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Motors run at 1/5th travel

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26 Aug 2016 09:10 #79462 by bobhare
bobhare created the topic: Motors run at 1/5th travel
After many days of toil i have managed to get all three motors doing something sensible. However if i command a traverse of 5 mm they only run for 1mm.
I have played around with multi-stepping in Linux CNC and with the dipper switches on the stepper driver all to no avail. The only way i found of dealing with it was to use a lead screw pitch of 1/5th reality; not, I'm sure, a good solution.
My equipment is:-
DB25 1205 BOB
DM542A Driver
23HS9430 Motors
and I'm running Linux CNC 2.7.6
My settings within STEPCONF are:-
Step Time 7000
Step Space 7000
Direct Hold 5000
Direct Setup 5000
Pin 2 X Step Inverted
Pin 3 X Step Inverted
Motor Steps/rev 200
Micro-stepping 2
Pulley 1:1
Lead Screw pitch 1.25mm/rev (8mm threaded bar)
Max v 25
Max a 750
This computes to 320 steps/mm
The dippers on the DM 542A are set to 1.91A. I've run it at 3A with the same results.
The DM 542A is also set for 2x micro-stepping.
From the DB25 1205 I have connected VDD to PUL+, DIR+ and ENA+.

Help much appreciated.
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26 Aug 2016 13:25 #79481 by tommylight
tommylight replied the topic: Motors run at 1/5th travel
It looks like you have the scaling not set properly,
[AXIS_X]
MIN_LIMIT = -1000.0
MAX_LIMIT = 1000.0
MAX_VELOCITY = 100
MAX_ACCELERATION = 5000.0

[JOINT_0]


TYPE = LINEAR
HOME = 0.000
MAX_VELOCITY = 100
# NOTE: the step generator module applies its own limits to
# acceleration and velocity. We have discovered that it needs
# to have a little "headroom" over the accel by the trajectory
# planner, otherwise it can fall slightly behind during accel
# and later overshoot as it catches up. In the long term we
# hope to come up with a clean fix for this problem. In the
# meantime, please set STEPGEN_MAXACCEL below to a few percent
# higher than the regular acceleration limit MAX_ACCELERATION
MAX_ACCELERATION = 5000.0
STEPGEN_MAXACCEL = 5200.0
BACKLASH = 0.000
SCALE = 6.6666 <=============
OUTPUT_SCALE = 1.000
MIN_LIMIT = -1000.0
MAX_LIMIT = 1000.0
FERROR = 1.270
MIN_FERROR = 0.254
HOME_OFFSET = 0.0
HOME_SEARCH_VEL = 0.0
HOME_LATCH_VEL = 0.0
HOME_USE_INDEX = NO
HOME_IGNORE_LIMITS = NO

Have a look, you need the drive microsteping, pulley ratio if any, ballsrew pitch, to calculate that.
The following user(s) said Thank You: bobhare
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27 Aug 2016 15:34 #79558 by bobhare
bobhare replied the topic: Motors run at 1/5th travel
Machines work in mysterious ways. I switched the machine on after my last post and lo and behold it was running at 5 times the travel so i input the correct leadscrew pitch and all is well.
I also found i had to reduce the velocity in the STEPCONF setup to get the motors to function properly.
All is well at the moment but who knows what the future holds!
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