A question of Scale.....

Thanks everyone, it looks like I have opened a rather large can of worms!

I feel my original post was badly worded, I was purely after the information of wether my 14 decimal places made a difference to Linuxcnc. Now I asked that because I use a spreadsheet designed by the original maker of my machine and that spreadsheet was targeted at Mach3. I have no idea (and could care less) if Mach3 can use anything but 3 decimal points in calculations of scale or steps per inch.

Here is a screenshot of the sheet with my 2 scenarios in the metric part of the sheet. The first 1 is default with 3 decimal points in the calc.



this second shot is the same but the value has been expanded to 11 decimal points.



Not wildly different, just accuracy in the calculation.

I know my self built machine is not going to be as accurate as a Haas for example, mine is for wood not metal etc etc. I was just looking for a definitive answer if LCNC could use any more than 3 or even no decimal points at all.

Rod, my machine has grabbed my t-shirt at stages, scared the hell out of me. I know I could feel the bloody thing rolling over fleshy bits if they got in the way!!

Cheers

I only meant for you to feel the 5 micron coating, not feel it tear through your flesh! I tried that and it isn't much fun!

PHOTO EVIDENCE DELETED

That high Microstepping kills all your Performence but ads allot of Issues to your machine
10 Microsteps as Fixed on the G540 Whow

pl7i92 wrote: That high Microstepping kills all your Performence but ads allot of Issues to your machine
10 Microsteps as Fixed on the G540 Whow

Not 10 microsteps, G540 has a divider by 10, it has NO microstepping. Had 2 of them, got rid of them. They are very nice and really powerful for such a small package, but i could not live with 9 steps doing nothing.

pl7i92 wrote: That high Microstepping kills all your Performence but ads allot of Issues to your machine
10 Microsteps as Fixed on the G540 Whow

I did have a Gexko G251x and I did not think it was anything special against the Chinese ones I use now. Don't forget the steps we send to the controller is not necessarily the steps the controller sends to the motor. Current stepper controllers do step morphing and I have seen no performance penalties on my system. Quite happy with the 21 m/min I get out of my steppers.

A red blood cell is about 5 microns wide. So then you need to ask yourself would a smear of blood only one cell thick affect your engineering outcome?

On ordinary machine tools and shop measurements, yes.

Five microns is doubled by Nyquist, and doubled again by radial-operation/diametric-result operations. So you're already at a granularity of 20 microns = 0.0005in in your digital representation of desired outcome. That's a larger number than the minimum finishing cut an ordinary machine tool can make (typically a few tenths 0.001in), so it is not excessively precise for the genuine material limits of machining precision.

A lathe machinist working manually with a 5-micron DRO can repeat 5 micron tool positions and repeatedly hit diameters to 20 microns (0.0005in). Surely CNC should be able to mimic and automate that, or you're surrendering the best precision the machine can physically perform.

If 5 microns didn't matter, then why do we need micrometers that read 0.0001in and gage blocks with micron precision?