Unsolved Mystery. Weird Z0 behavior around build perimeter.

[IFinnimore]

So this weekend I've read through this entire thread and I can say I'm throughly confused and not sure exactly where to go next. I see lots of thing to try but none of them seem to actually FIX the issue, just a bit of speculation mostly it seems.

The things I have tried have been the official method as was posted by seemecnc to fix this, as in updating the firmware to use the changed Carriage Horizontal Offset from 35 to 37.5, which after downloading the most recent firmware for the max v2 the amount isn't 37.5 but 38+ which someone mentioned and I never saw any response to which is the version that I'm supposed to be using. I assumed the most recent firmware is the one that I'm supposed to be using.

anywho here are some pics of my issue in particular. As you can see I have a very odd shape when printing, The very center seems fine, the location where Z and Y are printing seem ok, the letter X is half squished into almost nothing (a high spot), as is almost the entire arc directly across from X between the Z and Y towers. The middle of the arc between the X and Y and X and Z are low spots and the filament doesn't even adhear, depsite the glue and blue tape (I'm using ABS) And lastly the inner circle seems ok except for where it meets at the X conjunction where is squish (high point) on either edge. Also something to note about my printer, I didn't build it. I purchased it from the seemecnc fellas at the makerfaire back in May of last year, they didn't want to haul it back and I purchased printing and running fine as it was at the show. Only recently have I really been printing larger objects (past the inner circle) and then decided to try and print out to the edges and found this entire thread and the exact issue i'm also facing. Its a rostockmaxv2 (black).

thanks in advance - david.
http://www.dbclunie.com

Given the distortion pattern, the problem is obviously in the X tower, positioning "short" only when past the triangle. I would check arms, belts, joints, and skates for any play, especially in pulling and pushing on the platform. Tower tilt (out from center) may also be a factor, though I would expect a gradual deviation across the whole surface and not just past the triangle.

Crossing the triangle is where the force on the rod changes from tension to compression, so will abruptly change the platform position for the particular slop amount.

[626Pilot]

BTW, in your smoothie board software configuration, have you considered removing the tower radii as a configuration and replacing it with something that can be directly measured, like Tx - Ty Dist, Ty - Tz Dist, and Tz - Tx Dist? I am a fan of using settings that I can validate with a micrometer or calipers, and radii isn't one of those.

If you combine the tower radius and angles, that gives you the {x, y} coordinates of the tower centers. With some more figuring, you can determine the points on any two towers that are closest to one another. Then you will have something to measure and compare with the expected value.

[philosophy_rook]

ok ... so I have a theory on this.

From what I can tell by reading this thread there is nothing wrong with any of the hardware or electronics. I believe that this is a design issue of delta arm printers.

Delta arm printers use some pretty complex math to determine exactly where the positions of the cheapskates need to be, to set the extruder at a specific location in 3 dimensional space. I believe that math is based on the idea that the arms connect to a single point ... circular math functions would almost have to rely on that or they would become extremely complex. For the area's in the diagrams above where the delta arm printer is accurate the rays that represent the arms of the printer do come very close to intersecting at a single point but as we move outside of that triangle that assumption becomes less true.

A test would be to bring the ends of the arms closer together and recalibrate to see if that shrinks the inaccurate area. Replace the washer above the extruder with something that will accept a connection from 3 arms. Then remove the left arm from each cheapskate and attach the right arm to the new "washer".

I'm just spit balling here.

[Jimustanguitar]

An error in that dimension would definitely cause the measured geometry to deviate from the mathematical model, yes. I'd be skeptical to see if it caused an error as large as what people are fighting with though.

Is anybody set up to test that error virtually?

[KAS]

I’ve installed my magnetic setup and doing some dial indicator testing while waiting for the E3D to get here and noticed something weird.

I calibrated everything and show Zero on the dial in the X, Y, Z and Center axis. I do show the odd plus and minus number towards some of the edges between the towers, some not as great as others. I have the threaded metal balls and that’s proving a bit difficult to get exact uniformity between a printed effector/carriage and screws without a set spacer size between the balls and supports. /pita


Anyways, I calibrated with the bed cold just messing around. When I heated the bed, I noticed the numbers jumped up a few thousandths although not in an even and predictable fashion. Then something odd happens.

After about 30 minutes the bed starts shrinking again back to the cold values.

Code: Select all

Temperature	         X Axis	Y Axis	Z Axis	center
22.3	                        0	       0	        0	        0
80c instant	               0.005	  .00375    .003	 .00450
90c instant	               0.0045   .003	    .002	 .00275
90C @ after 30min	    0	       .0015	   0	        0

[626Pilot]

Anyways, I calibrated with the bed cold just messing around. When I heated the bed, I noticed the numbers jumped up a few thousandths although not in an even and predictable fashion. Then something odd happens.

