Auto Level - Auto Calibration Talk

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Re: Auto Level - Auto Calibration Talk

Postby edward » Sun Dec 08, 2013 12:55 pm

Bump for visibility. I made a minor update on the original post.
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Re: Auto Level - Auto Calibration Talk

Postby AndThenSome09 » Sun Dec 08, 2013 9:15 pm

Im not really having problems with my printer but am intrigued by the Z-Probe and I am definitely going to design my own probe and see what I can come up with using Repetier firmware. I think it would be a great tool to have when your in need of it or maybe just wanna show off something cool lol. But I plan on experimenting with it myself for sure, I am just waiting for my limit switch to get here in the mail.
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Re: Auto Level - Auto Calibration Talk

Postby 626Pilot » Sun Dec 08, 2013 10:20 pm

mrbi11 wrote:When I am talking about diagonal, I mean from top of print volume to calibration point, with mainly z axis travel.
Horizontal diagonal works fine.

I am saying if you go home, g28, then go diagonal to the calibration coordinates, you end up somewhere slightly different
than if you go home, then down, then to the same coordinates.

Like I said, it doesn't matter. My calibration scripts move Z first, then X/Y, but when I print it just moves diagonally to the start point. In both conditions the effector winds up where it's supposed to go. If it didn't work I would be agreeing with you.

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Re: Auto Level - Auto Calibration Talk

Postby AndThenSome09 » Mon Dec 09, 2013 7:34 pm

Does anyone know if the Rambo board has a spot where I could hook up a micro servo to deploy a z-probe?
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Re: Auto Level - Auto Calibration Talk

Postby geneb » Tue Dec 10, 2013 9:47 am

There's no connector on the RAMBo for a servo.

Then again, there's no need for it - you can build a mechanically deployed z probe pretty easily, but I'd wait until the auto-calibration actually works before spending the effort on the probe.

I'll keep saying this until people get it - unless your printer is perfectly calibrated, "auto level" will never work. If you've got your printer perfectly calibrated, there's no need for auto-level.

The "holy grail" here is auto-calibration not auto-level. So far, no firmware available can properly auto-calibrate a delta. They've come close a time or two, but never good enough to be usable.

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Re: Auto Level - Auto Calibration Talk

Postby 626Pilot » Wed Dec 11, 2013 7:56 pm

I think we would be lucky to see a working auto-calibration in the next six months. The Z-probe idea is good enough to convey the information the firmware needs. I think we can get by without a closed-loop position sensing system, but the firmware would have to know how to do everything in the manual - AND it would have to know how to do the tower rotations - AND it would have to check positions at multiple layer heights to adjust the delta arm length. That's a lot of work for an unpaid volunteer who has only one delta printer to test it on.

If they could just get the build height right it would be worthwhile, but even that's broken.

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Re: Auto Level - Auto Calibration Talk

Postby mrbi11 » Fri Dec 20, 2013 9:30 am

I have been working on the repettier firmware to prevent movement out of build area.
I have it in test now.

One of the parameters to leveling, i think the most important, is the printer RADIUS constant.
In the old repetier, this is a constant compiled in (see manual).

In my version, this has been moved to the eeprom, so it is no longer necessary to recompile to adjust this setting.

(As he finally gets to the point).
Auto leveling CANNOT adjust the compile time RADIUS constant, so has limited utility if for no other reason.

If the computation were adjusted to calculate up from say 100 points on the disk,
that might accomplish the same thing, but I see nothing in the software capable of that.

The RADIUS is more important to get right around the edges, otherwise just in front of the towers will
be too high and spaces between towers too low, near the edges. (or vice versa).
In the center where most people print it matters a lot less. You can just get close.

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Re: Auto Level - Auto Calibration Talk

Postby geneb » Fri Dec 20, 2013 12:03 pm

FYI, the v.90 beta of Repetier firmware does make the radius value available in the EEPROM. I recall Flateric was playing with it.

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Re: Auto Level - Auto Calibration Talk

Postby uwes » Sat Jan 11, 2014 7:19 am

626Pilot wrote:The endstop screws handle the rotation of the plane of the build surface first and foremost. The rotations must all be correct for the bed to be level. Imagine drawing a "T" across the build platform. You start out at the X tower, then draw a line to the center of the platform, and that's the vertical line of the T. Then you draw a perpendicular line across the top of that one, forming the horizontal line of the T, stretching from one side of the build platform to the other. That line becomes the axis about which the platform is rotated when you turn the X endstop screw. The phenomenon to be aware of is that RAISING the platform near a tower LOWERS it at the opposite edge, and vice versa.


isn't the rotation axis (the bar on the T) defined by the direct connection between the other two towers?. as long as the end stop at a tower isn't changed the height shouldn't change.

do i miss something?

