X-carve linux cnc upgrade tuning

LearningLinuxCNC wrote:

Seems to me that you don't have enough steps per inch. As it is right now if you are moving at 0.5 ipm (slow move) then linuxcnc will send a step pulse about once a second so you would definitely see start stop operation. It would move about 0.01" each second with an abrupt 0.01" step each second. This would get even worse at slower speeds.

I prefer to have my machines set up so that I get about 0.001" per step even if that means I need higher microstepping. In your case I would increase the gear ratio from the motors or the microstepping or both as required/applicable. I know that I don't actually get 0.001" resolution by increasing the microstepping but it does help with start stop jumps as you are describing.

i will try this tonight as well. do you have a suggested micro step setting? (currently at 8)

If you are just going to adjust microstepping then to get to approximately 0.001" steps you would need 1/64 microstepping. This would give 1040 steps per inch. If the torque is too low with 1/64 then try 1/32 microstepping. Keep in mind that your actual true resolution is going to be approximately 1/16" as you have with your current setup because 130 steps per inch/ 8 microsteps means 16.25 full steps per inch. Actual resolution is equal to one full step of the stepper motor. Microsteps will only help with smoothing out the motion at low speeds.

The stepper machines I am useing are all set up for 1/2 stepping with steps/inch of 1000-2000 (2.5-5 revolutions/inch). (I would recommend trying to increase your gear ratios to something similar .)
So right now one full revolution of your step motor moves your axis more than 12 inches?
(126.352steps/inch)/8X microstepping=15.794whole steps/inch, (200step/rev)/(15.794steps/inch)=12.663inches/rev

If this is in fact the case, it is no wonder you don't have smooth movement. (a 10 or 20:1 gear box would be money well spent)

my machine is set to 1/8 (if i'm not mistaken) on GT2 pulleys and belts. one revolution shouldn't be much more than an inch of movement but i can get exact measurements.

What size are your sprockets? Is it one belt directly driven by the motor, or multiple belts/sprockets/shafts?

Todd wrote:

What size are your sprockets? Is it one belt directly driven by the motor, or multiple belts/sprockets/shafts?

direct drive. 2mm pitch on the belts GT2 pulleys are 20 tooth

this may help clear some things up grab cad repo

In that case shouldn't one revolution move 40mm (or 1.5748inches) and with 1/8 stepping your scale should be about 1016steps/inch. (not the 126.352step/inch in your ini above.)

I agree entirely with Todd. Higher than 1/8 micro stepping with this belt drive configuration will not improve the performance. Please disregard my previous posts as they were based on incorrect information.

the more i adjust the settings the more i'm thinking that this may just be how the machine moves

the only setting on the drivers i haven't messed with is something refereed to as decay. i'm going to try it and see if it makes any difference.
update: no difference to be seen

could this be caused by my stepper drivers?

also if anyone wants to schedule a google hangouts video call perhaps that may help shed light. i appreciate all the help everyone!

hangouts email