Some thoughts about the EE
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  1. #1
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    Default Some thoughts about the EE

    Hello, all,

    I'd just made arrangements to buy a replacement large transformer for our module EE. The EE has been sitting dormant for quite awhile now, as the relatively little bit of turn work going through our little shop has been handled adequately, if not as conveniently, by the larger Monarch.

    I'm getting the large transformer cos I just have this 'gut level feeling' about the existing one, having heard a 'beenk' noise from the area of the back of the EE as something in the electricals seemed to malfunction......whatever the malfunction might be seemed to be causing some sort of resonance in that large transformer, or so it would appear......I could be totally mistaken, to be sure.

    I'm hoping that I can get a friend of ours, who is an electrical engineer, and works on industrial solid-state gear, to come out and diagnose the EE's problem....I hate to admit it, but I'm afraid of working around those high-voltage points myself, after nearly zapping myself when tinkering-up another tube drive Monarch some years ago. I suppose I've just 'lost my nerve' or some such.

    (we have all these friends who are electronics engineering types, who read the schematic for the drive and say......'oh, my, what an antique....so thats how they did that way back then.....look, its dead simple, the way it works' ....and on and on in that vein.....but when I ask them to please, please, check out and diagnose the EE for me, cos I'm the proverbial 'blonde joke' with electronic gear, they shrink back in fear from the voltages/wattages involved......'that kind of power could get you killed.....I'm not going to fool with anything like that, do you think I'm mad?)

    Well, alright, so be it.......but it has had me thinking about developing some realistic alternative to the vacuum-tube or other electronic widgetry involved in these machines for some time......and then Donie's recent comment about spending a lot of time and money to get his '80's vintage EE running well, but even then having problems should it be started/stopped too frequently nudged me into thinking a bit more.

    It seems to me that, considering the sheer number of EE Monarchs around which have drive problems, and the sheer headache value of the class of problems they develop, that there may be a worth-while opportunity for some small group of investors here.

    The idea is this......how about researching the possibility of contracting with some suitable electrical manufacturing firm (is Reliance still in business, and still making motors?) to build up a complete 'refit package' for the EE, consisting of a motor-generator set, a spindle motor (would the motors used with the tube drive work with a MG set, or could they be modified to work?), the pair of large rheostats needed for the MG drive, which could be located remotely with the MG set, the fwd/rev contact assembly, and related small parts.

    Now, think about this......there were some large number of MG drive EE machines, which simply ran like 'clock-work', serving well for many years with no intrinsic problems, other than the obvious maintenence issue of replacing the brushes in the motor and MG set after many hours of operation, re-greasing bearings as one does with any motor, and, after many years of operation, having to replace the tips of the 'fwd' contactor.

    The relatively very little bit of maintenence the MG drive needs can be done easily by any machinist or plant mechanic, and any electrical issues easily handled by anyone who can do ordinary three-phase machine wiring.

    The only 'down-side' to the MG drive EE's was the design error they made, presumably owing to wartime shortages, to use a 3600 rpm MG set. (quite possibly copied from the then-common Lincoln 'Shield-Arc' DC arc welding set, which used a vertically mounted 3600 rpm MG unit for the DC welding power)

    The horrid screaming whine sound as they run is identical, and is a serious morale problem for the operator of the machine.

    Now, in thinking about a re-fit drive system, its easy enough to envision a MG set designed to run at 1200 or 1800, for a gentle 'whirr' instead of a nasty whine, and to envision an acoustically insulated box, with a suitable quiet box fan for ventilation, to be mounted behind the lathe, or under a bench.

    So......assuming the system were to be offered as a 'package' with all the small parts needed for conversion, what might the potential market be like, considering the 'X' thousand EE Monarchs 'in circulation'?

    Would a run of, say, 500 or 1000 units be salable over, say, two or three years time?

    What price could such a refit system be built for, in those quantities, and who could build the various components needed for it?

