Which Type of Limit Switch

[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

[cropwell]

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"

[manofgresley]

Hi.

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

Ray

[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.

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

[EddyCurrent]

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

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

[manofgresley]

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?

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.

[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.

[irving2008]

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.

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

[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?

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

[irving2008]

Yes, as long as they switch to ground and don't have an internal pullup. You can check this by measuring the voltage between the black and blue wires when they are powered up. If it's always zero or there abouts then you can without any other parts. If there is volts then you need a resistor between the black wire and the Bob.