Movin on...

This is an e-mail I will be sending to my co-workers and select clients within the next two weeks. I thought I might post it here as a sort of repository. Read that carefully! Not suppository!

To my dear friends:

 Well…as stated at the recent company meeting, and I will paraphrase; “Gaff will be moving on to the next stage in his life.” That is true. Exactly what that “stage” is, or what it will encompass, will only be realized by the doing. As Yoda wisely said to Luke: “Do, or do not; there is no try.” I relish the opportunity to do it, and I will do it, to the best of my ability. And hopefully, with some style.

 It is not without some tinge of doubt, that I begin this new journey. Change can be the most unsettling of human perceptions. We all like to feel comfortable in what we do, and what we expect to do in the future. Sometimes, that just cannot happen. Change needs to happen, despite ones fear or dread of the unknown.

 I went through many, many changes in my thirty-five plus years with the company. Some of those changes were terrific, such as enrolling in the in-house 2,000 hour State of Connecticut, Journeyman Machining course. I had a great mentor, Bob Geisel, who steered me through the curriculum, and helped make the learning more relevant to the real world. Another positive change, was being asked to travel to foreign lands, meet new people, and represent the company. That can be pretty scary, but what a great opportunity for learning it provided.

 Some of the changes through the years were not so terrific. The changes that are foremost in this category, were the loss of co-workers and friends in untimely ways, and the havoc the economy would wreak on the company at critical times. These changes can only be faced and overcome by directly confronting the fear, and knowing that others were dealing with the same angst, trepidation, and loss. “Strength in numbers” is the axiom that defines a company’s ability to weather difficulties. Be they internal, or from external forces. We all should gain strength from each other, when faced with a common foe. Sorry, enough with the preaching.

 I am thankful for the opportunity to work with all of you, and I have gained a great deal of personal satisfaction knowing I have helped colleagues and customers alike, with my hard earned knowledge of manufacturing trivia. I do not suspect that the future holds much need for my limited knowledge of encoders, or Insulated Gate Bi-Polar Transistors, but who knows, that just means there is a whole new realm of possibilities for learning. That, is one piece of advice I tried to convey to my sons, learning is never finished. Learning is what makes everyday worth the effort. It is personal, instantaneous gratification of the highest degree. Don’t be complacent or contented with your knowledge-base. Grow and expand your mind in whatever ways please you. It will be worth the effort. I know I’m not done yet. There are going to be far too many interesting twists and turns in my journey to “the next stage”.

If I could indulge your patience for just one more thought…Please try to take time away from your connectedness. Everywhere I turn today, I see young people and adults enraptured in their smart-phones, tablets, or big screen, High-Definition televisions. They are so “connected” that the real world escapes their notice, often, to the detriment of their well being, and their personal relationships.  Must your friends (and the Mongols) know every move you make? Must you forever imprint that information in cyberspace? Turn your electronics off once in a while. Go outside and look at the world. Or, go to a library or museum and engage with the world. There is so much more to life than feeling real, deathly panic, when you forget to grab your iPhone. There I go again, with the preaching. Mea culpa.

 I will end this missive by borrowing a paragraph from a book my wife, Sharon, read to our sons many years ago…from: “First You Have To Row A Little Boat” by: Richard Bode.

“I come now, at this late juncture of my life, to this sudden realization: I have no destination, no real destination, in the literal sense. The destination, the place toward which my life is tending, is the journey itself and not the final stopping place. How I get there is more important than whether I arrive, although I will arrive, and what I must try to remember, now more than ever, is to listen to the wind, and the wind will tell me what to do.”

 I hope there is a steady breeze in each and every one of your futures. Be well.

Gaff

Thirty-Five Years Doing Anything, Is Probably Enough

I have been gainfully employed by the same firm for thirty-four years, three hundred and fifty-five days as of this writing. I decided at the end of last year to call it quits from my current line of work. This decision was hard fought with myself, but I finally won through to victory on the retirement side.