    What price would the generality of EE users be willing to pay to have an electrically reliable EE, with reasonable assurance of a decade, more or less, of reliable operation of the machine....that is, a 'make the investment once, then you don't have to think about the EE's electricals for many years of service' practical consideration?

    (Y'know, it is really and truly amazing that so many EE's are found in poor, sometimes un-repairable, condition just cos the owners got frustrated with their electrical problems and neglected them......compare those to all the geared head Monarchs of the '40's, '50's, and '60's which are still in regular revenue service in so many shops)

    cheers

    Carla

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    No, a fully electronic drive replacement kit would be the only viable method. If I could get rid of my MG set. If I could find a WIAD unit I would replace it in a second. No more RPC, less noise, less vibration.

    Two options. A VFD with a AC motor and integral back-gearbox or a fully electronic drive that runs the original motor.

    Either way both have their issues. VFD route you are going to have the expense of a motor and custom gear box. Or you could do as monarch is doing now and just installing a 10hp motor that has good power even at low speeds.

    The DC drive problem is that we need 240v DC for the armature. This is very difficult to do with 240v single phase. Going to have to involve a boost transformer probably. A EE friend of mine thinks he can come up with a design its just paying jobs come first. Heck, I would be happy with just a unit that would supply the variable voltage 240v and 120v to tun the original control box.

    The commercial drives that accomplished this were all three phase and very expensive. That darned 240v armature and field weakening...

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    "The DC drive problem is that we need 240v DC for the armature. This is very difficult to do with 240v single phase. Going to have to involve a boost transformer probably."

    The issue is the OEM motors were 230 volt armature, 115 volt field, whereas modern dc motors have a 180-200 volt armature, 90-100 volt field.

    A 180-200 volt armature, 90-100 volt field motor is perfectly compatible with a 230 volt single-phase source, whereas a 230 volt armature, 115 volt field motor requires a 277-300 volt single-phase source.

    It is not a coincidence that the WiaD and Modular (and the EE1000) have a 300-0-300 volt armature anode transformer, and a 150-0-150 field anode transformer (the Modular actually uses one-half of the armature transformer).

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    Well there is a current fix for balky drives, its a 7.5 or 10hp motor with a VFD for control. Monarch with all the engineering prowess they have, has choosen this as their fix.
    I recall estimates of 10-15000 EE's being build, how many are sitting around that need just a drive.
    I could think of easier ways to lose money, but designing a single user DC control for a product that has a decreasing population without an increasing demand, means you'll work hard and lose money. While there might be 1000 units that need a new drive, and everyone were to purchase a drive, what will you do next year, I doubt that there will be another 1000 that need a drive. Would you not think that the company that supports these lathes would have built something to replace the tube drive, I'd guess they tried and found from the costs of the VFD/AC were more acceptable to their customers.
    And for the most part their customers are NOT us.

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    The module drive is complex as whole, yet each individual circut is fairly simple. With just my basic automotive experience I was able to deal with it when, "I approached it one circut at a time".
    The first lesson I learned was to take the factory wire sheet and make sure "every wire is in the right place". On my machine, most likely others were working on it and replaced some of the wires in the wrong place. This was a costly mistake on my part as I fried some components thinking I had it fixed, after finding one wire out of place, and then powering up the machine.
    If I were to purchase another machine that had problems, I would block the machine up to a comfortable working height. This would make working on it much easier and less likely to get shocked. The basics of standing on a non conductive mat and keeping the other hand in your pocket while probing does apply here due to 500 volts coming out of the main transformer.
    If I apply the above, I believe I can completely rebuild a module drive machine in 40 hours, rather than the 100+ hours from my initial bumbling and causing more problems.
    Scott at Monarch posted here, "The module drive is a piece of cake". I agree, just a large slice!

    On the MG drive, I see no reason that a remote fan can not be used. Just remove the generator fan blade and power up the machine, its not very loud. I have gotten used to as is. Not even near the volume of my Fender Telecaster and Custom Hiwatt 100 amplifier.

