Monarch 10EE electrical noise suppression

Help!!
I recently completed the CNC conversion of my 1953 10EE (Ward Leonard drive unmodified with 7.5 hp RPC) see
http://www.practicalmachinist.com/vb/cnc-machining/monarch-10ee-cnc-conversion-complete-270004/
Everything worked fine except for the occasional split thread when running a thread program. I hooked up a scope and found that as I suspected there was an occasional noise spike making its way into the spindle index input of the controlling computer which made the controller think it was time to start the thread.....analogous to closing the half nuts at random.
I was able to greatly reduce but not completely eliminate the problem by covering the spindle encoder cable with braided sheath. By sheathing the cable I am basically treating the symptom rather than the disease. I really need to reduce the motor and or generator brush noise at the source.

Has anyone here attempted, successfully or not, to suppress the arcing EMI on their 10EE? I have obtained a half dozen Sprague .05 mf 600v "bathtub" caps that I intend to put across the brushes on the motor and generator. I think it will be tough to mount them very close to the brushes so they will probably have to go in the DC control box.

I was unsure where to post the question here or on the CNC forum but since I got so much help here when getting the machine up and running in its manual mode I thought there might be a source of similarly vast knowledge in the electrical area of this machine.

Any help greatly appreciated.

Cecil

Many OEM's use a differential output on the encoder along with Shielded twisted pair cable. These systems have better noise immunity than single ended output encoders.

The spindle encoder consists of a slotted opaque disk with 20 equally spaced shallow notches (approx .15 inches deep) with one notch cut deeper(approx .3 inches deep). The 20 shallow notches work with two carefully located photointerupters to produce an 80 edge per rotation quadrature signal with the A and B pulses 90 degrees out of phase. The index signal (the bad guy) comes from a photointerupter which reads the deeper notch one time per rev.
The photointerupter is a sharp GP1A58HRJ00F. See link for data sheet.

http://www.sharpsma.com/webfm_send/1554

It incorporates and amp and a voltage regulator and creates full clean TTL level output. I have a 1 microfarad cap from VCC + to VCC - directly on the chip socket. I have a 250 ohm resistor in the LED path to drive the LED at about 15 ma. I'm not sure what a pull down resistor would do but it looks like I could add a pull-up of maybe a few K to lower the impedance when the output goes high.

Probably one of the best solutions would be to make the index notch half the circumference of the disk. That would create a VERY long index pulse at least a unit of magnitude longer than any noise spike. I could then lowpass the index pulse and discriminate against any noise on the index line.

I could mount two index interrupters and generate a differential signal but this index is getting fed into the parallel port of the computer where it is processed by LinuxCNC. I'll have to do a little research to see if LCNC can take advantage of the differential signal.

The problem is that now the noise signal is low enough most of the time as to not be detectable. Unfortunately it rarely, occasionally, and cursedly appears just at the wrong time.

Back when I was trying to eliminate generator brush noise from mobile ham rigs, the best devices were coaxial feed through capacitors, mounted as close to the noise source as possible. There were also filters with an inductor as well as a capacitor. Of course, alternators eliminated brush noise, leaving only the mechanical regulator contact noise to cope with.

Bill

26LS31 and '32 are quad driver and rec. chips that are used for the purpose.
There are 4 sections on each chip, to handle your 3 channels.

You should have a .1uf cap across the power leads of each chip and the photo interrupter's pins 3 to 5.

The cable shield should be grounded at only 1 place (not at the machine), and each pair individually shielded.

Bill

Bill,
I'll get a few driver/rec sets and play with them. Probably good practice to use them by default.
I have a 1uf 25 volt cap installed 3 to 5 on all the interupter chips ( index and quadrature)
The cable shield (all the cable shields) are brought to a common ground point at the power supply box chassis (only).

