@Blurfl: Thank you for making this thread. I saw it this morning but I spent most of my day fighting with a stubborn point-to-point machine, sorry I’m late to the party.
I dug up my the test pattern I used in the Metal Top Pantograph Kit Available and made a few modifications:
I had mentioned in the referenced thread that the sled was a bit too close to the top edge when I ran it last time. I’ve moved it down to 150mm from the top edge. That should be a little more stable at the top. I plan on using a strip of plywood above the test piece to give me more of a fighting chance. If we want any other changes to be made to the test pattern let me know and I’ll take care of it.
One thing I did not do in my last test was check that the locations of each of the squares were in tolerance with each other. In my notes, the center squares 5 and 14 were dead on, so I will be using them as a reference for the other squares. I think that using the edge of those squares as a “datum” should be fairly reliable:
May also want to check if any of them are not colinear in the Y-Axis. I doubt that any of the triangular linkages would have enough error in the Y axis we’d be able to measure it effectively.
On the note of tool sharpness and feedrates, I plan on using the 1/4" single flute bits bits I’m always recommending. I have the feedrates dialed in pretty well on those, and I think they should be a good baseline. The 500 mm/min (~20 in/min) I’ve been using for them is slow enough that any “pendulum effect” should be minimal and we won’t need to worry about acceleration planning. Honestly, it’s probably best that I do this before feedrate tests I’m planning on doing. That way we are all working from the same baseline hardware.
I’m writing up a spreadsheet to track the information that we gather from these tests. When I have it somewhere near a final draft I will post that.
The NC file I’m planning on using:
BedAccuracyTest2_6mm1FL.nc (7.6 KB)