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    "I'd guess they tried and found from the costs of the VFD/AC were more acceptable to their customers."

    Other than system integration costs, which may be non-recurring, such an ac drive system incorporates devices which are largely commodities, and for which the integrator has some significant leverage as there are multiple suppliers.

    With a dc drive system, there are few competitors for the drive component, and perhaps only two for the motor component.

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    The Sundstrand drive was Monarch's first solution for the 10EE. It only lasted two years before the MG replaced it, but there are still 10EE's around with that drive, so the idea was sound.

    Would a modern fluid drive be a viable alternative?

    -Dave

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    "Would a modern fluid drive be a viable alternative?"

    Yes, I think so.

    So also would be a 180-200 volt armature/90-100 volt field shunt wound motor with a 240/277 single-phase SCR drive.

    240 for 240 single- or three-phase installations.

    277 for 277/480 three-phase installations.

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    Is there a preferred motor technology for current production high-precision CNC lathes and milling machines and machining centers?

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    Quote Originally Posted by Peter Miles View Post
    Is there a preferred motor technology for current production high-precision CNC lathes and milling machines and machining centers?
    AC Servo...lots of power in a small package

    a 14KW, 53Nm (continuous duty)motor is 175mm square by 33mm long and will deliver in excess of 200Nm for short periods (2-3 min).

    I use a 5KW(WAY overkill) motor as a spindle for my 10EE and works just fine with the following advantages;

    Precise speed control
    Torque limiting if required
    position control (my key always stops in the same position)
    when threading, I can tell the spindle to thread to a position and stop...precisely.
    By using feedback from the DRO I have Constant suface speed control.
    Totally silent except for a slight servo whine when loaded, with all the covers on you can't hear that even.


    Cheers,
    Sean

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    "... a spindle motor (would the motors used with the tube drive work with a MG set, or could they be modified to work?) ..."

    Same motor would work, if 3 HP.

    M-G machines were 3 HP (large frame Reliance, shunt wound).

    WiaD machines were initially 3 HP (small frame Reliance with essentially the same specs as the large frame Reliance except compound wound).

    Later WiaD machines were 5 HP (small frame General Electric, compound wound).

    Modular machines were 5 HP.

    Armature Regeneration machines were 5 HP.

    VFD machines were 7-1/2 HP with backgear or 10 HP without backgear.

    The larger rating for the VFD machines was likely to make up for the primitive V/Hz VFD drive. Today, with tachometer feedback and a vector drive, 5 HP should be fine, and there's at least one user-converted 3 HP vector drive machine out there which gives its user satisfactory results.

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    If I had to get an EE working with a new drive for minimal cost, I would suggest that you keep the original motor AND the original BIG tansformer (T3 in the modular I think). The rest of the electrical part of the control circuitry could be done in more modern analog electronics or, if you were willing to put a pickoff on the drive pulley you could go with a PWM fully digital system. You wouldn't even have to be too clever if you re-created the original very clever electronic functions in Si. Peter made an interesting suggestion a while back about using a hybrid system with small thyratrons along with some pulse shaping to drive SCRs but this still leaves you with the bulk of the old tube electronics and transformers. My understanding is that the big transformer is pretty tough with most of the failures being insulation where the leads enter and exit it (these are fixable). If so, keeping it lets you get the motor voltages without having to resort to crazy high-current voltage doubling schemes (or 440V service).
    The problem with all of this is that it is a nontrivial amount of work and would probably consume some $$ (mostly when you let the smoke out of the components while testing). Is there really enough of a market would be my question.
    Cheers,
    Steve

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    I've played with the idea of using a PIC like a 16C73 (built in PWM, one for armature and one field) driving IGBTs or MOSFETS as a motor controller. You could see an armature voltage equal to the input voltage instead of 180V as most commercial will generate, and if you used the original transformer you could hit the 250V desired.

