Kinematics for XYZAB mill

Aciera
Offline
Administrator

02 Dec 2022 15:25 - 03 Dec 2022 15:12 #258323 by Aciera

Replied by Aciera on topic Kinematics for XYZAB mill

Thanks Dewey, I just cobbled a comp together.

I got all enthusiastic and made a sim-config too (requires 2.9 as it uses switchable kinematics):

[Superceded by forum.linuxcnc.org/10-advanced-configura...mill?start=60#258432]

To install the kinematic comp:
$ halcompile --install halcompile --install <yourpathhere>/xyzab_trt.comp

I also whipped up a vismach model called 'xyzab-trt-gui.py' which you might need to set as executable.

All very good, only that the kinematics don't seem to be right or the vismach model isn't or both.
Anyway I'm out of time again...

[edit]Thanks for the video Rod, right to the point.

Last edit: 03 Dec 2022 15:12 by Aciera. Reason: Updated the comp

The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

andypugh
Offline
Moderator

02 Dec 2022 16:37 #258332 by andypugh

Replied by andypugh on topic Kinematics for XYZAB mill

I think that I would have fiddled about with maxkins swapping axes around until it worked.

github.com/LinuxCNC/linuxcnc/blob/master...kinematics/maxkins.c

I would previously have started with xyzac-trtkins but since switchkins was introduced I can't figure out how those kins modules work any more.

Please Log in or Create an account to join the conversation.

Aciera
Offline
Administrator

02 Dec 2022 17:25 - 03 Dec 2022 08:50 #258339 by Aciera

Replied by Aciera on topic Kinematics for XYZAB mill

Turns out all those sin² and cos² might cancel out.
Would be great if somebody could look that over (still doesn't fix the kinematic though):

Andy, my motivation is to understand how those kinematics were derived in the first place. Would be nice to be able to create a proper kinematic instead of trying to fiddle around with something that doesn't quite fit the requirements.
Although I have to admit I'm not exactly crushing this, yet.

Last edit: 03 Dec 2022 08:50 by Aciera.

Please Log in or Create an account to join the conversation.

rodw
Topic Author
Offline
Platinum Member

02 Dec 2022 19:15 - 02 Dec 2022 19:50 #258349 by rodw

Replied by rodw on topic Kinematics for XYZAB mill

Aciera,

Awesome thank you. Your interpretation of the machine is perfect!
It looks like the A axis is rotating the wrong way as shown here. I bet thats just not as easy to fix as changing the sign!

I started with the B axis at the bottom (eg arm vertical) with the spindle touching one of the white lines on the B axis table.
Jogging A generated the current tool path.

I think the B axis is OK as I can scribe a circle when the arm is horizontal.

@Dewey, thanks for the succinct summary. I was thinking more along the lines of having this included in KINS so it could be installed in the same way as XYZAC-trt et al but I guess that can be discussed after its debugged.

Its been very awesome work by a great team

Last edit: 02 Dec 2022 19:50 by rodw.

Please Log in or Create an account to join the conversation.

cakeslob
Offline
Platinum Member

02 Dec 2022 19:59 #258357 by cakeslob

Replied by cakeslob on topic Kinematics for XYZAB mill

Hey Rod, do you have this machine, the mira6? Ive had my eye on this company for a while because they are local(ish) and they are a distributor of the spindles I use, and make machines similar to mine. If you do have this machine, share your thoughts or comments?

Please Log in or Create an account to join the conversation.

rodw
Topic Author
Offline
Platinum Member

02 Dec 2022 20:11 #258359 by rodw

Replied by rodw on topic Kinematics for XYZAB mill

cakeslob wrote:
Hey Rod, do you have this machine, the mira6? Ive had my eye on this company for a while because they are local(ish) and they are a distributor of the spindles I use, and make machines similar to mine. If you do have this machine, share your thoughts or comments?

Sorry no I don't. They asked me if I could help them with linuxnc. I thought that would be straightforward until The XYZAB kinematics sunk in. I did not want to take it on until we had the kinematics sorted as I thought it would be a nice contribution to the cause!

They do look pretty impressive and have some amazing examples on their web site..

Please Log in or Create an account to join the conversation.

rodw
Topic Author
Offline
Platinum Member

02 Dec 2022 20:34 #258363 by rodw

Replied by rodw on topic Kinematics for XYZAB mill

So from what I can see the error is in the original term AAP because the signs of the sines have not been inverted as mentioned in the original model at the top of page 5

Please Log in or Create an account to join the conversation.

rodw
Topic Author
Offline
Platinum Member

02 Dec 2022 22:58 #258385 by rodw

Replied by rodw on topic Kinematics for XYZAB mill

rodw wrote:
So from what I can see the error is in the original term AAP because the signs of the sines have not been inverted as mentioned in the original model at the top of page 5

I went through this all for my own benefit. (25) changes some signs around and becomes

Cb.Px - Sa.Sb.(Px-Dy) + Ca.Sb.Pz
Ca(Py-Dy) - Sa.Pz + Dy
Sb.Px + Sa.Cb.(Py-Dy) + Ca.Cb.Pz
1

I think that makes sense because any term that includes Sa inverts the sign
I don't yet understand how to get to 26 but you could follow the same logic and chane the sign of terms containing Sa I guess.

Please Log in or Create an account to join the conversation.

rodw
Topic Author
Offline
Platinum Member

03 Dec 2022 00:30 #258389 by rodw

Replied by rodw on topic Kinematics for XYZAB mill

Got it!
It was just the matter of inverting the signs for any term in the kinematics model containing

sin(A)

revised comp attached.

The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

rodw
Topic Author
Offline
Platinum Member

03 Dec 2022 08:10 - 03 Dec 2022 12:20 #258402 by rodw

Replied by rodw on topic Kinematics for XYZAB mill

For those of you following along and don't have 2.9 installed, here is a quick video of Aceria's amazing simulation with revised A axis rotation...

A big thanks to all.

EDIT: Replaced video followig kinematics revisions.

Last edit: 03 Dec 2022 12:20 by rodw. Reason: New Video

The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

Time to create page: 0.122 seconds

Kinematics for XYZAB mill

Attachments:

Attachments:

Attachments:

Attachments: