Polar Kinematics shape issue

iamthebest22

Heyo, hope everyone had a great Christmas and happy new year! I finally got around to test printing my polar 3d printer, and it obviously has some issues with printing the correct shape.

it's suppose to print the calibration cube, but as you can see while it's close, not quite, what could be wrong?

dropbox pics:
https://www.dropbox.com/transfer/AAAAADbGxilY3jZMcjR0MpV1blfqPFHXcbmj3bg43tx1-wKuC1aZV2w all in one

separately:
2019-12-31 21.56.31.jpg
https://www.dropbox.com/s/c8zg04b8pnerext/2019-12-31 21.56.24.jpg?dl=0
https://www.dropbox.com/s/a8qq1m3yb9z624q/2019-12-31 21.56.21.jpg?dl=0
https://www.dropbox.com/s/61u4oentmq84csh/2019-12-31 21.56.14.jpg?dl=0
https://www.dropbox.com/s/ayn2ml12429zl8d/2019-12-31 21.56.08.jpg?dl=0
https://www.dropbox.com/s/ouf3uol63c4zpr4/2019-12-31 21.55.02.jpg?dl=0
https://www.dropbox.com/s/r1vdb5bly9c3dtb/2019-12-31 21.54.58.jpg?dl=0

I'm also cura the newest cura 4.4.1:
https://www.dropbox.com/s/qyy09e3ljeiz9wg/2019-12-31 21.56.41.jpg?dl=0

here's my config.g:

; General preferences
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves
M550 P"Circa Polar 3D Printer" ; set printer name
M918 P1 E4 F2000000 ; configure direct-connect display

; Network
M552 P0.0.0.0 S1 ; enable network and acquire dynamic address via DHCP
M586 P0 S1 ; enable HTTP
M586 P1 S0 ; disable FTP
M586 P2 S0 ; disable Telnet

; Drives
M669 K7 R0:89 H88.41 F30 A30 ; set Polar kinematics parameters
M569 P0 S1 ; physical drive 0 goes forwards
M569 P1 S1 ; physical drive 1 goes forwards
M569 P2 S1 ; physical drive 2 goes forwards
M569 P3 S1 ; physical drive 3 goes forwards
M584 X0 Y1 Z2 E3 ; set drive mapping
M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X80.00 Y34.00 Z401.00 E84.00 ; set steps per mm
M566 X900.00 Y900.00 Z60.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
M203 X3000.00 Y3000.00 Z360.00 E1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2)
M906 X1400 Y1500 Z1500 E1500 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

dc42

My guess is that the cut off bottom left corner is where it got too close to the centre of the turntable, and that either the print nozzle is slightly offset to one side of the radius that is is supposed to track, or the radius when homed isn't quite the value that you have configured.

iamthebest22

@dc42 yep pretty much on point, I also found another issue, it will require a redesign of the Y plate of the polar printer. There is play on the Y turntable, quite a bit too, I can turn the Y when it's printing by almost 5 degrees in the positive direction. It needs to be changed to use belts and metal wheels instead. that's what's causing that cut off. So close but I may have to make due with it so far, it's almost perfect if it wasn't for that stupid extra play. Thanks

iamthebest22

Update, waiting for the new closed loop belts to arrive, but got a question, the original design had 82 teeth for the Y axis plate, the new design has 90 teeth. The current correct esteps (in Polar this case is degrees) right now is 33.90 (really damn close). If I have more teeth, does the degrees go up or down? I'm thinking down right?

so it should be 80/90 which is 0.888889, then 0.888889 times current 33.90 which gives me 30.1333, or is it the other way around? Thanks.

dc42

If you mean the turntable is mounted on a gear with 90 teeth instead of 80, then the steps/degree will have gone down, so 30.1333.

Test it by sending G91 then G1 H2 Y360 F2160. It should turn exactly one revolution, in 10 seconds.

iamthebest22

Thank you very much! that worked, I just got a weird issue now, why is it that I have this point that just sticks up? if it wasn't for this, I would have everything within 0.2mm which is good enough for me? This is the result from bed leveling.
https://www.dropbox.com/s/2oxfi0j4gs6z5j4/2020-01-14 17.22.03.jpg?dl=0
https://www.dropbox.com/s/uvgug15q3lmvmkg/2020-01-14 17.22.08.jpg?dl=0

dc42

Are the radius arm and the turntable surface exactly parallel to each other?

iamthebest22

not exactly but very close, I have a 3 point be leveling system, and as you can from those pics, it seems to be almost parallel except at the weird point that sticks out, should I take some pics of the printer?

dc42

@iamthebest22 said in Polar Kinematics shape issue:

not exactly but very close, I have a 3 point be leveling system, and as you can from those pics, it seems to be almost parallel except at the weird point that sticks out, should I take some pics of the printer?

I don't see a point that sticks out in that image. Is it more visible from another angle?

iamthebest22

Hope these three new pics makes it more clear, you can see that single point that sticks out:
https://www.dropbox.com/s/qzvt8l0dtiiym6c/2020-01-15 12.08.34.jpg?dl=0
https://www.dropbox.com/s/k0a5s7xmdb8mi0i/2020-01-15 12.08.45.jpg?dl=0
https://www.dropbox.com/s/3r4l1axorshe5ep/2020-01-15 12.08.49.jpg?dl=0
https://www.dropbox.com/s/hbywiw2gafk5e1s/2020-01-15 12.10.04.jpg?dl=0