Diagonal rod length on delta printer issues.



  • @phaedrux said in Diagonal rod length on delta printer issues.:

    @clytle374 said in Diagonal rod length on delta printer issues.:
    M558 P0
    G31 X0 Y0 Z0

    Thanks for the reply, been crazy at work so just got back to this.

    That probes one point. How do I feed it multiple points and have it run the calibration? I've honestly looked for this a bit, maybe I'm missing something.

    Also, I can't easily get my computer to the printer and use my phone. On the smaller screen I don't get the fine z steps in the machine control tab, or the g31 command. Can this be changed?

    Thanks again
    Cory



  • You mean to probe multiple points to do mesh bed compensation? That would be G29

    https://duet3d.dozuki.com/Wiki/Using_mesh_bed_compensation



  • @clytle374 said in Diagonal rod length on delta printer issues.:

    @phaedrux said in Diagonal rod length on delta printer issues.:

    @clytle374 said in Diagonal rod length on delta printer issues.:
    M558 P0
    G31 X0 Y0 Z0

    Thanks for the reply, been crazy at work so just got back to this.

    That probes one point. How do I feed it multiple points and have it run the calibration? I've honestly looked for this a bit, maybe I'm missing something.

    Also, I can't easily get my computer to the printer and use my phone. On the smaller screen I don't get the fine z steps in the machine control tab, or the g31 command. Can this be changed?

    Thanks again
    Cory

    You need to set up a bed.g file with all your points in it then the calibration routine will move to each point in turn and ask you to jog down and then accept the point it will then move on to the next and so on

    If you don't have a bed.g then you can use DC42's generator to make one for you Bed file generator



  • Thanks again! I've reset my rod length back and running the probing and with 8 factor calibration. Have a few more questions.

    Can the Z steps be changed in the DWC? The phone is only .5mm and on my PC it's .05mm. Phone is unusable, and PC is still a bit course?

    config line it output

    • M665 L291.060:291.060:291.060 R144.059 H359.447 B140.0 X-0.407 Y0.338 Z0.000
    • M666 X0.128 Y0.253 Z-0.381 A0.15 B-0.34

    end of my bed file

    • G30 P15 X0.00 Y-70.00 Z-99999 H0
    • G30 P16 X60.62 Y35.00 Z-99999 H0
    • G30 P17 X-60.62 Y35.00 Z-99999 H0
    • G30 P18 X0 Y0 Z-99999 S8

    Z-probe in config file

    • ; Z-Probe
    • M558 P0 H1 F120 T1800 ; Disable Z probe but set dive height, probe speed and travel speed
    • M557 R125 S20 ; Define mesh grid
    • G31 Z8.55

    My indicator triggers about 8.55mm high. When I run auto calibration it resets my Z height. H367.55 to H359.447 so on the second run my probe is way too high. What am I getting backwards in the config?

    Cory



  • Second update.

    7 factor error was 0.0508
    8 factor error 0.3048mm after multiple iterations

    • Calibrated 8 factors using 19 points, deviation before 8.525 after 0.146
      Deviation before is obviously due to having something wrong with my probe setup and it changing my H number. Deviation after is overly optimistic like the least-squares calibration calculator online calculator I was using before.

    I am borrowing another square to see if my error is there. Still can not comprehend using an incorrect number (and math being done correctly) and getting such good results.

    video

    Cory



  • You can adjust the baby step rate in DWC

    0_1556723874149_80545195-f70b-40dd-b820-e47b7b6c9390-image.png (this is on DWC 2.0.0-RC6)



  • @dougal1957 said in Diagonal rod length on delta printer issues.:

    You can adjust the baby step rate in DWC

    0_1556723874149_80545195-f70b-40dd-b820-e47b7b6c9390-image.png (this is on DWC 2.0.0-RC6)

    That doesn't seem to effect the z steps in machine control or in the probing cycles.



  • So my square is within .1mm as confirmed with and indicator on a CNC milling machine.

    I'm back to what error can be covered up so perfectly by using a wrong number when doing the math.

    Below is a quote by dc42 in the other thread I linked too. Can anyone elaborate?

