I spent much of last night consolidating the control data from the stock kinematics. The first charts here are the data summary. I wrote in the calibration values for the sled at the top to show my work. On the side are the average, range, and median results of each of the criteria. The color coded charts are the errors I recorded in relation to where the test square is on the bed.
And here’s the raw data:
As to be expected, the stock kinematics is kinda all over the place. Along the top, there is significant distortion. Across the rest of the bed, the X-Y tolerances aren’t bad, though. The X-Y positional errors are pretty small until you get to the top and sides. It has a lot of trouble cutting square, however. I think because there are two fixed mounting points it is very easy for the sled to “drift” off the intended cut path. I believe that is partly due to the cutting forces, as the squares were consistently off. Around square 15, where there was a 1.7mm error in square, I saw the sled getting pulled a bit by the vacuum hose. I think this caused that large error there. This is another disadvantage of the stock kinematics. If there are any forces pulling on the sled, like the vacuum hose, it cannot adapt as well as the linkages and will cause distortion. So the machine needs more a more attentive operator.
So small parts will probably come out alright, but I would expect to see some distortion on larger parts. This lines up pretty well with our current observations.
My next goal is to run the benchmark test with the stock kinematics. I had a little trouble loading them from the advanced menu yesterday. I got this error message any time I tried to load it from the menu:
I’m running Windows 7 using the portable version of Ground Control (v1.03). I went to github and found the .nc file for the benchmark test, so I copied that to my C:\Post folder where all my G-Code is. I plan to run it like a normal program, because I can’t figure out which directory the file should go in so I can call it from the advanced menu button.
On a side note, I’m not sure that I will score very well with the benchmark test. Based on the program preview in Ground Control, it looks like the test squares are way out in the bad-tolerance areas of my last test. I will still run it, however, as it will help to compare all the data points. I don’t think that’s happening tonight, but I may be able to do it as early as tomorrow night.
I’ve now used up 1 side of my “testing” CDX, I can get 2 more tests out of the other side, but I may need to buy more plywood to do all the tests. Good thing sheathing is pretty cheap.