Mach2, pulses per sec, inches per min

[Bloy2004]

Anyone,
..does this make sense?....

I have a 12:1 gearhead and "made for" servo motor rated at 60V/Krpm.
Last night I "Plywood-boarded" a power supply giving 95.6VDC and
found the output shaft rotates at 132.8rpm. The motor shaft
therefore rotates at 1,593.6rpm (12 X 132.8).

Wanting to use an existing Gecko320 which cannot exceed 80VDC, I
will apply 75VDC to the motor. In theory, this would bring the motor
rpm down to 1,250rpm and gearhead shaft output at 104.16rpm (1250
divided by 12).

With direct drive, travel per 1 rotation of output shaft is 3.92857
inches. Hence, 1 inch of travel will equal .254545 of 1 rotation.
Multiplying this by 12 (gearhead reduction) yields 3.05454rpi
(Revolutions of motor Per Inch of travel.

If using a 500cpr (Counts Per Revolution) quadrature encoder, this
translates to 2000ppr (Pulses Per Revolution). Multiplying this by
the motor shaft rpi (Revolutions Per Inch) gives 6,109.08 pulses per
inch of travel (2000ppr X 3.05454rpi). This would be 0.00016 resolution?

Changing the 1,250rpm of motor to revolutions per second yields
20.8333rps (Revolutions Per Second). With 2000ppr encoder, total
pulses per second equals 41666.67 (2000 X 20.8333).

Mach2's max pps (pulses per sec) is 45,000 so as figured this configuration should
work with motor tuning setup at maximum velocity given ample power
of motor.

Inches Per Minute of travel (ipm) would be 409.2269 (1250rpm divided
by 3.05454rpi)

Assuming the motor has the power or the machine mass is within means,
this all should work?

Is this figuring correct? I need verification before construction.

Originally the $30 ebay buy was intended for only the gearhead, but
the motor came with it and both are in pristine unused shape. The planetary gearhead seems to have close to zero backlash, making this combo ideal for its intended use.

Bloy

[Bloy2004]

Here's a pic of the motor and gearhead and mock-up DC pwer supply

[Bloy2004]

Given the figures are correct above, how or what would be the possible options for reducing the shown power supply from 95.6VDC to 75VDC.
It is rated for 240vac primary but am using 120vac to get output of 60 some volts ac.

Bloy

[Bloy2004]

Are the above figures correct? Or am I missing some element that would throw off all the drive train figures?

Bloy

[HuFlungDung]

I'd say your calculations look to be correct.

The resulting resolution might be a little bit weird to work with, but I don't know if that really matters so long as you don't use incremental programming methods when you get it working.

[arvidb]

It looks right to me. Be careful with round-off errors though:

I guess you are going to use rack and pinion with a pinion dia of 1.25"? I get the pulses per inch to 6111.55 ( = 1/(1,25*pi/12)*2000), or resolution of 0.163625 mils (thousands of an inch).

Arvid

[Bloy2004]

Thanks Hu, Arvid,
You're right. I'm using rack and pinion. That motor pictured will mount nicely to the back side of the gantry and connect to the double pinion jack shaft crossing the gantry to provide drive to both sides. The linear bearings will be built high so there will be little extension of the gantry "arms". I should get 3 feet of Y travel and 3.5 feet of X travel. If need be, small ratio adjustment can be made through the connecting belt/pulley from gearhead to shaft.

Bloy