Very good thinking geryhlucas, I will have to think how to implement this idea into my setup

Thanks

Hi All,
garylucas has a great idea. The circuit as I've drawn it may well give Tarak problems when he tries to enable Mach at startup.
A Reset button like garylucas mentions would solve it.

I had in mind a software setup where the drive/drives were not monitored for faults until either Mach was enabled or was actually
machining, a complicated way of doing what garylucas suggests.

Craig

Thanks Craig/GaryhLucas, you've certainly given a bit to think about, I'll certainly look into it.

TaraK

Simple is good if it can be done.  A hardware solution like this is a lot more bulletproof.  No software problem can override the limits.

Hi All,
I had problems with my spindle stalling. Its a 24000 rpm VFD driven unit and I was trying to use it to drive 6mm endmills  cutting
steel. The problem is that high speed spindles have so little torque. Consequently you could only take the lightest of cuts and if
you over did it or your Gcode called for a plunge or similar temporary overload the spindle would stall. With the tool stalled but still
engaged in the material the XY movement would snap the tool no problems, my wee mill has near 500kg of thrust, 6mm endmills
don't stand a chance.
For this reason I monitor the VFD for excessive difference between commanded speed and actual speed to Estop in the event of a stall.
It works mostly, the VFD can take some milliseconds to signal a stall and so an Estop may occur too late to save the tool.

I have since made a servo driven spindle with 6.5Nm rated torque and solved the whole problem of stalls. Now I have enuf torque
to 'twist' smallish (less than 8mm) endmills off like a carrot!

Craig

I probably should've also mentioned I am also using a smoothstepper with the MB02 breakout board (Homann Designs).
I've attached the user manual for my breakout board, just in case you were interested.
For the most part, it's been a bullet proof system for quite a few years now, it's just this issue of tripping one drive, but continuing to machine, that rears it's ugly head every once in a while.

TaraK

Hi Tarak,
I use MB02's as well, I'm guessing you must be an Aussie whereas I'm Kiwi, either way Homan Designs is 'local'. In fact that's how I came
to suggest putting a diode in the circuit, I've blown the input buffer for just one pin on one of my MB02s. MB02s DO NOT accommodate
being reverse biased....nor are you doing yourself any favours by demanding that IOs either deliver or sink a great deal of current.

Depending on the actual IO MB02s are good for 24-32mA source and about the same sink. I personally like to keep it to 5mA or less. Having said that
I don't like to overload IO neither do I like it to loaf. In the example above I used a 5K resistor as pull-down, ie 1mA. I could have used a much
higher resistance, say 100k but the pull-down current would only be 50uA and therefore be subject to noise.

As garyhlucas has said the robustness of relays and the moderate voltages and currents used in such designs can prove to be a much better
performer in noisy environments compared to micro-power low voltage signals.

Craig

Hi Craig, yup sure am an Aussie.
I've had a good amount of success with the MB02, I only found that it was effected by noise a fair bit, until I set the debounce to 5000, then voila, all good!

TaraK