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Limit Switch Ideas Requested for Quill/Spindle

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I thought it would be appropriate, since I was one of the first ones to agree with the idea of this new section (but not the idea's originator), that I be the first one to post here...

I had a thread going a few months back regarding the conversion of my mill/drill/lathe to CNC with LinuxCNC, MESA electronics, and servos.  I've come quite far but the project is temporarily on hold through the summer, as I do a lot of kayaking and backcountry camping during the good weather.  I get out in bad weather off season too, but not nearly as often.  Back to the point though, I have the X and Y axes connected, configured, and controlled with limit switches and servos.  The Z axis, however, is causing my brain to hurt a bit.  The issue at hand is a good way to mount the limit switches.  I have two ideas, both of which I can find fault with, and wondered if someone else could maybe contribute something better that I hadn't considered yet.

My criteria are as follows:
- Limit modifications to the underlying machine
- Reliable and repeatable
- Doesn't interfere with anything
- Somewhat out of the way to avoid damage to sensors, wires, my own hands or head.
- Just generally makes sense

Idea 1:
Similar to how you'd attach a cheap DRO to the quill of a machine.  There would be a vertical rod connected to the end of the spindle, captured by some sort of linear guides affixed to the machine body.  Attached to the rod would be one or two flags that would activate sensors mounted nearby.

Pros: Easy to execute, likely no machining of existing castings and such, some parts already made
Cons: More parts to fabricate, spindle has freedom to rotate a few degrees back and forth so would need to be rigid enough to prevent this

Idea 2:
Mill slots or drill holes into the spindle body (quill), offset radially and axially such that sensors could be mounted to a fixed area of the machine to sense the slot/hole and indicate limit of travel.

Pros: Could be simpler, slots would not require limiting the inherent rotation freedom of the spindle body
Cons: Requires removing spindle and machining holes/slots in fairly accurate locations, limited chances to change design along the way, debris may get in hole/slot, sensors may stick from the machine more and may interfere or be damaged

I can mock this up in 3D if my descriptions are unclear, but was hoping to avoid it for now.  Just think of your typical Bridgeport design and a way to know when the quill is full up or full down without adding a bunch of extra stuff.  The difference with this machine is that I don't have the typical depth stop mechanism you see on knee mills, just the non-rotating part of the quill that moves up and down.  I'll see about adding a picture with my phone after posting this (from my computer).


Are you planning to fit coolant pipe work iff so maybe combine the two ? I have been fitting standard micro switches on the X and Y not got to the Z axis yet .


--- Quote from: chipenter on July 17, 2016, 05:09:28 PM ---Are you planning to fit coolant pipe work iff so maybe combine the two?

--- End quote ---

No plans for coolant on this machine for the foreseeable future.  I have nothing to catch the mess and no need to run hot and fast.  A few squirts from a bottle would do when I really need it.

Mount an upright to the spindle standoff and a couple of proximity sensors to the stepper mounting plate in such a way the limits are triggered when up and down as the standoff passes by. You might be able to get away with a single sensor that sees  metal for the travel and does not see it at each end.

Hey I know you mentioned not modifying the machine too much. But one, carefully drilled and tapped, hole in the side of the head would let you pick up the top of the quill, or the end of one of those slots with a simple proximity probe. It would be by far the neatest option.


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