    But while I still recall enough electronics to breadboard simple designs I don't know enough to put something like that together without replacing a lot of parts. When you're playing with high power switching the $$$ add up pretty dang fast.

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    HI Russ,
    You had better believe it adds up quick. Also there are some funny things that happen with power electronics. High Power Solid State stuff keeps gettin faster and faster. I built a switcher some time ago and it kept killing the output stage. It turns out that the 6" of #12 wire has an inductance of 100nH and the output stage was turning off ~100A in about 1nS.....making many kV across the output stage....first it took out the catch diodes and then the FET outputs. Total cost in parts by the time I figured it out was north of $300.....Ok, I'm slow and a power EE might have figured it out sooner but still it gets pricey!
    It you get the urge to try the PIC route, give me a call, I have a pretty good development system for them and probably a board we can kludge to try this. Still, I'll bet we end up making smoke along with our electrons!
    Cheers,
    Steve
    Cheers,
    Steve

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    Quote Originally Posted by jefferts View Post
    HI Russ,
    You had better believe it adds up quick. Also there are some funny things that happen with power electronics. High Power Solid State stuff keeps gettin faster and faster. I built a switcher some time ago and it kept killing the output stage. It turns out that the 6" of #12 wire has an inductance of 100nH and the output stage was turning off ~100A in about 1nS.....making many kV across the output stage....first it took out the catch diodes and then the FET outputs. Total cost in parts by the time I figured it out was north of $300.....Ok, I'm slow and a power EE might have figured it out sooner but still it gets pricey!
    Fortunately, we're not getting near those currents or frequencies. The problem is that if I do it I'd likely stick with what I know - bring in the AC, rectify it and run PWM with it, changing the duty cycle to vary the power.

    It you get the urge to try the PIC route, give me a call, I have a pretty good development system for them and probably a board we can kludge to try this. Still, I'll bet we end up making smoke along with our electrons!
    No doubt. I've been pushing for a PIC development system on a different project, might get it and be able to use it. It's on the other end of the problem scale and involves counting photons. But the real problem is that I have a working drive and spares, I need a donor 10EE with a really screwed up drive so there's some push to actually follow through and do this.

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    Hi Russ,

    "Fortunately, we're not getting near those currents or frequencies. The problem is that if I do it I'd likely stick with what I know - bring in the AC, rectify it and run PWM with it, changing the duty cycle to vary the power."

    I wasn't trying to go that fast either......its just that the power FETs are so fast these days that those sorts of switching times are common (without trying!).
    In any case I agree with the working drive issue...at the moment I've got a nicely working drive and a couple of spare tubes. I suppose I need a wreck EE to get excited about this, but at the moment I think I'd rather find a wire EDM! Besides which the hot water depratment might notice another 3k lbs lumb of cast iron moving into the garage.
    Cheers,
    Steve

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    Quote Originally Posted by jefferts View Post
    ...bring in the AC, rectify it and run PWM with it, changing the duty cycle to vary the power."
    You know, that is essentially what old FANUC VCUs used to do, in fact, we used to use them as quick and dirty jog units for the older motors. there are a few logic signals to deal with; but essentially all they used was a voltage input for velocity control.

    if you could find an old VCU and a motor like a 30R or so, you might be in business for not a lot of dollars.

    I found an old VCU manual in my archives...the following is an extracted section;