    • Having the arms go vertical or even beyond when printing close to a tower isn't a problem. What you need to avoid is arms going below about 20 degrees to the horizontal

    Thanks
    Cory



  • i got similarly whacked results when my frame wasn't as straight as humanly possible (i.e. calibration aids suggested absurd rod lengths). After rebuilding the whole thing I mounted a dial indicator instead of nozzle and manually adjusted the delta radius until it was flat.

    if i recall correctly if the center of the bed is low you increase the delta radius (or smooth rod offset or whatever its called in the various firmware). I think it will vary with bedsize but a factor of 4 gets you close quite fast. I.e. your center is 1mm low, add 4 to the radius; split the difference when you overshoot. (or if i'm mistaken, its the other way around, but you'll see)

    after spending days with auto calibration, re-doing the whole thing by hand took an evening, rebuild and all. The wiki highlights the important aspects of the physical build, get that right and the calibration is pretty straight forward by hand.
    https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer



  • Another source of error for me has been not having the belts parallel to the frame, caused by the toothed gears having slipped on the motor spindles. Measure belt-to-frame at each carriage and at the bottom just above the motor spindle, get them the same.



  • @bearer said in Diagonal rod length on delta printer issues.:

    i got similarly whacked results when my frame wasn't as straight as humanly possible (i.e. calibration aids suggested absurd rod lengths). After rebuilding the whole thing I mounted a dial indicator instead of nozzle and manually adjusted the delta radius until it was flat.

    if i recall correctly if the center of the bed is low you increase the delta radius (or smooth rod offset or whatever its called in the various firmware). I think it will vary with bedsize but a factor of 4 gets you close quite fast. I.e. your center is 1mm low, add 4 to the radius; split the difference when you overshoot. (or if i'm mistaken, its the other way around, but you'll see)

    after spending days with auto calibration, re-doing the whole thing by hand took an evening, rebuild and all. The wiki highlights the important aspects of the physical build, get that right and the calibration is pretty straight forward by hand.
    https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer

    I loosened all the bolts and re squared the printer before the last tests. I also checked between the towers with the outside of calipers, really annoyed that I didn't think of that myself. They are within .25mm of being consistent. Didn't have any luck with the way the frame is made getting them any closer, I think one might have a bit of a warp in it.

    Also the subject of changing the radius to get to the head to track center to outwards... This works great, until I get to the area between the towers. Or opposite a tower, however you wish to describe it.

    @robm said in Diagonal rod length on delta printer issues.:

    Another source of error for me has been not having the belts parallel to the frame, caused by the toothed gears having slipped on the motor spindles. Measure belt-to-frame at each carriage and at the bottom just above the motor spindle, get them the same.

    Thanks, I just checked that, no luck there either.

    I'm pretty stumped by this and have to get away from it for a while. Unless anyone else has a better suggestion, I'm planning to decrease the print area size and see if I get better results with the correct arm length.

    Thanks
    Cory



  • Hi,

    My first three printers were mini-deltas kits. I spent hours and hours tweaking them.

    Then I got a Folger Tech FT-5 kit. It worked so much better with so little effort I got rid of the deltas.

    Frederick



  • @fcwilt said in Diagonal rod length on delta printer issues.:

    Hi,

    My first three printers were mini-deltas kits. I spent hours and hours tweaking them.

    Then I got a Folger Tech FT-5 kit. It worked so much better with so little effort I got rid of the deltas.

    Frederick

    Thanks, I guess.

    So after many hours I can not repeat the extremely flat results I had before with the incorrect rod length I posted a video of. I don't know if my attempt to re-square the printer made things worse, or if I was able to compensate better by feel to set the tilt. I get slightly better results with the incorrect rod length than I do with the correct number.

    I rigged up a probe and have ran many tests. Much easier to do, but harder to feel for what is happening than using an indicator.

    I am still of the mindset that if you do the math right with the wrong numbers it is impossible to get the results in the video of my first post. Would be nice to have access to the actual step data, or actual axis position data. Something doesn't add up.

    Cory



  • Correct rod length 291.06
    2_1559950825174_Screenshot_20190607_193736.png

    294.9 rod length
    1_1559950825173_Screenshot_20190607_165629.png

    Messing with the tilt some more.
    0_1559950825173_Screenshot_20190607_084354.png

    Unlike in the video I have a bad high spot by the Y tower no matter what I do. But the regardless more of the bed would be usable.

    Going to try and forget about this for a couple weeks while I'm on vacation
    Cory


  • administrators

    Do the rods bend at all as the effector moves? If so then that will change the effective length of the rods, affecting the geometry.

    I am suspicious of rods with springs between them, because the stretch of the springs, the force they apply to the rods and the direction of that force will depend on the XY position of the effector.



