Fingers crossed it'll cut ally

[blackburn mark]

your right jonathan, i meant a helli ESC in govenor mode... iv switched it off, i read somwhere that it would hold revs under diffrent loads, sadly, no joy on that one, its just a slow wind up to speed to stop all the power stripping gears betwean the motor and the main helicopter rotor... maybe it will hold revs when it is flat out?

on the brighter side, my motor has enough power to drill 10mm holes through 40mm of alli without getting particularly hot :) the ESC gets a bit warm though but nothing to drastic... fingers crossed

that motor you have would be wasted as a router !! it may even be over kill for milling alli on your 3 axis... id stick that one on a bike and start doing wheelies up and down your street and use a similar size as mine to mill alli, i really cant see my 3 axis out performing a 2000w spindle

ps: you get extra points for getting your holes wrong on a CNC :) yeeeee Haaaaaawww !!!

[Jonathan]

on the brighter side, my motor has enough power to drill 10mm holes through 40mm of alli without getting particularly hot :)

Is that without a pilot hole? i.e. removing a 10mm diameter cylinder? If so that requires roughly 310W (at 'reccomended' rpm). What rpm did you use?

that motor you have would be wasted as a router !! it may even be over kill for milling alli on your 3 axis... id stick that one on a bike and start doing wheelies up and down your street

Yeah, I bought it to put on my bike, but that's not happened. I'm thinking of replacing the pathetic motor on my sieg C3 lathe with it. I still think it'd be good on my router for aluminium.[/QUOTE]

ps: you get extra points for getting your holes wrong on a CNC :) yeeeee Haaaaaawww !!!

I think I got a dimension slightly wrong, either that or I should have used a bigger clearance hole in the first place.

A long time ago in this thread I mentioned a method of controlling the ESC from mach3 using the spindle PWM output....so I thought I'd give it a go.

Basically I connected the ESC up to my normal radio system on the model car and used multimeter to measure the duty cycle, and frequency, of the signal at neutral, full reverse and full throttle. I measured 45.6Hz and 5%-6.7%-8.5%. That's a bit annoying as it's only using a small range, but nevermind.

So then in mach3 I ticked 'PWM control', 'Use spindle motor control output' and set 'PWMBase frequ.' to 46hz, and finally set 'Minimum PWM' to 5% (i.e. full reverse).
Then on the motor outputs tab I enabled the spindle and just set the step pin to the one I wanted (in this case pin 2).

Then I went to Config-->Spindle pulleys and set the max rpm to 1000 and left the rest. (more on why I chose 1000 rpm later)

Next I connected multimeter to the parallel port pin to check it was outputting the right frequency, and that the max voltage didn't exceed 5v since more would damage the ESC. Both were fine (I'm using laptop to test, which probably explains the port being 5v) so typed in 'S100 M3' to set the spindle moving at 100rpm. That way if I use the override slider 100rpm corresponds to 10% duty cycle, or more usefully 67rpm is 6.7% ... i.e. neutral.

Now I set it to 67rpm connected one of the parallel port ground pins to the black (ground) wire on the ESC signal connector, and pin 2 to the signal wire (the other side of the 3 pin connector). Esc initialised fine, so I upped the spindle speed a little with the override thing in mach3 and the car promplty shot off the desk :exclaim: and drew briefly half a kilowatt from the battery.
Connected it back up, and yes it works fine.

There's one issue though, at the moment 67rpm is motor stopped, and 85rpm is full speed - in this test 85,000rpm!

I think in my case I'm not going to be too worried about sending the motor backwards, so clearly I can use the forwards only setting on the ESC which makes things a bit simpler. You'll find the duty cycle values for your ESC will be slightly different - use my neutral (6.7%) as a starting point and you can do the normal calibration thing on the ESC to set the endpoints.

I'm sure with a bit of fiddling I should be able to get the RPM values in mach 3 to correspond to actual motor RPM, I'll have a think on that one and let you know.

Hope that helps, ask me if something isn't clear...

PS It took me a grand total of two bits of wire stuck in the parallel port to do this - you MUST check that the parallel port doesn't output more than 5V (5.1 in my case but that's close enough). If it's more then use a couple of resistors as a voltage divider to reduce it. Either way I strongly advise optically isolating the thing.

