Developments on my Home built 5C CNC Lathe - new spindle and progress on the ATC

27 Sep 2021 11:32 #221699 by spumco
Understood, thanks for the clarification. And good luck with modifying the kinematics.

I guess on reflection that if one is going to spend quite a bit of time writing/developing/testing software, the time would be better spent modifying LCNC rather than a post processor that would not be CAM-agnostic.

At the very least, your live-tool lathe would be useful for C-axis indexing as-is.

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28 Sep 2021 08:09 - 28 Sep 2021 12:38 #221729 by NoJo
We will see how we go with 'PolarKins".....

Can somewhere tell me how do I use  (in INI file under [EMCIO] ) TOOL_CHANGE_POSITION = XYZ on a lathe? - ( No Y..)
Or must I use G30?
EDIT - Sorted the above issue - Just entered 0,0,0 and the ATC went to home as I wanted...

I am having a hard time with tool table setup...
Regardless of choice of touch-off ; to workpiece or to fixture - selection , there appear two touch off options in AXIS Manual page - 
Touch Off
Tool Touch Off
Neither one when selected allows selection of the tool-table update option in the coord update field.
IAW, I cannot select 'tool-table' in the coordinate system drop down box ( as should appear in the attached image)- it does not exist - only a bunch of G's ( G54....G92)
Am I in the incorrect coordinate system? How do I verify?

Last edit: 28 Sep 2021 12:38 by NoJo. Reason: typo

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28 Sep 2021 15:21 #221750 by OT-CNC
Look into G43 to load and read in the tools.

Quick search brought this up. Is in the docs too.

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03 Oct 2021 13:56 - 03 Oct 2021 14:23 #222105 by NoJo
Post Deleted - redone under main topic heading..Sorry..
Last edit: 03 Oct 2021 14:23 by NoJo. Reason: redo post place

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03 Oct 2021 14:24 - 03 Oct 2021 16:02 #222107 by NoJo
Good Progress on the lathe and Polar kinetics...We kindly request some assistance and advice on a few things though please....

First the Polar Kinetics :
We are using custom kinematics based on userkins. The reason for requiring the custom kinematics is that we need to execute different kinematics depending on whether or not Polar Coordination Mode is enabled. (It is enabled using G12.1 and disabled using G13.1).
Linux CNC does not currently support Polar Coordination Mode.
The kinematics themselves are functioning.
However the problem is in knowing which kinematics should be active – something which could possibly be set in the iflags & fflags parameters passed to the forwardKinematics  and inverseKinematics functions.
We have remapped the G12.1 and G13.1 gCodes to .ngc files. These remappings are being executed as expected.
What we however need advice on is how to make the link between the .ngc file execution and the value of iflags / fflags sent to the kinematics. If this is not feasible, what alternative ways are there of achieving the same end result?

Second -  The G02/G03 Arc functions:

Nothing to do with the Kinetics question above...
I have joined the many many people traumatised by G02/G03.   My CAM package - Rhino-Cam from Mecsoft, generates the Gcode, to 5 decimal places, metric.
LCNC fails with the usual - Radius to end of arc differs from radius to start.....
with the other details after, and then the abs error value = 1.21
I am not ready to doubt the CAM software just yet...I set the [RS274NGC] CENTER_ARC_RADIUS_TOLERANCE_MM in ini to 2mm, but same error appears.
Cutting tool comp is off, tool tip radius is set to 0mm.
I can post details of the part, the Gcode, etc if needed. The part is simply a 20mm OD shaft, the end being machined into a hemisphere. The tool path follows the hemisphere arc in roughing, so the 1st arc is very small at the corner of the shaft. The last arc is the actaull face of the 'ball' and it parses correctly. 
Active G-codes include but not only -  G7 G18 G91.1 G43
Last edit: 03 Oct 2021 16:02 by NoJo. Reason: added info on active Gcodes

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04 Oct 2021 11:53 #222194 by Aciera
I presume you are on linuxcnc 'master' since kinematic switching is not supported in earlier versions.
You could have a look at /home/user/linuxcnc/src/hal/components/millturn.comp which was also created using the 'userkins' template file and creates a switchable kinematic.