After about 30 minutes the bed starts shrinking again back to the cold values.

Code: Select all

Temperature	         X Axis	Y Axis	Z Axis	center
22.3	                        0	       0	        0	        0
80c instant	               0.005	  .00375    .003	 .00450
90c instant	               0.0045   .003	    .002	 .00275
90C @ after 30min	    0	       .0015	   0	        0

That difference is equivalent to one step or less (at 32x microstepping). Could simply be the temperature of the printer components responding to the room temperature changing. In any case, it's far too tiny to mess anything up.

[KAS]

I understand it's small, just thought it was weird the heated section would expand then contract without cooling off. I would expect the expanding portion, I would of never guessed it would go back to cold measurements while sitting at 90c.

At max, I'm .007" off zero in certain positions around the clock between towers, in between Z and Y I'm within .002" I'm thinking that my arms/balls are not exact length even though it was built on a fixture. The printed effector with pre-cut hole angles could be an issues as-well. Just the lightest finger pressure on various arms correct the various offsets, but finding that magical number that works across the board is proving the challenge. It's amazing how little variations can make drastic changes on a micro level...

I'm new to this and experimenting myself, so much to learn.

[bot]

I bet the actual temperature on the surface of the glass is constantly fluctuationg. It probably would look like a turbulent ocean if you could visualize the heat like the water surface.

[lordbinky]

I bet the actual temperature on the surface of the glass is constantly fluctuationg. It probably would look like a turbulent ocean if you could visualize the heat like the water surface.

Speed this up since it's over a small area. Then do lots of exposures and time lapse them.

http://hackaday.com/2013/01/03/an-absur ... ng-camera/

[626Pilot]

I finally got around to redesigning my Z-probe so that it can be mounted perfectly to the center of the effector. The mount has been slightly modified to work with a "mount mounter," which is a yoke you bolt to the effector. This means you don't have to use probe offsets, and can get out towards the edge without trouble.

I managed to blow my SECOND Azteeg X5 after having it for something like 2-3 months. It started getting all stuttery and slow. I don't know if it was a defective CPU, or damage from ESD. I got a Smoothieboard. The wiring is more annoying and the steppers are 16x instead of 32, but it seems to be working OK. I had to recalibrate my extruder steps/mm because dividing by 2 didn't work (for some reason I still don't understand). The next time I push an update to GitHub, I will upload a Smoothieboard version of the config. Some options and pins are different, so you can't run it on an Azteeg X5 config file.

BTW, does anyone have a mounting plate for the Smoothieboard, so I can put it on the door? Right now it's just chilling on the bottom of the printer. The only thing I found on Thingiverse was a box that won't work with my cooling solution.

[img]http://thingiverse-production-new.s3.am ... atured.jpg[/img]

[Nylocke]

Thats great and all for smoothieware, but I'm trying to run a Kraken, and I haven't seen any smoothieware supported boards that can support the Kraken. Rich's marlin branch is old and it doesn't support the X3 Pro, and Johann's branch "works" but it leaves me with stuttering prints. .92 repetier supposedly works, but I'm entirely confused on how the g code commands work, since the documentation on their site is out of date. I started messing around with Pilot's original quadrant based leveling solution to adjust the tower rotations, but that is from a year ago, surely something has changed since then?

[626Pilot]

The Smoothieboard 5X or X5 or whatever has enough stepper drivers to run two extruders, but that's about it. Have you contacted the E3D folks? Surely they must have had some solution to test their four-headed hot end with.

[Nylocke]

I have an X3 Pro, so I do have a way of powering it, but its arduino based, so all that wonderful work that you've done with smoothieware is useless to me. The best I've been able to do is attach a dial indicator to the effector and do things by hand.

[mhackney]

626Pilot, I published a smoothieboard mount on thingiverse last year that you could use to mount on the rostock. It was originally designed to bolt to the tower on a mini kossel. This might actually be cool in the base. You could use one of the mount points as a rotating hinge point to be able to access the board with the door open and then rotate it back inside.

I have a question on your probe - not sure where the probe contact is? Does it pass down the middle of the hotend so you have to remove the filament, and nozzle?

[mhackney]

Nylocke, it is possible to add additional external drivers and thermistors and heat controls to the smoothieboard. It is a roll your own solution though. For now, the X3 Pro is the only off the shelf device that I'm aware of that has everything needed to run a Kraken.

