !important; background-repeat: initial !important; background-attachment: initial !important; background-origin: initial !important; background-clip: initial !important; box-shadow: none !important;">https://www.youtube.com/watch?v=gvynOpbJaUc</span><br/></p><p style="font-family: Arial, Helvetica, Verdana, Tahoma, sans-serif; font-size: 15px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; margin-top: 0px; margin-right: 0px; margin-left: 0px; line-height: 1.5rem; border: none; color: rgb(51, 51, 51); margin-bottom: 10px !important; background-image: none !important; background-position: initial !important; background-size: initial !important; background-repeat: initial !important; background-attachment: initial !important; background-origin: initial !important; background-clip: initial !important; box-shadow: none !important;">
</p><p style="font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; margin: 3px 0px 10px; color: rgb(51, 51, 51); background-color: rgb(255, 255, 255);">I have tried:
Tightened the belt,
Change the a4988 driver with a new one,
Calibrate the a4988 voltage and amperage,
Change the steps/mm several times,
Change the board from gt2560 to ramps1.4+mega,
Switch the X and Y wires but still the problem with my Y axis only still here.</p><p style="font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; margin: 3px 0px 10px; color: rgb(51, 51, 51); background-color: rgb(255, 255, 255);">Thanks for the help.</p>

Repetier

What exactly is this? Video shows only a lcd with axis position.

Try ALWAYS_CHECK_ENDSTOPS 0 to rule out endstop crosstalk (except during homing where it will be enabled of course).

shaolin30

Hi, thanks for the response. I'm having problem with my Y axis movement. I have 1.8deg motor, 1/16micro stepping, 20tooth pulley and this belt I bought from ebay: http://www.ebay.ph/itm/New-GT2-Timing-Belt-White-PU-Steel-cords-For-3D-Printer-6mm-width-RepRap-/331851043185?var=&hash=item4d43dd1171:m:m6ZcdbpEyMZBPgq2zCbSwyQ<div><br/></div><div>My X axis settings for steps/mm is 80 but if I put 80 to Y axis and move the Y axis 100mm distance from 0 position, I get 114.5mm total distance. If I wanted an exactly 100mm distance I have to put 71.4mm steps/mm but it will result to inconsistent steps/mm like what you have seen from the video, I'm moving the dial 1mm at a time but instead of 1mm I get 0.99mm. Thanks in advance.</div>

Repetier

The problem with rounding is no problem. It comes from the fact that we store positions in steps as this is the only lossless value to operate with. For display it is converted to mm and since you do not have exactly 100 steps per mm rounding can cause 0.99 or 1.01 to appear.

MartinH

shaolin30 said:

My X axis settings for steps/mm is 80 but if I put 80 to Y axis and move the Y axis 100mm distance from 0 position, I get 114.5mm total distance. If I wanted an exactly 100mm distance I have to put 71.4mm steps/mm but it will result to inconsistent steps/mm like what you have seen from the video,

Sounds like either you have different size gear on X and Y mototrs or maybe the belt is riding up an the Y gear flange

Roko

Do your pulleys have 20-teeth for sure? I read somewhere else that a person had a similar issue and it turned out the pulleys were made with an incorrect # of teeth. I think they were 1 off. Just suggesting.

shaolin30

I've counted all the pulley's teeth both X and Y and it's exactly 20tooth pulley. Right now I'm just using the 71.4 steps/mm value for Y axis and printed a 20mmx20mm cube for test and the result is weird because Y-axis measured exactly 20mm but X is 19.5mm only. :-<

Repetier

Print 2 cubes. 20x20 and 40x40 and see if the error grows or not. I have the same symptom and it is always the same difference. Might be backlash or something other hardware related. But with different sizes you see if the error grows => steps per mm wrong or if it is the same and has some hardware source.