New to me Mill

[Rocket Man]

You should be able to find a manual online. I found my, Bridgeport mill, Reid #2 surface grinder, Churchill Lathe, manuals online. I have not used my surface grinder in 15 years it needs to be gone, I don't need it for the hobby stuff I do now.

 

[gsg]

Hello,
I used this inverter for a single phase Motor 230V 1HP and just removed the capacitor. I relized no differnce to a a 3-pase motor. All what you have to do is the installation of a fan, which I mountet just above the Motor fan in blowing direction to the motor. It is neccesary because the motor fan losses his airflow at lower rpm.
https://www.amazon.com/XCFDP-220V-2...lja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1
XCFDP AC 220V/2.2kw 3HP

Best regards from Munich
Guenter

 

[Richard Hed]

You should be able to find a manual online. I found my, Bridgeport mill, Reid #2 surface grinder, Churchill Lathe, manuals online. I have not used my surface grinder in 15 years it needs to be gone, I don't need it for the hobby stuff I do now.

Where do you live? How big a foot print is that surface grinder? How much do you want?

 

[roncohudd]

Hi Richard, You have got your sensible head on as usual. The lack of gears was what stopped me buying the converted mill-drill! But the guy was an Electrical installation guy, so didn't appreciate torque, speed and power.
On my recent motor conversion on the SL lathe, I need to make a 3 x diameter pulley to retain the full range of belt-geared speeds.
I am using the Variable speed control to get the rpm and torque suitable for the machine, as the new motor runs at 3 x the speed of the original, but lower torque.
K2

For my 2 mills I bought a 5 hp Baldor 3ph and mounted a 1/4 hp pony motor on top. Push button start then switch on. Plenty of power to run both mills at the same time.

 

[Sprocket]

I'm pretty sure this is the current version of the one I have on my mill. Had a previous one for 12 or so years before it finally died.www.wolfautomation.com/vfd-2hp-230v-single-phase-ip20/ . Maybe it's even the same one

I ended up getting a second smaller one to run the power table feed.
They have been working well.
(No connection to the company)
Doug

 

[awake]

I am asking because my only experience is with "Cheap" PM motor variable speed, where as the speed is reduced, the power (limited by the fan cooling of the motor!!) drops-off dramatically at lower speeds, and likewise the torque.

Hmm ... my understanding is that the torque is the same ... but because the speed is reduced, the overall power is reduced. When gears or belts are used to reduce the speed, the power is constant, but the torque goes up as the speed goes down.

 

[Steamchick]

Thanks Timo. One picture says it all!
Andy, my premise is to do with "Ohm's law", etc.... but as a mechanician, I sometimes gets electrickery all muxed ip!
This is my mixed-up idea of what is happening...
In a DC PM motor (the motor I have), the field is constant, so the motor interaction force relies upon the armature current to generate the opposing magnetic field, derived from B=NI, so it is linear with current. This force - multiplied by the radius, becomes the torque "at that current". Power is the product of torque and speed, so torque is Power divided by speed.
I assume the max. current doesn't change, because it is based on the impedance of the armature (=resistance, when using a variable DC supply?). - Is this the flat-line at below 3000rpm shown for torque on Tim's graph in post #18? OR is there a magnetic inductance to consider because the windings of the armature are rapidly being connected and disconnected in sequence as the armature rotates? (Different from Tim's graph, which I assume as an AC induction motor - with Variable Frequency deriving the speed?). How does this inductance change with rotational speed of the armature? - I can imagine that as speed increases, there is less time to develop full field (saturation?) in each winding before the armature switches it off, so the torque (mean force x radius) will drop off at higher speeds when the field-charging time becomes less than needed for max torque? This idea matches with my childhood understanding that (DC?) electric motors develop High torque at zero rpm, and the torque drops off with motor speed.
But do I need to understand any of this? Or is it as simple as
"My bottom line?" I.E.
My Unimat SL lathe with original motor - rated at 90W at 4000rpm => Torque = 0.0225 x 60/2Pi. Nm.
My new motor is rated at 500W at 12000rpm. =>
Torque =0.04167 x 60/2Pi. Nm. (too fast and too much torque).
So if I want to LIMIT the motor torque to the "original motor" value, I need to slow the motor by 0.0225/0.04167 => 53% of 12000rpm... so 6000rpm should be OK? (to not strain the lathe more than the original motor). Then I'll use the gearing to get the spindle speed appropriate for the turning job.... or will the different gear ratio then give me 1.5 times (6000/4000) the torque at the spindle - which could strain the lathe out of accuracy?
Sorry if I am asking the wrong questions in this thread, but it did seem to be looking at similar problems to mine?
Thanks,
K2

 

[timo_gross]

So if I want to LIMIT the motor torque to the "original motor" value, I need to slow the motor by 0.0225/0.04167 => 53% of 12000rpm... so 6000rpm should be OK? (to not strain the lathe more than the original motor). Then I'll use the gearing to get the spindle speed appropriate for the turning job.... or will the different gear ratio then give me 1.5 times (6000/4000) the torque at the spindle - which could strain the lathe out of accuracy?
Sorry if I am asking the wrong questions in this thread, but it did seem to be looking at similar problems to mine?
Thanks,
K2

If you gear down the speed to let the chuck turn slower and leave everything else same, you will increase the torque. (apart from friction losses)
That is the reason to use geared motors.

Now I am heavily entering the dangerous half knowledge area...
At least some motors (all?, I do not know) run more efficient at higher rpm than at low rpm. At high torque low rpm the motor produces more heat.

Some of the invertes adjust the current and the frequency. Some Inverter drives can limit the current ( as a result the torque) or run lower current if the desired speed is reached to save some energy. With that sort of more sophisticated drive you will be able to run slower with lower torque if that is desired.

Greetings Timo

 

[SmithDoor]

I finally snagged me a knee mill. Lagun FTV-1. Going to order a VFD , and a DRO next week.

The seller inherited it from his farther who bought it new. He is sure there is a manual ,but hasn't found it yet.
In the mean time I would like to move the ram, but not sure how it is locked.

I've loosened the two nuts on either side of the crank handle (red arrows) and it will not move. The ways are completely dry, So it has not moved in many years. Some way lube will be applied.
I got on Lagun's web thinking I might find date of manufacture. That web site sucks.
My serial # SE8511
All help appreciated.

I do not if you had Bridgeport mill in past. The sliding heat and rotating gives a reach on part without un-clamping of about 4 foot or more. Handy for some types of work.

The only downside to Bridgeport mills is tilting head will auto till on heavy cuts.

Dave

 

[Iampappabear]

If you go with a frequency drive, do yourself a favor and procure a Allen & Bradley PowerFlex 40, there is no other drive on the market that has the smooth power at low cycles like this drive. Lots available used on ebay and other similar sites.

 

[Iampappabear]

Milling machine purchasing is a classic of the statement "timing is everything" I purchased a "Supermax" Bridgeport lookalike which only needed a new drive belt for $500.00 sold it 2 years later for $2,000 and could probably got more if I had not been in a rush to sell.

 

[Rich N]

Hi. I bought a Maxmill 3Ph. 3Hp. mill and got a Westinghouse single phase input three phase output VFD to be able to run it. My mill is belt drive so I just run 60Hz all the time. Yes I lose 1/3 the HP, so, a full HP which puts me down to 2HP but I do not do heavy work just hobby stuff. A side note is I was able to pick up a 3 Phase South Bend "Fourteen" which has a variable drive setup that is weird, and just mounted the VFD on the wall with an outlet below it so I just change plugs between uses. I am a novice and this works for me. Best of luck with the new machine.

 

[Noitoen]

Torque on VFD controlled 3~motors stays constant over the whole frequency until line frequency. AC motors have a linear V/F curve so, when you run s 400V 50Hz motor at 25Hz, the motor will be supplied with 200V. if you want to maintain the torque up to 100Hz you would need to supply the motor with 800V without harming the motor except eventual problems with the insulation that was not designed for such high voltage. Anyway this is not possible with our regular VFD's.

What is possible is, running a 230V 3~ on a 400V VFD as long as you parameterize it as a 230 motor @ 50Hz. In this way, the motor will have a constant torque up until 87Hz where the motor is being supplied with 400V without damage. The motor will have 73% more power and the VFD must also be rated for this power. (This is the way I run my lathe with a 1500 rpm motor pushed to 3000 rpm @ 100Hz)

In the case of @Steamchick's question, on DC motors, the speed controller type is very important. Most controllers use some kind of phase control to reduce the voltage to the motor to vary the speed and at low speeds, the torque is greatly reduced. Some controllers will try to monitor the speed and compensate for the variable load and "try" to maintain the speed constant.

Better control of dc motors especially those with magnets or shunt windings, is achieved with PWM control. In this way, torque reduction at low speeds is minimum.

 

[Rocket Man]

Where do you live? How big a foot print is that surface grinder? How much do you want?

I am 30 miles south of Nashville TN right next to I-24. Surface grinder is about 3 feet square the table is about 4 feet long. Price is $1500. It works good I have it wired to 240 volts we can run it so you see it runs good.

 

[Richard Hed]

I am 30 miles south of Nashville TN right next to I-24. Surface grinder is about 3 feet square the table is about 4 feet long. Price is $1500. It works good I have it wired to 240 volts we can run it so you see it runs good.

Dang! If you were on the West Coast, It would not bge a problem. But Shipping from east of the MIssissippi has gotten prohibitively expensive. I bet someone closer will snap it up. I know I would if I lived within 8 hr drive.