Sunday I should be back in the workshop. I have some new wood to try — Spanish Cedar. It doesn’t have the aroma of the cedar for a closet, but it does have a rich, golden color — like roasted almonds. If even a few things go right, I’ll be working with it tomorrow.
I’ve went over my machine. I checked the servo-motor brushes (no visible wear) and the spindle brushes (maybe 25% wear). The first wave of intense use loosened some parts and changed the alignment. After strengthening the parts that needed it, the leg length dimensions changed by a tenth of an inch or so. I was delighted — it was time to calibrate!
I had already written new calibration code to better estimate the construction measurement errors, and wrote last weekend new code to sample the data the calibration routine needs. The calibration code is exciting because it take advantage of modern computers to do a better job than my old calibration code. The code now runs multi-threaded and multi-core, pushing my Intel I-7 processor to the limits. It simultaneously estimates all seventy-two (72) simple sources of error, and does so based on a much simpler and more automated data capture system.
More importantly, though, I took a hard look at the results from my first calibration (something like three to five years ago), and saw that the results were terrible! Points that I know are (nearly) co-planar were deduced to be over an inch out of the common plane. I would have been far more accurate using my measurements than the results of my previous calibration.
So tomorrow, I may not be running with a completely calibrated machine, but it will be far more accurate than I was using before.
Now, will the accuracy actually make much difference? Probably not, since my process compensated for many distortions — including internal position errors. Tomorrow should reveal the difference.
Back to the Spanish Cedar… it has a great deal of harden pitch in the wood. I may choose to finish with oil diluted by mineral spirits, or perhaps I’ll go with shellac. I’ll check my references. I still want a stain resistant surface — it won’t do to have beet juice from the red horseradish stain the plate.