Retirement is not really a correct description in this case. Yes, I will retire from my place of employ on May 30, 2014; but I will not stop working. I will be working on many, many things that require time. Time, that I previously did not have the luxury of. Such as...

Mastering David Gilmore's guitar licks in "Comfortably Numb" (yeah right). RVing around the West, and walking to the bottom of the Grand Canyon (while I still can). Seeing Ireland (the Old Sod) is high up on the bucket list. Lowering my golf handicap past 4.7 (lowest it's ever been). Riding my Harley to Alaska (that's a tough one). Finding a 1942 Singer, M1911A1 that costs less than my house (that may be impossible). Ah! the world is my oyster.

Life transitions can mean many things, both good and bad. I am hoping this decision, and it's inevitable life transition, will be wonderful. Time will tell. And until time tells, I am going to try like hell to smile more, and be a bit kinder to my family members; and other weird people too.

Until next time...

Shoot Straight, and Do The Right Thing...

Gaff

The Trouble With Plastic

I spend a lot of time dissecting all sorts of mechanisms for one reason or another. It's been both a blessing and a curse at times. I enjoy "seeing" how things work. How they function,  how they are assembled, and inevitably, how they come apart. Hopefully, I pay close enough attention at disassembly, to remember how the blessed thing goes back together. That, is the reason for this entry.

A very large majority of our everyday possessions are constructed of some type of thermo-plastic. In fact, more and more items that once were solely made from metals, are now produced out of reinforced plastic, or composite materials.

One of the most important factors to remember when reassembling a device after you have successfully repaired it, (we will assume you are successful, otherwise the item might become fodder for the trash heap), is the proper reinsertion and tightening of the self-tapping fasteners.

When the item of interest is taken apart, the fasteners are usually metal screws with aggressive threading, that when originally assembled at the factory, cut spiral threads into the undersized hole in the mating component. When reassembling the device (properly), it is very important to "feel" for those precut threads to be sure the screw does not cut new threads, thereby weakening the fastener's hole.

To be sure I return the screw/s into the original threads, I simply start the screw into the hole and carefully rotate it in reverse (left-hand direction) with VERY little downward pressure. As the screw turns around counter-clockwise, I feel for the exact point in the rotation where the screw drops slightly into the original precut thread. Then, I simply reverse direction slowly and the screw should go into the threaded hole with very little effort, and tighten without threat of stripping the plastic receiving hole.

Sounds pretty trivial I guess, but if you plan on reassembling something for future use, and the screws do not tighten properly, that will prove to be a difficult problem to solve in a "professional" manner. I guess the duct tape, and hot glue gun people would not be phased by such a development. I however, tend to want to return the item in as close to factory specifications as I possibly can.

There you have it, turn left, feel for the drop, before you turn right to tighten. It will make a much better job of your fix-it attempt.


Thanks for taking the time to peruse this entry.  I hope it may help in some small way.

Gaff

How Do You Spell Pressure? R-E-L-I-E-F

Now that everyone has learned all they care to learn about an encoder... Yes, sorry, I should never have attempted to make that subject amusing in any way, shape, or form. Mea Culpa!

How about we turn to another of my hobbies for a little levity, and a bit of concentration on craftsmanship. That would be, Hobby Gunsmithing. OK, OK, maybe there won't be much levity...

I think this hobby was one of the reasons I gave up drinking. You can't have shaking hands or clouded thoughts when dealing with firearms. Whether working on their innards, or attempting to use them for the purpose for which they were designed. Clear heads MUST prevail.

What does a hobby gunsmith do? Very astute question. Answer; whatever his or her ability and or training and knowledge allow him or her to do competently. Nothing more, nothing less.

This is not like working on a toaster that only toasts one side of the bread. If you stick a screwdriver into that thing with the juice plugged in, the sparks and smoke will immediately tell you you did something wrong. You might even get tactile feedback with a shock, and, when the AC voltage drops midway through  the sine wave, you can let go of the toaster, onto your foot.

