Physical cuts wrong size?
- giggler999
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23 Jun 2013 20:35 #35950
by giggler999
Physical cuts wrong size? was created by giggler999
Hi,
I have a diy router, similar to early shopbot/mechmate (steppers no feedback drives). I have used stepconfig wizard which worked fine. I ran some gcode and measured the physical cuts.
My dual motors on X axis were supposed to cut 840mm. Instead they cut 841mm.
For Y axis, were supposed to cut 250mm. Instread it cut 249mm.
How do I adjust my settings to take into account of this? Odd is that both X/Y have same radio belt drives, motors and spur gear so you'd of thought they'd be the same. Maybe it was the speed at which I test cut MDF, 9mm depth of cut @ 2000mm/minute feedrate.
Anyhow any suggests much welcome. If you want me to post my ini no problem.
Regards,
giggler
I have a diy router, similar to early shopbot/mechmate (steppers no feedback drives). I have used stepconfig wizard which worked fine. I ran some gcode and measured the physical cuts.
My dual motors on X axis were supposed to cut 840mm. Instead they cut 841mm.
For Y axis, were supposed to cut 250mm. Instread it cut 249mm.
How do I adjust my settings to take into account of this? Odd is that both X/Y have same radio belt drives, motors and spur gear so you'd of thought they'd be the same. Maybe it was the speed at which I test cut MDF, 9mm depth of cut @ 2000mm/minute feedrate.
Anyhow any suggests much welcome. If you want me to post my ini no problem.
Regards,
giggler
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23 Jun 2013 20:52 #35951
by cncbasher
Replied by cncbasher on topic Physical cuts wrong size?
this could be down to belt tension and other factors in your drive train , such as any backlash or unwanted movement ,
it is possible to alter the steps scale in your ini file but this needs to be done carefully and plot the errors over a wider range .
although I would go for looking at your drive train in general and get rid of as much unused movement mechanicaly first
belts are prone to stretching , so can be a pain to get the tension just right .
it is possible to alter the steps scale in your ini file but this needs to be done carefully and plot the errors over a wider range .
although I would go for looking at your drive train in general and get rid of as much unused movement mechanicaly first
belts are prone to stretching , so can be a pain to get the tension just right .
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24 Jun 2013 00:40 #35954
by Rick G
Replied by Rick G on topic Physical cuts wrong size?
In addition to what cncbasher replied try the cuts at different speeds, a deep cut at a high feed rate may cause more flexing.
To check the SCALE I make the moves as large as possible (with the cutter in the air). So if your axis can move say 0" to 24" make a move from 0" to 1" (to take out back lash) and mark that location then make another move to 23" and measure the distance traveled.
Rick G
To check the SCALE I make the moves as large as possible (with the cutter in the air). So if your axis can move say 0" to 24" make a move from 0" to 1" (to take out back lash) and mark that location then make another move to 23" and measure the distance traveled.
Rick G
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24 Jun 2013 19:24 #35982
by BigJohnT
Belt drives will not be the mathematical ratio that you calculate. The belt tension can change the ratio, I know I have a belt driven plasma cutter. You will have to measure the actual travel and adjust your scale to get the travel you want. Also note that if you stress a belt it can have varying ratios along the belt and that will drive you nuts.
JT
Replied by BigJohnT on topic Physical cuts wrong size?
Hi,
I have a diy router, similar to early shopbot/mechmate (steppers no feedback drives). I have used stepconfig wizard which worked fine. I ran some gcode and measured the physical cuts.
My dual motors on X axis were supposed to cut 840mm. Instead they cut 841mm.
For Y axis, were supposed to cut 250mm. Instread it cut 249mm.
How do I adjust my settings to take into account of this? Odd is that both X/Y have same radio belt drives, motors and spur gear so you'd of thought they'd be the same. Maybe it was the speed at which I test cut MDF, 9mm depth of cut @ 2000mm/minute feedrate.
Anyhow any suggests much welcome. If you want me to post my ini no problem.
Regards,
giggler
Belt drives will not be the mathematical ratio that you calculate. The belt tension can change the ratio, I know I have a belt driven plasma cutter. You will have to measure the actual travel and adjust your scale to get the travel you want. Also note that if you stress a belt it can have varying ratios along the belt and that will drive you nuts.
JT
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- giggler999
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25 Jun 2013 15:53 #36031
by giggler999
Replied by giggler999 on topic Physical cuts wrong size?
OK thanks people for the replies. I'm working on it and will look at physicals but I had so much trouble making these drives, next time around I'd probably buy something off shelf. I could not key the output shafts due to lack of tools so my filed flats might not be flat enough or perhaps not bang on 90degrees aligning with set screws. Also while I have put locktite green on the spur; I have not on the large aluminium pully that drives it so perhaps that's one of th issues.
I will do some air movements and check distances then adjust accordingly.
Thanks again,
giggler
I will do some air movements and check distances then adjust accordingly.
Thanks again,
giggler
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