VFD milling question

A question for those running milling machine spindles from a VFD, do you tend to leave the mill in one gear/ belt position, and use the VFD to control speed, or do you find it necessary to still swap belts/gears for certain jobs.

Edited By Alan Waddington 2 on 02/12/2016 21:54:20

Installed an inverter on my (smallish) mill about six years ago and haven't touched the belts since!

I installed an inverter on my Chester Eagle 30 and it remained on single speed for long enough until I had reason to go even faster.....even though the inverter was set to 75 hz rather than 50...

All depends on what you are doing.....

I certainly don't change belt ratio nearly as often, but if working a large cutter hard at lower speed I will switch to a low ratio. This is on a VMB with the central pulley eliminated so have a 4 step cone pulley on motor and spindle. Fitting 3 phase motor and vfd has transformed the machine, also a link belt helps. Much smoother and quieter.

I have VFD on the lathe, pillar drill, and milling machine and I do change gear/belt ratios sometimes.

'Sometimes' in my case is about twice a year!

Ian P

Cooling can be compromised at low speed settings, unless the motor has separate cooling arrangements.

It would be common sense to change gear, rather than drop too low on motor speed, if long continuous heavy cutting at low speed is required.

Seriously overspeeding the motor can accelerate wear or lead to premature failure.

Some motors are more susceptible than others. Maybe think Chinese, as more prone to these possibilities (those built down to a price with 'looser' windings and lesser quality bearings).

I leave mine on the fastest belt position most of the time but change to the slowest if I need really slow speed, for example using a slitting saw.

I uprated the motor power by 50% at the same time to give better low speed torque.

Russell.

My CNC mill has a VFD and two belt selected speed ranges. I rarely use the lower range, as I run most cutters at 2000rpm and above. However, if I do need to run at lower rpm then below about 2000rpm I use the lower range to keep the motor roughly in the constant power area above base speed.

Andrew

The reason for my original question was the VS head on my Beaver is a bit rattly, so I'm weighing up if it would be worth doing away with the VS gubbins, and making it a direct belt drive running from a VFD. It still has a backgear, so i would still have high/low ratios to play with.

The other alternative is to strip and rebuild it, however unlike Bridgeports i doubt spares will be available at any cost. Thoughts on a postcard please.

I have a Centec 2B which has a 3*2 speed box, which is sort of 3 speeds plus backgear. I leave it in the middle ratio in the 3 speed box most of the time, but use the backgear if I've got a big flycutter on and so need slow speed. The VFD and 3phase transformed the machine, the old single phase motor made the cabinet vibrate and produce a very lod noise, Very much better with 3 phase.

I've fitted VFDs to the spindle and power-feed of my Centec 2B and now wouldn't be without it. I've changed the gears only a couple of times over the years, most notably to get the highest possible speed for a tiny cutter, but normally I keep it in the middle gear. With finger tip control of both speed and direction, I even use it for power tapping.

I've also fitted VFDs to my lathe and pillar drill - well worth the effort, in my opinion.

For the benefit of beginners and those new to MEW, might it be better to expand any terms used in our Headings? I know what a VFD is, because I have got one, but I didn't when I hadn't.

Such abbreviations are also a problem for those whose first language is not English. I know of no dictionary which translates VFD ...

Just a thought, so TTFN

Tim

I just simply entered 'vfd' into 'goggle' and guess what? Yep, it recognised it and all the first umpteen hits were in context or close to. I can understand that some acronyms need further explanation, but this one is very well used. The only thing I initially wondered about, was whether the poster was referring to a specific machine without maker's name included.

.

... Then pemit me to introduce you to: **LINK**

http://acronymfinder.com/VFD.html

MichaelG.

Seems sensible to use the acronym. If people don't know what it means, they're unlikely to have one, and equally unlikely to be able to offer practical experience, as asked for. Ideally it weeds out the pontificators.

Andrew

Slight update, it sprang to mind that i already have a VFD running my lathe, it's only 2.2 kw so wouldn't be any good for real work as the mill motor is 2.2 kw, but i figured it should run the spindle quite easily with no load.

Wired it up and ran the mill, to discover to my embarrassment that the back gear was engaged (engagement lever works opposite way to what i thought) hence the rattle when running from my undersized rotary converter yesterday.

Knocked her out of back gear and the head is virtually silent throughout the high range......result I thought it was weird, as i heard the mill running on true 3 phase when i bought it, and never noticed any undue noise, although the machine was outside at the time.

I'm now shopping for a 4kw inverter to run the spindle motor, and a titchy one to power the 1/3hp table feed motor.

Thanks for all the replies, much appreciated.

For the benefit of M Gilligan, a translation is not spelling out the multiple options in English of three letters. it is giving an answer that would be understood by a Frenchman, or a Ukranian, or a Brazilian.

Tim

For the benefit of Tim Stevens: Frankly, I don't care for your opinion ^^^

... except that I would like to see you do that in a Thread title.

[and please don't stop at just three Nationalities]

MichaelG.

Seems perfectly sensible suggestion to me, otherwise you risk leaving the reader in the dust. Take this example of VFD usage from Wordnik:

'We slept at my place after it happened, and for the rest of the time we were in town, because he said he never wanted to look out of the window at the VFD again'. This could be about a Model Engineer upset because his Variable Frequency Drive broke and he can't bear to see it smouldering by the dustbin. Somehow I doubt that, and, once confused, I will waste time decoding the meaning.

Dave

It would have been easier to say Inverter.