    3. Operation of the VCU
    The VCU receives a motion command signal VCMD from the Axis Control PCB VCMD is a positive or negative DC signal (depending on direction) in the order of 3.5V/1000RPM. A voltage of .687 x VCMD can be measured at test point CHI.
    This voltage is then summed with the tacho feedback signal VF which is derived from the pulse train of the APC after it has been passed through a frequency to voltage converter. Eighty percent of VF can be measured at test point CH2.
    The result of this summation is the torque command signal TC. TC can be examined at test point CH14.
    TC becomes the set point of a D/A converter whose digital input is the result of a rotor position calculation circuit which receives rotor positional data in the form of a gray code signal from the APC.
    The output of this D/A converter is a sine wave whose amplitude depends on TC (and thus VCMD) and whose frequency depends on the speed of the motor rotation.
    To obtain a 3-phase signal to drive the motor there are two D/A converters giving outputs 240 degrees out of phase with each other These outputs are summed to generate a third phase which is 120 degrees out of phase with each of them.
    The resultant 3-phase signals can be examined at test points CH7, CH8, and CH9. They are then summed with a 3-phase voltage corresponding to motor current feedback. This 3-phase feedback voltage can be examined at test points CH10, CH11, and CH12.
    The resultant summation is applied to a pulse width modulation circuit which, in essence, is an analog to digital converter. The on time of the output pulses is proportional to the amplitude of the input signal. The frequency of the output pulses are at the frequency of the triangle wave generator.
    This modulated output pulse train is then applied to an integrated circuit which accepts the three pulse width modulated signals and applies them to the bases of the corresponding drive transistors in order to achieve the proper direction. The transistors switch a DC voltage derived from the rectified output of the servo transformer
    The resulting simulated 3-phase output is then supplied to the motor field windings causing rotation of the permanent magnet rotor The duty cycle of the transistors determines the speed of the motors.
    When the motor on a major axes is told to stop and the transistors are no
    longer being fired the counter emf is fed through resistors in the discharge unit to give controlled braking
    In the event of an E-stop, as well as applying a mechanical brake, the controller de-energizes the MCC contactor, the contacts of which close, shorting out the motor windings and assisting to stop motion





    Sean
    Last edited by lennoncs; 02-02-2008 at 01:05 AM. Reason: added VCU information

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    Well, I'm ever so impressed with all the discussion of ultra-sophisticated electronic technology, and I can understand that it is indeed a fascinating and enjoyable field of experimentation for those who are into electronic engineering.......but, from another point of view.....what of those folks who are just 'not electronic' as many of the people in this world are just 'not mechanical'?

    Its all well and good, for those who have the relevant knowledge and capability, to develop sophisticated solid-state electronic power systems, and, of course, technical advances are always desirable.....some become 'blind alleys', others go on to become 'state of the art', and ever so valuable.....possibly patentable or licensable, and worth some real money to their developers. I'm not saying anything at all against the on-going efforts of those who develop sophisticated electronic technology.....quite the opposite, in fact....more power to you, gentlemen, and may you develop better and better technology as time goes on....

    Back to the original item, tho.......I can tell you from first-hand practical experience that the old Ward-Leonard drive with the motor-generator set is an optimal system for the actual needs of the little Monarch, given its use by machinists who are not electrical engineers, often under time pressure to produce close-tolerance high-finish parts, in the machine shop environment.

    The MG set is easily understood and maintained by machinists and plant mechanics, an important difference not easily understood by those for whom sophisticated electronic systems are an 'open book'.

    Aside from the obvious maintenence items of brushes, bearings, and contact tips, all of which will give years of reliable service before requiring renewal, the MG drive is a 'known quantity' in that its 'stable' and not 'finicky'.

    It may well be argued that the MG set is 'old technology' and 'obsolete'.....and, yes, thats a fair argument. It may well be argued that a new run of MG sets may not be 'cost effective', and that is certainly possible.....in fact, it may not be possible to have them built at all, at least to anywhere near the quality level of the Reliance drives of the 1950's.

    The MG set has one major 'virtue', tho.....the rotating mass serves as the equivalent of a 'reservoir' so to speak, to easily provide for the intermittent loading of the spindle motor when starting......and its an electrically 'simple' technology, a sort of 'brute force' if you will.

    The practical advantage of the MG drive for the EE is simply that it works well, and continues to work well with a very low maintenence requirement. The operator simply presses the 'start' button at the beginning of his/her shift, and the 'off' button at the end of the working day

    (in actual practice, our MG drive EE ran 'around the clock' at times, when we had large numbers of small parts to do under time pressure.......our MG drive EE, and the little Hendey gage lathe we had, were reliable in this respect.....our tube drive EE would run alright for sometimes a few weeks, sometimes only a day, before it would start 'hunting' under load, and require its potentiometers adjusted.

