[durbinmachine]

I'm considering adding a newer vf-1 or 2 to my shop (non ss model), currently I have a 97 vf-2 with the gear box. I've looked at a few of the newer vector dual drive machines and was wondering what are the limitations of these machines compared to their gear box equipped brothers. Does anybody have both a gearbox and dual drive machine in their shop? If so your opinions would be greatly appreciated.

Thanks!

[Donkey Hotey]

Vector dual-drive is simply on-the-fly switching of the motor windings between wye and delta wiring. It increases torque at lower motor RPMs. You can still get a gearbox or not, depending on what you order. I think ALL of the Vector Drive mills (everything but the Toolroom mills) have dual-drive wiring.

[HuFlungDung]

I'm not really acquainted with what wye and delta switching does in 3 phase motors.
What is considered 'standard configuration'?

Does it have to do with number of 'poles' of the motor being doubled or halved?

I've gleaned over time that a 4 pole motor is probably standard for 1725rpm motors, and has the maximum torque available, and that you'll never get 'more torque' than a standard motor by wye/delta switching, but you might enjoy more speed and less torque.

So if you are used to a gearbox machine and have applications that need the increase in torque, then a dual drive without a gearbox is not likely a valid substitution.

I might be wrong, so school me if you know better

[durbinmachine]

The difference is 75ft lbs (dual drive) vs 250 ft lbs (2 speed gear box). Ideally if someone has both in their shop or has run both types I would really be interested in their opinions/experience between the two.

Thanks for the responses.

[Donkey Hotey]

My opinion is that one has more torque than the other and costs more. What exactly are you wanting to know? Drawbacks? Yeah, cost.

I've bought two machines with the two-speed gearbox and have no regrets. Unless I absolutely needed a spindle with more than 10K rpm, I wouldn't order a machine without it. If you're talking about used machinery, then it's all about what you can live with or without.

Cutting aluminum all day? You can live forever without the gearbox. Cutting titanium where you want to cut deeper, and harder but with low RPM? You aren't going to do it on these machines without a gearbox unless you work with small parts, small tooling and low material removal rates.

[Donkey Hotey]

I'm not really acquainted with what wye and delta switching does in 3 phase motors.
What is considered 'standard configuration'?

You'll have to wait for Geof to chime in on this one. I can't remember the traits of each wiring option. I've got a book on industrial motors around here somewhere that explains all of it but, I don't remember.

[Ydna]

The motor itself contains windings that can be configured as either delta or wye depending on how they are wired together. If you want low speed you'd wire it as high-voltage wye, alternately high speed would be low-voltage delta. The CNC can switch the two at its discretion which is ultimately what yields the machine's torque curve. If it were a manual machine you'd be tasked with wiring the motor to your power source depending on whether you had 240(3) or 480(3).

The on-the-fly winding switch combined with the vector drive is what gives the machine high torque even at super low speeds (down to sub-100 RPM speeds). It's why the CNC torque curves look odd even if there is no winding switch, like on the TM's (if I recall correctly).

I'm no expert, just filling in a few gaps here and there....it's interesting to see the level of control we get even with a so-called "budget" CNC machine like this.

[Geof]

You'll have to wait for Geof to chime in on this one. ...

Do I gotta?

Al The Man is really the font of wisdom on motors but I can fumble up a bit of an explanation. Four pole single phase does indeed give 1725 rpm and two poles gives twice that.

Three phase needs multiples of three (I think) but the principle is the same, double the number of poles and halve the rpm for a given frequency.

Switching poles like Haas does in their "Vector" drive gives a larger useable rpm range with better torque at each end of the range. Note I put "Vector" in quotation marks because really it is just marketing bumpf and doesn't really mean anything.

Here is the way I understand dual drive.

Changing the number of poles is a bit analogous to changing gears in a car. We all know that gasoline engines, and diesels to a lesser extent, have a limited rpm range in which they produce acceptable torque so it is necessary to choose the correct gear to match the load with the speed. An electric motor driven at a variable frequency is something the same. When the frequency is high to make the motor run fast the voltage has to be high to push enough power into the motor against the impedance created by a high frequency so the torque drops off. Conversely when the frequency is low not much impedance is created so the voltage has to be lowered to avoid shoving too much current through the motor. By switching the number of poles the rpm range is increased. At low speeds the motor runs on a multiple of three poles and goes through the useful frequency range. Then it switches to half the number of poles so the rpm for each frequency is doubled and the top rpm is increased.

[durbinmachine]

You guys are gettin a bit carried away here, all I want to know is how does the non gear box machines compare to the gearbox equipped ones, If I got a non gearbox machine would I be limited to only cutting aluminum on it? I'm a job shop so I don't know whats coming in next. I cut anything from plastic to 17-4 stainless.

Has anyone owned or operated both types of machines? did the non gearbox ones come up short anywhere?

[Geof]

Hang around and you will see us get even more carried away.

I don't have gearbox machines but my understanding is that they are needed for really good low end torque such as is needed for running big facemills with a healthy cut. My VF2s will poop out running a 2" facemill in steel and are not capable of taking the cut and feed you need for best tool life.

Similarly if you plan on driving taps, especially taper pipe thread taps into steel at any size above 1/2 you need the low speed torque that a gearbox gives.

[Donkey Hotey]

I'm a job shop so I don't know whats coming in next. I cut anything from plastic to 17-4 stainless.

Why didn't you post that in the first place? Buy the 10K spindle with the 2-speed gearbox. I bought it on both VF series machines I've purchased for exactly the same reasons: don't know what's coming and don't know what it'll be made of.

Now can we get back to delta-wye wiring?

[Pondo]

I had a 2001 VF-3 with a 15K direct drive spindle. It could barely drive a 1/2-13 tap in HRS plate but nothing bigger.
I used it 95% of the time on aluminum and plastic though, and it was brilliant on that.
If you use smaller dia mills and keep the RPM up (HSM techniques) you can get decent metal removal rates. It may take a little bit of rethinking the old ways though.

[durbinmachine]

I had a 2001 VF-3 with a 15K direct drive spindle. It could barely drive a 1/2-13 tap in HRS plate but nothing bigger.
I used it 95% of the time on aluminum and plastic though, and it was brilliant on that.
If you use smaller dia mills and keep the RPM up (HSM techniques) you can get decent metal removal rates. It may take a little bit of rethinking the old ways though.

I'm old school, I like my corn cob roughers. I'm not really up to speed w/hsm. Seems like alot of wasted motion to me, but if the mrr is higher than conventional methods maybe it aint so bad after all.

Sounds like the machine you were running was an SS model?

One machine I'm looking at is a VF-2D with 7500rpm and no gear box. Maybe I should wait till a gearbox machine comes up. Not many available right now.

Thanks for getting back on topic

[Web.eng]

I run a VF5 with the geared head and a VF1 with direct drive. Both machines are 20Hp 10000 rpm. The VF1 is usually only used on aluminium and the odd mild steel job so is fine but the VF5 is mainly used on 316 grade stainless and does a lot of tapping. I use it for tapping upto about 20mm x 2.5mm in stainless which the direct drive machine would not do. If i were to buy another machine I would definately buy the geared head machine as it is so much more capable than the direct drive machine. It really depends on what you want to use it for. In a jobing shop the geared head machine wins hands down in my opinion. For what it's worth, I would also buy the side mount tool changer.

Regards,
Dave.

[Ydna]

FWIW I second the idea of a 10,000-RPM spindle with gearbox, if you have the cash to float it. It's certainly a relatively expensive double upgrade but you do get a good mixture of both worlds. We're running that setup on a VF-2.

Myself I wouldn't get a gearbox if I were running as much non-steel jobs that I do, but it makes life easier when tool steels come into the work envelope, that's for sure!

[Pondo]

One more thing to consider - the 2 VF-4's I ran at my last job were 100% reliable EXCEPT for the gearboxes. The only time they were down were for gearbox related problems in the 7+ years I worked there. One needed a completely new gearbox, one was down twice because it would not shift into low gear. The VF-3, VF-0, and my current Minimill are all direct drive and have had 0 issues mechanically.

[KenFoulks]

I agree with the encouragement of obtaining a mill with a 10k and a gear box (GB), but if you do not have a GB, here are some tips. In addition to HSM techniques, there is tooling that can compensate for a lack of GB. For example, instead of tapping; use thread milling. You can also use better tooling and different tool paths. Instead of 1" corn cob at .25" DOC 1" WOC, use a 3/4" 5-Fl at 3/4" DOC and .1" WOC with a trochoidal tool path.