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Author Topic: Limits - Am i being too smart ;)  (Read 5778 times)

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Offline Davek0974

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Limits - Am i being too smart ;)
« on: March 12, 2016, 11:02:59 AM »
Finally got round to testing my new mill build, all motion is 100% which was most pleasing ;)

Then I got too big for my boots and tried fitting a limit switch, using inductive sensors this time, NO type.

My brilliant idea was to use one sensor on the moving part of the axis and have two adjustable targets, all good so far;)

Got that lot fitted and set X+, X- and X-Home all to one input (this was the smart bit I thought)

But....

The limits work but I cannot jog off of either end - it just shows "Limit switch triggered" immediately after pressing Reset, and the home works but immediately throws a limit fault after homing.

So...

Am I correct in now thinking that I am indeed a twat and you must have TWO sensors or have I missed something simple??

These sensors seem to not flip on or off - they flicker a little as the target gets near - is this normal??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Davek0974

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Re: Limits - Am i being too smart ;)
« Reply #1 on: March 12, 2016, 11:51:05 AM »
Another brain-fart (had a coffee);)

Use the single sensor as X-Home only and then apply soft-limits and slow-zones??

Another single sensor for Y axis home.

Z axis?? - Home is at top of travel for mill (as opposed to plasma) am i right??

AFIK soft-limits are in Machine co-ords and being a mill, having it homed accurately would be pretty important i think?
« Last Edit: March 12, 2016, 11:53:04 AM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Hood

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Re: Limits - Am i being too smart ;)
« Reply #2 on: March 12, 2016, 01:12:22 PM »
Do you have Auto Limits Override enabled?

If your sensors are flickering then that is not a great thing, try some debounce Interval.
Hood

Offline Davek0974

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Re: Limits - Am i being too smart ;)
« Reply #3 on: March 12, 2016, 01:16:50 PM »
I've just found the auto limit override on my laptop setup - i searched the settings screens but it was tucked away on the settings page, will apply it tomorrow.

I am slightly concerned about the sensor flickering, my previous experience was that they just flicked on and off, but those ones were like £30ea, the are ebay ones and i got 6 for about a tenner ;)

Maybe they are just sh1te.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Hood

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Re: Limits - Am i being too smart ;)
« Reply #4 on: March 12, 2016, 01:26:07 PM »
The flickering would be the equivalent of bounce on a mechanical switch and will cause lots of problems.
Debounce may help though.
Hood

Offline Davek0974

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Re: Limits - Am i being too smart ;)
« Reply #5 on: March 12, 2016, 01:40:17 PM »
hmm thats not sounding good, what sort of value would you start with for debounce?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Hood

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Re: Limits - Am i being too smart ;)
« Reply #6 on: March 12, 2016, 01:41:13 PM »
Try 2000 and if it helps work down until it stops working then bump up a bit.
Hood

Offline Davek0974

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Re: Limits - Am i being too smart ;)
« Reply #7 on: March 12, 2016, 01:44:00 PM »
Thanks Hood, will be on it tomorrow;)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.
Re: Limits - Am i being too smart ;)
« Reply #8 on: March 12, 2016, 09:23:12 PM »
Try 2000 and if it helps work down until it stops working then bump up a bit.
Hood

I have good quality mechanical swtiches that homing wont back off from, read about debounce, tried 4 (I thought it was 4 time 40ms?!?), no change...will put 2000 in tomorrow and see if it fixes it!

Offline Davek0974

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Re: Limits - Am i being too smart ;)
« Reply #9 on: March 13, 2016, 06:33:53 AM »
Sorted :)

These switches cannot be used for combined homing/limits - the flickering immediately triggers a limit fault after homing as it sees the flicker as the next sense input. Probably just crap sensors.

My fix was to use them for homing only, then add soft limits to control the position limits on all axes - the mill will always be homed when in use so this seems a safe option.

However, as the sensors all use one input, it sees the flickering as the next axis sense and just zeros all the dro's - did i say these sensors are crap?

The fix - modify the home-all button script to something like this for all axes...

DoButton( 24 )
While IsMoving()
Wend
DoOEMButton(133)
While IsMoving()
Wend
Code "G53 G1 z-3 F500"
While IsMoving()
Wend

This runs the home, zero's the DRO, then steps back 3mm which is enough to get the target clear of the sensors, then it moves onto the next axis and so on. It works perfectly but does leave the tool at X3, Y3, Z-3 but then you can jog back if it matters as the soft limits will stop a crash. It does NOT work without the While IsMoving lines in there. Debounce does NOT make any difference and is now set to zero.

I guess I could add a move to zero on all axes after the homing finishes, just to park it all at zero.

A video of homing working nicely...
https://youtu.be/T2CeluqhRl4

Now i can start final wiring and finish the build, damn good fun playing with it though :)
« Last Edit: March 13, 2016, 06:38:59 AM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.