The LED is supplied from a 5v 800ma regulated supply with a 250 ohm dropping resistor. The chip VCC is supplied from the same source. There is a 1 microfarad 25 volt bypass cap directly across pins 3 and 5 (VCC to common). The output from pin 4 goes by way of the shielded cat5 cable to the parallel port of a PC running LinuxCNC where the index is processed and used to trigger the z axis so that it follows the spindle position. The parallel port is the onboard port on the computer and is running at standard TTL logic levels.
The first thing I did was to blame my homebuilt encoder (light leaks, scratches or pinholes allowing light to go through when it wasn't supposed to etc.) but I laid all those thoughts to rest when I discovered that the noise spikes occurred even when I slipped a piece of foil over the receptor(no legitimate pulse possible) and when the noise was still there even when the spindle was at rest).

It should be noted that the noise spikes appear on the scope occasionally even when the lathe spindle is not moving (scope in free run triggering). That probably indicates that there is noise from the generator brushes which is either instead of or in addition to the drive motor brushes. (no noise spikes when the lathe drive unit is completely off)

Last night I replaced the spindle encoder cable with a "factory" cat 5 shielded cable which has an aluminized mylar foil shield under the braided shield. This is of course much better E-field shielding than just the braid I had previously used to cover the "standard" cat 5 cable. At this point I cannot see any noise spikes and after several threading runs have had no false starts. It would seem that in light of the corrective action working that I must be dealing with "radiated" fields with my cable acting like an antenna as opposed to conductive or ground loop problems. The better shield attenuates the E-field and the 5 turns per inch of the cat 5 attenuates the M-field.

For the record I shall make it a rule on any future retrofits to :
1. Use "real" foil shielded under copper braid cat 5 cable and ground at power source.

2. use differential encoder technology.

3. If I build the encoder disk I will make the index notch VERY long even half a revolution so that I can lowpass it if necessary.

4. Try to avoid retrofitting 70 year old noise generators.

Thanks for the input.

Cecil

"26LS31 and '32 are quad driver and rec. chips that are used for the purpose."

These are the gold standard for the high-speed/low-noise signals in hard drives.

Single-ended TTL on the driver input, single-ended TTL out the receiver output, balanced in between.

Grounding of the shield is recommended.

Usually on the sending end. But there is some controversy on that particular point.

Cecil,
Great job on your CNC 10ee. If I may get some advice from you, Bill or others, I would be most appreciative. I picked up a 1955 10ee that had been gutted of electronics and has a Leeson 7.5 hp motor (213T) with ~ 8.1" pulley on a 1.125" shaft. There was a 460V Sabina drive included but never got working with the motor. I will be replacing the drive with a Fuji Frenic Multi 230V 20 hp inverter drive (FRN-020-E1S-2U) wired as single phase to run the 3 phase motor. I would like to connect an economical encoder with the optional PG interface card (OPC-E1-PG 5V or OPC-E1-PG3 12V). The card's range is 20 to 3,00 ppr. Can you provide suggestions as to spindle vs motor shaft encoder, mounting considerations, type of encoder, resolution, etc? I don't understand all the technical info in this thread, but my friend who is graduating soon with an Electromechanical Technology degree will be helping to wire and set up this drive. TIA and again kudos for a job well done. Tom

tschulte said:

Cecil,
Great job on your CNC 10ee. If I may get some advice from you, Bill or others, I would be most appreciative. I picked up a 1955 10ee that had been gutted of electronics and has a Leeson 7.5 hp motor (213T) with ~ 8.1" pulley on a 1.125" shaft. There was a 460V Sabina drive included but never got working with the motor. I will be replacing the drive with a Fuji Frenic Multi 230V 20 hp inverter drive (FRN-020-E1S-2U) wired as single phase to run the 3 phase motor. I would like to connect an economical encoder with the optional PG interface card (OPC-E1-PG 5V or OPC-E1-PG3 12V). The card's range is 20 to 3,00 ppr. Can you provide suggestions as to spindle vs motor shaft encoder, mounting considerations, type of encoder, resolution, etc? I don't understand all the technical info in this thread, but my friend who is graduating soon with an Electromechanical Technology degree will be helping to wire and set up this drive. TIA and again kudos for a job well done. Tom

Click to expand...

