Problem with x,y, axis Printing squareness issue ?

Ortorea

Can anyone help me solve a rather odd problem I have, I have spent hours trying to work out what could cause my (Y) position to be printing slightly longer on the left side of the bed than it does on the right side of the bed. I have squared up the Z axis with a 'square' and checked alignment between the left and right of the bed but even if this was out it would not explain why my prints come out longer on the left side than the right by about 1mm so what I have done is print an exact square of X50xY50mm at 1mm height but their is a very slight twist or something going on here im baffled any idea's how to solve this ?

Printer details: Prusa I3, Home Built, using firmware 0.92.6
controller LCD: RepRapDiscount Smart Controller
www.bigtree-tech.com

It has a red pcb extention board to interface with the LCD cables then to the LCD

Rather than uploading a photo that wont help much I will try to do a roughe text based graphic to help.
yyyyyyyyyyy
x|----------------|
x|----------------|
x|----------------|
x|----------------|
x|----------------|
x|----------------|
^
1mm ^shorter 49mm -1mm
51mm

Michelle

Repetier

Firmware uses same steps per mm over complete x axis. So from the signals it sends left and right should not differ in size. Of course steps per mm can change size but without difference left to right.

Have you validated the slicer generated gcode to have same distance for a square? Also does it move around in same direction rotation wise?

I agree that it very starnge and also have no idea why this could happen.

Ortorea

I really am not very good at understanding Gcode would it help if I posted my gcode generated for the sliced square here ? it should not be a big file as I only printed about 2 layers to save plastic for the test print. Could the problem be caused by me having different x,y, max length ? my x max length = 200, and my y max length = 197, let me know if you want me to post the Gcode here or on dropbox or somewhere ! Regarding the rotation I think my circler objects are also printed slightly more oval on the left side than the right so it effects all shapes I print which is what is annoying me as I cannot print perfect circles so obviously this poses a big problem when printing threaded screws and bolts I printed the puzzle box threaded thing off thingyverse it came out distorted but still works just looks weird. I uploaded my Gcode to my own website as it seems dropbox is not free anymore http://www.book-stores.com/files/calibration-square.txt Michelle

Ortorea

I made 2 video's doing some measurements on the problem.

x,y, axis measurements
Part one https://youtu.be/oUZA5ZPpN_I part two https://youtu.be/ldBUSoP-U_s Michelle

Repetier

Measuring only the first layer can be a big error! If Z distance to bed differs left to right the first layer perimeter will be wider or more narrow depending on z distance. That does not really mean x changes over axis. Print a 20mm cube left and right and measure again near the top. Single perimeter prints deform too easy to measure at that height.

Ortorea

Thanks Repetier, but in this case I doubt it is the problem as only reason I did the calibration square was that taller prints were bigger on the left than the right. I know what your saying though think its referred to as elephants foot! I did take extra care to measure the distance with a sheet of paper if anything the left side is slightly larger gap due to a slight warp in the glass bed. I find the edges of the plate are always bigger gap between nossle and glass sheet than the centre.

Michelle

Repetier

No, elephant foots are a bit different. You get them when the bed is too hot, then the bottom flows a bit outwards when you print the next layer.

What I mean is that perimeter thickness differs if z height to bed is different. I saw you measured the inner hole or outer diameter. Both include the perimeter thickness. So you should also measure if perimeter have same width on bed. That is the error I meant.

Ortorea

OK I understand, well for the moment I am 3D printing some new brackets as I did find some tiny discrepancies in vertical alignment not that this is the cause of my problem but I want to remove any errors I can to better track down my problem see video on this. after I get the new parts fitted and re-true the printer we can take it from there.

https://youtu.be/E-xsrrnX4Hs Michelle

RAyWB

simple suggestion:

try to fix a pen or pencil to your hotend and draw a square. that´s much more precise

Ortorea

RAyWB said:

simple suggestion:
try to fix a pen or pencil to your hotend and draw a square. that´s much more precise

good idea Ray will try thx

Ortorea

RAyWB wrote
simple suggestion:
try to fix a pen or pencil to your hotend and draw a square. that´s much more precise

OK so after running the Pen drawing test it has shown some opposite alignment issues which means I have moved something that half corrected the problem but moved it to the other side, I am uploading the video now and will be LIVE while fitting new brackets. https://youtu.be/mvll2e236mQ Video of the pen draw test is here might still be uploading:
https://youtu.be/iIF_NBExJYk Thanks :)

Michelle

Repetier

I have the feeling the circles inner/outer perimeter cross each other.
There is one effect that may be a problem and that is backlash. With that head does not directly move only after x has moved a bit. A last thing that also causes different sizes is a excentric pulley. See if on fast x moves you see that pulley stays at position and does not wobble. Also check if x belt has a good tension. Both might cause the problem.

