Automatic braking of axis if no motion required in next gcode line?

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02 Dec 2019 16:37 #151762 by ross_dev
Hi

We would potentially like to be able to automatically apply a brake to our y axis, for example when carrying out a motion with no y component. This is to aid with the fact our axes will be quite heavy.

Is there a baked-in means of auto-applying brake when there is no motion in a particular axis? We were thinking of using gcode M62 / M63 and a gpio pin on the mesa to control it as one way, but of course this means somehow getting a CAM post processor capable of recognising the lack of movement and outputting the M62 command.

If we map the brake to a HAL pin, can LCNC somehow automatically detect a lack of motion, drive that pin high and activate the brake?

Cheers!

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02 Dec 2019 18:05 #151763 by PCW
LinuxCNC can detect a lack of motion but because of the significant delay in releasing the brake you would need some kind of look-ahead to use this at a hal level (perhaps by embedding it in the gcode as you mentioned)

If you are not using spindle synchronized motion you could also delay the actual motion commands in hal (there's a component for this is MachineKit, not sure about LinuxCNC)
so you have the required lookahead at the hal level
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03 Dec 2019 00:46 #151796 by andypugh
I have long thought that the limitation that LOCKING_INDEXER can only be used on rotary axes is illogical and counterproductive in cases like this.
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03 Dec 2019 10:13 #151829 by ross_dev
Hi Guys

Not to worry, we are going with the standard braking scheme now (off at power on, ON at fault / power off).

Thanks as usual for your help!

Ross

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03 Dec 2019 10:50 - 03 Dec 2019 10:50 #151834 by Leon82
You could program a certain way to make it feasable for super heavy cuts

Tangent lead in and only cut in 1 direction.

Step to depth desired.

Unlock
Shift y
Repeat
You can use a manual entry to unlock and lock and make each pass it's own toolpath.

Won't work on a square profile but for facing or slotting you could do it
Last edit: 03 Dec 2019 10:50 by Leon82.
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