G200x Discussion

[CNCadmin]

Wow, I've been looking at the new G200x coming out and it's quite impressive.

[ViperTX]

Well...I certainly want to get all excited about this until it hits the store shelves. I wonder if the encoder inputs are differential?

[Mariss Freimanis]

The encoder inputs are single-ended. There are not enough terminal connections available for differential inputs and everything else as well (96 terminal connections).

Mariss

[CNCadmin]

When will this be available?

[Mariss Freimanis]

Shooting for sometime in April. Pre-production boards are running right now.

Mariss

[Evodyne]

Mariss,

April? Right around the corner! What is there in "pre-release" documentation floating around and when will your site be updated? I'm curious to learn more-including pricing.

As long as I have you for a second or two, I've got some of your G210's and I love them. Thanks for a wonderful product.

Lance

[turmite]

Hey Mariss,

Would you be so kind and to tell us (me again) how fast you have spun a stepper using one of these. You told me on the ph one time and I am afraid to repeat it for fear of getting ! Btw I was talking with Art this week and am patiently waiting till everything is in place and then I order!

Mike

[Mariss Freimanis]

It's not the controller, it's the drive that gets mind-bending RPMs from a motor.

The G200X has a maximum step rate of 4,194,304 step pulses per second. Seems like a lot but what if you are using a 250 microsteps / step drive? That step frequency will get you almost 84 revolutions per second or a little over 5,000 RPM.

We test each G201 to see it reaches 6,000 RPM on the test stand motor. We spec the drives at a 200kHz max step pulse frequency. Each has to demonstrate it can get there. A tricked-up G201 can spin the motor to over 10,000 RPM.

The fastest I've ever spun a step motor? A little over 100,000 RPM. A number of years ago Portescap was pushing a ceramic disc rotor step motor. I think it was called "Disc-motor" or something. The motor had very low inductance and rotor inertia, allowing it to easily rev to high speeds.

I was curious to see just how high so I went for it. The motor disintegrated (as in pieces flew all over) past 100,000 RPM. I didn't get the exact speed because it seriously distracted me. Later I worked out the tangential velocity on the edge of the disc and it came to a little over 1,100 feet per second; by curious coincidence that is the speed of sound at sea-level.

The rotor may have been destroyed by shock waves as it exceeded Mach 1. Or it could have been centripital forces, who knows. Either way, I'm not trying that experiment again; the explosive destruction and resulting shrapnel was a sobering lesson.

I still like to think I took a stepper supersonic though. :-)

Mariss

[HomeCNC]

Mariss, At the high RPM of your bench test of 6000. Does the stepper loose all strength? I would think that at that speed you could stop it with your fingers, if it did'nt burn you first

[skippy]

And Mariss' competitors at the time anounced "STEPPER DESTROYED BY MACH1" which I guess is true depending on which Mach1 we're talking about (product or speed of sound)
Skippy

[Mariss Freimanis]

A stepper is pretty much useless at 6,000 RPM. Torque falls of as the inverse of speed, meaning it would still have the same power at 6,000 RPM as it does at 600 RPM. In reality it doesn't because detent torque is always present and always a loss.

Let's say a motor has 100 in-oz of torque at 600 RPM (44.4 Watts). Ideally it would have 10 in-oz torque at 6,000 RPM (still 44.4 Watts). Now let's take a real motor that has 8 in-oz of detent torque. At 600 RPM detent torque loss is 3.5W, leaving 40.9W available at the motor shaft. At 6,000 RPM detent torque loss is 35W, leaving only 9.4W available to do work (2 in-oz).

The motor will stall at 7498 RPM no-load. (RPM = Watts * 1351 / in-oz) or (RPM = 44.4W * 1351 / 8 in-oz).

Mariss

[Mariss Freimanis]

And Mariss' competitors at the time anounced "STEPPER DESTROYED BY MACH1" which I guess is true depending on which Mach1 we're talking about (product or speed of sound)
Skippy

It was actually all young Art's fault. As a result he quietly abandoned Mach 1 and later went on to fame and fortune with Mach 2 and Mach 3.

Mariss