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VFD for M-Head Bridgeport. need advice.

garyd

garyd

Aluminum
Joined
Sep 29, 2004
Location
Connecticut
I have a M-head mill in my shop. it is a step pulley driven head and for this reason I cannot get slow enough speeds for some boring operations. I understand that a VFD ought to be able to provide a speed reducing capability along with phase converting. The fine points of power management are not among my strong points. Will this particular VFD get the job done for me?

Variable Frequency Drive, MYSWEETY AC 220V/2.2KW 3HP 10A VFD Inverter Frequency Converter for Spindle Motor Speed Control (1 phase INPUT and 3 phase OUTPUT)

Variable Frequency Drive, MYSWEETY AC 220V/2.2KW 3HP 10A VFD Inverter Frequency Converter for Spindle Motor Speed Control (1 phase INPUT and 3 phase OUTPUT) - - Amazon.com

Gary
 
You are looking at 3 HP VFD's, but I am pretty sure the M heads were shipped with much lower power motors. The one I owned had a 1/2 HP motor. A smaller VFD would probably cost less and there are 1 HP and smaller VFD's that run on 110 V single phase, making wiring pretty easy.

Larry
 
VFD for M-Head Bridgeport. need advice.

Thanks for the reply Larry.

All my machine motors are three phase. I run a 220 1PH line to a dynamic phase converter that provides three phase to a circuit that powers the machine motors (six of them). The M-head has a 1hp motor powered by this circuit. I would separate the M-head from the 3ph circuit and install the VFD between it and a single phase 220 feed. The VFD listed on Amazon is a bit of over kill.

The first question is this, will a VFD (any VFD?) provide a reduced (adjustable) spindle speed for my mill? If so, how does it do this? Is there a power penalty etc? The second question is will the VFD linked to provide this utility for me?
 
VFD stands for variable frequency drive. Induction motors run at speeds determined by frequency, which is 60 HZ in the USA. The motor nameplate will tell the RPM of the motor at 60 HZ. If the VFD is set for 30 HZ, the motor will run at half speed. At frequencies below 60 HZ, the motor will have constant torque. Power of the motor is a direct function of torque and speed, so half speed will give you half nameplate power.

At very low frequency, most motors will not run smoothly. That, together with the very low power at very low frequency, means boring performance will suffer if you dial the frequency down too much. So yes, the VFD will slow the motor, but there will be a practical limit for you to discover by trial and error. You will still probably find it advantageous to use the step pulleys for various jobs.

Larry
 
Thanks Larry;

Appreciate the advice. Looks like if need be, I could "step up" the pullies to a higher mechanical speed and use the VFD to slow the motor to the needed speed. it'll take some trial and error.
 
Not sure you wrote what you meant to say, but you'd want to have more reduction between the spindle and the motor (smaller pulley on motor, larger on spindle) then run the motor faster than 60Hz for higher speeds. So "step down" to a lower mechanical speed.

garyd said:
Thanks Larry;
Appreciate the advice. Looks like if need be, I could "step up" the pullies to a higher mechanical speed and use the VFD to slow the motor to the needed speed. it'll take some trial and error.
Click to expand...
 
Drives like this run the motor in constant torque mode below nameplate speed, and constant horsepower mode above nameplate speed. This means at lower speeds you will not lose torque but will lose power: P = speed x torque. One thing you want to be sure is the VFD you purchase can be run in "sensorless vector" mode which can provide full smooth torque down to around 10 Hz speed. Also it helps to have the drive with an "auto tune" capability where the drive 'learns' the system details with that particular motor, pullies, and spindle all together.

I've used one of the Hitachi drives and am impressed with their performance. Teco's not bad also.
 
It is a good idea to get one of those Chinese VFDs rated for twice the power of your motor. Chinese vendors are famous for taking shortcuts and building stuff out of random often underrated parts. These units are programmable, so you want to limit the max output to match your motor so you don't fry it. Should work otherwise.
 
Bottom line when it comes to casual VFD conversions of anything with a conservative motor fit with a decent power margin over what would normally be needed :-

Operating over ± 1/3 rd of nameplate speed "just works". Especially with a decent vector drive type.

Operating over ± 1/2 of nameplate speed usually works just fine on a vector drive system but you may need to dig into the book to find the "torque boost" setting if you run high loads at the lower end of the speed range. Old style Voltage - Frequency type drives can struggle over this wider range.

