Reducing the space in my garage.

**Rich** · 27-10-2014

Lol - yes, I'll edit. Thanks for the link!

**Rich** · 03-11-2014

Spent last week tidying up the gantry, fitting flange bearing and reading, mostly about stepper motors:

http://homepage.cs.uiowa.edu/~jones/step/an907a.pdf
https://www.mpja.com/download/18304ms.pdf
http://www.haydonkerk.com/Portals/0/...uators_101.pdf
http://www.selene.co/Blog/2011/08/se...motor-winding/
http://www.micromo.com/microstepping...-and-realities

The aim was to understand how the choice of motor i.e. chopper motors, effects the design of the circuit. Without the depth of knowledge to fully understand everything I have read, there where a number of points I need to carried forward:

(1) Motors can be driven at between 10-24 times there specified voltage. Increasing the multiplier will increase the stiffness of the motor.
(2) A motor is most effective when is it operating within the 'slew' range of the speed torque curve.
(3) Micro-stepping increasing the machines efficiency at the expense of the available holding torque.

The last point is important as it helps limit my expectation of micro-stepping i.e. it won't make up for accuracy lost within the design or the build ) I would imagine this last point is reflected in the 'motorcalcs' spreadsheet, which includes a significant safety factor?

**EddyCurrent** · 03-11-2014

Originally Posted by Rich

The last point is important as it helps limit my expectation of micro-stepping i.e. it won't make up for accuracy lost within the design or the build ) I would imagine this last point is reflected in the 'motorcalcs' spreadsheet, which includes a significant safety factor?

From what I've read, 1/8 microstep seems to be the most popular and is a good starting point, that's what I use anyway and it's working fine.

**Rich** · 03-11-2014

Thanks Eddy, that helps with my working out.

At 8 microsteps the resolution using a pinion with a pitch diameter of 23.87mm is 0.0149mm, and that is good enough for me ) But the holding torque is reduced to 19.5% peak value, per the linked paper. However, with a gear ratio 2.8, holding torque is increased to 54.6% peak value. It seems to follow when the gear ratio is include that 4 microsteps provide a resolution of 0.0106mm, with no loss of holding torque.

**JAZZCNC** · 03-11-2014

Originally Posted by Rich

At 8 microsteps the resolution using a pinion with a pitch diameter of 23.87mm is 0.0149mm, and that is good enough for me )

Nope you forgot the to include mr Pie.!! . . . .23.87*pi=74.989 /1600=0.0468

Also you shouldn't really think of Micro stepping in terms of increasing resolution. It has more affect making motors smoother.
If you need resolution then best to achive it by lowering the pitch.

Regards voltage then you can easily run those motors above the guide given on Gecko site. They easily run at 68Vdc without any trouble and the extra voltage gives that bit more torque and speed.
The amp you'll require will depend slightly on the type of PSU used. With Unregulated toroidal supply you'll only need aprox 60%-70% of total rated motor amps. IE: 4 x 4.2a=16.8 / 65%=10.92A

**Rich** · 04-11-2014

Thanks for those three points Jazz, they help a lot!

I've corrected my calculations and marked them down as 'guidance only'. The main issue I was focused upon within the calculation was the effect of microstepping on the available holding torque. It appears with a 2.8 gear ratio, set at 4 microsteps, the machine retains 100% peak holding torque.

Having used your original recommendation as a starting point for the research, I now see that I have the option to spec the machine according to what is required, circa 1.5Nm Nema 23 low inductance or over spec the machine and carry the electronics forward. More reading to be done!