[blackburn mark]

What rpm did you use?

i didnt clock the revs... just dailed until it was cutting sweet, less than 1000rpm id guess

[blackburn mark]

Is that without a pilot hole? i.e. removing a 10mm diameter cylinder? If so that requires roughly 310W (at 'reccomended' rpm). What rpm did you use?

haha! no chance! im using an old pc power supply at the moment thats probably only putting out 300w on 12v, besides that i cant get the levarage to drill 10mm in one go... im using one of my linear slides up-ended with a live centre attached just to guid me in straight :)

if i push the motor hard the pc power supply trips out... iv got a 12v 30a supply and two 12v 45a power supplies but iv not got around to sorting them out and as im getting by with the one im using iv percivered with it... the large motor dosnt get warm at all... the ESP worries me now and again, its a turnigy 85a so im thinking the heat is normal

Yeah, I bought it to put on my bike, but that's not happened. I'm thinking of replacing the pathetic motor on my sieg C3 lathe with it. I still think it'd be good on my router for aluminium

im thinking of buying another of the larger motors i have to run my cowels 90 lathe, it knocking on a bit now and the motor bearings are a tad noisy

Some nice research there Jonathan!!!!!!!! im going to have to pick your brain when iv absorbed what you have up to now... sounds like your nearly there, it would be a winner if it can be sorted... im still on the mechanical side of things at the moment but another week or so and i should be mounting my steppers and wiring the whole thing up

iv built a low profile pc out of my scrap box that im fitting into the base, im just hoping the hard drive can handle a bit of vibration

[Jonathan]

Double post...

[Jonathan]

I remember trying 12mm drill with 5mm pilot hole in steel on my mill ... at 2150rpm as I couldn't be bothered to change it. That was fun, but right at the limit of the motor.

Anyway I've concluded that there's no way to get mach3 to read the actual motor rpm with this method, so instead you're going to have to use the following formula I just worked out to convert.

Spindle rpm = (u*x-v*Kv*L)/(u-L)

Or rearranged for x:

x=(rpm*(u-l)+v*kv*l)/u

Where:
u=max duty cycle, so in my case 8.5.
L=neutral duty cycle, 6.7 for me.
v=voltage to motor
Kv=motor rpm/volt
x=rpm mach 3 reads out
rpm=actual spindle rpm
(formula simplifies nicely once you've got the values, tell me what they are and I'll do it for you in Excel if you like)

For that formula to work you need to set the 'Max speed' in 'Spindle Pulleys' dialogue to:
v*Kv*100/L

So for instance with the 7700kv motor I was testing with earlier, on 11.1v ... that's 11.1*7700*100/8.5 = just over a million rpm. Putting that value in means that if you put the correct max rpm of your motor in the spindle speed, then the motor will spin at that speed. It's only true for the max speed though, for other speeds you need to use the other formula.

More to follow, my posts are getting long...

[blackburn mark]

7700kv motor

youll be able to drill holes in alli with a human hair at that speed!!!!!

its a shame its so complex... (it is to me)

im sure i read somewere that the servo tester pot might possably be removed and driven by mach but no more was said about it... any chance of you casting your skills on that one jonathan?? :)

[blackburn mark]

Maybe open up your servo tester and take a picture...

dont know if you will make any sense out of these... its just a magic box to me

i do have a mulimeter but the pc with mach on it is in bits ready to go in my base but i will take you up on the offer of help when i get to that point in the build, iv only had a quick play with mach up to now.

iv just orderd a "MICRO MAESTRO 6-CH USB SERVO CONTROLLER ASSEMBLED" £12 ebay
im not sure if it will solve our mach spindle problem but i thought id give it a punt

im hoping mach will know what to do with it :question:

[blackburn mark]

micro maestro 6-ch usb servo controller

[Jonathan]

Ok disregard that, just had another look. It should be simple to get the servo tester connected.

:idea: Here's a step by step guide.

1. Remove the potentiometer, or just desolder the pin connected to R32.
2. Solder a wire to the pin of R32 that was connected to the potentiometer.
3. Connect the other end of that wire to the chosen output pin on the parallel port...say pin 14.
4. Solder a wire to the negative of the circuit board, e.g. pin labled '-' on connector JIN, and connect it to any ground pin on the parallel port.
5. Set PWM frequency in mach3 to something high, like 1000.
6. Under Config-->Spindle Pulleys set max speed to the max RPM of your motor.
7. Cross fingers...it should work as normal with the rpm show in mach3 corresponding correctly.