Going further away from nameplate its time to put your engineers hat on.

As Jim says good vector drives can run remarkably smoothy at low speeds. But the constant torque nature of the drive means the actual power output may not be particularly useful in the context of what the machine was made to do and motor sized for. CNC machines, VMCs in particular, tend to have much larger motors than manual machines of similar capability simply to maintain the necessary torque at lower speeds.

Clive
 
FWIW if you can't download the manual to verify the VFD will do what you want, pass it up. Most of us use analog buttons for start/stop, reverse, and a potentiometer for speed control. I have a Chinese VFD that the schematic indicates a 10v control voltage circuit, but the manual doesen't have any analog settings. I use it direct input, on an M Head as it happens, but don't like it. Had a used ABB that worked great until the 10v control circuit died.

Can't offer any additional information on low speeds, other than the issue of low speed torque often comes up on converting a Monarch 10EE to AC & a VFD
 
I bought a Frejoth mill a Fe months ago just for drilling holes and boring out end bells for electric motors.
It is a beefy mill, and I don't have to take the vice off of my main mill that had digitals and power table feeds.
The VFD for it is a cheap one from Amazon. It converts single to 3 phase, and I can slow it down to real low RPMs if boring out a large 6" bore.
This has been a real advantage for me.
If the VFD craps out, I'll buy a better one. But for now it'll do and pay for the mill and itself quickly.
It doesn't seem to lose any torque, either.
 
garyd said:
I have a M-head mill in my shop. it is a step pulley driven head and for this reason I cannot get slow enough speeds for some boring operations. I understand that a VFD ought to be able to provide a speed reducing capability along with phase converting. The fine points of power management are not among my strong points. Will this particular VFD get the job done for me?

Variable Frequency Drive, MYSWEETY AC 220V/2.2KW 3HP 10A VFD Inverter Frequency Converter for Spindle Motor Speed Control (1 phase INPUT and 3 phase OUTPUT)

Variable Frequency Drive, MYSWEETY AC 220V/2.2KW 3HP 10A VFD Inverter Frequency Converter for Spindle Motor Speed Control (1 phase INPUT and 3 phase OUTPUT) - - Amazon.com

Gary
Click to expand...

I have this VFD running a 1 1/2 hp 2x72 belt grinder. It has all the usual analog options for external start/stop, 10k pot speed control, forward/reverse. It's also quieter than my other VFD.

That said, the manual is terrible. If you know how to set up a VFD, and all you need is program codes, it's fine. If you have never set up a VFD, it will test you.

The schematics are very basic, and some of the manual isn't even translated to english.
 
I can't be bothered with cheap Chinese electronic junk, and fight all the issues, and hope I can figure it out.
Look out for a brand name, like Hitachi, Teco, etc. I get great support from Fuji engineers directly by phone (1 have 5 of them).
Make sure the VFD output current, when supplied by single phase, is equal or more than the motor full load current. (When VFD's are supplied by single phase, they need to be down-rated).
Good luck,
Bob
 
On my M head round bar Bridgeport I use an ABB VFD the motor is a 1/2 hp 3 phase i come off my CB panel with 220 30 Amp double pole breaker. ABB manufactures a great product, a little more expensive than the Asian throw away stuff but worth it to me. For what it is worth Good luck
 
L Vanice said:
You are looking at 3 HP VFD's, but I am pretty sure the M heads were shipped with much lower power motors. The one I owned had a 1/2 HP motor. A smaller VFD would probably cost less and there are 1 HP and smaller VFD's that run on 110 V single phase, making wiring pretty easy.

Larry
Click to expand...

Those VFDs typically also output at the same line voltage. How would a 220 motor feel running on that lower voltage ? Can the higher frequency compensate for it ?
 
I have a Teco on a 3hp lathe. It is not in a production setting. I got it because 3ph power isn’t available and I don’t want 2 electric motors running (roto-phase). I like it a lot. Motor wires up directly to it. Can program it to cushion the start and stop, and dial the cycles. I have a start/stop switch connected to it via the low voltage control circuit. There are others for remote speed control but I just set that up directly on the vfd panel. Really a nice setup, I think it was under $200, rated for 3hp. 220 single phase input.
 
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