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Object move after few layers

Posted: Mon Aug 08, 2016 10:16 pm
by lezabour
Hi,

Still some issus with my Prusa I3 Pro C, but i'm touching the goal!!

problem is simple: the firsts layers (around 10 of a 40 layers objects) are printed very good. Extruded is well positioned, good distance from heating bed, everything is OK. But after few layers, the extruders is more and more touching the printed objet, and it finally make it move... The object move and the print is going to garbage.
IMG_2073.JPG
You can see the extruder touching the object in the border...
IMG_2073.JPG (208.76 KiB) Viewed 4974 times
I have tryed several things, and modify the printer a little bit:
- i have add the auto bed leveling, with an inductive sensor.
- i have modified the marlin firmware to mait work.

Every print i make, no matter the object (only calibration object for now), it's same results: the 1 to 10 (around) first layers are perfect.
IMG_2061.JPG
firsts layers are perfect. Extruder is well positioned from bed, and everything is good
IMG_2061.JPG (254.74 KiB) Viewed 4974 times
And after,the extruder seams not to get enough height, and begin slowly but surely to touch the object.
IMG_2080.JPG
extruder has touch object too much. object has moved, and now it can't finish printing
IMG_2080.JPG (235.32 KiB) Viewed 4974 times
Don't know how to solve that...
I tryed to higher to extruder from the bed, but if so, i have bad print quality for firsts layers, cause it's too far from bed.

Thanks for your help, i become crazy!! ;)

Re: Object move after few layers

Posted: Tue Aug 09, 2016 10:59 am
by William
lezabour wrote:Hi,

Still some issus with my Prusa I3 Pro C, but i'm touching the goal!!

problem is simple: the firsts layers (around 10 of a 40 layers objects) are printed very good. Extruded is well positioned, good distance from heating bed, everything is OK. But after few layers, the extruders is more and more touching the printed objet, and it finally make it move... The object move and the print is going to garbage.
IMG_2073.JPG
I have tryed several things, and modify the printer a little bit:
- i have add the auto bed leveling, with an inductive sensor.
- i have modified the marlin firmware to mait work.

Every print i make, no matter the object (only calibration object for now), it's same results: the 1 to 10 (around) first layers are perfect.
IMG_2061.JPG
And after,the extruder seams not to get enough height, and begin slowly but surely to touch the object.
IMG_2080.JPG
Don't know how to solve that...
I tryed to higher to extruder from the bed, but if so, i have bad print quality for firsts layers, cause it's too far from bed.

Thanks for your help, i become crazy!! ;)
Hi,
You said "make it move",what temp is your heat bed?Did it reach the preset temp?And if the bed's temp is right,i think there may be some installation issues on Z axis...

Re: Object move after few layers

Posted: Tue Aug 09, 2016 3:16 pm
by lezabour
Hi

I have made different test
with bed a 70, 80 or 90
Effect is the same.
But we clearly see that it come from a z axies problem, since, it begin well for the first 5-10 layers, and after it doesn't goes UP enough, so finish by touching the object.

I know it's a Z axies problem, but really don't understand what....

Re: Object move after few layers

Posted: Tue Aug 09, 2016 3:26 pm
by William
Check it carefully plz,and good luck!

Re: Object move after few layers

Posted: Tue Aug 09, 2016 3:45 pm
by lezabour
lol...
check what? check how?
i have no idea what is the problem except the Z axies.

I have tryed every change i could in the firmware nothing works.

I have 2 options
1) re-calibrate the distance that manage the printer, their must be a problem with distance (exemple; when need to move 1mm, maybe it move 0.9 or something like that) ---> how can i do that?
2) the threaded rod to change, maybe bad quality -> i hope this is not that, cause the printer is new.

Otherwise, don't know what to do, or what it can be

heeelpppp please

Re: Object move after few layers

Posted: Tue Aug 09, 2016 4:43 pm
by William
The second option you can check,i think...
Also,have you tried this setting before?Enabling this option will cause the nozzle to lift up a set distance above the previously printed layer before moving to a new location. When it arrives at its final location, the nozzle will lower back down to prepare for printing.
QQ截图20160809172157.jpg
QQ截图20160809172157.jpg (61.48 KiB) Viewed 4444 times

Re: Object move after few layers

Posted: Fri Aug 12, 2016 4:30 pm
by lezabour
Hi,

Just to tell i solve the problem, if anyone have the same

It came from
#define DEFAULT_AXIS_STEPS_PER_UNIT {78.74,78.74,2560,95} // MXL, Z M8=1.25, MK8

I replace it by
#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,4000,95}

Re: Object move after few layers

Posted: Fri Aug 12, 2016 5:53 pm
by ggg666
Hi,
How do you ensure the value is that the problem exists?And are you sure the value is right?

Re: Object move after few layers

Posted: Fri Aug 12, 2016 9:05 pm
by lezabour
Hi

Yes it seems correct.
At least, it solve 2 problems i had:
1) a lot of noize when Z axies moves
2) Z axies won't move enough during the printing, so step by step, the was closer to object.

All has been corrected by changing to {x,x,4000,x}

For all, i used this calculator
http://prusaprinters.org/calculator/