How to. 2 or more motors on one axis. Gantry

tommylight
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7 years 1 month ago #146707 by tommylight

Replied by tommylight on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

You have them set as two separate axis, they should be the same axis but with two joints.
Attach the hal and ini files.

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pl7i92
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7 years 1 month ago #146709 by pl7i92

Replied by pl7i92 on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

i guess you will use gantryhoming
[KINS]
KINEMATICS = trivkins coordinates=XYYZ kinstype=BOTH
JOINTS = 4
## so joint0=X joint1=yA joinit2=yB joint3=Z

Code:

[JOINT_1]
TYPE = LINEAR
# final home position machine-unit/sec
HOME = 70 #where the mashine ends after homing is finished
MIN_LIMIT = -0.001
MAX_LIMIT = 200
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
STEPGEN_MAXACCEL = 937.5
SCALE = 200
FERROR = 1
MIN_FERROR = .25
# FIRST MOTOR OFSET TO BE SQARE
# use this to square the gantry
HOME_OFFSET = 0.1

# machine-units per sec next 3 lines
HOME_SEARCH_VEL = 10
HOME_LATCH_VEL = -6
HOME_FINAL_VEL = 20

HOME_USE_INDEX = NO
# has to be -ve for gantry
HOME_SEQUENCE = -1

[JOINT_2]
TYPE = LINEAR
# final home position machine-unit/sec
HOME = 70
MIN_LIMIT = -0.001
MAX_LIMIT = 200
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
STEPGEN_MAXACCEL = 937.5
SCALE = 200
FERROR = 1
MIN_FERROR = .25
# second SIDE ofset to be square 
# use this to square the gantry
HOME_OFFSET = 0.5

# machine-units per sec next 3 lines
HOME_SEARCH_VEL = 10
HOME_LATCH_VEL = -6
HOME_FINAL_VEL = 20

HOME_USE_INDEX = NO
# has to be -ve for gantry
HOME_SEQUENCE = -1

the AXis Y will travel both till the first reatch A switch then it will be homing one after the other and then travel to HOME on Both

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deemoss
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7 years 4 weeks ago #146791 by deemoss

Replied by deemoss on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

Thanks Guys!

I (kind of) fixed it after reading your comments by adding the second Y to:
[TRAJ]
COORDINATES = X Y Y Z

Now when I go to Machine -> Homing i don't see the Y axis (is this correct?) see screenshot homing.png.

Also, after I do Home ALL (actually that does not include homing Z because I have no sensors on it - #HOME_SEQUENCE is commented out) and then try to jog Y, I get this error which refers to joint1 (part of axis Y) not being homed. The strange thing is that I can jog Y after I Touch Off Z. Screenshot Moving Y-after homing ALL.png.

I also attached my INI and HAL files.

Dimos

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dgarrett
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7 years 4 weeks ago #146802 by dgarrett

Replied by dgarrett on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

Code:

If HOME_SEQUENCE is not specified then the joint
will not be homed by the HOME ALL sequence (but may be
homed by individual joint-specific homing commands).

Ref: linuxcnc.org/docs/2.8/html/config/ini-homing.html
Specifically:
Ref: linuxcnc.org/docs/2.8/html/config/ini-ho....html#_home_sequence

Use "Immediate homing" for the joint that
corresponds to the Z coordinate (joint 2 in your case)
if it has no home switches

Code:

Immediate Homing

If a joint does not have home switches or does not have
a logical home position like a rotary joint and you
want that joint to home at the current position when
the "Home All" button is pressed in the Axis gui, then
the following ini entries for that joint are needed.

    HOME_SEARCH_VEL = 0
    HOME_LATCH_VEL = 0
    HOME_USE_INDEX = NO
    HOME equals to HOME_OFFSET
    HOME_SEQUENCE = 0 (or other valid sequence number)

Ref: linuxcnc.org/docs/2.8/html/config/ini-ho...ml#_immediate_homing

When using trivkins for a gantry with two joints for a
coordinant, it is recommended to use kinstype=Both in
order to see the homing condition for each joint.

The attached ini file is a sim config based on your ini
file for demonstration (it is a simulation, no hardware
required):

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pl7i92
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7 years 4 weeks ago #146806 by pl7i92

Replied by pl7i92 on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

the Z limit woudt be the one needed most
sa it is for Toolmesure workpice mesure against the Mashine coordinate system
youshoudt realy have there one

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mrmike
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6 years 10 months ago #151765 by mrmike

Replied by mrmike on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

I'm having issues with the homing and travel of the gantry. I have both motors mounted on the backside of the CNC, and 2 home switches on the back as well. If I free pull the gantry to the back, the switches are pretty close to closing and opening at the same time. I can get both steppers to travel but once the switches are engaged, Y1 stepper wishes to keep traveling in the same direction. Once the homing is done (I don't have the gantry connected), and I have the X Y Z on the program, if I try to jog the gantry, Y2 stepper goes the right way either on the + or the -, but Y1 only goes one way. Any suggestions?

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Todd Zuercher
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6 years 10 months ago #151767 by Todd Zuercher

Replied by Todd Zuercher on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

Make sure you don't have the step and dir signal wires crossed going to the Y1 drive. A stepper drive with the step signal connected to the dir pin, will often behave this way.

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mrmike
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6 years 10 months ago #151777 by mrmike

Replied by mrmike on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

I had an extra digit in the hal config y1ldir instead of y1dir

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Jalfrezi19
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6 years 10 months ago #152902 by Jalfrezi19

Replied by Jalfrezi19 on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

Hmmm, strange things happening to my setup:

My goal is to move the gantry (not just one motor) jogging, and I currently only have two motors connected (y1 & y2) of the four.

When I activate the Manual Control and select the axis in the GUI and use the - / + buttons:

X does nothing as expected (not connected)
Y only moves the motor connected to pin 56, would be nice if it would move the whole gantry instead
Z does nothing, as expected (not connected)

When I activate the Manual Control and use keyboard keys:

left/right do nothing as expected (X, not connected)
up/down only moves the motor connected to pin 56, would be nice if it would move the whole gantry instead
pg up/pg down moves the motor connected to pin 89 (:S ???)

I've tried

Code:

kinstype=both

but that gives me the option to control individual joints, and I would like to move two motors with one command...
Any suggestions?

Sander

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Kitwn
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6 years 10 months ago #152905 by Kitwn

Replied by Kitwn on topic How to. 2 or more motors on one axis. Gantry LinuxCNC 2.8 Master

Have you homed all the axes before trying manual control? Strange things happen until after homing is complete but I don't know why!

Kit

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