Recently I had some issues with exactly locating through holes in Altmill stringers. Today I had the opportunity to re-check my machine square. As it turned out, it was about 1.3 mm off over an x and y distance of 1000 mm. It’s not a lot but I can see that affecting the locations of my holes by more than the tolerance allowed for.
Here is where the ‘PSA’ portion of this post comes in: Both ‘y’ sensors had loose fixing nuts! Not loose as in ‘flopping around’ but loose in the sense of maybe 0.5 mm play. Again, not a lot but it all adds up. I was really surprised that these nuts came loose!
Moral of the story, check your end stop sensors every once in a while to see if things are still tight!
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It’s easier to fix a model-t than a model-s.
Ableit me being mostly green with envy when it comes to the Altmill, my Longmill comes with its perks. One of them is lesser fail points and easier to fix, maintain and return to its initial starting position after going out of alignment.
I reset my mill running into the back, resquaring and resetting any missed steps before a new project or creating a new jig. This will get it back pretty close to the state it was in 2.5 years ago, aligning it back to my insert grid perfectly.
Me being me, this kind of easy fix fits me and I would not want it to be more difficult, If I can prevent that.
How will you reallign your machine to your grid now your switches have been moved? Can you deactivate them and do a grunt, like I do?
I am not gloating, just curious. I am eyeing switches of my own and it seems I need to keep in mind that they are not a replacement reset. I better make sure they mount on the front of the machine.
Thanks for the insight.
I am not sure that I understand what you are asking. If you are referring to my saga of attaching my mill table from the top then I can answer the question - the changes were tiny tiny but on top of that, I ended up expanding the fastener holes by a tiny bit and ran the tool path again. While things were ever so slightly out of whack before, this time there was no issue. I am not sure if this because I increased the diameter of the mounting holes a tiny bit, if everything fits better because I adjusted the machine square a bit or if it fits better because I fixed a stupid design error. Also, because I was paranoid about possibly cutting into the stringers in my first go-around, I elevated the mill table to be using slats on top of some stringers. I didn’t use enough and there was some distortion due to clamping. It is unknown if that distortion was of any significance other than in the counterbores.
@Jens Good advice. Probably a lot of the screws/bolts/nuts need to be periodically tightened.
Chris stated that the z axis sensor will now be inserted into a threaded hole in the aluminum plate. It wasn’t clear if the same will be done for the x and y sensors.
Considering how infrequently the need to remove the sensors arises it might be worth using a dab of non-permanent thread locker on them.
If the AltMill sensors are the same as mine, having nuts on both ends, if they come loose how do you know they are in the same location after tightening them back up?
Oh man, I didn’t put any thread lock on mine and now I’m wondering if I should. Decisions, decisions…
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You don’t. After tightening you need to re-square the mill.
Note that you MUST run a home cycle after you adjust the home position sensors and before running the squaring test.
There is a big gotcha in all this if you have a model that depends on the exact location of the mill table. In my case I need to mill holes in the mills table to be able to run fasteners into tapped holes in the mill’s stringers. Not surprisingly, when you move the sensors, you loose position and need to adjust for that. I made my mill table a few mm short in x and y so I can tweak it’s position a little bit. I also make sure I set the machines x and y zero coordinate to the front left corner of the mill table. Note that x/y zero is not reachable with the spindle once this is done.
I am contemplating fixing the Y sensor nuts (and possibly the X sensor nuts) with a dab of epoxy. The reason for thinking about epoxy rather than loctite is that (IMHO) you need to apply the loctite before the nut is screwed on but there is a lot of back and forth involved before you hit the right spot. Once you have the magic spot, it makes no sense to loosen the nut, apply loctite and tighten it back tableup because invariably you will be off.
The whole thing is still an ongoing experiment as far as I am concerned so make your own decisions.
I would like to add that for 99% of what we do with a mill, the home position isn’t really important as long as the mill is squared. If your tool path cuts all 4 sides of your model then who cares if the X/Y zero position is a few mm either way.
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The AltMill is more complicated than my LongMill because I only have one Y sensor. The sensors don’t have anything to do with squaring for me. If the position of them changes my mill won’t line up to my grid and any holes for locating pins that I’ve made is all.
I don’t have any holes right now because I just replaced my spoilboard. In the past for double sided work I’ve made holes for each corner of the work and used the center of my spoilboard as the zero position for the job. I know about the three hole method but that way doesn’t let you go back to the first side again unless I’m missing something.
I have also considered hot glue because that could be done after they are all tightened up. I’ve never used hot glue for that purpose though.
So yeah, like you said it’s not the end of the world if they come undone just something I’d prefer to avoid.
Good luck, and may your sensors never loosen!
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I think that hot glue might be more maintenance friendly than epoxy if things ever need adjusting!
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