TCP 5-axis kinematics

Hi everyone,

I am trying to get xyzac working in my machine and for the most part everything seems fine.
When I try to align the z axis with a point (10 cm ~ the same distance as when a fixture is fit on the bed) above my bed and then switch over to xyzac kinematics and jog only the a axis I notice that z and a are not following each other.

How do I begin to calibrate the axis for xyzac mode?

Thanks in advance,
Abhishek

There are HAL pins that need to be set with the correct offsets, mentioned in the docs:

linuxcnc.org/docs/html/motion/5-axis-kin...inematics_components

set offset parameters
net :tool-offset motion.tooloffset.z xyzac-trt-kins.tool-offset
setp xyzac-trt-kins.y-offset 0
setp xyzac-trt-kins.z-offset 20

Hi,

I tried to mess with z-axis by giving different offsets(as per the guide) but nothing seems to be working.
As I jogged A-axis the ideal case should have been that my Z-axis follows A-axis at the same specified equidistant, but my Z- axis is not following A-axis and instead move further away from it.

Do anyone have any idea how to move forward in solving this issue

Regards
Abhishek

 

I would like to help but it's impossible to troubleshoot like this from afar. You give no information about your machine other than that it is an xyzac type.
Anybody trying to help would need to know:
- what does your machine setup look like? (a picture would give a general idea).
- what are the physical offsets in the rotary assembly (ie dy,dz) and in which direction are they measured (from the rotary face to the rotation-point or the other way around)?
- where do you have the machine reference point (home position), is it in the center of the c rotary table or in the rotation-point or elsewhere?
- what do your current ini and hal files look like?

Hi Aciera,
Thanks for the reply.

Point1:-

Here is a picture from the front of the machine:
ibb.co/4s86kGv

And this is a illustration of how the Lateral and Rotational Movement are seen from the front:
ibb.co/rZSBm4J

Point2:-
So from what I understand, the only offset is dz and that is 29.70 mm. (the bed rotates at the intersection of the x and y axis with no offset and the bed is elevated 29.70 mm above the a axis rotational point.

Point3:-
My machine reference point (home position) is in the center of C-Rotary Table with the z axis home position at the top. ie. z0 is at the top and when the tool touches the bed it is a negative value.

Point4:-
To correct the axis movements some joint have a negative scale value to invert the motion.

 

Regards
Abhishek

So from what i understand tcp tracking works for rotations of the c axis but doesn't work for rotations of the a axis?

I don't have a 5axis machine so maybe you can explain something I have generally wondered about:
I notice that your joint HOME values in the ini file are all zero. Also your 'rot-point' values are all zero. Are you sure that your machine home position is located exactly in the center of the rotary C table? If you home the machine and you position a dial indicator on the center of the rotary C is the absolute coordinate position (G53) really (0,0,0)?
I just have difficulty to believe that a machine builder would go through the trouble of setting the machine up in a way that it homes the x,y,z joint so that it EXACTLY coincides with the center face of the rotary C table. I would expect there to be a parameter setting in the machine controller that can be used to calibrate the position of the rotary assembly in the machine.

[edit]
I notice you use absolute encoders, does the signal come from the drive or the encoder itself?
Also by how much is the A axis tracking off ( just a little or way out)?