CNC limit switches

[ptjw7]

Hi All
As a newby to CNC (in process of building micro mill conversion) a question has bugged me as to limit switches.
The x and y switches are fine and self explanatory their sizes do not change.
The z axis is worrying me a little in that the lower position will vary as to whisch cutting tool and holder is fitted, so question is is the lower z axis limit switch made adjustable or am I unduly worrying!!

[sdantonio]

Not having set limit switches myself I am not the best source on this, but I would think that the z limit (as with all the other limits) would be set to the size of your table, not the size of your work. So the z limit would be just before the bit hits the tabletop. Though I can also see a benefit in setting the x and y limits to the workpiece so you don't start cutting into your holddown clamps.

Also, to avoid hitting your clamps and checking your code you might want to look into something like vericut or some other simulator.

Steven

[ptjw7]

setting x and y to miss clamps etc would I suspect be part of the programming you set for the job. As I see it the limit switches are there to stop physical damage which could be caused at each end of the travel in anay direction which for the x and y travel would normally be permanently fixed as would the z axis highest position the only variable one I can see would be the z axis lower setting which could prevent table damage due to wrong parameters being set!!

[sdantonio]

Exactly, that was what I ment by setting limits to the size of the table. And with good programming you wouldn't have to reset them to the work.

Have you had a chance to luuk up vericut. It's designed to check your programming to make sure you don't hit clamps or amything by running your code as a graphic simulation. You can also check to see if the finished part in the simulation is what you really expect based on that you programmed in with your code so you don't waste and substrates or stock.

Steven

[Bubba]

I have a lower Z limit set on my quill so I won't damage the worm gear on the micro feed (don't even ask how I know this can happen!)

For me, the Z limits are ONLY to keep from damaging the feed mechinsim from over travel in either the up or down condition. Before I had the limits, I did break teeth on the microfeed worm on my RF31 mill drill because I attempted to over travel in both directions. MY .02¢ and I'm sticking to it!

[ger21]

If it were me, I'd set the limit to stop it before the toolholder hit bottom, or you run out of travel, whichever comes first. Like Bubba says, it's to protect the machine, but you can only protect it so much.