Truth about quoted accuracy statements

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msimpson
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Joined: Tue Mar 30, 2004 6:19 pm

Truth about quoted accuracy statements

Post by msimpson »

The KRMx02 has a resolution of 1909.86 steps per inch on X and Y, and 4000 steps per inch on Z.
These are standard numbers utilizing a 20 tooth and 20 Pitch Rack and pinion system with a G540(10 microstep)
These numbers should be considered the maximum limits and what are often quoted by designers or CNC manufactures.
That said, it’s not going to happen. There are too many factors that affect accuracy. Anyone who spouts accuracy numbers without some sort of qualification is just blowing marketing smoke.
There are many factors that bring these numbers down to reality.

Router Run out
Machine Tuning
Stock being milled
Clamp types and number
Table surface type
Speed of cutting
Thickness of bit
Lead Screw accuracy
Rack Accuracy
Micro stepping error
ACME Nut Wear
Router bit wear
Rack Wear
Rack and Pinion Tension

And the list goes on.

That said, the KRMx02 gets the job done. When properly tuned it should be up to any task you can throw at them.

What it comes down to is how much effort you put into building and tuning the machine. With the KRMx02 you should get +/- 0.005 with little effort and repeatability at +/- 0.002 or better.
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