Kylehopestolearn wrote: I plan on having a variable height table top as I want the ability to work on materials 1/2" thick to a rough cut log 2' thick. From what I gather this isn't a problem as long as the frame doesn't flex from weight or table top movement between jobs.
Interesting idea, it ought to work just fine.
1. Jitter - Most of what I've read involves video tests to stress the system. LinuxCNC doesn't stess the video much right? I understand it uses the CPU clock to run the motion and any video that consumes cycles on the cpu can be bad but really the Jitter value is just a value needed when the cpu is under heavy load right?
It isn't entirely about load. Some peripherals can get in the way of realtime (in effect they get priority over our realtime code, and delay our execution). Video hardware is one common culprit, which is why running glxgears (to exercise the OpenGL system) is often recommended.
2. Linear Motion - Are there pro's and con's to mechanical gearing vs microstep's?
Yes, but it's complicated.
It you single-step and gear down then ever step will definitely result in motion. (unless it disappears in backlash or stretch in the drive-train). At high microstep ratios ever step might not result in a move. You have a magnet balanced between two coils, one pushing and one pulling. When you make the field of one ever so slightly weaker and the other ever so slightly stronger the actual torque delta between the two positions might be too small to cause movement. In fact it might take a few steps, but then the motor will make up all the backlog and might slightly shooth through. You will often read that microstepping reduces the motor torque, but this is not the case. The torque of a single step might be pretty small, but after a full set you have exactly as much torque as you would with single stepping.
(And if you consider a hypothetical system that only just has _exactly_ enough torque to move when single stepping, but you are running 256x microstepping then you would have to send 256 steps to see any movement at all. But that's a hypothetically bad design and no real machine will be quite that bad.
