TL;DR: What x and y tolerance is the HDM capable of holding across its entire work area, and how can I make sure mine is squared correctly?
I’m getting ready to machine two aluminum fixture plates to replace the t slots, with each one measuring about 15x26 in. They combine together to form one large fixture plate, so there has to be a space between the two plates so they can be properly aligned.
I currently have the space between them as 0.15mm or 6thou, which I think is too high but I don’t want to risk setting the gap too low and not being able to properly align the plates because the machine can’t hold a smaller tolerance.
I did a x y travel test as well as a squareness test by marking 4 points on the travel and then measuring with a tape measure. They looked accurate but of course I’m not going to be able to tell if it’s off by a few thousandths. Can I lower this gap?
I got mine to within less than 0.005" across the whole table.
To calibrate & square I made a test path of an 8" square. My calipers are 8" or I would have gone bigger.
I cut it out of acrylic, measured it, then adjusted my steps/mm in GRBL to adjust.
Then I cut the corners off, essentially making it a 8" circumscribed octagon, and measured corner to corner to determine squareness.
I was able to get the machine calibrated & square within 0.001" over 8", so 0.004" - 0.005" over the whole travel of the machine. For Z I measured a 100mm 1-2-3 (25-50-100) block with the machine & adjusted from there.
You can dial your tolerance in pretty tight, but you’ll need a precision measuring device. Tape measure ain’t gonna cut it.
My squares were whatever scrap acrylic I had, 1/8" - 1/4" thick. I wasn’t concerned with the height, just that it was something rigid enough to hold a dimension I could measure.
