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Author Topic: accel and velocity  (Read 13469 times)

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Offline Hood

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Re: accel and velocity
« Reply #20 on: February 04, 2012, 05:16:51 AM »
Step and Direction should be shielded and the shield properly grounded to a star point in your control cabinet.
Personally I use differential step/dir as that saves having to be extra careful and no shielding is required, just twisted pairs. Obviously you need to make up or buy a line driver to do that and also if your drives dont accept differential step/dir (mine do) then you will need to make or buy a receiver to go at the drives.
As said though if using single ended step/dir as long as its properly shielded and grounded it should be fine.
Hood
Re: accel and velocity
« Reply #21 on: February 06, 2012, 01:06:48 AM »
I have been playing with settings and its still overtravelling the same amount very consistently. My steps per unit for x and y is at 15000 and z is at 20000. With a dial indicator its correct if I run each axis individually. Just running a program (fanuc post) that runs multiaxis at a time that it acts up. I don't see anything in the code that looks out of place. Its in inch and absolute program.

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Offline Hood

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Re: accel and velocity
« Reply #22 on: February 06, 2012, 02:50:18 AM »
Can you attach your xml and also what line encoders, any reduction between motor/screw and what pitch screw? Also what type of motors/drives do you have?
Hood
Re: accel and velocity
« Reply #23 on: February 06, 2012, 11:13:59 AM »
i attached xml and replied, it said that name existed so i renamed and sent again. there seems to be a delay so im not sure if it posted. i will check back in a bit. thanks
Re: accel and velocity
« Reply #24 on: February 06, 2012, 01:48:39 PM »
i have posted this twice but havent seen it on here, gonna try again.  ;D i have 500 line count encoders, which would be 2000 counts per rev in quadrature. the encoders are mounted to the motors. thread pitch is .200 on x and y, .18 on z.  there is a belt reduction of 2:1 on all axis' . im using dugong drives from cnc4pc. i have SEM motors ( 30M4-59 ) max rpm 2400, max volts 142, pulse amps 30. i checked and they have 110 volts being supplied to the dugongs. thanks again  ;D

Offline Hood

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Re: accel and velocity
« Reply #25 on: February 06, 2012, 02:36:51 PM »
X and Y axis calcs from your figures
500 x 4 x 5 x 2 =20000

Z axis from your figures
500 x 4 x 5.5555555 x 2 = 22,222.22222

So seems like you have your steps per units set wrong on all axis.

For your velocity you should be able to get in the region of 1690 rpm so for X and Y that would equate to 169 IPM and Z 152 IPM
Hood
Re: accel and velocity
« Reply #26 on: February 06, 2012, 02:40:05 PM »
Thank you. Did the xml look fine?

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Offline Hood

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Re: accel and velocity
« Reply #27 on: February 06, 2012, 02:45:31 PM »
Apart from steps per unit being wrong, velocity being lower than I would expect and also accel would seem slow for what I would expect from servos.

Sounds to me like your tuning in your drives may be needing tweaked.
Hood
Re: accel and velocity
« Reply #28 on: February 06, 2012, 04:37:29 PM »
I guess that my steps per unit being too low meant it was turning the axis' more times than needed thus creating the overtravels. Thanks a million.  I will plug those numbers in and check servo tuning.  Y and z are quiet but x is a little noisy so im sure it needs it.  Hopefully I can test run it again tonight after my regular job. ;D

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Offline Hood

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Re: accel and velocity
« Reply #29 on: February 06, 2012, 05:17:49 PM »
It would actually under travel with the settings you had. For example you tell Mach to move it 1 inch then Mach would send out 15,000 pulses (as thats what you had set in motor tuning) but to actually move 1 inch you would need 20,000 pulses so the axis would only move (1/20,000) x 15,000 = 0.75 inch
I am not sure but I think the Dugongs have electronic gearing in them, maybe you have that set to something other than 1:1?
Hood