How to Make The Four Mounting Points Planar
(monoplanar? coplanar?)
Of course what to search for is not always as easy it seems, but I used the search on both the Facebook group and the official forum.
I am trying to figure out how to make the 4 mounting points planar. Level would be nice, but not completely necessary. All in one plane seems to be the pivotal key to accuracy for everything else. I can pick up a 72" construction level and get roughly close, but construction and machine level are different orders of magnitude. Of course as I stated my goal is all in one plane, with level being nice, but not absolutely necessary.
I am building my own table, and I can certainly shim or even make adjustable the four mounting points, but I am not sure how to make them as planar as possible.
I’m laying out a steel frame table with steel mounting points, and most likely a solid aluminum main table surface, but that is only provided for information. I’m not seeking advice or approval on that. Just on how to make the 4 mounting points planar. Not how to make them adjustable or how to use a shim. I can do both of those things. I’m trying to figure out how to actually measure that the 4 points are in the same plane. I’d probably settle for within a couple thousandths, but better is better.
Oh, yeah. I have seen that. It should be good to within the diameter of the fishing line anyway. Perhaps a little better with some care and dead reckoning after you achieve contact. I can always adjust one mounting point with a dial indicator by one radius after achieving contact. With some care that might get within a few thousandths.
If you’re shooting for better than the radius of a piece of fishing line, a Master Precision Level may be the tool you need. A friend of mine recently used one to precisely level his Avid. He said that the thing was incredibly sensitive, but he eventually achieved near perfection. Due to the way the levels are made, setting the machine up at true level is by far the easiest way to go.
But be aware that the tubes on a Onefinity are not perfectly rigid. On my Journeyman, equipped with a Stiffy and a Makita router, the X & Y rails sagged a combined 0.010" when the spindle is at the center of the working area. It’s currently probably even a little more than that, as I’ve installed a 2.2 kW spindle since taking those measurements. So the coplanarity accuracy you’re shooting for may not have much practical benefit.
A master precision level is probably out of my budget, but I do have a decent machinist level. I don’t really see how it makes it easier to get the mounting points into a single plane. The most elegant solution I have found so far is to mount a temporary fixture in the middle of the table and sweep the mounting points to get them in tram. A scrap piece of rod with a nail point on the end could do that, and its not hard to stick an indicator on it either. My first tramming tool was a piece of scrap aluminum with a stud threaded into one end and an indicator ont he other. It was no less accurate than one of those fancy tramming tools with two indicators, and better because I coule make it any length that was useful instead of being stuck with the short distance of the over priced purpose built tools. I think that would get me within the couple thousandths I’d like to see.
Yeah, I am aware of the issues with sag. Part of what I want to do with this machine is process testing for another machine I am building. An in between size with very little sag due to alternative design.
Just so you know this is not my first CNC operated bridge mill (router), and I have a several CNC mills of various sizes in my shop. Five under power right now, and one in process of retrofit to a newer control. Maybe a Masso after I see if I like the Masso on the OneFinity enough to pay for it for that machine. More likely it will get LinuxCNC on a PC.
I like your temporary tramming-fixture idea for getting the mounting points coplanar. That should be less fussy than using a precision level with a precision beam to bridge pairs of them.
My thought with the MPL was to check the Y-axis tubes after the machine is assembled onto the base, in lieu of the fishing-line method. The one at Amazon has a V-groove in the base. So I’m assuming that you could simply place it on the tubes, and then adjust them both level to within about 0.001" over their full lengths. That would also compensate for machining tolerances in the feet.