Tom,
I am not familiar with the control system you are to use but my first question would be ...what is the encoder signal to be used for. Are you going to convert the machine to CNC as I did or are you just trying to get a spindle speed signal? Are you using V-belts from motor to spindle or timing belts? V-belts slip! If you use V-belts as I did with the original motor drive and you are using the encoder for spindle position feedback as you would for CNC threading then you will absolutely have to put the encoder on the spindle either directly mounted as I did or with a timing belt drive to maintain a synchronized signal consistantly monitoring the spindle position.
If you use timing belt between the motor and the spindle then you can put the encoder either at the motor or at the spindle or on the belt between the two.
If you are using the encoder signal just for speed feedback to a VFD or other controller it is not important where you put the encoder. Answer these questions and we can talk more about the type of encoder and where to mount it or even if you need one.

Cecil

tschulte said:

Cecil,
Great job on your CNC 10ee. If I may get some advice from you, Bill or others, I would be most appreciative. I picked up a 1955 10ee that had been gutted of electronics and has a Leeson 7.5 hp motor (213T) with ~ 8.1" pulley on a 1.125" shaft. There was a 460V Sabina drive included but never got working with the motor. I will be replacing the drive with a Fuji Frenic Multi 230V 20 hp inverter drive (FRN-020-E1S-2U) wired as single phase to run the 3 phase motor. I would like to connect an economical encoder with the optional PG interface card (OPC-E1-PG 5V or OPC-E1-PG3 12V). The card's range is 20 to 3,00 ppr. Can you provide suggestions as to spindle vs motor shaft encoder, mounting considerations, type of encoder, resolution, etc? I don't understand all the technical info in this thread, but my friend who is graduating soon with an Electromechanical Technology degree will be helping to wire and set up this drive. TIA and again kudos for a job well done. Tom

Click to expand...

My 10EE is not CNC-anything, nor expected to become so. But I had dealt with the same noise issues in automating OTHER machinery many moons ago so...

Keyence FU series right-angle FO heads and their associated amplifiers will do the slot-detection. For an ignorant tacho input, not servo. Passel of 'em arrived over the last two weeks.

EMI/RFI-immune Fiber give me some 'distance' not only from electrical noise but the magnetic field and the HEAT of that motor.

The 'usual suspects' as hitandmiss Bill and others have already mentioned still apply to the REST of the circuitry and PSU.

They just don't have quite as tough a task when boxed and shielded at the quieter and cooler end of the boat.

Bill

purplepicker said:

Tom,
I am not familiar with the control system you are to use but my first question would be ...what is the encoder signal to be used for. Are you going to convert the machine to CNC as I did or are you just trying to get a spindle speed signal? Are you using V-belts from motor to spindle or timing belts? V-belts slip! If you use V-belts as I did with the original motor drive and you are using the encoder for spindle position feedback as you would for CNC threading then you will absolutely have to put the encoder on the spindle either directly mounted as I did or with a timing belt drive to maintain a synchronized signal consistantly monitoring the spindle position.
If you use timing belt between the motor and the spindle then you can put the encoder either at the motor or at the spindle or on the belt between the two.
If you are using the encoder signal just for speed feedback to a VFD or other controller it is not important where you put the encoder. Answer these questions and we can talk more about the type of encoder and where to mount it or even if you need one.

Cecil

Click to expand...

Cecil,
FYI: I noticed a typo in my previous post. The optional Fuji PG card goes from 20 to 3,000 ppr. No plans at this time to convert the 10ee to CNC, although it would be cool. The lathe did not come with any belts from motor to spindle, but does have the double pulleys. I mainly am looking to get speed feedback to the VFD, but basic position control would be nice if it can easily be done. I plan to add a DRO system using magnetic scales and TouchDRO (sends data via bluetooth to a tablet) which can support RPM on the readout using quadrature input. I've looked at numerous options, but don't know which way to proceed. Thanks for your help.
Tom

purplepicker said:

V-belts slip! If you use V-belts as I did with the original motor drive and you are using the encoder for spindle position feedback as you would for CNC threading then you will absolutely have to put the encoder on the spindle either directly mounted as I did or with a timing belt drive to maintain a synchronized signal consistantly monitoring the spindle position.
If you use timing belt between the motor and the spindle then you can put the encoder either at the motor or at the spindle or on the belt between the two.
If you are using the encoder signal just for speed feedback to a VFD or other controller it is not important where you put the encoder.