[Nylocke]

The only other board capable of running all 4 with "stock" stuff is the Duet with the x4 attachment board. I looked around a bit yesterday and thats all I could find. Its Due powered, which from what I understand its programmed via the Arduino IDE? I'd prefer an OTS solution.

[626Pilot]

I have a question on your probe - not sure where the probe contact is? Does it pass down the middle of the hotend so you have to remove the filament, and nozzle?

There are two Nd magnets, one fixed and under the sensor board, and another in a channel that allows it to move up and down. The moving magnet has a metal rod hanging off the bottom that passes through the probe and emerges from the narrow end. As the probe descends, the rod (McMaster-Call calls it an "axle" I think) touches the print surface. The magnet correspondingly moves up, and as soon as it gets close enough to the Hall sensor, triggers it. If it moves up high enough, the moving magnet will snap all the way to the top of its channel to meet the fixed magnet. (They don't actually touch.)

I've been leaving the fixed magnet out. The probe doesn't retract, but on my printer it helps repeatability to use probe deceleration (a feature I added to the Z-probe core). That way, instead of jerking to a full stop the instant the probe hits, it lets it decelerate. Without that feature, I was losing steps. However, my probe has a lot of runout, so it can keep traveling past the trigger point. Someone using an endstop switch or FSRs would be better off not using probe deceleration.

You can side-mount the probe to your hot end, but after working with calibration code, I don't recommend it. The error you get from using any offset in the XY plane makes the calibration significantly worse. It can get better than stock, but it's just not a good idea. Offsets might be a better choice for Cartesian, but the math on a Delta ties the three axes together in a non-linear way. The absolute best calibration will come from mounting the probe dead center. The calibration code saves the delta geometry offsets and (if you use it) depth mapping to the SD card, so it isn't something you have to run every time you fire up the printer. The only trouble is that the SDfat library in the firmware is utter s*** and will corrupt config-override, so I've been typing M503 (dumps config g-code to console) and just pasting that into config-override.

[mhackney]

Thanks! I agree with your assessment that probe offset is suboptimal. I'm still not sure how you eliminated that in this design. Are you simply removing the hot end and putting this probe in place?

[Mac The Knife]

Thanks! I agree with your assessment that probe offset is suboptimal. I'm still not sure how you eliminated that in this design. Are you simply removing the hot end and putting this probe in place?

Scroll up to the picture he posted,,,

[mhackney]

Maybe I am just having an elderly moment, I don't see what's up. I can't tel if that out of focus red/brown thing under the mount is the top of the hotend or something else.

[Nylocke]

Well, from what I can tell, and by judging how close the effector is to the bed, that is the reflection of the Hall sensor mount off the glass.

[Tonkabot]

Thats great and all for smoothieware, but I'm trying to run a Kraken, and I haven't seen any smoothieware supported boards that can support the Kraken. Rich's marlin branch is old and it doesn't support the X3 Pro, and Johann's branch "works" but it leaves me with stuttering prints. .92 repetier supposedly works, but I'm entirely confused on how the g code commands work, since the documentation on their site is out of date. I started messing around with Pilot's original quadrant based leveling solution to adjust the tower rotations, but that is from a year ago, surely something has changed since then?

I am developing a smoothie-like board that runs smoothieware but of course is [on paper] much much better! It should be able to handle 6 or 7 extruders on a delta printer.

this is the thread that I would like feature requests / constructive criticism to be posted in: http://forum.seemecnc.com/viewtopic.php?f=82&t=7526

[626Pilot]

Thanks! I agree with your assessment that probe offset is suboptimal. I'm still not sure how you eliminated that in this design. Are you simply removing the hot end and putting this probe in place?

Yes.

I am developing a smoothie-like board that runs smoothieware but of course is [on paper] much much better! It should be able to handle 6 or 7 extruders on a delta printer.

Good.

[rpress]

If you think about what the printer is doing, every movement is relative to the steps/mm. Essentially the belt is what makes 80 steps == 1mm. So rather than change that, you change everything else.

It's still possible the belt is wrong. If you have a precision ruler/calipers you can count the teeth of the belt over some long distance.

I'm starting to think the belts are indeed my problem (dipping between towers). Assuming the belts are accurate when made there still is the stretch to account for, as we use the belts under tension.

I've set my steps/mm to 81.0 and proportionally reduced the arm length and delta radius. This gives me the same flatness but better dimensional accuracy. And the programmed arm length matches what I measured off the machine.

[Mac The Knife]

I've pondered what sort of chaos would be created trying to install ballscrews in place of the belts.