    Doubtless, the real underlying problem was one or more components which had become unstable from age, but we couldn't develop even a guess as to which components might have been the problem, and didn't have time to fool with the machine, as we had to get the work out. This, of course, is a problem associated with being a little 'hole-in-the-wall sub-contract shop, as compared, say, to being the experimental shop of a well-financed firm where time and money are more readily available. We had no choice but to 'get the work out', and reliable equipment was a necessity)

    The electronic drives, even tho designed for a similar service, and intended to be adequately capable of handling the hundreds of thousands of intermittent loadings imposed by the starting and braking of the spindle motor, do seem to have their inherent flaw, that of component degradation over time. This is quite understandable, and doubtless inevitable, given the sheer number of components which make up the electronic drive systems, and the wide range of loading cycles they experience in normal use.

    Actually, its easily arguable that one of the major design flaws of the EE is the requirement to start, stop, and brake the spindle motor itself to start and stop the spindle.

    Envision, if you will, developing a design for a friction clutch/brake assembly to be mounted within the driving pulley on the nose of the back gear box, operated by the same general layout of clutch lever used on the larger Monarchs. Designing such a system is a bit of a challenge, to be sure.....some friends and I drew up a possible version of this idea, some twenty years ago, but just never had the time and funding to pursue it. As we'd drawn it, this was 'clutch/brake only', so that one still had to reverse the motor when backing out a tap.....equally as with the larger Monarchs.

    To put this item in perspective, consider the LeBlond Regal small lathes, which had no clutch, so that the operator had to start/stop the spindle by starting/stopping the motor, usually plugging it to a stop. Compare that to the convenience of a 12CK or similar Monarch, in which the momentum of the motor helps to bring the spindle up to speed easily when the clutch is engaged.

    cheers

    Carla

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    Macona,

    If your EE runs well as it now is, aside from 'noise and vibration', I'd like to strongly recommend that you 'fix only that which needs fixing'.

    There should be no perceptible vibration whatever when an EE is running, even up at its max spindle speed. Note, tho, that the earlier EE's had the MG set bolted directly to the base casting, whereas the later EE's using the MG drive had rubber shock mounting between the MG set and the base. If yours is the earlier style, adding rubber mountings would be cheap and easy, just run a good large braided copper ground strap between the MG set frame and the base casting.

    If you experience a vibration from the MG set, then the correct procedure is to have the set apart, and send the rotor assembly out to a reliable specialist balancing firm. From the photo, yours may be a wartime machine.....some of the wartime machines weren't balanced up as well as should have been.....

    Likewise, have the spindle motor rotor out for balancing, and have the drive pulley balanced. That, along with good belts, should make a difference. If yours is flat belt to spindle, correct belt splicing to avoid any 'lumpiness' is critical. If yours is v-belt, understand that some belts, even seemingly 'best quality' new ones, can be inherently ever so slightly 'lumpy'.....we ran into that situation on one machine, and the little bit of vibration was cured with another set of new belts.

    There is a good, realistic answer to the noise issue of a rotary phase converter and a noisy MG set.....that being to mount them up remotely, in an enclosure with adequate acoustical insulation and ventilation.....running some conduit and wiring is relatively cheap and easy, compared to finding and rebuilding a 'works in a drawer' drive for your EE.

    I'd strongly suspect that the machine work involved in replacing the large rheostats with the little box for the duplex speed control pot would, in itself, be bit of a job. In short, fix only that which really needs fixing........if you really would strongly prefer an electronic drive EE, I'm sure you can find someone who will happily trade you one for your EE.....assuming condition of ways, screws, spindle, etc, are good.

    cheers

    Carla

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    I have run into two causes for unstable spindle speeds on the modular. Old style diodes loosing contact when heated up, and or weak field tube.


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