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Author Topic: Mach 3 outputs 15hz to vfd instead of 0  (Read 309 times)

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Mach 3 outputs 15hz to vfd instead of 0
« on: July 11, 2019, 02:43:50 PM »
Hello there,
i am using mach 3 which is talking to my VFD via the Controller card. Everything was ok until today. now when i set the RPM to 0 in mach 3 and when i press F5 to start the spindle the minimum Hz is 15. It doesnt go below that. I dont really know what the problem is. I tried the synch spindle feature but things got worse instead of better. I am driving it with 0-10 Volts signal. When i switch off the mach 3 control and use the potentiometer and the VFDs own start/stop button, then everything is ok. 0 corresponds to 0. It seems that it needs to be set up in mach 3 somehow?
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #1 on: July 11, 2019, 02:54:07 PM »
Hi,
the most likely explanation is that Mach3 or your BoB doesn't quite go all the way to 0V.
With a multimeter measure the 0-10V signal and confirm the range it actually achieves, especially the bottom end.

Note that is  not correct to stop the spindle in Mach  just by specifying zero speed (S0.00). You should use M5 because
this opens the ON/OFF relay. If you rely on S0.00 any noise or linearity fault could cause the spindle to turn unexpectedly
because the relay is still ON. This could have injurious consequences if you were doing a manual tool change.

Craig
« Last Edit: July 11, 2019, 03:00:41 PM by joeaverage »
My wife left with my best friend...
     and I miss him!
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #2 on: July 11, 2019, 03:04:55 PM »
If i press F5 in mach 3 the spindle turns off completely. Im not relying on the 0 rpm, i understand that it can go off on its own.
I tried now the Multimeter and the BoB is receiving 0,33v when its on 0 rpm in mach 3. Any clue?
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #3 on: July 11, 2019, 03:23:29 PM »
Hi,
the most likely explanation is that Mach3 or your BoB doesn't quite go all the way to 0V.
With a multimeter measure the 0-10V signal and confirm the range it actually achieves, especially the bottom end.

Note that is  not correct to stop the spindle in Mach  just by specifying zero speed (S0.00). You should use M5 because
this opens the ON/OFF relay. If you rely on S0.00 any noise or linearity fault could cause the spindle to turn unexpectedly
because the relay is still ON. This could have injurious consequences if you were doing a manual tool change.

Craig

Excuse me i was wrong. The BoB is actually sending 0.33V to the VFD and not the VFD to the BoB. It has a constant voltage on the Terminal Pin...
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #4 on: July 12, 2019, 04:01:41 AM »
Hi,
while its not perfect it is about what I would expect.

PWM is quite hard to achieve if you must also have perfect 0% modulation simultaneously with perfect 100% and linearity.

If your demands are that stringent then you should consider a step/direction servo and matching servo drive as a spindle.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #5 on: July 12, 2019, 05:30:18 AM »
Hi,
while its not perfect it is about what I would expect.

PWM is quite hard to achieve if you must also have perfect 0% modulation simultaneously with perfect 100% and linearity.

If your demands are that stringent then you should consider a step/direction servo and matching servo drive as a spindle.

Craig

Hey Craig,
The thing that  only bothers me, i have made the enclosure myself this was my third attempt and this time i nailed everything.
Now the electronics are playing around.

But i can live with thar i guess :)

Can you tell me more about the recommendation of yours with the servo as a spindle? A could imagine that the servo would be perfect for milling metals aswell, since it can operate at low rpms.

You have more info on that?
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #6 on: July 12, 2019, 06:29:23 AM »
Hi,
I made a miniature bed mill. I fitted a 750w German made 1 pole pair asynchronous spindle motor and 400Hz VFD
for 24000 rpm. In my naivety I thought it would cut steel. It can cut steel but only with really small tools, less than 3mm,
and very light cuts with coolant. Its tediously slow.

Asynchronous spindles tend to have low torque and especially so at low rpm. I'm happy with my spindle, it does all the PCB
stuff that I want and it will do aluminum , brass, bronze etc with smallish tools, say less than 6mm, with coolant at 12000 rpm
or so. What I wanted was to be able to spin 16mm tools in steel. That requires much lower rpm and much higher torque.

I ended up buying a second hand 1.8kW (4 pole pair, 3500 rpm) Allen Bradley AC servo and matching drive. I got lucky and
was able to buy off the New Zealand auction site and got for  $900NZD ($630USD) delivered. I still had to get the cables
(specialized) and I bought the set up software so all up I paid about $1000USD for it. I matched that with a Swiss made
Rego-Fix ER toolholder and NSK P4 angular contact bearings and made my own spindle. Its great, it has 6.2 Nm continuous
and about 18Nm overload. It chews up steel and stainless like its going out of fashion.

This was my first real experience with modern AC servos....they are just that far advanced over any other motor.
You can run them with analogue voltage much like a VFD, called velocity mode. You can also run in torque mode so that
the motor produces a torque proportional to the analogue voltage applied irrespective of motor speed. I imagine that
would be real handy in printing equipment or conveyor type applications.

If you want tight control you run in position mode. The controller produces step/direction pulses and the servo and drive
can achieve VERY TIGHT and ACCURATE position control far exceeding any stepper in terms of accuracy and overload.
You can also use this mode to drive a spindle in free running mode which produces EXCEPTIONALLY TIGHT LINEAR speed
(and position control to the order of 2 arc min) control. Rigid tapping is possible.

I highly recommend you get yourself a modern AC servo, even just to experiment with. I know you will find as I did
that the control options, flexibility, torque density will blow your mind. You'll never buy another stepper ever again!

