[JerryFlyGuy]

Ok, I'll keep this short and sweet, I'm building a gantry style mill/router. I've become concerned about the noise that is going to be generated by a router style head. I don't want the neighbour's or the wife complaining.. and I too.. would like to sleep through the night w/ out the noise of a router screaming away for hr's on end. I did some searching on here and read much about how quiet a VFD style drive is. I've heard an VFD in operation and it was nearly silent. However it wasn't milling anything at the time.. just the motor turning. I'm interested in setting up a VFD and spindle on my gantry, however I don't want a HUGE wart on the side of my z axis. I hope to advance to a 5 axis head design at some point and don't want to have a huge motor and spindle etc all mounted the the B/C axis of the mill. Anyone done a decently compact VFD and spindle which can generate some router like [ 10k] rpm's in at least 1.5+hp. I don't mind spending some cash on it if it's what I need. A good quality router is several hundred $$ anyway so.. double or triple that and I get a great VFD that is software controled and I'm a VERY happy camper.. I'm asking for the moon you say?? Their's no point is shooting for less is there??

[2muchstuff]

One manufacture that comes to mind right away is Kavo.

[Bruggles]

You could also look into a dc motor with a speed control. The speed controls can be very good, and do the same thing as a vfd, but the frequency isn't changing since it is dc. The benifit of this would be that the motor could be much smaller for the same horsepower and from what I understand a dc motor has more constant torque through the rpm range. Just something to think about. If you do decide to go with a VFD and an ac motor, ebay seems to have good deals on vfds with all sorts of features, but like you say the motor will be huge.

[Al_The_Man]

The down side to the DC motor is the rpm limit, 2k~3k unless you gear up and then this means a larger motor, If you want 10k+ rpm's and VFD then you have to go with the high quality high frequency 3phase spindles, they can be run off of single phase.
Al.

[2muchstuff]

Who says motors have to be huge.

http://www.kavo-drives.com/english/p...pindeln_ac.asp

Housing diameters from 25.4mm to 60mm
Power output from .15kw to 1.4kw
RPM up to 80,000

[Al_The_Man]

Who says motors have to be huge.

Thats the one's I meant, compact 3 phase.
Al.

[NC Cams]

DC motors and "constant torque". Hmmmm. I dunno about that???

Many of the torque curves I've seen for PM and the few shunted DC motors I 've seen have linear but not "constant" torque output.

That is, the torque curve is pretty much linear in that it consumes peak current and outputs peak torque at stall and puts out min torque at min current draw at free rev/no load condition.

Constant power and constant torque are NOT the same...

HP = torque x rpm /5252

where torque in ft-lb and rpm is rpm.

1 Hp = 745.7 watts.

1VA = 1 watt

A bit of math will enable you to draw power curve if you have torque and rpm...


A PWM speed control applies peak voltage at a chopped pulse width - either full on or full off. A 40% duty cycle on results in 40% rpm but peak torque while current is flowing.

[2muchstuff]

See I'm not as useless as the wife says. I do on occassion remember things. :banana:

[JerryFlyGuy]

http://www.kavo-drives.com/english/p...pindeln_ac.asp

2much thanks for the link! This is EXACTLY what I was looking for, now I just have to figure out what kind of money and where to get them.. Being as they are made in Germany.. I'm thinking their gonna be pretty pricey but that may be ok if it does what I want!

I'll keep ya'll posted as to what this ends up costing.
I'm not terribly excited about having to run water cooling to the spindle but if thats what I have to do.. then so be it.. I just hope the water doesn't leak in the echain beside the rest of my electrical stuff

Jerry

[Bruggles]

More constant torque was what i said, not constant torque. But that three phase motor looks like it would be an excellent option, I was just giving some ideas.

[walter]

The down side to the DC motor is the rpm limit, 2k~3k unless you gear up and then this means a larger motor, If you want 10k+ rpm's and VFD then you have to go with the high quality high frequency 3phase spindles, they can be run off of single phase.
Al.

Can I add one question? I`ve seen dealers selling small 3 phase HF spindle with 3 different drive options: 120v 1 phase input, 240v 1 phase input and third one was 3 phase input. Same spindle. I`m wondering about spindle performance, power, etc when using these 3 options. Any differences? Please explain.


Thanks

[JerryFlyGuy]

Walter, I'll take a stab at it.

As I understand it, there are three ways to power the same motor, as you've stated. What happens is, each power style is connected to the HF drive which then will convert this power [ if its of a single phase variety] over to 3 phase and then transform the power level to the level it desires. Then it outputs the HF power to the motor in three phase. In the case of 115v single phase, the drive would convert it to three phase and [possibly] send this 115v three phase power to the motor. In the case of 240v single phase the driver [ most likely a different driver from the 115v listed one] would transform the power down to 115v, then convert it to 115v three phase and send it to the motor. In the case of a 115v or 240v three phase input, the drive would either just control the Hz of the AC to the motor for speed [ in the case of the 115v] or transform the power down to 115v [in the case of the 240v three phase] and control the Hz of the AC to the motor for speed.

In short, the driver takes the power you give it, and transforms and converts it to the power style it needs to run the motor. In all three cases the motor still runs on 115v three phase. { I'm assuming this as for every motor it could be different}

Hopefully that clarifies.. not confuses

Jerry

[walter]

Thanks for the reply.
So basically there would be no performance tradeoff when using any of three drives? I think I`m lacking some vere basic electrical knowlege...

[trevorhinze]

This might be along the lines of what you are looking for, but it is up to allmost a grand with less than a day left. Good Luck.

http://cgi.ebay.com/PRECISE-HIGH-SPE...QQcmdZViewItem

[JerryFlyGuy]

Thanks for the reply.
So basically there would be no performance tradeoff when using any of three drives? I think I`m lacking some vere basic electrical knowlege...

Yup, thats my understanding. Basically the motor can only use so much power regardless of how it gets it. I'm sure one of the styles would be more effecient than the others, but I don't know which one

Jerry

[JerryFlyGuy]

This might be along the lines of what you are looking for, but it is up to allmost a grand with less than a day left. Good Luck.

http://cgi.ebay.com/PRECISE-HIGH-SPE...QQcmdZViewItem

No kidding.. looks great, however It doesn't tell ya anything about the power needed nor the power output and I have no idea if that would be a good price or not.. Kinda buying in the blind at this point. Not to mention its sat for 5 yr's according to the seller.. I wonder how the bearings would be after sitting that long..??

Jerry

[ger21]

How about one of these belt drive spindles, with a cheap 3 phase motor and a VFD?
http://www.finleyspindles.com/50-13-spindles_desc.htm

[JerryFlyGuy]

Gerry, that also would work. The catch is if a person can get some decent RPM and power, yet small motor's. Anyone know of any small 3phz motor's that can put out 2hp and 10k RPM?

Jerry

[ger21]

Yeah, you don't want to hang a huge motor off of it.

[drk]

Hi,

I have been using Kavo and other HF spindles for a while now.

As for Kavo, they are very expensive I would say. A small 150 watt spindle alone can cost upto 1500 euros and another 5-800 for the drive.

I would suggest you pick up an 80K rpm Quietdrill ( 1 Hp) spindle refurbished from Jevco for about $900, should be as good as new and you can drive it straight off a Danfoss VLT 2800 series drive at about 60K rpm.

Some issues you could have is that the spindle comes with a 1/8" collet and is watercooled as compared to some of the Kavo spindles.


Best of luck