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Author Topic: Spindle (AC Servo vs VFD)  (Read 3155 times)

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Offline Katoh

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Spindle (AC Servo vs VFD)
« on: November 07, 2016, 06:04:03 AM »
G'Day friends
Its being a while since visiting or contributing, Work seems to have a hold of my life at present leaving this good stuff on the back-burner! :(

I am close to finishing my Bridgeport mill conversion but have come to crossroad, I am examining the use of using an AC servo as the spindle drive instead of using the original 1.5hp induction motor VFD controlled, What I am asking is what advantages and disadvantages is there on using one or the other. I am also looking into this for my lathe which please forgive me I must update my build thread as it works tremendously well, but can be better as we all know in the threading area.

One other thing I came across was VFD feedback by adding an encoder to the induction motor shaft, now this sounds very interesting and could solve the threading issues but again would it be better to simply use a AC servo and have total spindle control, Maybe?

I also had a thought of using the servo on the mill as a C rotational axis only in deg mode, and by machining a planetary head that fits the r8 collet, I could rotate the head around x or y and using one of those cheap light weight spindle motors you could make a six axis mill easily, but the programming and concept is really playing with head and making me turn to drink ??? This might be a future topic, lets just start with servo or vfd as spindle?
« Last Edit: November 07, 2016, 06:06:07 AM by Katoh »
Cheers
Katoh

Offline Davek0974

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Re: Spindle (AC Servo vs VFD)
« Reply #1 on: November 07, 2016, 06:58:54 AM »
I have just finished this exact job on a Bridgeport ;)

I asked the same questions re servo or induction drive.

The overwhelming response and what i went with in the end is to fit a 3Hp induction motor, VFD and if using a CS-Labs controller like mine, throw in an encoder too.

This little setup gives me Mach3 speed control from 300 to 3000 rpm without using gears, rigid taping, and its much quite than the old vari-speed mechanical system that it replaced.

The thing with a servo is that it needs to be big to get proper torque and power input, big is easy but big AND fast is not  - they are £££££ and for little benefit as the BP has not got much chance of having an ATC so no need for spindle indexing.

Rigid tapping made it worth doing on its own :)

If yours is the normal BR2J head machine, I have a file for the adaptor plate if you want it that mounts a standard frame 3Hp face-mount motor. I used a Bosch VFD and braking resistor although I only have it stop in 3s as instant stop is a big strain on the old girl.

Belt was 30mm HTD 8 and pulleys were 1:1 ratio.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Katoh

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Re: Spindle (AC Servo vs VFD)
« Reply #2 on: November 07, 2016, 07:29:14 AM »
Thanks for the quick response  :)

Yes 2Jb head, mine is only 1.5hp model but cant see upping the hp as any great problem, I have already got rid of the veridrive system and am going to use a 1:1 timing bet in HTD 8m  but only a 20mm belt, already bought so I’m going to use it.
You basically answered all for me, maybe a new induction motor with encoder? do you have a link to the encoders? I have looked and found nothing on encoders but have discovered my VFD's don’t have encoder feedback, Bugger!
You also Have a low gear on the Bridgeport, or have you dismantled that?

Rigid tapping????? Using an Induction motor and VFD, Again ???? Will that work on a lathe too???

Sounds almost too good what you have done, Any drawings will be mighty appreciated, must also ask how did you set your quill drive up as well?

Thanks muchly!
Cheers
Katoh

Offline Davek0974

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Re: Spindle (AC Servo vs VFD)
« Reply #3 on: November 07, 2016, 08:24:36 AM »
All is in here, pull up a chair, its a long read :)

http://www.machsupport.com/forum/index.php/topic,32513.0.html

The encoder came from Zapp Automation, it does not connect to the VFD but to my controller, that is why i mentioned CS_Labs, the one i have is the CSMIO-IP/A with ENC module and MPG module add-ons. The encoder is not used for closed loop control - its used by the controller for rigid tapping.

The 3Hp is needed to get the torque down in the low speeds, the mechanical drive did a good job with this but as thats gone the torque is replaced by using a big motor, the 3Hp one had insane power at all speeds so was a pretty close match, its no bigger than the 1.5Hp I pulled off and sold on eBay :)

No idea about the lathe, sorry.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Katoh

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Re: Spindle (AC Servo vs VFD)
« Reply #4 on: November 08, 2016, 04:36:03 AM »
SH*TE
I thought some of my previous threads where long, Well done Sir! Lots of reading there indeed, only problem I like picture books, HaHaHa!

Wonderful job on your mill, I actually came across one of your Youtube Vids a while ago, But never really paid attention to it, thought what’s this Joker on about, but must say impressive build and some great ideas.
The terrible thing about this you have actually steered me in a different direction, with the CS LABS UNIT, when I first started I thought all these put together units where for people that cannot understand anything but plug and play systems, but I see now I’m having trouble keeping up considering I built my router in 2006, lathe in 2012 and started the mill the same time but the lathe and router are still going strong! Just simply So OUTDATED!!!

