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Delta auto calibration

Posted by mcrum 
Delta auto calibration
October 17, 2019 02:17PM
I've been working on a Micromake D1 for a while now. I've upgraded to an SKR 1.3 board and bl touch. My problem is with auto calibration or bed leveling. The print head comes down and stops a bit above the bed then moves down to probe but doesn't reach the bed and the bl touch isn't triggered. This results in the calibration failing. Any suggestions?

Thanks,
Michael
Re: Delta auto calibration
October 18, 2019 04:57PM
Quote
mcrum
I've been working on a Micromake D1 for a while now. I've upgraded to an SKR 1.3 board and bl touch. My problem is with auto calibration or bed leveling. The print head comes down and stops a bit above the bed then moves down to probe but doesn't reach the bed and the bl touch isn't triggered. This results in the calibration failing. Any suggestions?

Thanks,
Michael

Please don't take this as snarky...
My recommendation is to square the towers, level the bed and ditch the bl touch. I have a Folgertech 2020 delta with a 200mm diameter bed. I started out using a couple of different bed levelers and the bed leveling Marlin option. After a while I got tired of dealing with the "auto" bed leveling, got the the square, read "Digital Dentist" pages and leveled the bed. Now all I ever do is reset the Z height when I change nozzles. It prints its full volume with no issue.
BUT
I spent a lot of time getting my delta radius correct and aligning my end stops to get it right. But now, I don't deal with the time wasted (and in my case, the quick snatch removal of the bed detector) to start a print. This printer isn't one of the "industrial strength" units, but as long as I am very careful about moving it (and fussing the tower alignments), it is my most reliable printer.

It may not be what you want to hear, but it is worth your effort to take the "mechanical alignment" path over the bed leveling adjustments for a smaller bed delta.
Now, the answer is different with a monster bed printer where there is NO WAY the entire thing will be level...

YMMV,
DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
October 19, 2019 12:25PM
I appreciate the advice. I have leveled the bed manually and now everything works great. I'll probably ditch the BLtouch like you said but I'll leave it attached for the time being.

Thanks!
Re: Delta auto calibration
October 21, 2019 09:20AM
Dlc60, I am trying to calibrate my FLSUN Mini using the manual method and have been having problems because the guides I have followed all refer to final adjustments to the “DELTA SMOOTH ROD” setting which I cannot find in any version of Marlin I can download.
I tried to search for the “DigitalDentist” pages without success, can you provide a link to those articles please?
Thanks
Re: Delta auto calibration
October 21, 2019 11:00AM
Quote
NAP1947
Dlc60, I am trying to calibrate my FLSUN Mini using the manual method and have been having problems because the guides I have followed all refer to final adjustments to the “DELTA SMOOTH ROD” setting which I cannot find in any version of Marlin I can download.
I tried to search for the “DigitalDentist” pages without success, can you provide a link to those articles please?
Thanks

Try this one:
[drmrehorst.blogspot.com]

There are others, he gives a really good discussion on three point bed leveling using "pitch" and "roll". This is what finally gave me my "aha" moment on my printers.

DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
October 21, 2019 07:27PM
Dlc60, good technical article with much of it very way over my head and understanding.
I read the 3 point process very carefully but this seems to be for a Prusa type printer not a Delta.
I could find nothing that helps me solve my DELTA_SMOOTH_ROD dilemma.
Re: Delta auto calibration
October 22, 2019 12:06AM
Quote
NAP1947
Dlc60, good technical article with much of it very way over my head and understanding.
I read the 3 point process very carefully but this seems to be for a Prusa type printer not a Delta.
I could find nothing that helps me solve my DELTA_SMOOTH_ROD dilemma.

I am willing to bet that your delta has three screws to level it. The same rules apply, trust me.
The DSR dilemma comes because that element of the delta setup is old fashioned and not done anymore. In the old Marlin firmware you had this relationship:

#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)
You used all those offsets to define your DELTA_RADIUS, kind of over-complicated.

The new Marlin ditches all that unnecessary obfuscation and just does DELTA_RADIUS = the horizontal distance between the centers of the bolts that hold your delta arms on when the delta is "homed". You will then do some adjustments to "flatten" your bed because when this value isn't exactly right, you will appear to be either concave or convex when the end effector moves across the plate. Check out this REPRAP thread:
[reprap.org]

DLC


DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
October 22, 2019 10:45AM
OK, I think I am getting a handle on this, yes I have 3 bed screws.
If I use a clock face to explain, the towers are located as follows, X tower is at 8, Y is at 4 and Z is at 12.
The screws are at 7, 3 and 11.
If I understand this process 2 of the screws should lie along either the X or Y axis.
Mine do not.
For your information I am using a 1/4” flat aluminum bed which is heated. This is Epoxy metal glued to the original 1/8” aluminum plate which I warped.
The new plate was checked for level and true by a machinist who also milled it to a 220mm diameter.
The warped bed was what started me down this road.
I have also braced the 20x20 aluminum uprights at top and bottom and installed a plate on top of the printer towers for additional stiffness.
Should I reposition my bed mounting screws so they are aligned with towers, before I start the process?
Re: Delta auto calibration
October 22, 2019 06:53PM
Quote

Should I reposition my bed mounting screws so they are aligned with towers, before I start the process?

For the life of me, I don't know. I didn't even look on my deltas, I just did the leveling. The leveling screws are in the X/Y directions on a Cartesian printer because the supports for the bed are in X and Y, so that might just be coincidence.

DLC

Edited 1 time(s). Last edit at 10/22/2019 06:53PM by dlc60.


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
October 22, 2019 08:41PM
This process has been a very steep learning process for as my high school math is now almost 60 years old and memory is not what it used to be.
Any way we know the X axis runs between the X and Y towers and the Y axis runs on a line perpendicular to the X axis and straight back to the Z tower.
As none of these are parallel to the lines between the adjustment screws setting the printer up should be a matter of making small adjustments to 2 screws instead of one as described in the process blog. I am going to try that and if it does not work I will make new bed supports that place the adjustments screws directly in front of the 3 towers and start again.
This is a hobby not an obsession, right?
Re: Delta auto calibration
October 22, 2019 10:44PM
Quote
NAP1947
This process has been a very steep learning process for as my high school math is now almost 60 years old and memory is not what it used to be.
Any way we know the X axis runs between the X and Y towers and the Y axis runs on a line perpendicular to the X axis and straight back to the Z tower.
As none of these are parallel to the lines between the adjustment screws setting the printer up should be a matter of making small adjustments to 2 screws instead of one as described in the process blog. I am going to try that and if it does not work I will make new bed supports that place the adjustments screws directly in front of the 3 towers and start again.
This is a hobby not an obsession, right?

Don't worry, you'll be an expert after you get your first printer working. smileys with beer


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
October 23, 2019 03:49AM
Quote
NAP1947
Should I reposition my bed mounting screws so they are aligned with towers, before I start the process?
You should position your bed so that it is perpendicular to all the towers. That is because many delta kinematics do not allow for tilted bed in relation to the 3 parallel towers. Most delta kinematics do not alow for non-parallel tilted towers as well.
Re: Delta auto calibration
October 23, 2019 11:18AM
I have rechecked all of the level settings with a square to ensure all the tower to bed angles are 90 degrees.
I have adjusted and stiffened the towers so they are all parallel, top and bottom measurements are as follows, X to Y 285mm, Y to Z 285MM, X to Z 283mm.
So if I have these correct and my end stops at each tower are adjusted to 276.6mm and my Z height is 276.9mm, how exactly to I adjust for this discrepancy?
If I change the Z0 or the tower end stops the Z0 is always 0>30mm out.
This was my original issue that I perhaps did not describe accurately in the first question.
Thanks for all your help.
Re: Delta auto calibration
October 23, 2019 12:05PM
Quote
NAP1947
I have rechecked all of the level settings with a square to ensure all the tower to bed angles are 90 degrees.
I have adjusted and stiffened the towers so they are all parallel, top and bottom measurements are as follows, X to Y 285mm, Y to Z 285MM, X to Z 283mm.
So if I have these correct and my end stops at each tower are adjusted to 276.6mm and my Z height is 276.9mm, how exactly to I adjust for this discrepancy?
If I change the Z0 or the tower end stops the Z0 is always 0>30mm out.
This was my original issue that I perhaps did not describe accurately in the first question.
Thanks for all your help.

I do not think that I understand what you are saying. Your end-stop height will be considerably higher than your end-effector nozzle height. Does Z0 == the Z height when the nozzle is in contact with the bed? And, does >30mm mean that when you tell the printer to go to 0,0,0 it goes to 30mm above the bed?

DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
October 23, 2019 12:27PM
OK My rookiness is showing again.

What I should have said was "If I change the Z0 or the tower end stops the Z0 is always 0.30mm out"

If I do a G1 Z0 the nozzle stops at the bed.

If I do a Z0 at any of the 3 towers it is always 0.30 above the bed.

It is this 0.3mm I am trying to finesse.

Does that make more sense?
Re: Delta auto calibration
October 23, 2019 06:03PM
Quote
NAP1947
OK My rookiness is showing again.

What I should have said was "If I change the Z0 or the tower end stops the Z0 is always 0.30mm out"

If I do a G1 Z0 the nozzle stops at the bed.

If I do a Z0 at any of the 3 towers it is always 0.30 above the bed.

It is this 0.3mm I am trying to finesse.

Does that make more sense?

THAT makes sense. You have a "concave bed" and you need to decrease your DELTA_RADIUS value. Experiment with adjustments, how much effect the reduction has depends upon your arm lengths.

DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Delta auto calibration
November 01, 2019 03:59AM
Hopefully final update.
It took a lot of time but I have the DELTA_RADIUS almost perfect.
I am taking a forced break as I succeeded in frying my board, new one is on the way.
I want to thank the folks that responded to my request for help, your patience and clarity are greatly appreciated.
I have certainly learned a lot.
Cheers
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