microstep uniformity

[John S]

Bloody hell you could eat a packet of Hob Nobs in that time..............

[leadinglights]

How big a packet of Hob Nobs?

The Proxxon is limited to about 160mm by 40mm movement in X and Y. As the 1Nm steppers are only driven by 13.5V it could probably be sped up a bit, but a typical job might be a 25mm dia brass gear, or maybe a 80mm by 30mm PCB.

[leadinglights]

I have just been playing with the numbers on toothed belt drives and stepper motors but I don't know if the answer I have come up with are right.
Using the formulae given in the Transdev datasheet for Syncroflex toothed belt drives, I get a figure for tooth shear strength when using a 10mm wide belt and pulleys of 16T and 40T, 6 teeth engaged, of just a tad under 200 Newtons at the stepper motor. The Tension Member is not much better at about 300 Newtons.
Although I haven't settled on a stepper motor yet, the most likely candidate, the so-called 3Nm NEMA 23s that are available at the moment, put out about 2Nm at stall - about 160 newtons at the periphery of a 16 tooth pulley.
Is toothed belt really that wimpy, or have I lost a decimal place somewhere?

Hmm, a quick edit here. Looking at the datasheet for Zapps SY60STH88-3008BF, the maximum radial load is given as 75 Newtons. I assume that if you are applying a torque of 2Nm at a 12.5mm radius then you will get something like 160 Newtons of radial force reacting to it. I may have to think a bit more about the motors as well.

[Robin Hewitt]

Hmmm

2Nm torque, 5:2 reduction, 5mm pitch screw gives a driving force of 0.63 tons.

Probably best if the belt fails before something else does :naughty:

Robin

How to calculate it...
! rev = 5/2.5 = 2mm
2mm/(2*pi)= 0.3183mm = 0.0003183m torque radius
2Nm/0.0003183m = 6283N = 0.63 tons

[leadinglights]

Hmm, I had better apply myself to Irving's tudorial and motor calcs program. I had avoided that until I get some idea of the masses that I will be throwing around.
(Also, avoid getting finger trapped between table and frame at 0.63 tons)

[Robin Hewitt]

f=ma

So 6283 Newtons would accelerate a mass of 18.5kg to Mach 1 in approx 1 second.

Robin :heehee:

[leadinglights]

But I will be using Mach3, does that take 3 seconds?

[John S]

1.85638543287408 Hob Nobs [approx]

.

[Robin Hewitt]

But I will be using Mach3, does that take 3 seconds?

Indubitably