Question , The VFD you used does it have feedback, Or does feedback go back to your CS Labs Board? What CS board did you use? Also What Encoder Model did you use on your induction spindle?
I realise I could probably answer all this by reading the entire thread but the problem will be after the second page the mixture of dribble/wine or dribble/scotch will short out my keyboard and start fire and kill us all as I fall asleep reading, OLD MAN's DISEASE!
Cheers
Katoh

Offline Davek0974

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Re: Spindle (AC Servo vs VFD)
« Reply #5 on: November 08, 2016, 04:47:29 AM »
LOL

Heres the encoder...
http://www.zappautomation.co.uk/electrical-products/encoders-36/isc3806-001g-1024bz1-5l-1000-line-optical-encoder.html

the feedback only goes to the CSMIO - its only used for rigid tapping as i haven't managed to successfully close the speed PID loop yet but i am not sure if i need it really - the VFD is in sensorless vector mode and auto tuned to the motor and seems to regulate speed pretty well on its own.

The controller is CSMIO-IP/A plus ENC module and MPG module, a fantastic controller, really easy to work with.

The VFD...
https://inverterdrive.com/group/AC-Inverter-Drives-230V/Bosch-Rexroth-EFC5610-2K20-1P2-MDA-7P/
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Katoh

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Re: Spindle (AC Servo vs VFD)
« Reply #6 on: November 08, 2016, 08:11:52 AM »
You Sir are a Gentlemen!

Thanks for the info, no doubt I will go down my own path on this one like all the others, funny thing is my servos work on Step and Direction like a stepper control, mind you They have being sitting here for 3 years now. I would have to look at the IP/S to make it work as I bought 4x 0.75Kw servos back then, two I used on the X, Y axis,  Z is still in the making, but now I’m thinking the the 0.75kw maybe to large, might have to go smaller? or just keep them all the same for the hell of it.
The spindle Feedback looks excellent and not only do I want to use it on the mill but the lathe too.
My Dilemma
I have a smooth stepper unit here (new Ethernet style) that I was planning to use on the mill, but looking at the price and what you have done makes more sense both in functionality and economically. Maybe I use the smooth stepper on the lathe which is running twin parallel ports and go for an IP/S on the mill with all the bells and whistles, I don’t know, going into uncharted territory here.
Cheers
Katoh

Offline Davek0974

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Re: Spindle (AC Servo vs VFD)
« Reply #7 on: November 08, 2016, 08:19:25 AM »
Glad to help :)

The Cs-Labs stuff is top-notch, their help is also as good.

I have 700W on X & Y, 400W on Z but could have been smaller still i think - the ball screw gives a massive increase in torque.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Katoh

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Re: Spindle (AC Servo vs VFD)
« Reply #8 on: November 10, 2016, 01:46:16 AM »
Oh Dear I have being  swayed once more, Dave0974 you have just cost me a lot dollars! Not that its a bad thing some of this stuff looks mighty good.

I bought a new 3HP induction motor for the Mill AU$190 "can't complain there" I will as you did put an encoder on it and wish it all the best, but I have kept the low gearing in the head for low speed threading or what ever.

The lathe on the other hand I decided to go with a 2KW AC Servo and use it both as a Spindle and a rotational  Axis around Z. My headaches start here but I will start a different thread for this one, this is where the dollars start rolling out the door or through the phone line? Au $650 for a 2Kw  2500RPM Servo with encoder and cables, delivered to the wonderful land of OZ, shipping is expensive but the witch only flies here on alternate twisters. Thinking of using a direct drive with timing belt and slight reduction of 1.25:1 will give me a top end speed of 2000rpm but still should grant me enough torque down around 100pm to thread.

I sent an Email to the chaps at CS-Labs just asking the question,  do I use the IP/A or the IP/S as I am new to Servos, and also a question  when using the threading module can I use the reduction gear of the Bridgeport and still have feedback even though its motor feedback not spindle, but yet to have a reply, maybe I simply confused them with my questions?

I know my drives can use both step/direction or the analogue 0-5v input, but the analogue refers only to constant velocity not so much positioning, maybe I’m wrong here, its my first time playing with servos, steppers are a walk in the park compared to this.

Thanks Muchly

Cheers
Katoh

Offline Davek0974

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Re: Spindle (AC Servo vs VFD)
« Reply #9 on: November 10, 2016, 02:14:03 AM »
Money seems to be the biggest down-side to this fun ;)

The motor will be good, i kept the gears too.

I know nothing of cnc lathes so can't comment here but AFIK step/dir servo is pretty much as easy as a stepper system.

I think, that when using ENC for threading it must be reading the spindle direct so after any gearing etc. but as i said i am not sure.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives