Which Type of Limit Switch

Hi

I have a 3 axis Milling machine which i have converted to CNC with the help from members of this forum, i have installed, a maximum travel Limit Switch (Mechanical Lever Type) to each axis, wired through the PILZ relay i am using, so complete shut down on activation. I now wish to install "HOMING" switches, but which type ? Mechanical or Optical. I am using Mach 3 software, or can this be done in Mach 3. Can anyone supply the relevant info?

Regards

Ray

Don't forget to include an over-ride switch, so when you hit the limit, you have some means of getting off it. "looking for a smiley that means - Painted into a corner" :hopelessness:

Hi.

I have left the hand wheels on the motors for this purpose.

Ray

Optical or proximity would work, difficulty with either, on a mill as opposed to a router, is finding somewhere they can be kept clean and dry. Also where is 'home' on a mill? nominally its the centre of the table (as opposed to one corner on a router). Mach3 homing is to detect the homing switch change of state then back off til it changes back again. a bit tricky to do for the middle of the table.

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Originally Posted by manofgresley

Hi

I have a 3 axis Milling machine which i have converted to CNC with the help from members of this forum, i have installed, a maximum travel Limit Switch (Mechanical Lever Type) to each axis, wired through the PILZ relay i am using, so complete shut down on activation. I now wish to install "HOMING" switches, but which type ? Mechanical or Optical. I am using Mach 3 software, or can this be done in Mach 3. Can anyone supply the relevant info?

Regards

Ray

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Is this any use ? it might solve the issues Irving rightly brought up.

http://www.cnccookbook.com/CCMillCNCHomeSwitches.htm

Thanks for the advice, i have a ZP5A BoB, the voltage on the Bob for the HOME limits is 5 volts, i am no electrician, could you recommend a type and brand of switch i could use?

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Originally Posted by irving2008

Optical or proximity would work, difficulty with either, on a mill as opposed to a router, is finding somewhere they can be kept clean and dry. Also where is 'home' on a mill? nominally its the centre of the table (as opposed to one corner on a router). Mach3 homing is to detect the homing switch change of state then back off til it changes back again. a bit tricky to do for the middle of the table.

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If you use a proximity switch such as the LJ12A3-4-Z/BX, you will need a supply voltage of 6 to 36v. anything below 10v won't work reliably (I found to my cost). The advantage of this proximity switch is that it is a sealed unit, you just need to keep swarf away from the sensor end.

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Originally Posted by cropwell

If you use a proximity switch such as the LJ12A3-4-Z/BX, you will need a supply voltage of 6 to 36v. anything below 10v won't work reliably (I found to my cost). The advantage of this proximity switch is that it is a sealed unit, you just need to keep swarf away from the sensor end.

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Which is tricky on a mill, also the mill itself is a big chunk of iron so mounting proximity switches so they're not affected isn't so easy. Optical sensors as shown in the link on Eddie's post in suitably sealed boxes are a neater solution. A suitable sensor is this one: http://uk.farnell.com/omron-electron...ive/dp/1348961

I f i read it right, this unit you recommend is fixed on the mill bed and a peice of metal is attached to each axis, the metal inserts between the 2 posts of the switch and makes the contact?

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Originally Posted by irving2008

Which is tricky on a mill, also the mill itself is a big chunk of iron so mounting proximity switches so they're not affected isn't so easy. Optical sensors as shown in the link on Eddie's post in suitably sealed boxes are a neater solution. A suitable sensor is this one: http://uk.farnell.com/omron-electron...ive/dp/1348961

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Originally Posted by manofgresley

I f i read it right, this unit you recommend is fixed on the mill bed and a peice of metal is attached to each axis, the metal inserts between the 2 posts of the switch and makes the contact?

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Yes its an optical switch that is to say an invisible beam of light it being shone across the gap in the sensor and then when use pass a piece of dark plastic or metal into the gap it breaks the beam and triggers. ..Clive