  • @dc42 said in Diagonal rod length on delta printer issues.:

    Do the rods bend at all as the effector moves? If so then that will change the effective length of the rods, affecting the geometry.

    I am suspicious of rods with springs between them, because the stretch of the springs, the force they apply to the rods and the direction of that force will depend on the XY position of the effector.

    I tried removing the springs early on and didn't see any real improvement. In the thread I linked to in the beginning I think they were having the same issue with magnetic rod links.

    It seems that longer rods help. But then you trade build height, torque, and resolution

    Thanks
    Cory



  • Going to reinstall the old control board to test when I get back from vacation. Seems that 3 motor and 3 home switch connections are about the quickest next test. Thanks
    Cory



  • So after more exhaustive testing. I did find that the wood frame under the onyx bed was warped up(convex) pretty bad. I flipped it over and shimmed it to the frame. It was warping the glass a little bit. I kept checking the glass for flatness, but not on the machine. Now unfortunatly the onyx bed isn't really supported and the glass is the structure there. All in all that setup sucks and I'm thinking though a better option. Problem is every time I start thinking I end up with a whole new machine with a metal frame and linear ways. And, and, and. lol

    I removed the vibration dampers I had on the motors, I had pretty much forgotten they didn't belong. With the duet board it is way quieter without them than the rambo board was with them. That made the largest improvement. They add deflection, plus moved the pulleys way out on the shaft to give the angular deflections more deflection. If that makes sense.

    Of course the rambo board didn't do any better, but I was stuck on the thinking the Duet must be making an calculation error since others had the same results.

    Latest results, with the correct arm length. Big improvement over previous results.

    0_1561632813763_Screenshot_20190627_064952.png

    I think the belts are tight enough but the screws have pulled into the wood frame, so I'm going to make some plates so I can tighten them a bit more. Might try the longer carbon fiber arms for the rostock too. Seems to help others.

    I'm thinking this is far from ideal, is this close enough for bed mapping to handle? Most of the issue is way out on the corners. Should I map with a closer spacing than 20mm?

    Thanks
    Cory



  • Went ahead a put .9 deg steppers in.
    Some tests suggested by dc42

    [code]
    Position Trigger heights
    X0 Y0 6.224, 6.217, 6.224
    X100 Y0 6.235, 6.235, 6.229
    X140 Y0
    X100 Y0 6.210, 6.210, 6.217
    [/code]
    Looks pretty good to me.

    So I'll try with some numbers over by the towers.
    [code]
    Position Trigger Heights
    X0 Y0 6.249, 6.242, 6.242
    X86.6 Y-50 6.263, 6.276, 6.263
    X121.24 Y-70
    X86.6 Y-50 6.226, 6.226, 6.220
    [/code]

    If I go anywhere on the bed and feed Z down to zero the indicator, jog Z negative direction, then back up, I'm within .001" of being back at zero. The numbers in my first test at X100 and X140 matches pretty much exactly the ,001"(.0254mm) backlash I've been seeing. That is how you check machine tools for backlash, seems like it should work here. Actually seems to work, at least in normal realm... Not over near the towers when quantum mechanics seem to take over. But it's still not horrible.

    So I wrote a little program to pick back and forth over in the trouble area. My bedmap was done at 13mm spacing. So that is the number I'm using. Points and trigger heights listed, moving one direction, then reversing the path.
    [code]
    G28
    G1 X120. Y-70. Z11. F1500. ;point #1 Stopped at height 6.383 mm
    G1 X120. Y-57. Z11. F1500. ;point #2 Stopped at height 6.295 mm
    G1 X120. Y-44. Z11. F1500. ;point #3 Stopped at height 6.271 mm
    G1 X107. Y-44. Z11. F1500. ;point #4 Stopped at height 6.232 mm
    G1 X107. Y-57. Z11. F1500. ;point #5 Stopped at height 6.310 mm
    G1 X107. Y-70. Z11. F1500. ;point #6 Stopped at height 6.315 mm
    G1 X107. Y-57. Z11. F1500. ;point #5 Stopped at height 6.260 mm
    G1 X107. Y-44. Z11. F1500. ;point #4 Stopped at height 6.244 mm
    G1 X120. Y-44. Z11. F1500. ;point #3 Stopped at height 6.340 mm
    G1 X120. Y-57. Z11. F1500. ;point #2 Stopped at height 6.364 mm
    G1 X120. Y-70. Z11. F1500. ;point #1 Stopped at height 6.364 mm
    [/code]
    These seem to sometimes look like backlash, but other times be pretty good.