As for the actual switching of the kinematics you may find it helpful to look at the 'millturn' simulation configuration /home/user/linuxcnc/configs/sim/axis/vismach/millturn/millturn.ini. The relevant remap scripts can be found in the 'millturn' configuation folder.

I hope somebody else can help you with the arc-radius problem.

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04 Oct 2021 12:29 - 04 Oct 2021 12:30 #222196 by NoJo
Thank you for your valuable info! We had implemented the re-map along the the lines in your referred docs, and got it to work yesterday! But rather comforting to have what we did confirmed as the way to do it! Thank You.

So we can issue a G12.1 now - and that's where the complications arise...
We have joint following errors, etc all due to the kins being entered into poorly. We suspect(ed) this is due to parameters not set up in the transfer, etc, and your words 'switchable kinematics' are the key! We are digging in there now and will see how we go. Again - Thank You! This is deep in LCNC's heart we are playing and we have a lot to learn.
Just to be sure re your first sentence - We are using LinuxCNC 2.8.2 Debian 10 Buster PREEMPT-RT ISO download from the LinuxCNC website - is that what you mean by 'master' ?
Last edit: 04 Oct 2021 12:30 by NoJo.

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04 Oct 2021 14:18 - 04 Oct 2021 15:03 #222198 by Aciera
No, LinuxCNC 2.8.2 does _not_ have the switchable kinematic feature.
I'm actually surprised you got as far as you did with 2.8.2.
Note that Python2 is no longer supported in master (aka 2.9pre) .

Once you get 'master' installed you should be able to start the simulations with switchable kinematics by going to sim/axis/vismach/millturn or 5axis or others. (these can be found in the configuration picker that appears after starting linuxcnc.
Last edit: 04 Oct 2021 15:03 by Aciera.

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04 Oct 2021 14:23 - 04 Oct 2021 14:28 #222199 by NoJo
Ok, so still a lot to learn here!
What is 'master' and what do I need to do to load 'master'?
And how will that effect what I have done already WRT my C axis ( component by Andy), the ATC component we did, etc?

Do I need switchable Kinematics? or is there another way to pre-set the inputs so that there is no joint movement demand on entry.
Also, I suppose, what are the implications of sticking with 2.8 in terms of future updates, ie, when 2.9 becomes the general user download?
Seems I should really move to 2.9..
Last edit: 04 Oct 2021 14:28 by NoJo.

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04 Oct 2021 15:27 #222203 by Aciera
Version 2.8 is the current stable release. No new features are added but there are have been two point updates that fix bugs.
2.9pre (master) is the current development branch so sometimes it gets broken but usually things are fixed very quickly. The recent move to drop python2 has made for a bit of a bumpy ride and a few 3rd party add ons like 'nativecam' no longer run.
All my machines run on a master version mostly because I'm a fan of the switchable kinematics feature.
Your current configuration should be working without any problems. As long as you don't have any Python2 or GTK2 scripts anywhere.

The update procedure depends on how you 2.8.2 installed. If you installed it from a premade ISO then you need to add the repositories in the 'synaptic package manager' (Settings->Repositories).
For debian 10 'buster' you will need these two:
deb buster master-rtpreempt
deb-src buster master-rtpreempt
Choose 'Binary (deb)' -probably already selected
paste '' to the 'URL' field, 'buster' in the 'Distribution' field and 'master-rtpreempt' in the 'Sections(s)'.
then do the same for after selecting Source (deb-src)

More info here:

You might need to add the repo keys as documented in the above link. Note that there have been problems with the keyserver not working. I haven't installed linuxcnc this way for a long time since I usually build from scratch. but that has it's own challanges.

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