Lathe repowering

[Susquatch]

I forgot to include a Wiki link. Ctrl-F the word 'output' & there are many examples across various industries, even among motors & engines. No debate about Output vs Input (efficiency), I'm just saying I see many examples of watts referenced on the output side. Its actually quite common in compressors where input relates to gross heating value of NG mass (or whatever fuel) which derives back to Joules over time, but the equivalent imperial units are ultimately interchangeable. I agree, the nameplate specs on many of our machine motors are largely ambiguous.

Its really a dogs breakfast isn't it! I remember an effort by the auto industry to standardize on HP and Torque Ratings. We engineers were all on the same page, and wanted to create a standard to stop the marketing guys from abusing the data to drive sales. Essentially HP sells and torque doesn't. Too many requests to rejig the data and too much BS amongst the media. We got nowhere beyond an industry wide engineering agreement.

Doesn't 'brake' (output power term) date back to the handle / engagement mechanism on the output shaft from back in the day? Might even come rom locomotive days pre ICE days? Where is AI when you need it haha.

That is my understanding too but today it is a term that refers to a dynomometers ability to hold (brake) an engine across its full range of operating conditions. This can be full load output or partial loads for tuning purposes.

The problem here, like so many other fields, is common language, common test methods, and common standards. They do exist, but just like automotive, the marketing guys gotta sell product. It's also a lot harder to get the global electric motor industry to agree on things. You have all these standards that they do agree on and then this motor manufacturer on Mars says no way I wanna do it like this and there is nobody to stop them. (Insert big sigh here)

We machinists need to use our own good common sense. As I said earlier, the difference isn't big enough to quibble over.

 

[Ironman]

This helps me to understand why I am confused anyway
On another note, Yesterday I turned a hub for a fan. I was able to reduce a 1.5" HR steel rod to 1.25" in one pass with no effort and the amp gauge hardly changed 2 points. Then I parted it off with the new P-type blade I bought, and modified a holder for.
Got to say I am happy on both counts. I would have never known about the P-type without this forum.

 

[Susquatch]

John Deere apparently understands better than you do,

I didn't know that you are qualified to know who actually understands this better...... Frankly, that's an offensive way to say that Trev.

Better words that are less offensive to me would be to leave out the part about them knowing better than I do and simply point out what John Deere says which appears to contradict what I said.

Please don't lump yourself in with Deere to back your views while throwing me under the bus......

as they list the outputs of their tractors in both Watts (OK, kiloWatts) as well as HP as representing the same measure. Not the first time in history that the same unit name has been co-opted into several different and varied meanings, making the context in which it is used, fairly much key to understanding what folks are ACTUALLY talking about.

Deere, like many other engine manufacturers actually use a dynomometer to measure output horsepower. Their motors are not (yet anyway) electric so they can't measure input power. They can only measure output. Regardless of whether that is done with an electric brake or a water brake, they measure the output and then publish those numbers in both units - KW & HP. In both cases, they are outputs so they convert exactly.

Interestingly though, there is a lot of debate about tractor output power in the agricultural equipment community. There are significant efficiency losses between an engine and a PTO. Many manufacturers list both and some list only one or only the other. Why is this? Fundamentally, PTO output is more meaningful for DRIVING Impliments, and engine out is more meaningful when PULLING Impliments. Now go talk to farmers and see what they think...... LOL!

Engine power, PTO outputs, etc. I kinda lean away from the idea that they are in any way doing jiggery-pokery with the math, to try to define the output power via electric motor equivalents... You? Still? LOL!

Trust me on this Trev, THEY ARE PLAYING JIGGERY POKERY. We can agree to disagree on that but I stand very firm in my knowledge that they do.

I don't do either one. I speak all languages quite fluently. As long as one understands the big picture from an engineering thermodynamics perspective, it really doesn't matter.

Maybe give the itch a scratch, sit down and learn a thing or two about the system the REST of the world attempts (because really, legacy measures will ALWAYS be with us!) to use to make sense of stuff!

