The Shop > CNC
Limit Switch Ideas Requested for Quill/Spindle
sparky961:
--- Quote from: PK on July 18, 2016, 06:00:09 PM ---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.
--- End quote ---
This definitely has potential. I'll check out the feasibility tomorrow evening. Thanks, its an angle from which I hadn't considered things yet.
sparky961:
So, after some delay due to much time spent in the wild Canadian outdoors with some pretty amazing (frighteningly warm) weather this summer, I've returned to this part of my seemingly endless CNC saga. One of the big differences this time is that I've been able to use the machine along the way to make or modify other parts. Having a handwheel (MPG) on the machine means that even if other things aren't quite set up yet you can still drive the axes around as though it were a manual machine. I wouldn't undertake another conversion without one.
I decided on PK's idea of drilled and tapped holes into the side of the head, picking up on the existing slot. I've had a few miss-steps along the way.
1. I quickly learned that the proxy sensors I have are triggered when deep in a hole surrounded by metal, not just metal at the end. I think there are versions that only sense at the face but those aren't the kind I have. This was solved by drilling and tapping the hole oversized and adding an aluminum bushing tapped inside and out.
2. Unfortunately while working away at it a bit too late into the evening and my judgement clouded by sleep, I was using one of the sensors to turn thread an early prototype into the hole. The threads were too tight and I ended up snapping one of the sensors. Foolish, yes. But it happens. I went to bed directly thereafter. A new one (plus a spare) is coming from China - maybe. Until then, I more carefully made two more bushings and they are installed and waiting. I tested where the switch is tripped by installing the remaining "good" one in either hole and I'm happy with the results.
3. After getting all of this sorted out, I went to re-install the driven timing pulley. Argh.... I knew it would be close but didn't think it would interfere with the sensor. Yup, it does. This is where the project remained while I went away for a week on vacation. Probably a good thing lest I get frustrated and break something in my impatience to get it done. The time away did some good because when I returned I decided it would be a fairly simple matter to turn down the timing pulley to the next suitable size. Since I got the rotary axis working first and I still have the profile cutter I used to make it in the first place, it should go pretty smoothly. And it did. Instead of having an 80 tooth timing pulley, I now have a 64 tooth pulley. The new diameter clears the sensors and the belt path will run between them.
Video of the timing pulley being cut below. No audio, and no apologies for shaky video and poor lighting. :P
Oh, and if you watch through to about 2:15 all that clattering around is the broom I knocked over while bumping into the shelf behind me..... yes, small space indeed.
This was the simple hand-written program I used. I ran a few iterations of the program taking about 0.010" cuts and continually checking and increasing the depth to a maximum of 0.055" deep.
--- Code: ---G90 G00 Y2.0700 X0.0000
#<TEETH>=64.0
#<CURRENT_TOOTH>=0
O101 WHILE [#<CURRENT_TOOTH> LT #<TEETH>]
G90 G00 A[360 / #<TEETH> * #<CURRENT_TOOTH>]
G00 Y1.9550
G01 F10 X-1.2500
G00 Y2.0700
G00 X0.0000
#<CURRENT_TOOTH> = [#<CURRENT_TOOTH> + 1]
O101 ENDWHILE
G90 G00 A0
M30
--- End code ---
4. These things are never ending when you're working by the seat of your pants instead of a completely thought-out design. Because of the new belt path requirements and to use the existing belt, the motor mounting plate needs to be redesigned. The motor will be raised and the center distance increased. I plan to have a new plate laser cut but for now I just sawed the thing in half and drilled two new holes. It works better than I'd have thought, but it's on the list of things to replace as things progress.
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