Speed / accuracy? Mach 3, Power supply, GeckoDrive G320 or servo motor?

[alexandrud21]

Hello every body. Sorry for poor English. Is not my native language.
I finished my 5'x5' machine about year ago. Almost everything works fine.
The problem is Speed/accuracy.
I just did one test to run the same poly line shape at different speed(50IPM, 100IPM, 150IPM) and the result is day and night.
My machine is approx 5' x 5'
The motor is nemma 34 aprox 1200oz.
The power supply is from Kelling and is 72V and 20A
The servo is G320 Gecko drive.
All the ball screw is 1605 with and bearing support.
The speed set in mach3 is 6000 mm/min.
Acceleration is 200 mm/s/s
The bit used in application is 1/8".
When i mill at 50 in per min seems to be ok but when I run at 150 in per min the result is bad. Just look in the pictures DSCF5271 and you will understand.
Anny advice please.
Thanks.
Alexandru

[Bubba]

Looking at your first picture, and ASSUMING that your running Mach3 as your controller, it looks like your getting rounding of the corners due to CV (Constant Velocity) moves to keep the speed up during angular movements.
You need an "Exact Path" type of movement or at worst, turn CV off and use "Exact Stop" type of movement to get the correct path.

[alexandrud21]

Thanks. Bubba.
What you mean You need an "Exact Path" type of movement?
I just think about power supply is to small. This power supply give 20A but in 4 output. I not sure if this is 5A per output or 20A per total.
Thanks Again.
Alexandru

[Bubba]

In Constant Velocity mode, the controller "attempts" to follow the desired path as close as it can, but if your acceleration parameters are not/can not be met, it will "round off" the corner changes in direction.
In Exact Path, the machine will exactly follow the path intended by even coming to a complete stop if necessary to make the change in direction. In Exact Stop, it will execute the block and then stop and start the next one.
As for your power supply, based on the first picture, your only moving in the X and Y axis and therefore, I would say that you can apply (if evenly split) 10 amps to each servo.
IF the servos you have are the Kelling, they are rated at 7.8 A continuous. So I would not expect you are really pushing the power supply. The rule of thumb for sizing the power supply is total amperage * .67 . Not sure in the picture, but to do the test board you need a max of 3 servos. So 3*7.8*.67 ~15.6A so your supply should be sufficient.

HTH