Need help ASAP! Losing travel from stepconf to cnc

I have my desktop mill set up properly in StepConf. When I do an axis test from min 0 (home) to max 12" It goes from home to 12" exactly and returns. When I open up the CNC controller and jog the axis I am hitting the limit stop after only 4.7" of supposed travel in the program. The carriage is moving a full 12" but the controller only thinks it is moving 4.7".
Again, it is set up properly in StepConf and I have verified it moves inch by inch properly in StepConf.
All units are set in inches, the Gcode is in inches, the machine is set up in inches, everything *should* work, but when it comes time to execute the code the travel is some how 1/4ered. Thankfully I have the travel speed low enough that it doesnt slam into the travel stops or rip a belt, but this is nuts!

HELP!!!!

is it consistent? meaning it is always out the same amount?
That would indicate the scaling is wrong for some reason.

in the INI file under [AXIS 0] (and 1 and 2)

the scaling is found

SCALE = something

see if that number makes sense.

Chris M

Yes, it is consistent.
Makes sense is not exactly what I am thinking..

I dont know if that number is supposed to be huge, or small.
[AXIS_0]
TYPE = LINEAR
HOME = 0.0
MAX_VELOCITY = 3.18080357143
MAX_ACCELERATION = 1000.0
STEPGEN_MAXACCEL = 1250.0
SCALE = 2488.88888889
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -0.01
MAX_LIMIT = 12.0
HOME_OFFSET = 0.0

[AXIS_1]
TYPE = LINEAR
HOME = 0.0
MAX_VELOCITY = 3.18080357143
MAX_ACCELERATION = 1000.0
STEPGEN_MAXACCEL = 1250.0
SCALE = 2488.88888889
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -0.01
MAX_LIMIT = 11.0
HOME_OFFSET = 0.0

[AXIS_2]
TYPE = LINEAR
HOME = 0.0
MAX_VELOCITY = 0.102018900344
MAX_ACCELERATION = 3000.0
STEPGEN_MAXACCEL = 3750.0
SCALE = 77600.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -1.0
MAX_LIMIT = 2.0
HOME_OFFSET = 0.0

Hi

If the distance travelled is consistant eg commanded distance = 100 actual distance moved = 50, that will be down to one of a few things.

1) Scale is incorrect, this is calculated from the other info you input, so perhaps look at this directly last.

2) You are using double the micro-stepping that you declared or thought you were using eg you are set on 8x not 4x as you thought

3) Your pulley ratios, thread pitch or another drive chain factor is out by that factor.

If the distance is inconsistant, the cause is likely to include lost steps through mechanical binding, too high velocity and acceleration settings etc

Go back through the calculations by hand and see if you agree with the figures stepconf gave
This is the formulae for this example from the docs

For example, on a 1.8 degree stepper motor with half-stepping, and 10 revs/inch gearing, and desired machine units of inch, we have:

regards

I will double check my calculations.

I set up the stepconf according to the LinuxCNC guide for the machine I have in stock configuration. I had to make some minor adjustments to get the travel correct. The set up gave 12.5 rev/in but that gave me about 10" of travel when I had asked for 12. I adjusted it to 14 rev/in and it is spot on 12"=12" when I run the "test this axis" in stepconf.
My controller board is set for x16 micro stepping, and that is what I have stepconf set to.

can you tell us all the info we need to calculate the scale, then we can check if stepconf's makes sense.

What version of linuxcnc are you using?

you have some weird numbers in there:
z axis is aprox 6 inches a minute max velocity but 3000 inches per second per second acceleration

Chris M

I am using 2.5.3 on Ubuntu 10.04

X:
REV: 200
Micro: x16
M:L 18:1
Pitch: 14r/in
Vel: 6in
Acc: 6in/s

Y:
(same as X)

Z:
Rev: 200
Micro: x16
M:L 1:1
Pitch: 24.25 r/in
Vel: 1
Acc: 1

When I cycle the axis in "Test this axis" everything is spot on, inch for inch. When I load up a program everything is thrown out of scale.

Here is the rest of the ini.
# Generated by stepconf at Sat Feb 22 22:52:01 2014
# If you make changes to this file, they will be
# overwritten when you run stepconf again

[EMC]
MACHINE = ShapeOko
DEBUG = 0

[DISPLAY]
DISPLAY = axis
EDITOR = gedit
POSITION_OFFSET = RELATIVE
POSITION_FEEDBACK = ACTUAL
MAX_FEED_OVERRIDE = 1.2
INTRO_GRAPHIC = linuxcnc.gif
INTRO_TIME = 5
PROGRAM_PREFIX = /home/dana/linuxcnc/nc_files
INCREMENTS = .1in .05in .01in .005in .001in .0005in .0001in

[FILTER]
PROGRAM_EXTENSION = .png,.gif,.jpg Greyscale Depth Image
PROGRAM_EXTENSION = .py Python Script
png = image-to-gcode
gif = image-to-gcode
jpg = image-to-gcode
py = python

[TASK]
TASK = milltask
CYCLE_TIME = 0.010

[RS274NGC]
PARAMETER_FILE = linuxcnc.var

[EMCMOT]
EMCMOT = motmod
COMM_TIMEOUT = 1.0
COMM_WAIT = 0.010
BASE_PERIOD = 60000
SERVO_PERIOD = 1000000

[HAL]
HALFILE = ShapeOko.hal
HALFILE = custom.hal
POSTGUI_HALFILE = custom_postgui.hal

[TRAJ]
AXES = 3
COORDINATES = X Y Z
LINEAR_UNITS = inch
ANGULAR_UNITS = degree
CYCLE_TIME = 0.010
DEFAULT_VELOCITY = 0.67
MAX_LINEAR_VELOCITY = 6.70

[EMCIO]
EMCIO = io
CYCLE_TIME = 0.100
TOOL_TABLE = tool.tbl

Are you sure everything you are doing is in inches?

Is there a G20 or G21 in your g code program?
linuxcnc.org/docs/html/gcode/gcode.html#sec:G20-G21-Units

Is G20 or G21 showing in the active G codes window in MDI?

Rick G

looking at your x and y pulley calculation.

Do you really have the motor running faster then the leadscrew?

you specified 18 teeth on the motor and 1 on the leadscrew.
This increases the rpm of the leadscrew - usually people gear down the leadscrew.

Chris M