Maximum speed is clipped much below the capability of the servos

Hello,

I am changing a machine to linuxcnc. All axis are working but i am encoutering one problem i have not found a solution for yet. The max_velocity is clipped by the software to a point way below the capability of the servo drives. These servo's in step/dir mode can easily reach 20000mm/min. but the max velocity i can give in without clipping is 140mm/s.

using master version 2.8
mesa setup 6i25 + 7i85s + 7i85s + 7i84
firmware 5i25_7i85sspx2

Some help please. Thank you very much!

# Joint 0
[JOINT_0]
#********************
TYPE = LINEAR
HOME = 0.0
FERROR = 1.0
MIN_FERROR = 0.25
MAX_VELOCITY = 140
MAX_ACCELERATION = 750
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 160
STEPGEN_MAXACCEL = 937.50
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
# these are in nanoseconds
DIRSETUP = 1000
DIRHOLD = 1000
STEPLEN = 5000
STEPSPACE = 5000
STEP_SCALE = -500.2437358
MIN_LIMIT = -5
MAX_LIMIT = 1450
# Axis X
#********************
[AXIS_X]
MAX_VELOCITY = 140
MAX_ACCELERATION = 750
MIN_LIMIT = 0
MAX_LIMIT = 1450

You do realize that 140mm/second is equal to 8400mm/minute?

Edit,
Oops sorry reread your post and you said 20k mm/min not 2000.

What do you mean by clipping?

there is an error message popping up in linuxcnc upon enabling the machine. From that point on my speed will be limited to this clipped value, which is way to slow for the servo.

ERROR MESSAGE:

"stepgen.02.maxvel is too big for current step timings & position-scale, clipping to max possible"



Stepgen max_vel is limited to a lower amount than requested in the hal file. ( I would like to set 300 as max_velocity)

Have you tried setting all of the MAX_VELCITY = 333.33 and the STEPGEN_MAXVEL = 416.67 in your ini? (according you the snippet of your ini you posted you have them set to 140 and 160mm/sec.)

hi

ofcourse i tried with higher number, but 140 is the first number i don't get the error message. So when i set 141 the message of clipping will appear.

Stephanisk wrote:

there is an error message popping up in linuxcnc upon enabling the machine. From that point on my speed will be limited to this clipped value, which is way to slow for the servo.

ERROR MESSAGE:

"stepgen.02.maxvel is too big for current step timings & position-scale, clipping to max possible"



Stepgen max_vel is limited to a lower amount than requested in the hal file. ( I would like to set 300 as max_velocity)

In that case, shorten your
STEPLEN = 5000
STEPSPACE = 5000
to something like
STEPLEN = 2000
STEPSPACE = 2000

alright but we are working already at 1000 and still that error.

We calculated that for the moment with a stepscale of 500 we are generating 66.6Khz which should be way below MESA capability.

sorry. Wanted to say we already tested at steplen and stepspace of 500 and 1000 and 2500 but the error remained.
( accoring to leadshine manual el5 d1000 we should put 2500 as steplen )

I think the manual says that the timings should be >1000 if you use differential inputs. How do you have them wired?

the drives are wired single ended as far as i know. ( step, dir and a +5V wire)