Click to expand...

tschulte said:

I mainly am looking to get speed feedback to the VFD, but basic position control would be nice if it can easily be done.

Click to expand...

Those are rather long belts, whether Vee, or converted to PolyVee/MicroVee. or synchronous. There can be flex - even some stretch - as well as slip. More with some than others.

At one end, the motor's wound-armature or solid rotor has significant mass, and the other, the spindle, workholding system, and work being turned have a separate package of mass.

So there is latency plus hysteresis 'to some degree' in the feedback / response to it.

Not looking for precise positioning on my one. Can tolerate a 'Dutch Roll' as a requested RPM is settled onto.

But.. highly stable holding of any given RPM / SFM under varying cutting load IS a goal.

One of MY concerns is to not introduce oscillation with the 'improvements'.

This is harder when the supply is an SCR-class DC Drive, because it marches to the beat of the line frequency, always and ever - regardless of spindle RPM. A 'missed opportunity' to apply a correction must needs await the next pulse.

A VFD, working off its DC bus, can set its own correction interval, does so, and they CAN apply more frequent/finer grain inputs to the shaping of their output.

I've no idea which VFD do the better job of that, or if even they bother, because.. they do not ordinarily HAVE to do...

Servos exist. Steppers with slew mode exist. Each marching to control systems with drummers of their own devising.

For poor-man's simple DC Drive, I may put encoding onto both motor end and spindle end if only to compare them on the record. Averaging them would be OTT even for me..

That said, I do also have a 'creep' rather than hard-jog mode, so.... there could be a situation where I switch from one sensor input to the other.

Not to forget .. we are re-inventing bits and pieces of various wheels that were being managed for Naval 'rifles' and Anti-Aircraft gunnery long before War TWO. At great expense, of course. Commercially, anyone with deep-enough pockets can just go out and buy 'generally better' machinery ready-made.

Beating - nor even matching - today's top-end CNC makers is not going to happen in even a very well funded small shop.

But one could get 'close enough' .... and on-the-cheap, so...

...don't let us lose sight of the 'fun' aspect - or educational value - of these projects when someone comes along and sez 'just go and make chips!'.

I don't HAVE to make chips. Others have that covered well-enough already.



Bill

Adding VFD

I don't wish to stomp on OP's thread, but reply to Tom's post.The encoder is only needed if your vfd does not have auto compensation. My lathe works fine with just the auto system.

The motor is assumed to not have the Monarch gearbox, and has an oversize pulley to boot. Without changing that pulley, low speed operation will be a problem, cogging and little power will result. Although if the motor is a 6 or 8 pole it might be workable. Waht is the rated rpm of the motor. If 1140 or lower it might work for you, but 1750 will surely be an issue when slow speed and high torque are needed. It will feel like an 8 cylinder engine with 3 fouled plugs.

Toms Wheels said:

I don't wish to stomp on OP's thread, but reply to Tom's post.The encoder is only needed if your vfd does not have auto compensation. My lathe works fine with just the auto system.

The motor is assumed to not have the Monarch gearbox, and has an oversize pulley to boot. Without changing that pulley, low speed operation will be a problem, cogging and little power will result. Although if the motor is a 6 or 8 pole it might be workable. Waht is the rated rpm of the motor. If 1140 or lower it might work for you, but 1750 will surely be an issue when slow speed and high torque are needed. It will feel like an 8 cylinder engine with 3 fouled plugs.

Click to expand...

