Slaving X and A axes
23 Dec 2016 19:15 #84644
by Dave H
Slaving X and A axes was created by Dave H
To slave the A axis to the X axis, as in tandem drive gantry machines, does the machine need to be setup as an XYZA configuration in StepConfig? Or can it be left as XYZ, and just make the changes to the A axis setup in StepConfig to be the same as the X axis setup? This second arrangement was tried and failed, although I saw it done on YouTube (old EMC2 video) that way.
If the first scenario is true, don't you then lose the ability to add an A rotary axis unless the machine is then setup as an XYZAB machine, and B is then slaved to the X?
Thanks,
Dave
If the first scenario is true, don't you then lose the ability to add an A rotary axis unless the machine is then setup as an XYZAB machine, and B is then slaved to the X?
Thanks,
Dave
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- Todd Zuercher
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24 Dec 2016 03:13 #84660
by Todd Zuercher
Replied by Todd Zuercher on topic Slaving X and A axes
How familiar are you with the idea of joints (motors) versus axis (1 dimention of Cartiesian movement). Linuxcnc has a separation of these 2 concepts. Unfortunately until recently Linuxcnc has blurred and muddied this separation a bit, but the current development version this has been (or is being) corrected. In that version of Linuxcnc it is relatively simple to assign multiple joints to one axis letter. So in this way having multiple X axis will have no impact on your ability to add a true A axis.
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24 Dec 2016 03:29 - 24 Dec 2016 03:31 #84661
by Dave H
Replied by Dave H on topic Slaving X and A axes
In the above scenario I understand that there will be 4 joints (motors). 2 for the X axis (synchronized not reversed), 1 for the Y axis, and 1 for the Z axis. Can the 2 X axis joints be synchronized by just changing the A step and direction settings in StepConfig to X step and direction using a XYZ mill configuration? Or does the configuration need to be set to XYZA, or possibly XXYZ?
Or is there a lot more to it than that? Mach 3 seems to handle this pretty simply without losing the A axis option.
I am hoping to build a gantry style machine in the near future, want to use LinuxCNC, so would need to have this figured out before then. I am using version 2.7.8.
I can't seem to find any clear info on how to do this anywhere I look.
Thanks
Or is there a lot more to it than that? Mach 3 seems to handle this pretty simply without losing the A axis option.
I am hoping to build a gantry style machine in the near future, want to use LinuxCNC, so would need to have this figured out before then. I am using version 2.7.8.
I can't seem to find any clear info on how to do this anywhere I look.
Thanks
Last edit: 24 Dec 2016 03:31 by Dave H.
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27 Dec 2016 01:57 #84728
by andypugh
If you are setting up a gantry for the first time now then I would definitely recommend using LinuxCNC 2.8 even though it is not actually properly released yet.
However, even 2.8 doesn't have a version of Stepconf that really understands gantries.
What you need to do it set up a normal XYZ machine and then make some changes to the HAL file (The HAL file is your config, it is your file to edit as you wish. In fact the whole point of that file is as a human-editable layer between software and hardware) according to the information here:
linuxcnc.org/docs/devel/html/getting-sta...#_kinematics_modules
For further examples look at the sample gantry HAL file here: github.com/LinuxCNC/linuxcnc/blob/master...m/axis/gantry_mm.hal
Which uses values from the INI file here:
github.com/LinuxCNC/linuxcnc/blob/master...m/axis/gantry_mm.ini
(Anywhere the HAL file contains [THIS]THAT it is looking in [THIS] section of the INI file for THAT.)
The main thing to notice is that the INI contains {AXIS_X] [AXIS_Y] and [AXIS_Z] only, but there are 4 joints from [JOINT_0] to [JOINT_3]
You might prefer to install 2.8, open the sample gantry config that matches your hardware so that it is copied to your ~/linuxcnc/configs directory, then just change the INI file values in that config to match the ones that stepconf gave you.
Replied by andypugh on topic Slaving X and A axes
In the above scenario I understand that there will be 4 joints (motors). 2 for the X axis (synchronized not reversed), 1 for the Y axis, and 1 for the Z axis. Can the 2 X axis joints be synchronized by just changing the A step and direction settings in StepConfig to X step and direction using a XYZ mill configuration? Or does the configuration need to be set to XYZA, or possibly XXYZ?
If you are setting up a gantry for the first time now then I would definitely recommend using LinuxCNC 2.8 even though it is not actually properly released yet.
However, even 2.8 doesn't have a version of Stepconf that really understands gantries.
What you need to do it set up a normal XYZ machine and then make some changes to the HAL file (The HAL file is your config, it is your file to edit as you wish. In fact the whole point of that file is as a human-editable layer between software and hardware) according to the information here:
linuxcnc.org/docs/devel/html/getting-sta...#_kinematics_modules
For further examples look at the sample gantry HAL file here: github.com/LinuxCNC/linuxcnc/blob/master...m/axis/gantry_mm.hal
Which uses values from the INI file here:
github.com/LinuxCNC/linuxcnc/blob/master...m/axis/gantry_mm.ini
(Anywhere the HAL file contains [THIS]THAT it is looking in [THIS] section of the INI file for THAT.)
The main thing to notice is that the INI contains {AXIS_X] [AXIS_Y] and [AXIS_Z] only, but there are 4 joints from [JOINT_0] to [JOINT_3]
You might prefer to install 2.8, open the sample gantry config that matches your hardware so that it is copied to your ~/linuxcnc/configs directory, then just change the INI file values in that config to match the ones that stepconf gave you.
The following user(s) said Thank You: Dave H
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27 Dec 2016 14:29 #84746
by Dave H
Replied by Dave H on topic Slaving X and A axes
Thanks Andy.
Although a fair amount of that is Greek to me, there is enough there for me to figure out what I need to do. I had downloaded a HAL and INI file for a gantry machine that I found here just the other day, and they seem to match what you are saying.
Since I do not plan on building the gantry machine right away, I have some time to digest all of this and, now, hopefully be ready when build time comes.
Thanks again!
Although a fair amount of that is Greek to me, there is enough there for me to figure out what I need to do. I had downloaded a HAL and INI file for a gantry machine that I found here just the other day, and they seem to match what you are saying.
Since I do not plan on building the gantry machine right away, I have some time to digest all of this and, now, hopefully be ready when build time comes.
Thanks again!
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