Delta Calibration: Bed-Nozzle distance increases only at -y axis

Hi all,

I was just finetuning my Chinese delta printer. Firstly I only made a few small prints without any problems, but with bigger prints there seems to be a small problem.

When the nozzle is going to the -Y axis (or below the X axis the nozzle distance to the bed suddenly increases by about .5mm. I've already played around with delta radius correction (making a bowl/dome shape) and read about the bed tilt correction etc.. but tilt will make the +y axis nozzle distance smaller.

So if I draw a line at the X axis everything above that line is perfectly calibrated but everyting below the line doesnt stick to the bed because the distance is too big.

is there anybody who knows how to fix this problem?

Thanks in advance!

Are you sure the change is that abrupt as you describe it? I used to have the a similar issue, but on the X axis, and the error was accumulated with the distance... I.e. Getting worse the further away I go to the -X direction.
It turned out to be the effector tilt. You can by a cheap bubble-level and check for that to see if there is something happening across the X axis...

Thanks for your reaction!

And indeed i didn"t explain it well enough, The distance becomes more the further away the nozzle is from the X axis. at -40Y it was about .5mm.

My effector is indeed a bit tilt. So apparantly my diagonal rods aren't equal. Ill try to fix it tomorrow and hopefully it helps.

It's worth making sure your belts and pulleys are in good order. I had a real saga with one belt stretching causing a slant to - x in prints which stopped after 50mm as it was only the section of one belt at the z=0-50mm range that was affected. Simple fix but it took 2 weeks and 6 reprappers to figure it out.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
Morph1
My effector is indeed a bit tilt. So apparantly my diagonal rods aren't equal. Ill try to fix it tomorrow and hopefully it helps.

It might not be the rod lengths, there are other things that cause effector tilt. See [duet3d.com].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi,
Who's able to tell me exactly where I must take measurements to find the physical value of the "Delta sooth rod offset"
in order to put it into my config.h
I have found this information for a cartesian 3d printer, but noting for my 3d printer seems like the attached picture:

Is it from center hot end effector axis, and the edge of the belt, or fron center to the external face of the linear carriage
or, between the center and the surface of the sliding rail, or between center and the middle of the vertical mounting 20x20 rail?

Thank a lot for your help.

JC

Depending on how you intend to calibrate if it's wrong it will get autocorrected, i.e. by software autocalibration or manually using escher3D least squares online calc.

Make sure you rod length is correct by measuing from joint/ball centre to centre.

One the calibration routine determines the smooth rod offset then you can change the rod length to adjust your object XY size.

Edited 1 time(s). Last edit at 03/02/2017 07:12AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions