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

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29 Jan 2021 09:24 #197042 by Clive S

Clives explanations were very helpful, but I don't understand the difference between HOME_LATCH_VEL and HOME_SEARCH_VEL yet.


HOME_SEARCH_VEL is the speed at which you want to run to the home switch (which is generally slower than a G0 move) The search for home is at a reasonable speed and might overshoot slightly.

HOME_LATCH_VEL Is the speed Usually very slow to back off the home switch (this is the final trigger and accurate move) when this is done you use the HOME to move away from the latch so that it will not get false triggers (this can be 1mm to the other end of the table if you want.

Once this is all done and homed the soft-limits will work correctly.

As Rod has said you need a switch (sensor) at either side of the gantry to be able to square it with the HOME_OFFSET.

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02 Mar 2022 19:36 #236211 by jtrantow
I updated the github 2.8 configs/by_interface/parport/gantry configs.

I also attached a zip to the following thread.
forum.linuxcnc.org/49-basic-configuratio...tors?start=20#236206

My intent is to have a good gantry example included in the released configs. I think this example includes most the great information found in this thread. My update uses XYZY, instead of XYYZ favored in this thread because it matched the initial stepconf XYZA config better.

I think it's significant to include gantry_joints.ini to use the same .hal and minimal changes to allow joint mode jogging (while debugging the machine). But once the machine is wired correctly there is no reason to deal with joint mode.

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11 Jun 2022 16:40 #244941 by Gruntled Raptor
thank you joel for making a go of making the impenetrable accessible to people such as myself. im wondering if you might be able to offer some insight into editing my own HAL file. i am unfortunately forced into using a 7I96S which is proving slightly harder to use as only the mesaCT configuration wizard seems to provide help with it. consequently i am completely lost as my own HAL file is not all that recognizable compared to your examples.

i am specifically lost at the assigning pin stage as quite simply im not even sure which lines are even assigning pins to begin with. that being said i cant verify my editing of rest of the file is accurate without being able to assign said pins for testing so its very possible im making errors on that front too.  joint 2 and join 3 of my file represent the Y0 and Y1 motors as it where of this attempt. i simply copyied joint2 whole sale and change any joint 2 reference to joint 3. i had hoped that my pin assignment was somehow burried within and thus would be covered by this as i cant seem to find any direct pin maping. 

ive been staring at this for so long now everything is all starting to swirl so if any of our more seasoned config aficionados can take a look at the attached hal and assist in my understanding of what needs to be done i would be most gratefull.


 
Attachments:

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11 Jun 2022 21:41 #244958 by Clive S
It might be useful to add the ini file as well

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11 Jun 2022 22:19 #244960 by PCW
For another example configuration, there is no reason you cannot use a pncconf setup for a 7I96 with a a 7I96S (just replace 7I96 with 7I96S in the hal/ini files)

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12 Jun 2022 15:43 #245005 by Gruntled Raptor
I was under the impression that they used different FPGA's? Which made me think i had best not use anything other than something that supported the 7I96s exactly.

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12 Jun 2022 16:01 #245006 by PCW
All Hostmot2 cards are basically interchangeable at the hal level
Though newer cards may have features not supported by older
versions of LinuxCNC

This means that HAL/INI files are portable between almost any Mesa FPGA card type
by just changing the card name (and driver name/config line if the card interface
is different)

Note that you must not attempt to load firmware that is not specific to the
exact card.

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13 Jun 2022 10:11 #245062 by Gruntled Raptor
Ah, I think I may have been getting some amount of confusion concerning the firmware flashing as I had assumed that my configuring of the HAL/INI file via the mesaCT was also making necessary changes for these change to work on the card by altering the firmware, meaning I felt I had to flash the firmware each time I made a change.

I'm guessing the only situation I would be making alteration to the firmware is if it was changing core functionality of pins.

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13 Jun 2022 12:02 #245065 by tommylight


I'm guessing the only situation I would be making alteration to the firmware is if it was changing core functionality of pins.

Exactly.
And even for that in some cases there is no need to flash the cards, any unused stepgen/PWM/ecnoder counter frees up the pins as normal IO.

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