Thanks for the reply. The Leeson motor is 1750 rpm, but was mounted with an adapter plate to the Monarch gearbox. I was unable to use the lever to get it to go into back gear however, so I may need to pull the gearbox apart and see what the problem may be. I did order a new set of gearbox gaskets from Monarch. The original tachometer has been replaced and the new one sticks out about an inch from the casting and goes from 0 to 50 and is time 100, so it doesn't have many graduations to tell rpm speed. The Fuji VFD manual is here:



http://www.americas.fujielectric.com/sites/default/files/Multi Brochure MEH531.pdf and the 20 hp model is FRN020E1S-2U. It does support auto-tuning if that is the same as auto compensation. Sorry, but I'm new to all this electronic stuff. The VFD does support a potentiometer, I'm just not sure how to go about that integration with the 10ee.

I still may want to upgrade to CNC like Cecil did in the future, so if I can get some of the right parts in place now that would be great. I just came across the NYC CNC YouTube channel and have been exploring the videos heavily and it is stimulating my interest in CNC. I plan to take the CNC class at a local community college and I took their machining class last summer. Thanks for all your help keeping the project moving forward.
Tom

Depending on the year of your lathe, there is a blocking solenoid which prevents shifting into backgear when the motor is running. However the lathe has to be ON to power solenoid. That is the likely reason you can't shift, just follow the linkage, if its there you can see it.
Its normal to turn the spindle by handto get the gear dogs to line up.

It was made in 1955. No power to it yet, as the VFD will be wired as single phase. There were no drive belts, so moving the spindle didn't matter. I removed the connecting rod and tried shifting it by hand while slowly moving the motor pulley. Thanks.


Tom

tschulte said:

It was made in 1955. No power to it yet, as the VFD will be wired as single phase. There were no drive belts, so moving the spindle didn't matter. I removed the connecting rod and tried shifting it by hand while slowly moving the motor pulley. Thanks.


Tom

Click to expand...

And was there a solenoid? Or not?

And did it then allow you to shift when linkage was disconnected? Or not?

Entirely possible the PO trashed parts of the gearbox, most especially if his conversion did NOT incorporate the blocking solenoid.

Or even that he inherited a bad one.. and used it to run single-speed because he needed it to fill the space and present the pulleys. Until he could find a working one as a bolt-in replacement. Or repair this one.

Bill

Bill,

I don't know where the solenoid would be, but the entire base cavity was empty except for the motor, gearbox and pulley assembly. No, I haven't been able to get it to shift into back gear with it pulled out of the base. There was another gearbox included where the three arms of the mounting bracket had been torch cut away. So between the two, there should be parts to make one good gearbox. Thanks.



Tom

I don't think WIAD machines had the lock out solenoid, IIRC it is a feature in modular machines. I know my 1976 has it.

Steve

tschulte said:

Bill,

I don't know where the solenoid would be, but the entire base cavity was empty except for the motor, gearbox and pulley assembly. No, I haven't been able to get it to shift into back gear with it pulled out of the base. There was another gearbox included where the three arms of the mounting bracket had been torch cut away. So between the two, there should be parts to make one good gearbox. Thanks.



Tom

Click to expand...

Tom,

I have but one gearbox for three motors, but it can be shifted at the clevis attach point with the naked hand, applied firmly. No linkage rod or tools required.

Wants to drop back to 'direct' when not on a linkage to prevent that, BTW.

You might want to take a 'detour' and see whether you are going to be good to go even with the other gearbox as spares, one for the other. They are much less often available than the motors - DC or AC.

A year-plus search has not turned up any stock item that could directly replace that configuration, either.

Closet substitute approach so far has been seen a few times wherein a motor output shaft was pointed TS-ward, pulleys and jackshaft carried power back HS-end-ward.

To the good, relatively few ops on a typical 10EE even NEED to drop into low gear.

And .. with the right combo, a 10EE COULD have (at least) two directly belted ratios by use of synchronous belts or PolyVee/MicroVee instead of "A" section vee belts.

Each can carry more power in the same width as the twinned "A" section Vee belts AND do so even if wrapped onto smaller diameter pulleys. A 3:1 - perhaps a bit more - ratio is doable, and generally would be good enough to be worth it vs no change at all.

IOW - 'No fear'. One way or another, she can make chips.

Be happy it isn't an 18-speed gearhead with even two or three busted gears, let alone hydra-shift or the like.



Bill