Craig
« Last Edit: July 12, 2019, 06:31:15 AM by joeaverage »
My wife left with my best friend...
     and I miss him!
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #7 on: July 12, 2019, 06:44:01 AM »
Yep thats probably the way to go since i really was thinking about the same idea some time ago. Will probably buy one for testing and from there i will see.

You just gave me an idea for my next project ;) thanks!
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #8 on: July 12, 2019, 06:58:05 PM »
Hi,
good AC servos and drives still command a price premium over asynchronous motors/VFDs and steppers/stepper drives.

I would commend you look at DMM and Delta if buying new. Good quality at very reasonable prices. There are even cheaper
Chinese brands, often made to look alike Delta servos, even using the same or similar part numbers. Don't be deceived.

http://www.dmm-tech.com/index.html
https://www.deltaww.com/Products/CategoryListT1.aspx?CID=060201&PID=23&hl=en-US&Name=ASDA-A2+Series

DMM is  a Canadian company and enjoy a good reputation for support. They manufacture in China and that is how they can
sell at the prices they do. If you want a spindle motor then you'll be looking at their 1kW, 1.3kW and 1.8kW models. Note these
three models have a rated speed of 1500 rpm and a maximum speed of 3000 rpm. You may well consider that 1500 rpm
will require a belt or gear reduction/increase to match spindle demands.

Delta is nominally a Taiwanese company and have been in the business of servos and VFDs for many years.
Their flagship servo models are the A3 series. They have a 24 bit multiturn encoder....very flash, but not really required
for hobby use. The A2 series I have linked to is the previous generation and is very suitable. They have 17 bit and 20 bit
encoders.....more resolution than you can shake a stick at. In the range 1kW to 2.2kW (the largest practical size for
single phase 230VAC input supply) the low inertia models can be had with rated speeds of 3000 rpm (4500 max)
and medium inertia models at 2000 rpm rated.

Just beware the some Chinese merchants have even earlier models which are by no means bad but they lack the functionality
you really want. Beware also that there are 'look a like' servos out there and despite their price you don't want them.

The other alternative is second hand. I have had a good run with my unit. I have become familiar with the Allen Bradley
range and can recommend them. For instance this is on Ebay:

https://www.ebay.com/itm/Allen-Bradley-Servo-Motor-MPL-A430P-HJ23A-Marked-A42099/113211316441?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Its 2.2kW but note the rated speed, 5000 rpm and continuous torque of 6Nm. Very Very useful as a spindle motor.
It needs to be matched with a servo drive and you can't go past the Ultra 3000 series.

https://www.ebay.com/itm/Allen-Bradley-Ultra-3000-Series-C-Digital-Servo-Drive-for-Servo-Motor-Used-Good/311641997971?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

This is the DSD-020 model, really a little undersized but fairly readily available at reasonable prices.

https://www.ebay.com/itm/ALLEN-BRADLEY-ULTRA-3000-2098-DSD-030-DN-1PH-120-240VAC-30-PEAK-SERVO-DRIVE/223556432252?_trkparms=ispr%3D1&hash=item340d00717c:g:Ya4AAOSwkHxcRTxo&enc=AQADAAAB0KX%2FKt4E1xf3SDqEdBclaYaKy9QPwpoy5ZyVplcr3WY8dFWZDBfEaedWu%2BGcWwgfKJQ2i9CoDEZB3QU5L8a%2FsDDqzAbDB0NpXGqrbfFEsqzLHXpk%2F1pq%2Fum4mVp7NEZfYdG0zl23prr43GnIY3D4jT4jfQb0qNum0HccefoPeBwzsAhobIHwBJqmr085CnFPECQ5wdh5pTXBCz4aV3RxOPNOZ34aSMY3uYB9krMdalJBYxAv3WnqXK4wlHqCJFbpAK1Hc8P8EuIEAM6hW5YzY2tjXr7fQHVC0I2mxO4atQURW1T6657AKxix7WvaHVW9DHtzA4rz5ssWY1R2nEDrA2KiyeyJlR5gKTl38SvogtaiBXL35AEB%2BBpLjm35VF%2By8C2%2BfDAz2ABxLL0fYm0O13k6d7NpbjTk5gvGgUsG%2BtJea8TPkUva7%2FVRS3%2FTvFZ3qHlMohkQPu%2Bzo3Y2TYaUsvyKqbtI5sKaHh%2BYDI8h6MjBKSKoPHgN9A9R2kUGzVJEFoTHHym%2BpRuHSwkfDIeyaYdruSKhCZCXwnwKnsvZMkaYYnYfSWRMnQ4g%2B5RO2I1OORZxM7tn6jHa4gF5VlRF9LZamm9mdVkWx80ctVxZK32W&checksum=2235564322521774c7050596450d987ef57856c7c7e9

This is the DSD-030 model and is the biggest 230VAC single phase input servo drive I know of. Somewhat harder to find
especially at a good price but perfectly matched with 1.8kW, 2.0kW and 2.2kW MPL-A********* series servos.

As you can see you pay a very distinct premium for Allen Bradley servos even second hand. They are on the other hand very
good quality. In general European, Japanese and US made servos and controllers are very expensive. You will pay as much
and more for second hand as you will for new DMM or Delta.

As I said earlier I was lucky to find a 1.8kW Allen Bradley servo AND DSD-020 servodrive for a very good price. Maybe if you
troll Ebay you too will find a good deal.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach 3 outputs 15hz to vfd instead of 0
« Reply #9 on: July 13, 2019, 04:32:19 AM »
Thank you for your time to weite such a informative post. I will take a look into those.