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Reference switch issue
« on: December 08, 2012, 08:07:23 AM »
Dear all,

I am trying to set-up reference switches. These are magnetic ones and go ON when a "reference metal block" comes nearby. (See picture "BF 20 version 1 59 Z.jpg")

It was done with the automated set-up of Mach3 (demo version), using a screw driver to trigger the contact. Each time a nice beep was heard.

With the machine in operation, each time that the "reference block" comes nearby, the LED of the reference switch goes ON, BUT the motors stop only when leaving the reference switch, as soon as the LED goes OFF.

I would prefer to see the motor stopping as soon as the LED is ON.

Here are "diagnostic" screens :

1) Approach. The LED is OFF.
in attachment see file "Reference before and after the switch.jpg"

2) switch above the reference metal bock. The LED is ON.
in attachment see file "ReferenceLEDon.jpg"

3) switch just beyond the reference block, the motor stops when the LED goes OFF.
in attachment see file "Reference before and after the switch.jpg"

If I do a RESET, I can jog in any direction.

I have tried to fiddle with Active Low inputs, without success.

Regards, Philippe

Offline ger21

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Re: Reference switch issue
« Reply #1 on: December 08, 2012, 08:14:47 AM »
That's the way Mach3 works. When Homing, the machine moves towards the switch until it triggers, then backs up until it's off the switch. That is your home position. There's no way to change the behavior.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Reference switch issue
« Reply #2 on: December 08, 2012, 08:47:38 AM »
Gerry,

I can understand this if as on the picture of my first post there is room to go just beyond the "reference metal block" and then stop. I would call this a "side" approach.

I have another switch where there is a "frontal" approach, in the axis of the reference switch. In this case I would fear the behaviour you describe, as the process would be :
- approach, the LED is OFF
- about 1mm from the switch, the LED goes ON
- Beyond the switch, after a crash I presume, the LED would go OFF and the motor would stop then.

I would think that the motor should stop when the LED goes ON. The alternative is to modify the position of the reference switch, but this would be strange. I am building a German kit that is clearly designed with this frontal approach.

In attachment the view of the X axis. The table comes close to the reference switch, frontally.

One attached picture show the reference switch (without the table). The second picture shows the table. The inner side (grey/blue) of the table travels in direction of the switch, frontally.

Regards, Philippe
« Last Edit: December 08, 2012, 08:54:53 AM by pdussart »

Offline ger21

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Re: Reference switch issue
« Reply #3 on: December 08, 2012, 09:16:24 AM »
The "Frontal Approach" is a very bad design and should never be used, in my opinion.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html