Homing Switches

[m_c]

What are people using for limit switches?
And how accurate are they?

How homing is implemented has always been a bit of a mystery to me, and I've tried to avoid it, however with the new lathe, I now need to learn about it, and decide what switches/sensors to buy.
So, any guides/suggestions/tips/links will be welcome!

[Lee Roberts]

Hi,

If you go with Home Switches then you don’t need to have Limit Switches as you can setup Soft Limits in MACH3, it’s funny you would ask such a question as last night I started thinking about making a video on how to set them up and what to include.

People use different types of switch; the most common is a micro switch with an attached lever, so this would be classed as a mechanical type.

The ones I have for my machine I got from the USA, they are the basic type but they have a small bronze bushing on the end of the lever to act as a roller against the edge that triggers them. You setup your Home position based on each axis, so you look at what you would like as the travel for each axis, in each direction.

Once you are happy with that, you then setup Soft Limits, again this is done in the MACH software. You should note as well that sometimes limits could be triggered or tripped by the noise in the stepper motor wires. So it would be best to run the wires separately and to play it safe, use shielded cable.

Normally you would jog each axis to its limit manually and then zero each yourself, with home switches you get the same but its automated and you only have to click the button once. Now when you click the “REF All Home button”, each axis will move to the same spot every time, so you also gain repeatability from having them.

So in a nutshell, you’re giving the software a point of reference so it knows the limits of travel for each axis.

Lee

[m_c]

Thanks for that. I'm sure the software side will become more understandable once I've used it.

At the moment, I'm more concerned about accuracy and repeatability, and am really needing pointers towards what switches to buy. Are normal microswitches accurate enough?

[Lee Roberts]

Yea i think so, not seen anyone report one failing in 3 years. You could go proximity reed switch if you wanted to or maybe some sort of laser system would be better ?


http://www.youtube.com/watch?v=C-FpWceRnFc