Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: JM2018 on January 06, 2019, 09:10:06 AM
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Apologies if this is posted in the wrong area but I’m new to the site and have not managed to find a solution to my homing issue.
Running Mach3/Parallel Port/WinXP
When selecting [Home Ref All] the Z axis travels toward home, hits the home switch and continues to run until the switch is released, once released the DRO will zero and then the Y axis starts until the (Y axis) home switch is activated however the display will not zero until after the home switch is released then the same happens with the X axis.
Have isolated the machine from my break out board and connected 3 micro switches to simulate home switch activation.
As before when selecting Home Ref All each axis runs in their respective direction, actuating the home switch and will only zero the display when the switch is released (not when the switch is initially actuated) at which time the next axis in sequence repeats the same problem
Any help would be appreciated.
Many thanks,
JM2018
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That's how Mach3 works. It hits the switch, and then reverses and backs off. When the switch opens, the axis is zeroed.
If your machine is driving past the switches, then you may have a noise issue.
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Thank you for responding quickly.
It does not automatically reverse until the switch is released, while the switch is held down the motor runs as though the switch has not been activated.
When the switch is released the system responds as it should, reverses the prescribed amount - zero’s the DRO and proceeds to the next axis and repeats the same process.
To eliminate any noise issue I wired switches directly to the break out board, actuated them manually and the same result occurs.
This happens on all three axis, must be something simple I’m missing?
JM2018
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If you look at the diagnostic page, are the LED's showing the switches activated when you push them manually?
In General Config, try setting the Debounce to 5000, and see if it makes any difference.
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Yellow LED’s definitely light when the switches are activated but the motors keep driving in the same direction until the switches are released when Drive is reversed and the DRO, go to zero.
Set bounce & debounce to 2000 previously but no change.
Will try setting to 5000 and see what happens.
Many thanks Ger21.
JM2018
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I don't have an answer for you, as the motors should reverse when the switch is activated.
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Thank for trying to help Gerry.
Hopefully an answer will materialize.
I can of course manually set limits and offsets each time the machine is started but for obvious safety reasons I want to have the Ref All Home function operating.
Will keep pondering!
Regards,
John
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Set denounce to 5000 still have the same problem.
Increasing the debounce time seems to slow down the systems response to the switch actuation.
Other than that the system changes axis only when the switch is released.
Very puzzling,
John
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witch BOB are you using?
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I’m located down under in Australia.
My BOB is an Ocean Control KTA-205 (12V version without charge pump)
JM2018
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ok that is a normal PP BoB.
can you post some screenshots of your motortunig Screens.
maybe your acceleration is so "soft" that the axis is not able to stop on the Limit Switch ?
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just a thought, if you are using the same switches for homing and limits, make sure the ports and pins page is set up to reflect this.
Do you have individual pins assigned to each or are they all going to one pin?
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maybe your acceleration is so "soft" that the axis is not able to stop on the Limit Switch ?
What do you mean with "soft" in the above context ??
Thomss
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I think this means that the acceleration/decelleration values are so low that it hits the limit switch and overruns due to the motor's programmed wind-down rate.
With this said Mach3 treats limit switches and home switches differently, hitting a limit should trigger a hard emergency stop but a home switch just acts as part of the homing process and won't interrupt anything.
Is it possible on your machine for the actuator to climb over the switch and release it before the motor has finished slowing down? I've never had this condition but it might cause wierd homing. Have a look at it and see if you can keep the home switch held as long as possible, raise the motor acceleration slightly or slow it down a little if this is a possibility.
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normal home procedure is:
1.go towards Limit Switch until Limit Switch is hit
2.then ramp down with Motortuning->ACC
3.then go with lower Speed in reverse direction until Limit Switch is free
so if the rampdown pt.2. is to "soft" (low) and the Motor is not able to stop within the range the Limit Switch is
enabled (goes over the Limit Switch), then is in pt.3 the Limit Switch allready free again and it will finish
without reversing.
excuse my bad english
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^ that's it exactly
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maybe you can post
-a screenshot of your motortuning
-a screenshot of Homing/Limits
-a photo of the fixture from the Limit switch
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Response to the home switches became erratic and the DRO would Zero occasionally when the switches were activated and not other times.
In order to eliminate the break out board I ground the pins on the parallel cable where it plugs into the BOB and simulated switch actuation at that point hoping to eliminate a number of variables.
When the symptom persisted I concluded the BOB was not at fault and the cause lay elsewhere.
Checked the BOB XML file size in the Mach3 directory it was not the same as supplied by the manufacturer so it was reloaded/reconfigured and all appears to be working as it should (and as described by TPS in his post).
System now homes as required when pressing 'Ref All Home', just need to sort out some additional settings and we should be good to go.
I'm retrofitting and old Gravograph engraving machine and by design it homes X at 0, Y at the top of its movement range and Z also at the top (as is the case with other mill set ups).
Will sort out settings for Y axis, offsets G55 etc. next.
Steep learning curve but interesting none the less.
Many thanks to all for your suggestions, no doubt will have more questions in the future.
Regards,
John
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I set my debounce to 8000 and also added
while IsMoving
Wend
Code "G53 G0 X10"
Code "G53 G0 Y10"
While IsMoving
Wend
so it moves the gantry clear of the switch
Les