/uwe

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Re: Auto Level - Auto Calibration Talk

Postby 626Pilot » Sat Jan 11, 2014 7:56 pm

geneb wrote:FYI, the v.90 beta of Repetier firmware does make the radius value available in the EEPROM. I recall Flateric was playing with it.

It has printer radius and also individual radius deltas for all three towers. I wasn't able to get anything but bad results from adjusting the tower radius deltas, but I align my printer by clamping all three towers together so it's unlikely they need to be moved. If all three towers are touching the inside of where they pass through the top and bottom plates (or as close as they can be without breaking something) the radius deltas can probably be left alone.

uwes wrote:isn't the rotation axis (the bar on the T) defined by the direct connection between the other two towers?. as long as the end stop at a tower isn't changed the height shouldn't change.

do i miss something?

It's influenced by them. Towers B and C being level (and properly rotated) is what nails down the plane for tower A.

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Re: Auto Level - Auto Calibration Talk

Postby cancermachinist » Fri Feb 14, 2014 11:02 am

I have created a quick dial test indicator holder that mounts on the extruder, it is the best way I have so far to check the movement. I run the program with an adjusted z level for the indicator and holder and take readings as the extruder head runs post to post. once you have the measurement differences from centre to end you can use a vernier caliper to adjust the screw by that amount and get a pretty good result. as soon as I can figure out how to add a picture I will.

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Re: Auto Level - Auto Calibration Talk

Postby jmick » Mon Feb 24, 2014 9:35 am

Why not clamp a dial indicator to the hot end assy and set the appropriate Z depth to account for it and run a 10 inch diameter circle path as well as a 4 inch diameter circle path to check for table radii warping!!!

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Re: Auto Level - Auto Calibration Talk

Postby 626Pilot » Mon Feb 24, 2014 5:09 pm

I usually don't have my dial indicator "draw" any lines because dragging it against the glass surface tends to make it move around in the mount. Instead I just have it touch the glass at different points. Repeatability is a lot better that way.

I have a spreadsheet set up with all sorts of observations but I haven't figured out how to turn it into useful calibration advice. Tried reading a research paper on delta robot kinematics but it appears to have been written in heiroglyphics!

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Re: Auto Level - Auto Calibration Talk

Postby Maco » Thu Mar 06, 2014 1:42 pm


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Re: Auto Level - Auto Calibration Talk

Postby edward » Sat Mar 08, 2014 3:50 pm

Maco wrote:Hi I found this anyone related?

https://groups.google.com/forum/#!topic ... rmxHMxdgBE


Looks like it could be interesting. I didn't see any mention of a successful auto-calibration in that thread besides the code author.

I'll have to keep that thread bookmarked. If anyone tries this firmware and has success, let me know as I'm still here!
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Re: Auto Level - Auto Calibration Talk

Postby mhackney » Sun Mar 09, 2014 5:41 pm

I've downloaded and gone through the calibration routines in the code he posted and it looks good and should do the job. We just need to port it to Repetier. It is also possible to use the math in his code, make the measurements manually with a dial indicator to populate the matrix, run the calculations and then set the parameters in Repetier.

Just out of curiosity, how important is a self-deploying probe to everyone here? Would a removable probe be acceptable? My preference is a removable to keep weight off the effector (I already have a Kraken so don't need to be slinging more mass!)

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Re: Auto Level - Auto Calibration Talk

Postby artexmg » Sun Mar 16, 2014 10:28 am

mhackney wrote:I've downloaded and gone through the calibration routines in the code he posted and it looks good and should do the job. We just need to port it to Repetier. It is also possible to use the math in his code, make the measurements manually with a dial indicator to populate the matrix, run the calculations and then set the parameters in Repetier.

Just out of curiosity, how important is a self-deploying probe to everyone here? Would a removable probe be acceptable? My preference is a removable to keep weight off the effector (I already have a Kraken so don't need to be slinging more mass!)

cheers,
Michael


Removable for me is good!

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Re: Auto Level - Auto Calibration Talk

Postby Batteau62 » Sun Mar 16, 2014 11:07 am

The more I think about multiple head changes (pen holder, E3d, Stock, J-head, Kraken, indicator or Z-probe...) I'm liking the auto tool changer path in the future ;)
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Re: Auto Level - Auto Calibration Talk

Postby Eaglezsoar » Sun Mar 16, 2014 11:12 am

Batteau62 wrote:The more I think about multiple head changes (pen holder, E3d, Stock, J-head, Kraken, indicator or Z-probe...) I'm liking the auto tool changer path in the future ;)


I tend to agree, a probe is fine if it is removable but it would be nice if the effector could be programmed to pick up the probe and put it back when finished rather than a manual
approach.

