1. Configuring LinuxCNC
  3. Basic Configuration
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Reverse Z-Axis for Servo

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02 Jun 2019 14:36 #135634 by HueyHQ
Reverse Z-Axis for Servo was created by HueyHQ
My retrofit Z-axis works correctly as originally intended, in that a positive movement is downwards into the material.

From what I've seen on this forum and in some post-processors, it seems the general practice is that positive movement should be upwards? This would also match the keyboard jog Pg-Up and Pg-Down.

I read somewhere that for a stepper, making the STEP_SCALE negative will do this, but what parameter do I change for a servo? I would prefer not to physically rewire the servo and encoder.

Also, I realise I will need to change my homing parameters polarity; do I need to switch my MIN_LIMIT and MAX_LIMIT accordingly (I'm guessing I do)?

#******************************************
[AXIS_Z]
MAX_VELOCITY = 83.333333
MAX_ACCELERATION = 300.0
MIN_LIMIT = -1.0
MAX_LIMIT = 140.0

[JOINT_2]
TYPE = LINEAR
HOME = 0.0
FERROR = 10.0
MIN_FERROR = 1.0
MAX_VELOCITY = 83.333333
MAX_ACCELERATION = 300.0
P = 0.5
I = 0
D = 0
FF0 = 0
FF1 = 0.0585
FF2 = 0
BIAS = 0
DEADBAND = 1e-05
MAX_OUTPUT = 0
ENCODER_SCALE = 80
OUTPUT_SCALE = 10
OUTPUT_MIN_LIMIT = -10
OUTPUT_MAX_LIMIT = 10
MIN_LIMIT = -1.0
MAX_LIMIT = 140.0
HOME_OFFSET = 0.000000
HOME_SEARCH_VEL = -15
HOME_LATCH_VEL = 5
HOME_FINAL_VEL = 0.000000
HOME_USE_INDEX = YES
HOME_SEQUENCE = 0
#******************************************

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02 Jun 2019 17:38 #135647 by pl7i92
Replied by pl7i92 on topic Reverse Z-Axis for Servo
Change
ENCODER_SCALE = 101981
OUTPUT_SCALE = 10.0

to
ENCODER_SCALE = -101981
OUTPUT_SCALE = -10.0

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03 Jun 2019 02:43 #135689 by HueyHQ
Replied by HueyHQ on topic Reverse Z-Axis for Servo
Seems simple enough; I'll give it go, and work out the other stuff as I go.
Thanks.

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03 Jun 2019 07:31 #135706 by andypugh
Replied by andypugh on topic Reverse Z-Axis for Servo
You probably also want the top of travel to be machine zero, and the Z to run from zero downwards as negative numbers.
In principle this shouldn't matter, except that many CAM systems assume that a G53 G0 Z0 is a good and safe thing to do at the beginning of a programme.
(and that assumption has cost at least one builder here a brand-new spindle :-(

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03 Jun 2019 07:40 #135710 by pl7i92
Replied by pl7i92 on topic Reverse Z-Axis for Servo
if it is not only your mashine
it is better to get a wirer change to the ISO coordinate movement on machine Power

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03 Jun 2019 09:10 #135717 by HueyHQ
Replied by HueyHQ on topic Reverse Z-Axis for Servo

(and that assumption has cost at least one builder here a brand-new spindle :-(

I read that. Which is when I decided it was a good idea to ask the question, and not risk the same fate.

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03 Jun 2019 09:13 #135719 by pl7i92
Replied by pl7i92 on topic Reverse Z-Axis for Servo
trixing on cable wire ring is always not a good idee as it is software bahavior even if you need 2days to change swap 2 wirers it is the best way to go

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  1. Configuring LinuxCNC
  3. Basic Configuration
  5. Reverse Z-Axis for Servo
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