@WillAdams I did the Diamond Circle Square test on my Pro XXL and am not sure how to interpret my results. Are they as good as I should expect? I don’t know what the specs for “within tolerance” are.
I cut in MDF and my measurements are below. Admittedly, the less than firm nature of the MDF could be throwing off some of these.
The Y axis on the square is .007 > than X.
The Y axis on the circle is .0105 > than X.
Then I tried a modified version of your calibration bars with teeth. The overall pieces are 24.25" long. Each tooth is 1" with a 1" gap between and a 1/2" bottom for the teeth.
I did X and Y axis and they fit together very tightly. Maybe hard to see in the photo, but once you skip the first tooth that was in the SW corner there is a very slight gap at the bottom of each tooth on the Y piece. By the time you get to the top (what would have been the NW and SE corners) that gap has shifted to the top of the tooth.
Doing the raw math above .007 x 24.25 = .16975 of a difference across the whole length, but it certainly doesn’t look like that kind of discrepancy.
Should I repeat the Diamond Circle Square test in a firmer material to get a better measurement?
Are there any obvious adjustments I should try or should I just be happy ?
If the precision/accuracy is workable for your needs, then continuing on to cutting projects is the thing to do.
If you want things to be better/more accurate, then chasing that is a rabbit hole which many of us here have been down — but you should only do it if you want to, and if you think you will be doing work which warrants the effort in material the cutting of which would actually benefit.
Accuracy is heavily dependent on a lot of factors. Some ones that may be effecting your results:
Diameter of the endmill. If it has an even number of flutes you can measure it with a caliper to see if it is the proper diameter.
Toolpaths. Did you run finishing passes? They are standard practice when going for accuracy.
Material. As you pointed out MDF is soft and absorbs moisture. If I’m really dialing in a machine I will use plastic or aluminum for my circle/diamond/square tests.
But I have made adjustments to all of the belt driven Shapeokos I have had for belt stretch. The ballscrew ones are more straight math between the steppers and ballscrew pitch and have been pretty dead-on.
I have found acrylic to be a good material. The PVC coated fiberglass sounds interesting. Just be sure to have good dust collection and air flow in your shop. Composite fibers are no joke.
Just be sure to have good dust collection and air flow in your shop. Composite fibers are no joke.