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Re: Auto Level - Auto Calibration Talk

Postby bubbasnow » Sun Mar 16, 2014 2:06 pm

there are a few videos floating around where people are using pressure resistors under the build plate, and the hot end just taps to get readings.. no probes required.

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Re: Auto Level - Auto Calibration Talk

Postby 626Pilot » Sun Mar 16, 2014 9:03 pm

bubbasnow wrote:there are a few videos floating around where people are using pressure resistors under the build plate, and the hot end just taps to get readings.. no probes required.

I recently got email from the Deltaprintr guys that they are switching to that technology. Previously they were going to do a deployable probe calibration. I think the nature of their design makes tower angle errors unlikely, so hopefully their Marlin auto-level is good enough.

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Re: Auto Level - Auto Calibration Talk

Postby bubbasnow » Sun Mar 16, 2014 10:37 pm

626Pilot wrote:
bubbasnow wrote:there are a few videos floating around where people are using pressure resistors under the build plate, and the hot end just taps to get readings.. no probes required.

I recently got email from the Deltaprintr guys that they are switching to that technology. Previously they were going to do a deployable probe calibration. I think the nature of their design makes tower angle errors unlikely, so hopefully their Marlin auto-level is good enough.


right i think the current limitation is that the resistors don't do well under a heated plate. im sure there is an easy fix for that

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Re: Auto Level - Auto Calibration Talk

Postby 626Pilot » Sun Mar 16, 2014 10:52 pm

bubbasnow wrote:right i think the current limitation is that the resistors don't do well under a heated plate. im sure there is an easy fix for that

There is! It's VERY easy. The deltaprintr only does PLA. :D

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Re: Auto Level - Auto Calibration Talk

Postby Flavored Coffee » Tue Jun 10, 2014 12:51 am

Neodymium magnets will not give you an even magnetic field. A flat spiral coil the same diameter as the hot bed will. From what I can see, the heating coil is a flat spiral, no need for any magnets, they have curved fields. I have a Gauss meter, I tell you what, when I finally finish building it, and fire it up, I'll start by measuring the magnetic field produced by that flat spiral winding. I would think, if the magnets were posted on the top of the machine at the three corners. It might start low near any arm, and way up in the middle, like saw a small peak somewhere. Magnetic fields drop off based upon the inverse square law but, they are curved. So, if it's all opposing fields, that's one set of curves, if one is attracting and two are repelling that's another set of curves. The hall effect sensors would work because the hot bed is a flat spiral, and as long as there are no permanent magnets around, it should work beautifully.

James.

626Pilot wrote:I realigned everything but Marlin is back to doing that thing where it moves the axes in the wrong direction after running G29. I don't know what the deal is with that. Pretty irritating. Marlin overall seems more glitchy than Repetier.

Without autolevel, even after the realignment, it STILL acts weird around the X axis. I tried rotating the X and Y towers to 59 and 61 degrees but that didn't fix it. (I want to leave Z alone and use it as the reference tower, so it's level with the center, and then bring X and Y in line with it, because it's mathematically simpler.) Maybe I need to try something more aggressive.

At this point I find it unlikely that a Z-probe can take any of the work out of aligning a Rostock MAX by itself. I'm going to keep trying, but the results so far are not encouraging. Rotating tower positions is the only thing I find likely to work, and even that hasn't shown results yet. Maybe I'll stumble into some other solution.

I think the best autolevel system would be fully closed-loop during calibration. Three Hall effect sensors, one one each tower, a neodymium magnet on the effector, and a Z-probe as well. The firmware moves the effector to various positions and triangulates where it actually ends up using the Hall sensors, which would probably have to be plugged into the three unused thermistor inputs. (Hall-O boards have a raw signal line in addition to the "stop" line, which is strictly either high or low.) Since it can move the effector to a theoretical position and then measure the actual position with the Hall sensors, it can figure out the error between where it thinks it is and where it actually is at any point. With this we can derive the printer radius and delta arm length, and correct for any geometry errors. Additionally, the Z-probe lets it map the surface of the build platform, so it also knows exactly where it's laying down filament.

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Re: Auto Level - Auto Calibration Talk

Postby McSlappy » Tue Jun 10, 2014 1:00 am

Wish I had a gauss meter...
I loved my Rostock so much I now sell them in Oz :)


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