Auto Calibration with Parameter S6

Hi all,

when I´m doing the autocalibration with Parameter S6 enabled it is giving me this result:

M665 R179.65 L345.35 B140 H379.13 X0.46 Y0.17 Z0.00

But I recognized that square boxes are not really right-angled from X to Y direction.

When I set X0.00 Y0.00 Z0.00 in M665 and do the autocalibration with S4 Parameter they are coming out perfeclty square with 90°

Another small issue I have with dimensional accuracy. But thats really small.
Printed Boxes. One 30x30x10mm, 60x60x10mm, 90x90x10mm. All hollow. Wall thickness is 2mm.
Walls are 2mm one the spot, height is on the spot.

Cube 30x30 is in X=30,02 in Y=29,89
Cube 60x60 is in X=60,02 in Y=59,90
Cube 90x90 is in X=90,03 in Y=89,90

Printed now 6 of each. They are all the same within 0,01-0,02mm tolerance.

My Delta build is very accurate. All angles are nearly perfect. Effector is parallel to the printbed. Arms are all within 0,05mm Tolerance.

But why are all prints in Y-Direction 0,1mm to small, but in X-Direction nearly perfect?
No matter what I do, Y-Direction is 0,1mm smaller than X-Direction, independant from size of the Testparts?!
And this issue is independant from autocalibration with S4 or S6.

But what is causing this? S6 is giving me wrong X and Y in M665. And all prints are in Y-direction exactly 0,1mm to small.
Can´t find the bug and have no idea what to search for. Everything seams to be perfect. Effector is travelling parallel to the Bed. Dial Indicator shows differences within 0,02mm.

Any ideas?

ah, forgot to say that´s on my Delta (Big Kossel)

Edited 1 time(s). Last edit at 05/24/2016 05:25AM by critical_limit.

First check that your Z probe is giving you the same trigger height all over the bed. If it isn't, then either find out why and fix the problem, or correct for the variation using the H parameter on the G30 commands in bed.g.

The difference in X and Y dimension suggests that you have a geometrical error somewhere, probably one of:

- bearing spacing at one end of a pair parallel rods not quite the same at both ends
- one or more carriages rotated slightly about either the Z axis or perpendicular to the face of the carriage, so that it's impossible for all 3 pairs of rods to form perfect parallelograms at the same time
- towers not quite perpendicular to the bed - this is a common problem when using printed frame vertices.

If the difference in X and Y dimension is the only problem you have, you can correct for it using the M579 command.

---

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].

Thanx David,

I already checked all this and can´t find a fault.
What I don´t understand is, that all Dimensions are ok exept Y-Direction.
Also I have no answer to this autocalibration thing. Why autocal is making the delta crooked?

Manuelly set X, Y, Z to zero in M665 is resulting in 90° angels which is perfect and tells me my Delta is well built.
Autocal is setting X and Y to a value where X to Y angles are out of 90°. Don´t understand.

But will recheck all again. But I don´t understand why autocal is doing this.

Is M579 for Delta Printers also? Wiki says its for cartensian printers. So I was thinking X, Y, Z Values in M579 are for the physical axis?!

Edited 1 time(s). Last edit at 05/25/2016 03:09AM by critical_limit.

I had written below stuff for the Fisher, but it may apply for any delta.

The 6 parameters add to the 4 parameters test the angular position of the X and Y columns (they search if the triangle is not equilateral), as this is a current default on "Kossel type" printers. This is why there is only X and Y angle, the Z angle being the reference angle.
For a construction like the Fisher, these defaults are nearly inexistant, however there are others defaults not researched by the algorithm:

• Balls not in a plane - common default on Fisher due to construction
• Balls not having the same space on effector and on carriage. Again, common default on Fisher (and other deltas)
• Top and bottom twisted. May occur if the construction is not good.
• Tilted bed. in principle limited on a new Fisher, but not adjustable and not quite measurable. Will evolve in time. Check standoff tigthening from time to time.
• Bed not flat.

The problem is that the calibration algorithm attempt to transform all these defaults in angular position fault. Generally speaking, the algorithm find a solution with angles which minimize the hotend/bed calibration error, hence helps to have a nice first layer. These found angles may be way off the reality.
The problem is that it may drive to significant faults in dimensions and perpendicularity of the printed parts.
So, if you want to print a statue, vase or something not needing accuracy, using 6 parameters calibration is ok.
But if you want accurate parts, you shall NOT USE the 6 parameters calibration.

On the Fisher, it is reasonnable to consider there is no angular fault.
If the algorithm found large deviation, you may try to rebuild carriage and effectors more accurately.

For other printers, you shall print delta calibration part to research your angular faults, then enter the corrected angles in the M665 command in the configuration file (or in the G-code windows, but this is lost at restart). After enter of the corrected angles, reprint a new delta part till finding the good angle.

Then use 4 parameters calibration. There will be a larger calibration error between the hotend and the bed, but your parts dimensions will be more accurate.

I have the impression that the worst for the algorithm is a non flat bed.

Quote
critical_limit
Thanx David,

I already checked all this and can´t find a fault.
What I don´t understand is, that all Dimensions are ok exept Y-Direction.
Also I have no answer to this autocalibration thing. Why autocal is making the delta crooked?

Manuelly set X, Y, Z to zero in M665 is resulting in 90° angels which is perfect and tells me my Delta is well built.
Autocal is setting X and Y to a value where X to Y angles are out of 90°. Don´t understand.

But will recheck all again. But I don´t understand why autocal is doing this.

Is M579 for Delta Printers also? Wiki says its for cartensian printers. So I was thinking X, Y, Z Values in M579 are for the physical axis?!

---

Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

Thanx Pierre.

I Think I´ve dialed it in now.
Calibrating with S4 giving the best results for me. My Testboxes are now rectangular and I used the M579 Y1.02 to correct the Y-Direction fault.

First Layer is a dream now. Before it was good, but due to calibrating with S6 it has some minor issues. Never thought about that S6 is giving values for X Y Z in M665 so far away from reality.

Actually I´m printing a technical Part (Effectorplatform for magnetic ballarms) that I never managed to hold dimensions as designed. I´m really curious if it will work now.

Thanx to all for helping me out!

cheers
Dirk

Quote
critical_limit
Thanx Pierre.

I Think I´ve dialed it in now.
Calibrating with S4 giving the best results for me. My Testboxes are now rectangular and I used the M579 Y1.02 to correct the Y-Direction fault.

First Layer is a dream now. Before it was good, but due to calibrating with S6 it has some minor issues. Never thought about that S6 is giving values for X Y Z in M665 so far away from reality.

Actually I´m printing a technical Part (Effectorplatform for magnetic ballarms) that I never managed to hold dimensions as designed. I´m really curious if it will work now.

Thanx to all for helping me out!

cheers
Dirk

I'm glad it's working for you. If your build is super-accurate - including the tower spacings being exactly equal - then calibrating with S4 should give good results, and changing to S6 shouldn't change anything. The fact that changing to S6 make such large corrections to the tower positions but messes up straight lines suggests that something is not quite right, but it isn't the tower positions, nor is it towers leaning in radial directions.

What deviation does calibration with S4 return, and what deviation does calibration with S6 return? Also, after calibrating with S4, can you run calibration with S-1 so that it reports the height error at each probe point, and post the results?

Edited 1 time(s). Last edit at 05/26/2016 04:50PM by dc42.

---

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].