    Am I asking too much from the printer? Is this normal? I've burnt up so much time on this it's getting ridiculous.
    Thanks
    Cory

    Machine info:
    .config
    [code]
    M665 L291.060:291.060:291.060 R144.257 H368.890 B140.0 X-0.009 Y0.368 Z0.000
    M666 X0.088 Y0.191 Z-0.279 A-0.09 B-0.24

    ; Drives
    M569 P0 S0 ; Drive 0 goes forwards
    M569 P1 S1 ; Drive 1 goes forwards
    M569 P2 S0 ; Drive 2 goes forwards
    M569 P3 S0 ; Drive 3 goes forwards
    M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
    M92 X160.0 Y160.0 Z160. E92.5 ;92.65 Set steps per mm
    M566 X800.00 Y800.00 Z800.00 E1200.00 ; Set maximum instantaneous speed changes (mm/min)
    M203 X18000.00 Y18000.00 Z18000.00 E1200.00 ; Set maximum speeds (mm/min)
    M201 X2000.00 Y2000.00 Z2000.00 E2000.00 ; Set accelerations (mm/s^2)
    M906 X1500.00 Y1500.00 Z1500.00 E800.00 I30 ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout

    ; Axis Limits
    M208 Z0 S1 ; Set minimum Z

    ; Endstops
    M574 X2 Y2 Z2 S1 ; Set active high endstops

    ; Z-Probe
    M558 P4 H3.3 F30 T1800 ; Disable Z probe but set dive height, probe speed and travel speed
    M557 R140 S13 ; Define mesh grid
    G31 Z6.256
    ; Heaters
    M307 H0 B0 S1.00 ; Disable bang-bang mode for the bed heater and set PWM limit
    ;M305 P0 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 0
    M305 P0 T100000 B4425 R4700 L0
    M143 H0 S120 ; Set temperature limit for heater 0 to 120C
    ;M305 P1 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 1
    M305 P1 T100000 B4725 C7.060000e-8
    M143 H1 S280 ; Set temperature limit for heater 1 to 280C

    ; Fans
    M106 P0 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P1 S1 I0 F500 H1 T45 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on

    ; Tools
    M563 P0 D0 H1 ; Define tool 0
    G10 P0 X0 Y0 Z0 ; Set tool 0 axis offsets
    G10 P0 R0 S0 ; Set initial tool 0 active and standby temperatures to 0C

    ; Automatic saving after power loss is not enabled

    ; Custom settings are not configured

    ; Miscellaneous
    T0 ; Select first tool

    [/code]
    Bed map file
    0_1563076106043_heightmap.csv



  • I realized that I skipped a post here as this is on going on 2 forums. Here is what I was getting.

    0_1563248057785_Screenshot_20190702_041255.png

    I found a macro posted by dc42 to test backlash, I lost the results, but they were good at the X100 Y0 points. Then I rotated the program to run to the X tower and back, then the backlash shows up there.

    I tightened the belts tighter again, I have washers under the heads and nuts so they hold without pulling into the wood(whatever it's spelled). Not much improvement there. They are too tight in my experience with timing belts, but I'm aware my experience isn't really valid here. At home position, the resonate frequency of the belt below the skate is around 130hz. Anyone know a good number?

    The only play I can find in the system is that end play in the R4ZZ bearings in the cheapskates. The old ones had it and the new ones have it too. I looked for a couple hours in vain to be sure no one made a suitable bearing this small. It does make sense that it only shows up when the arms are so horizontal and the load is sideways on the skate. Another plus for longer arms, they'll shift that play into a direction of less influence. But there goes more build height. I was sure it wasn't effector tilt, because I assumed it would tilt about the center and that would take an obvious amount to create the error. But no, it tilts about the balls on the arm that is vertical.

    So the auto-calibration route is obviously messed with by the crazy numbers at the towers. I added g1 x0 y0 z10 f6000 before every probing point in bed.g to pull the lash the same direction. Looking at the new bed map I should feed inwards before probing instead.

    But this map is better for using the machine, I ran a large test print last night and got good results.

    0_1563247998797_Screenshot_20190715_043301.png

    Coming from it as a machinist, then machine tool repair tech, I nearly have a new printer designed in my head. I'm certain that I'd be assembling it by now if I'd not spent all this time on this printer. And at this point I feel it is the next step.

    Thanks
    Cory