Again insulting Trev. Best to just not say stuff like that. It does no good at all to the subject at hand.

FWIW, when I last had some instructor droning on about Horsepower, it was defined fairly well as a measurement of the ability to do work over time, same as wattage of electric systems. Just measured in different units, supposedly to provide some semblance of universality (which it pretty much failed at, IMO, else there would not be fun convo's like this one happening!

You might as well have been listening to me drone on. I taught Thermodynamics in University to undergraduate engineers for many years. Your memory of it is good. There is zero difference between watts and HP. Both are different units of the exactly the same thing and they convert exactly between each other. As long as you define the system parameters correctly, they mean the same thing. The nuance I have been trying poorly to explain is the difference between input and output. For electrical systems, it is very convenient to measure input, for engines it is more convenient to measure output. But input and output are different depending one what the system between them is all about. That was my initial quibble and still is.

But perhaps I should not have been such a perfectionist.

 

[trevj]

I didn't know that you are qualified to know who actually understands this better...... Frankly, that's an offensive way to say that Trev.

Better words that are less offensive to me would be to leave out the part about them knowing better than I do and simply point out what John Deere says which appears to contradict what I said.

Please don't lump yourself in with Deere to back your views while throwing me under the bus......



Deere, like many other engine manufacturers actually use a dynomometer to measure output horsepower. Their motors are not (yet anyway) electric so they can't measure input power. They can only measure output. Regardless of whether that is done with an electric brake or a water brake, they measure the output and then publish those numbers in both units - KW & HP. In both cases, they are outputs so they convert exactly.

Interestingly though, there is a lot of debate about tractor output power in the agricultural equipment community. There are significant efficiency losses between an engine and a PTO. Many manufacturers list both and some list only one or only the other. Why is this? Fundamentally, PTO output is more meaningful for DRIVING Impliments, and engine out is more meaningful when PULLING Impliments. Now go talk to farmers and see what they think...... LOL!



Trust me on this Trev, THEY ARE PLAYING JIGGERY POKERY. We can agree to disagree on that but I stand very firm in my knowledge that they do.

I don't do either one. I speak all languages quite fluently. As long as one understands the big picture from an engineering thermodynamics perspective, it really doesn't matter.



Again insulting Trev. Best to just not say stuff like that. It does no good at all to the subject at hand.



You might as well have been listening to me drone on. I taught Thermodynamics in University to undergraduate engineers for many years. Your memory of it is good. There is zero difference between watts and HP. Both are different units of the exactly the same thing and they convert exactly between each other. As long as you define the system parameters correctly, they mean the same thing. The nuance 8 have been trying poorly to explain is the difference between input and output. For electrical systems, it is very convenient to measure input, for engines it is more convenient to measure output. But input and output are different depending one what the system between them is all about. That was my initial quibble and still is.

But perhaps I should not have been such a perfectionist.

I am sorry you took my comments as insulting. Not meant to be worse than maybe, considered tongue in cheeky, but I guess I missed that mark. I was taking a minor poke at your seemed position that wattage could ONLY be used to express an electrical power rating. Apologies for any offense. I had thought the smiley would have been enough to point out the tone it should be taken in...

On the tractor horsepower front, one guy said it along the lines that the problem with horsepower, is that horses come in so many different sizes! Little ponies with their legs just a-flying, all the way up to Clydsdale-plus sizes. We have progressed somewhat from when you looked at tractors based on how many plow blades they were rated to pull! Somewhat, anyways.

Honestly, beyond comparing like to like (say, buying a replacement 3600 RPM rated gas motor for a lawn tool), most of the manufacturers horsepower ratings are pretty much just fit for estimating where they fit in that makers lines of products, rather than a precise picture of what you get. While an Engineer may run the math and calculate out exact requirements, in use, there is always the fly in the ointment that determines whether the life span of that installation is going to be useful, or barely adequate.