No, working with and on firearms is very serious business. Every, and I mean every, firearm is different. Despite the appearance that two seemingly identical model firearms sit side by side, they are not identical. Even in this modern age of precision CNC (Computer Numerical Control) machining centers, able to produce parts with incredible accuracy and tolerances, when precision firearms are assembled (by the hand of man or woman), they inevitably will not be identical in one way or another. They will be very close to the same, but not identical.

Each firearm is unique, the fit of the parts, the quality and rarity of the wood in the stock/s. The crispness of the trigger pull, the uniformity of the finish can all contribute to this uniqueness. Considerable consideration must given to each firearm, because the possibility of ruination looms mightily with each tool that is touched to its surface.

I have personally experienced dread and fear as I plunged a Pfeil D7/10 gouge into the walnut of my M1A Springfield rifle to begin a relief carving. There was no going back, that cut could not be repaired. The reason for the dread was, this happened after completing 40+ hours of checkering to this formally plain, military stock. The checkering came out really well, and I did not want to ruin this thing after all that work. I had never attempted something like this before. Yes, I had carved a few things in the past, but a cedar sign is not a 1990's era M1A National Match, with a "perfect" walnut stock. Besides, this was MY rifle, what if it was a friend's one-of-a-kind?...holy heartburn.

So, after completely carving the "test" shamrock in some scrap walnut first, and being satisfied I could pull it off, I plunged that razor sharp gouge into the stock. "God help me, I'm committed now." Well,  the first shamrock came out very well, and I'm knee deep into its mirror image on the other side of the stock. Here is what it looks like before application of six coats of finish...

I reckon I have more than succeeded in making this unique rifle even more unique.

More to follow...thanks for reading.

Do the right thing.

Gaff

The Browning Insult

The following has nothing to do with optical encoders, far from it, but it does deal with another of my interests. I might go as far as to call it a passion. Modern firearms.

Somehow I got pulled into an on-line discussion about semi-automatic pistol designs. Specifically, the .45 caliber 1911 Combat Pistol. The reason I was sucked in...well, the discussion got a bit ugly at one point with severe criticism of the 1911, its reliability, its "old" design, etc. Here is an excerpt of one of the comments: "The 1911 is, at its core, a dogshit design. I’d never trust my life to one of those crapfests, no matter how ‘tuned’."

Being an admirer of John Moses Browning, I had to jump in with both "guns a blazin'". My response was the following:


"100+ years ago, a genius named John Moses Browning gave the US Army what it was asking for. A reliable combat pistol with one shot knock down power. In order to “pass the test” the pistol needed to fire 6,000 rounds continuously, only stopping to eject and insert magazines. It did just that flawlessly.
As far as the design being less than good…I might suggest that when any other combat pistol gets 100+ years of experience under its belt, then the design comparisons can be drawn.
Mr. Browning does have a couple of designs that seem to be classics. Take the MA-2 .50 cal. Heavy Machine gun. Is that a piece of shit design too? Or, his .30 Cal Light Machine Gun, which I believe still holds the sustained fire record of around 48 minutes at 600 rounds a minute. Nearly 29,000 bullets sent downrange. The only reason it stopped then, was it ran out of bullets in the pre-made bandoleer.
Are there better semi-auto pistols available in the marketplace today? Undoubtedly. However, I would posit that their designs are more complex, require more machining, and contain more components than JMB’s “classic” 1911."

O.K., so I should not have gotten sucked in. It's too late now. Why did I come to the defense of a design that needs no defense? The man that designed it had a sixth grade education. Yet, he holds more firearm patents than any person living or dead.

In my slightly less than humble opinion, when the .45 ACP, 1911 pistol is manufactured as it was in John Moses Browning's day, by craftsmen, machinists, and armorers that are the "best of the best", and used with ammunition it was designed to fire, there is no better, more lethal, more ergonomic, more reliable hand held firearm on the planet. Again, that is just my opinion. Which, I have come to accept, carries very little weight...I'm jiggy with that.

Until next time, or not.