Ortorea

Repetier said:

I have the feeling the circles inner/outer perimeter cross each other.
There is one effect that may be a problem and that is backlash. With that head does not directly move only after x has moved a bit. A last thing that also causes different sizes is a excentric pulley. See if on fast x moves you see that pulley stays at position and does not wobble. Also check if x belt has a good tension. Both might cause the problem.

Thanks, well I have just upgraded my belts from 3.5mm to 6mm widths to keep in-line with modern standards my former pulleys were for 3.5mm MXL-15T so as my pulleys were not wide enough for the newer 6mm wide belts I ordered new one's from china but these have not arrived in the post yet so 3D printed some for temporary usage so they may well be excentric as you say !!!

I think this could be part of the problem, so will hope these new pulleys arrive soon before November, meanwhile will just calibrate as best I can. :)

The pen test did show some crossing lines yes ..... Not sure how to fix that ?

Michelle

RAyWB

well, i watched the livestream for a couple of minutes. seems the printers frame is quite weak at all.

may be you try to get the frame more rigid.(looks like made from plywood so it should be easy makeable)

for the pen test may be its better just to send some manual commands

f.e. on a low feedrate

G1 X0 Y0 F1000

G1 X200 ( i don´t know your max numbers so i just guessed)

G1 Y200

G1 X0

G1 Y0

that should draw a perfect square

Ortorea

RAyWB wrote
well, i watched the livestream for a couple of minutes. seems the printers frame is quite weak at all.
may be you try to get the frame more rigid.(looks like made from plywood so it should be easy makeable)
for the pen test may be its better just to send some manual commands
f.e. on a low feedrate
G1 X0 Y0 F1000
G1 X200 ( i don´t know your max numbers so i just guessed)
G1 Y200
G1 X0
G1 Y0
that should draw a perfect square

Thanks so much Ray, well in fact when my friend sent me this printer in the mail all the way from the USA it took one hell of a beating and the frame was shattered I will post a video here of the damage it suffered, I basically used steel re-enforcing washers on the lower part of the frame and a new 10mm bolt to secure the back chassis so it is fairly rigid. The problem might be it is distorted as theirs some bend in the upper beam bar were the Prusa I3 logo is laser etched onto it.

Taken In January 2018
https://youtu.be/u93UDdurTEw Full Extent of Damage Just after Christmas 2017
https://youtu.be/JUrjs1G3H1A Since that time I spent a lot of time and effort fixing the frame. I also riveted steel laminations to the base of the printer bed mounting square section so all this is solid now.

I will try out your manual commands after this print is done for the new Z axis homing switch bracket and after I have eaten some food, so give me a few hours say 3 hours and will try the code you gave me. I have re-calibrated the squareness again!

Michelle

RAyWB

OOps... printer in fragments.... wouldn´t it be better to kick that frame and make a complete rebuild ?

Ortorea

RAyWB wrote
OOps... printer in fragments.... wouldn´t it be better to kick that frame and make a complete rebuild ?

I have considered it yes but its cost, really im on a fixed income so money is tight at the moment, but I do have an engineering background so made some rather hefty strong repairs its just squaring it up really :)

Its always an option however if it turns out thats the only solution.

Basically this is the frame mine uses
https://tinyurl.com/ycolu4ze Michelle

Ortorea

I will be going live in a few minutes to try out the commandline square writing with a pen on 3DP https://youtu.be/o71koCDrFbM

Ortorea

Did more measurements printing a 2.4mm tall square their better but still slightly out maybe I should not complain as its about 0.7mm I think on Y-Axis.

RAyWB

try to print a square in half size , same height.

if error is half then , adjust the steps /mm