Brother TC-225 / TC-229 adventure!

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03 Feb 2017 16:59 #87228 by Todd Zuercher
I would think that since the Z move would almost certainly be in the positive direction, the W-3 move would cancel, causing the blended move to possibly be slower. Returning to W0 might also be a problem, but since any associated Z move would also likely be negative, it may not matter.

However I question the need for this whole process. Why does the Z travel need to be restricted in the first place? What happens in the restricted area that would cause a problem with normal movement?
I have seen several machines that do need restricted areas for tool changers in the X or Y but I'm having trouble picturing a scenario that would require restricting Z. If the spindle is merely raising and lowering to remove/insert the the tool holder taper, why would it matter if the axis to go to the higher position during normal operation.

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03 Feb 2017 17:06 #87231 by ihavenofish
if the z goes above the working area travel, the tool releases, automatically. there is no air cylinders or hydraulics or arms and whatnot. it moves up, a 10" up, the tool begins to release, at 13" its fully out of the spindle. the carousel rotates, and then the z moves back down, picking up the tool sand moving to the work area.

i think this is going to be a hal thing or hardware switch thing were we just swap what limit switch is being used during a tool change request, and do not use soft limits.

heres the newest version, which is a little faster, but the function is identical.

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03 Feb 2017 17:57 #87238 by Todd Zuercher
In that case using the W axis to command an offset component added to the joint.2.motor-pos-cmd, might be just the ticket. It would still allow the Z axis to use it's soft limits to keep it out of the restricted zone. A little logic could probably make W remain 0 at all times except during tool changes. W commands could then be used for all the tool change movements. The same could also be done just by sending commands directly to the offset component, but properly controlling the motion of the tool change moves (accelerations and velocity) would be a little more complicated.

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03 Feb 2017 19:39 #87244 by tommylight
That looks like a single Z axis, but i might be wrong.
As far as i can see, the other Z axis ( or W in this case ) has only a strict move from-to with no servo controll needed. Go up-stop-wait-go down-done. Some more logic for checking if Z is homed and spindle stoped should do it.
Do not shoot me if i missed something ! :)

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03 Feb 2017 19:42 #87245 by ihavenofish
not sure i get what ya mean.

of course its a single z. andys idea with the w, is similar to the idea of using a c axis to rigid tap. its the same axis, but hes using W to separate its function from the working z axis.

his idea might work, if it doesnt cause a conflict and can interpolate between the 2 stages of travel smoothly like a constant velocity move..

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03 Feb 2017 20:15 #87249 by Todd Zuercher
Why would having a pause at Z0 be a problem other than being slightly inefficient?

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03 Feb 2017 20:25 #87250 by ihavenofish
being slightly inefficient is a problem :P

its just about restoring its original function, speed, etc. if it can change tools in 2.8 seconds instead of 3.5, thats worth a little effort.

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08 Feb 2017 21:33 - 08 Feb 2017 21:34 #87606 by ihavenofish
well, got me my mesa 7i77. machines arrive next wednesday (a bit late due to forklift availabilties).

this week im going to build up the pc and get linux installed and ready to configure.

i did learn a little more about the ATC. the carousel has a 4 bit absolute encoder - 4 optical switches that pass light through a wheel with coded holes on 4 tracks. theres a 5th track, that looks like a 50% duty cycle pulse, much like a standard encoder. i suspect this one is just to determine movement/speed, etc it looks single channel though, so not likely able to detect direction like quadrature can..

i assume it should be pretty easy for linux to read 4 inputs and then turn their binary values into a number right?

Last edit: 08 Feb 2017 21:34 by ihavenofish.

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08 Feb 2017 21:52 #87609 by tommylight
I used this, easily modifiable and exactly what i needed it for.
I had the same feedback but with mechanical switches.
Regards,
Tom

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09 Feb 2017 00:09 #87621 by andypugh

i assume it should be pretty easy for linux to read 4 inputs and then turn their binary values into a number right?


Yes, we have a HAL component for exactly this purpose:
linuxcnc.org/docs/devel/html/man/man9/carousel.9.html

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