 

[Susquatch]

I am sorry you took my comments as insulting. Not meant to be worse than maybe, considered tongue in cheeky, but I guess I missed that mark. I was taking a minor poke at your seemed position that wattage could ONLY be used to express an electrical power rating. Apologies for any offense. I had thought the smiley would have been enough to point out the tone it should be taken in...

Ya, you missed that mark. But I accept your explanation. We are good Trev.

For the record, I NEVER said

that wattage could ONLY be used to express an electrical power rating.

If I implied that, I need to fix it. Both wattage and hp are perfectly acceptable units for all forms of power. They are both only different units of measure for exactly the same thing. Can you point out where you think I was saying that so I can fix it or at least make the message clearer.

 

[trevj]

If I implied that, I need to fix it. Both wattage and hp are perfectly acceptable units for all forms of power. They are both only different units of measure for exactly the same thing. Can you point out where you think I was saying that so I can fix it or at least make the message clearer.

Posts 14 and 18 were the ones that left me thinking that you were stuck on Watts being only suitable as input, and electrical measure.

FWIW, that was my read anyways.

Context issues on my part maybe. Happened before, likely gonna happen again.... LOL!

 

[mbond]

It should be noted that input for induction motors is often quoted in terms of VA (volts * amps). This should be equivalent to Watts, but is quoted this way to imply power factor (impedance of the motor) so that the correct size of wire can be readily determined (take the A number and go to the chart). Its kind of the same way that AC voltages are typically quoted in RMS (root mean square) units so that the power can be quickly determined by multiplying Volts and Amps - ignoring the time factor. The peak voltage is root 2 times larger, but it comes and goes as the voltage alternates.

It should also be noted that AC induction motors produce 'zero' power unless they are under load. Power is generated as current is drawn through the motor as the armature lags the rotating magnetic field. That lag also produces the torque (or moment) because the angle between the magnetic fields produces force at a distance. They increase in lock step until the armature 'slips' out of the magnetic phase - and the motor stalls.

 

[trevj]

It should be noted that input for induction motors is often quoted in terms of VA (volts * amps). This should be equivalent to Watts, but is quoted this way to imply power factor (impedance of the motor) so that the correct size of wire can be readily determined (take the A number and go to the chart). Its kind of the same way that AC voltages are typically quoted in RMS (root mean square) units so that the power can be quickly determined by multiplying Volts and Amps - ignoring the time factor. The peak voltage is root 2 times larger, but it comes and goes as the voltage alternates.

It should also be noted that AC induction motors produce 'zero' power unless they are under load. Power is generated as current is drawn through the motor as the armature lags the rotating magnetic field. That lag also produces the torque (or moment) because the angle between the magnetic fields produces force at a distance. They increase in lock step until the armature 'slips' out of the magnetic phase - and the motor stalls.

Pretty much the origin of "Sears" horsepower ratings on shop vacuums. For a BRIEF instant, just before the circuit trips out, or the motor fries, that is the figure that they used to calculate the so-called HP of the Shop vac! Certainly not getting there using the accepted wattage calcs, on a 120v 15A breakered circuit!

Electric motors can be both fun, and very frustrating things to have to deal with, if you do not understand the way that they will draw current, right up until they are running as they see fit to, or the current supply is tripped or exceeded, or the windings simply melt. Makes trying to replace a IC engine with an electric motor a bit of a challenge for folks that don't understand the differences in power delivery and torque that are the respective natures of each type of power. A lot in common with the problems relating to the example above, of a 6HP rated diesel with 47 ft/lbs of torque on tap, vs the Honda, with the same hp rating, but only 6 and a 1/2-ish on offer. Different sized horses were used, apparently! LOL! The math don't lie though, provided you can get reasonably accurate measurements of inputs or outputs, and compare like to like, IMO.

