Prototype Calibration Pattern (with G-Code)

[Aaron Seltzer]

My Shapeoko is doing the same thing. There is a long scan from the second horizontal line (just over the concentric squares) over to the center vertical line. That is the exact spot mine messes up, repeatedly. The centerline, and everything after that is shifted left by about a 1/10th of an inch. Very repeatable. Not sure why yet. Have tried turning down the seek rate in GRBL but no improvement, but will work on it more tomorrow.
...

The area it messes up is marked in yellow in the photo...

[JimHung]

Any chance you could provide a GRBL $ dump of your setup? Thanks!

Absolutely, here you go:

$0 = 87.49 (steps/mm x)
$1 = 87.49 (steps/mm y)
$2 = 640.00 (steps/mm z)
$3 = 30 (microseconds step pulse)
$4 = 500.00 (mm/min default feed rate)
$5 = 500.00 (mm/min default seek rate)
$6 = 0.10 (mm/arc segment)
$7 = 28 (step port invert mask. binary = 00011100)
$8 = 25.00 (acceleration in mm/sec^2)
$9 = 0.05 (cornering junction deviation in mm)

Pretty much exactly how I got it!

Jim

[Aaron Seltzer]

Okay, I think I have solved my problem!

All of my other tests, including patterns I have made, etchings, etc, have all worked flawlessly, but this test pattern kept failing at the same point. When it drew the horizontal line (second one down), it stopped short and then everything else from that point on was shifted to the left by about a tenth of an inch.

Should have been obvious to me, but the carriage was hitting on the right side, shifting everything. With my dual drive setup, I have lost an extra 0.25" or so, and this pattern is just a bit too large for my machine!

Might want to keep that in mind for future test patterns!

Anyway, thanks for this great pattern, it certainly helped me debug a few things...

[LineKernel]

hi Jim
i start playing with Pycam , to learn , and use to draw on paper for now , but i can t find how to set the Z not to go to 2.5cm everytime to lift the pen up
first it take quite some time to go up and go down again , second it make some unnecessary work on my delrin nut
is it because i use engraving i maybe i should use something else ? Or do you do it in post path export and replace all the Z250.000 with a script ?
outside of it it works great and it is perfectly scaled

here is the your pattern

DSC_5583 resized.JPG (389.32 KiB) Viewed 3008 times

[JimHung]

Hey LineKernel,

If you go to Settings > Preferences, then click the GCode tab, there is a setting called 'Safety Height'. This is the height that that your Z axis will raise to when its travelling - by default this is set to 25mm. Change this to something smaller if you want to cut down on Z-Axis movement when you are drawing!

Hope that helps,

Jim

[LineKernel]

hi Jim
yes i just found out , and tried it , i was coming back to the forum to post the answer , but you beat me of few minutes

thanks you

EDIT* one hour

[jluther]

for rapid prototyping machines we used to build hollow rectangles that were about 0.1" thick, 0.5" tall, 0.5" wide and from 1" to 5" long and spread them across the build platform with one of them placed in the center. Measuring them with a caliper for length outside and inside, then entering the numbers into a spreadsheet we could determine the positional accuracy in X, Y, and Z, as well as the drift to each corner.

[loopingz]

Interesting test for accuracy and stepper driver stress test!

[kurt6string]

Hi Folks,

I just assembled a ShapeOko full kit and tried the cal pattern gcode above, on a pc. Even with my machine at the front left corner the horiz center line causes the x head to bump the right side, causing what sounds like two belt skips...what's up with that?

Thanks,
Kurt

[JimHung]

Hey Kurt,

Thanks for trying my pattern - i havent had much time to improve it, it definitely needs some work on optimization. Im going to redo it by hand with some of the suggestions people have given soon (i hope).

As for your problem, thats a little strange - it works fine on my 2nd batch Shapeoko. Unless there are some changes to the design im unaware of (im quite out of the loop right now), it should be ok. It could be that your drivers are overheating and the overrun on the horizontal center line is a product of that? Mine would do similar things before i tweaked the current pots as per the grblshield instructions.

Cheers,

Jim