I’ve found that when I’ve tried to cut my design on a full sheet of plywood.
On the top, a slight curve happen when I cut.
On the bottom left and right side, the extreme corner of each cut is rounded like there is something preventing the sled to go further (there is nothing apparently) and then it looks like it tries to go back on track.
I have wondered around the forum and I found two things Deformation along to the top... Normal? - #4 by Onelonedork
and Straight line curves down at top of the sheet (solved) - #85 by blurfl.
It seems that I can rule out the warping chain link because I’ve observed (and listened) closely and the chains seems to work fine.
Maybe it is the weight of the sled ?
You’ll find here my log and some pictures. The curves happened at almost 2inch on the left and right sides of the cut.
log.txt 2.zip (2.9 MB)
attachments (1).zip (2.9 MB)
Bar seems to get all the way around a 4*8 plywood but it seems that I need a good buffer around my cutting of 4 inches all around at least… which means a lot of scrap wood left. On your experience, do I need to redo a complete calibration?
Is there a way to correct the chain sag (maybe one of the source of the problem?). I’ve seen that when the sled is on the top left or the top rifght the chain on the far side is bit slacker.
Thank you for your feedback!
Can’t be seen on the picture. Is that curve symmetric? (biggest in the middle of the sheet?
A incorrect setting for the motors distance could be a cause, according to the simulator.
A flex in the top beam could also be a reason.
In the low corners the angle of the chain gets to steep (example left) for the left motor to pull more left and all relies on gravity. A waxed sled and/or a wider top beam can help to an extent.
thank you for your feedback!
The curve is symetrical indeed and at the biggest around the middle of the curve as you’ve shown in the simulation.
So It seems that a first step is to recalculate the distance between the motor. Do I need to go through all the calibration steps to do that or is there a way to enter the measure manually?
If the curve is created my the machine measuring a to small distance, that’s an indecator for flex in the top beam. I would hand measure without the sled attached and again with the sled pulled up to the top middle.
You can set the distance manually in the GC settings.
So i’ve tried to set the distance between the motors but groundcontrol tells me that the chain lenghts need to be reset. I don’t think so because the chain are the same I’ll keep you posted if this message is in fact an other source of problem
If you are sure the chain length is ok you can try > Actions > advanced > set chain length manually
ok so I.ve tried with the modification of the distance between motors.
From calibration i had 3002.42 mm
without the sled : 3009mm
With the sled positioned on the top of the work area : 3011mm
both seems weird but not significantly higher than the one calculated by the calibration.
i’ve tried to cut a straight line from the top of the sheet but the curve still happens : i’ve got 7.4 cm from top of the work area on the left and 8.6 cm on the middle.
I’ve also tried to recut the triangular test pattern but it doesn’t want to enter new values saying the calibration is impossible
Where do i go from here ?
I.ve check the work area values and everything is in order
Are you saying that when you measured the distance between motors, manually, without anything attached (i.e., sled not attached) the measurement was 3009 mm but when you attached the sled and moved it to the top of the work area, the manual measurement was 3011 mm? In that it increased by 2 mm?
Yep weird i Know. we dit that at two people so i am putting that on the human error so instead so i’ve entered a distance of 3010mm in groundcontrol
Measure it again until you are satisfied. That’s an extremely critical measurement in the calibration.
Can you please upload the groundcontrol.ini file? Not sure if there is something to find, but worth a try.
I’ve check the measure again 3011mm without the sled and 3010 with the sled.
Here is the file groundcontrol.ini (1.4 KB)
The machine settings look OK. Nothing unusual on first sight.
Has anyone seen this port before? comport = /dev/tty.usbmodem1411
What OS is this running on?
Ok, was tempted to fire up the mac mini collecting dust, but it might be misleading anyway and looking at the bottom of my glas I will give up for today
No problem thanks @Gero for your help
So i think if i am recalibrating today just to be sure that the chainlenght is right it might help groundcontrol to rencognize my new distance between the motors.
Tell you more after
So i’ve recalibrated everything from the start.
I still have a slight curve on the top of the sheet i’ve tried to measure and it seems that the difference between the highest and the lowest point of the curve is inside 1 cm. for example : if i cut a straight line near the top and starting at from 7 to 7.5 to 7.85 to 8 to 7.85 etc…