FWIW, one of my 'longer-term' projects has been a repower of my Colchester 2500, with a lower HP 3PH motor. IIRC, it was a 5HP, 575V unit that was in there, and I have a 3HP 220v 3Ph motor and VFD to use as it's replacement. As I will never be expecting the lathe to work for a living, I am firmly of the opinion that it will work just fine for me!

 

[mbond]

There really is too much here for a few forum posts.

IC engines are much more complex. Both 2 and 4 stroke engines produce and waste power when not under load. But they also produce torque first (force applied at a distance) to the shaft, and power second - limited by the geometry of the piston and shaft layout and the fact that not all cylinders can produce torque (power) at once. Common layouts like inline 4, v6, v8 seek to even out the production of torque (power) as well as reduce the amount of mass (weight) moving in different directions - which make vibrations as well as unexpected gyroscopic effects. Rotary designs are inherently more efficient, but greatly increase these gyroscopic effects. The various sorts of jet engines avoids most of these limitations but are obviously much more complex.

Electric motors are generally of 3 kinds

DC motor
AC induction
AC synchronous

By far the most common for machine tools are the AC induction motors.

There is way too much here

 

[Ironman]

Now that the lathe is on steroids, I have been really enjoying it. Seems smoother and quieter, and serious power even when turned down to a crawl. I threaded a 7/8x14 thread with a tap and it turned it effortlessly, until the threaded part started to slip in the jaws.
I most commonly use the two gears that give me 140 in low and 750 in high range. Well, this morning, I grabbed the laser tachometer, and found at 60 hz that it was turning at 189 and 1040. To get the speeds embossed on the headstock, I had to drop down to 47 hz. I don't suppose it matters much. I have never changed the sheaves since I got it and they are still original, and there is not any room for anything larger.
I have been using DC injection braking, and it was ok...
I have come to the conclusion the Injection is nice but I'd rather be blown. I had bought a 16 ohm 1000 watt resistor for the mill and have avoided putting it on, so I temporarily hooked it up the the lathe VFD and dropped the decel down to 1 second....and yes, from 1040 rpm to 0 in one second. Very nice. Did the start stop thing 10 times looking for heat in the resistor, and could not detect any.

This means I have to spend another $40 for a second brake resistor now.

 

[Susquatch]

I temporarily hooked it up the the lathe VFD and dropped the decel down to 1 second....and yes, from 1040 rpm to 0 in one second.

Wow! I'd be afraid of stripping a gear. Is that using the e-stop or regular decel?

I am getting close to swapping a bigger 3ph motor into my lathe and this subject has been haunting me. It would be nice to separate the two functions so the lathe stops fast when I hit the e-stop but stops more gently when simply turned off.

 

[Ironman]

Wow! I'd be afraid of stripping a gear. Is that using the e-stop or regular decel?

I am getting close to swapping a bigger 3ph motor into my lathe and this subject has been haunting me. It would be nice to separate the two functions so the lathe stops fast when I hit the e-stop but stops more gently when simply turned off.

It is not a crash, it is braking, and it is smooth. There is a belt drive to the gearbox that also absorbs shocks. I once experimented with my gearhead DP and set to 0 seconds...that was a crash and I thought I had done damage, and that was just DC injection.
It may be possible to separate the brake systems, one of the factory techs may have an answer. As it is hard to run my watch and the VFD simultaneously I may be off a second in my button pushing, but I am happy with the stops. Still have to hook up the terminal switches. I often turn my lathe on and of checking progress and measuring, especially when sneaking up on a final bore measure. It is nice not to have to watch it spin down very long like when it was single phase.
I'd like to try a video but the system probably won't allow it.

 

[Susquatch]

It is not a crash, it is braking, and it is smooth. There is a belt drive to the gearbox that also absorbs shocks.

Ya, it's not a crash. But lathes have a lot of inertia - especially with a heavy chuck and a heavy part. I think it's entirely possible to break a tooth someplace stopping too fast. Yes, the belt helps.

FWIW, I also think that inertia could be a problem upgrading to a bigger motor on a lathe. That's why I like the idea of programming in a slow ramp acceleration on a VFD.

 

[Ironman]

I think you are worrying too much about inertia in a 3 hp. You know your machine and may have reason for worry.
With respect, quoting from Practical Machinist:
A few years back, there was a nasty machine shop accident at a nuke powerplant. A contractor's millwright had chucked an Acme threaded valve stem in an American Pacemaker geared head lathe to polish it with emery cloth. He was wearing rubber gloves (whether the stem was "hot" or not I never found out). The millwright wrapped the emery cloth strip around his rubber gloved hands and started polishing the threaded valve stem. Predictably, the lead thread grabbed the emery cloth. Just as predictably, the friction on his rubber gloves and the fact he had wrapped the emery cloth around his hands figured into what followed. The emery cloth and the attached millwright (millwrong ?) got wrapped around the valve stem just that quick. Another man saw what was happening and got that lathe stopped. The millwright had a major destruction of one shoulder and arm. Upper management in my own employer's house decreed all lathes would be retrofitted with some kind of emergency brake or junked.

What I did on our bigger lathes was to convert to programmable VFD's. These have a braking feature. The normal program is for a controlled deceleration/braking. We added emergency stop (mushroom type) buttons that lock in and must be reset. These are wired to the programmable VFD's to apply full braking effect. It is almost instantaneous. We've tried it once on each lathe ( a LeBlond that swings work 60" over the cross slide x 24 ft between centers) and a LeBlond NK series that is 25 x 96. We never tried it with a job in the lathes. I did try to tell corporate that lathes never had emergency brakes and it was up to the machinist to be aware of what he or she was doing and be careful. No dice, the word was put brakes on the lathes, so we did the best we could. On the smaller lathes, we used eddy current brakes and emergency stop buttons to energize them while droppng out the motor contactor.

I never saw a brake on a lathe in my life until this particular incident happened.I really never saw a need for a brake on a lathe, and I've been around engine lathes of one sort or another since about 1965.

My accel is 4 seconds if I remember correctly. I may experiment and slide the decel up to 1.5 and see how it is.
The E-stop button, when I get the time to wire it, will disconnect the com terminal which which shuts down any operating direction. Don't think it will change the braking at all.
I am using latching push buttons forward and reverse, one push on, one more push off. If the E-stop is hit, and then released, rotation would resume, unless you pushed the stop button before unlocking the E-stop. May need a sign to that effect.
That is the one dislike I have over not having a latching relay, but if any one hits the emergency they are going to be trying to unwind themselves or remove a cutting tool from the chuck first.

 

[Susquatch]

I think you are worrying too much about inertia in a 3 hp. You know your machine and may have reason for worry.
With respect, quoting from Practical Machinist:

I think you misunderstood me.

No need for worries or respect. I get the need for e-stop vs braking. If you read my very first question you will see that is what I asked you about.

I'm not worried about broken lathe gears in an emergency. If it saves my life or someone else's, break some gears! I am only worried about regular routine stops.

There are thousands of injuries just like the one you quote. Shit happens. That's what an e-stop is for. But I want my routine F/N/R to be more gradual.

Regarding your plans, I'd be careful about shunting the output of a VFD through contacts of any kind. They don't generally like that. Let the VFD decide how to do it within its own control systems.

I think you are worrying too much about inertia in a 3 hp. You know your machine and may have reason for worry.

It is entirely possible that I am worried about nothing. But keep in mind that my lathe is currently a 2Hp single phase system. Converting that to a 3Hp 3Ph motor is adding a lot of power into the system. Most lathes see their max power usage during the starting wind-up. So that's what the gears are designed to handle. Going to 3Hp 3Ph is adding at least 50 more load to the gears during startup than they were likely designed for. Programming in a slow start looks after that.

My worries whether warranted or not are that regular repeating stops done at max decell would be just as bad or worse than an uncontrolled startup.

I'd rather be safe than sorry.

For e-stop though, I want it stopped as fast as possible.

Right or wrong, that's my thinking on the matter.

 

[John Conroy]

FWIW the Teco 510 vfd's that I used on my lathe and mill have 2 different program selections for braking parameters. Setting #14 gives "rapid stop" and setting 15 gives "base block". The rapid stop decel time is adjustable. Base block is another term for coast to stop, no dynamic braking. I use base block when the mechanical brake is employed on either machine so that the deceleration rate is totally controlled mechanically.

 

[Dabbler]

For those listening in, Around the greater internet e-stop has two meanings. One is as is used here, as an emergency 'fast stop'.

In the *old* TECO documentation, and around the internet, the term e-stop is also used to describe an condition where there is an electrical problem. In that case, you wan to shut down the electrics/electronics which leads to a coasting stop as the VFD is shut down into a safe mode and all power is removed.

In the new TECO L510 documentation, there are several programmable stops - I'm currently programming one for a member here - You can program a 'normal stop' 5-10 seconds, and other far more rapid stops. A rapid stop will heat more than just the resistor, as the electronics get a little toasty also. It heats them the same as a rapid acceleration under load, which a lathe usually is.

---

I program 7 seconds accelerate and 7 seconds decelerate for normal operation on a mill. I probably use the same for a lathe so I'd have the same expectation everywhere. I don't (yet) have a VFD on a lathe but woud consider to program the rapid stop to .75 to 1 second.

In an emergency most people will respond in greater than 200 milliseconds. so the additional second isn't going to change the outcome in a meaningful way.

 

[trevj]

The school I took some of the formal part of my machining training in, had three E-Stop buttons on each lathe. One at the operators position, the other two at the ends of the bed, where they could be reached while either egressing a dangerous situation, or by a passerby witnessing same.

The only lathe I have used that was equipped with a spindle brake, was a Schaublin 150, and the rate that it would decelerate to a dead stop from flat out, was fairly impressive, I would estimate no more than a couple revolutions of the spindle once you tapped down on the stop pedal mounted in the base.

And yeah, soft start and E-Stop with a braking resistor (have seen stove heat elements used on some CNC mills) is a pretty solid reason for having one mounted up and programmed for more than simply outputting three phase poser!

 

[mbond]

Adding to what Dabbler has said, I would think it would be rare that any 'emergency stop' button does anything except kill the power. Without knowing the nature of the emergency (and no switch can ever 'know'), a lot can go wrong with powered breaking, and there is a good chance it makes things more dangerous rather than more safe.

I can well appreciate that management types who have never used a lathe might require something like this, but I find it hard to believe that it is universal or even common practice.

With respect to the issue of momentum that Susquatch raised, I think he is talking about a sudden change from forwards to reverse power. This is something that is easy for an AC induction motor (especially 3 phase) to do, but is not so easy for a drive train to absorb. Manual cars are getting rarer these days, but think of driving along at say 50 KM/h and suddenly shoving it into reverse, standing on the gas and letting the clutch right out. Something in the drive train will not be happy. You don't want to use that as your normal method of slowing for a stop sign.

 

[RobinHood]

Wow! I'd be afraid of stripping a gear.

You may not be giving the designers of these machines enough credit for how strong they built them…

@Ironman stops the spindle from 1040rpm to zero in 1 sec with his new setup.

Here is an excerpt from my Cholchester Master 2500 manual regarding set-up of the clutches.

They want an acceleration of a 8” 3J chuck from zero to 2500 rpm in 2 to 2.5 seconds max.

When switching back to Neutral (from either FWD or REV) the electromechanical brake will stop the spindle in about the same time.

The acceleration / deceleration to 1030 rpm is in the range of 1 second or maybe a little less on my lathe.

You can use this lathe all day long like this - does not hurt the machine one bit.