Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION

Manel.

You can use those with a higher reduction between the screw and the servo. Typically, there is a 2 or3:1 reduction with a .200 or 5mm per revolution screw. You would need approximately 4 times that reduction to retain the servo resolution per rev. I would go with like an 8-10:1 reduction then use a 200 or 250 quadrature encoder and a Gecko320. The reduction would undoubtedly need to be a two stage arrangement. Two belts running in parallel, each one with a 4 or 5:1 reduction. The belt on the servo could be half the size of the belt on the screw. Lets see, 20 mm/8:1 reduction=2.5mm traverse per servo rev. 2.5mm/1000 servo counts per rev (250 encoder quadrature)=.0025mm traverse per pulse step. 1mm/.0025 =400 steps per unit in perhaps Mach2 "motor tuning" menu to calibrate the axies. This represents units selected as millimeters. This is basically the same as a mill with 2000 steps per unit in inch units having a .200" lead ballscrew. .0001" traverse per step. 8:1 reduction, Gecko320
and a 250 count encoder 1000 steps per rev. would work well.

Ron


mfmiranda <mfmiranda@...> wrote:



I'm older to this list but this is my first question to the forum.
I'm looking at putting together my own CNC mill. I already have two
superb 40" german x/y linear assemblies and the servo motors (54V, 7A,
3000 RPM), everything saved from junk. I intend to use Gecko 340 and
Mach2.

The question I have regards to the TPIs of my ballscrews �they are
20mm - (0.8") - per revolution. This seems very large to my purpose.

I would like to know if some of you kind folk would take a moment to
figure the way I can use it with a minimum of acurracy, say 0,01mm,
using belt reduction, I guess.

Thanks very much,

Manel Miranda
Braga, Portugal









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