Gaff

"Commutation Breakdown". No; not the Led Zeppelin Song

In this last of the Encoder Woes series, (I can hear a collective sigh of relief), I would like to touch on the non-touchy subject of digital commutation. First, a basic explanation of analog commutation in a familiar "brushed" commutator type motor.

Take your hairdryer or cordless electric drill, well, don't take them anywhere, just think about them for a moment. The cordless electric drill is a fine example for our, ahem, study. I am sure you have seen the small sparks that are emitted from the rear end of the motor when the trigger is pulled and released. Those sparks are from the hard carbon brushes that contact the segmented copper commutator on the drill's motor rotor (spinning part).

These carbon brushes conduct DC voltage and current to the many winding coils on the rotor. When this happens, the rotor becomes magnetized. Since the non-spinning part of the motor (stator) has permanent magnets or wired electro-magnetic coils, it does not need a commutator to energize the "magnets". They are energized by direct wire connections or by their inherent magnetic structure.

When the DC voltage is transmitted to the different rotor windings as you pull the trigger, the magnetic coils quickly change polarity from positive to negative and back to positive again as it spins. The stator magnets stay magnetized in one orientation. This switching of polarity causes the rotor to be attracted to, and repelled from, the different stator magnets. Voila! rotation. The more you pull the trigger, the more voltage and current flow, making the rotor spin faster. When you release the trigger, the motor becomes a generator momentarily, and sends DC voltage and current back toward the battery. However, most modern cordless drills "shunt" this voltage to a power resistor. This acts as a brake, and dissipates the regenerated energy into the resistor and ultimately out, as heat.

O.K. so now, you know where those little sparks come from. (Carbon brushes rubbing quickly against a copper commutator.) Now, let's take your "brushless" AC Servo motor. You do have one? Of course you do.

The reason it is brushless is because it is an inside-out motor. The rotor in this case, needs no voltage and current supplied to it because it is made with permanent, (Rare Earth, Neodymium), magnets around its circumference. "So", says you, "how does it spin?" "Well," says I, that's where the encoder, (remember the encoder?) really shines. Unfortunately, more explanation becomes necessary. Sorry.

Not to confuse matters any more than they most likely are already, a Brushless AC Servo Motor is actually a Brushless DC Servo Motor, in that, the AC like sinusoidal wave forms sent to the motor are actually DC voltage that is made into sinusoidal waves by the Servo Amplifier. It is called PWM, or Pulse Width Modulation. It is made by the very fast switching of a three phase transistor (Darlington). Those three phases are connected to the three stator (outside case) windings of the motor.

So, think of those smooth flowing sine waves made by AC, and imagine a close up of the wave edge that looks like a set of rolling stairs going over a gentle hill and down into a deep valley and up and over another hill. From afar, it looks smooth, in fact, it is many on and off cycles of the Darlington transistor in increasing and decreasing magnitudes of voltage and frequency.

Now, how does the Servo amplifier know which of the three phase/s needs to be powered at any given time? Or, how does it commutate the voltage and current? Answer: The encoder. Quite simply, the exact position of the encoder relative to the stator, gives the Servo Amplifier its ability to "know" where the rotor is, and which stator phase or phases to give power to to hold position, rotate forward or reverse and what polarity to provide at any given microsecond.

This is why it is so critical not to disassemble the encoder from the motor. That is, unless you have some expensive equipment handy to realign it. The realignment process uses the encoder itself, the three phases of the stator, software, the amplifier, and possibly an oscilloscope to accomplish this exacting procedure. In other words, don't try this at home. Leave it to the professionals.

If your eyes are still not glazed over, congratulations! I think that is enough on this topic of encoders and their possible woes. Of course, my explanations are rather simple in nature, in hopes to make the ideas a bit more palatable. In fact, the processors and their algorithms necessary to accomplish the powerful, smooth running performance of a modern servo system are fairly complicated. Thankfully, most servo drive manufacturers have done the hard part for us all. They have, for the most part, made the systems "Plug-and-Play".

Until such time as I think of some other earth shatteringly important subject to wax poetic on...I remain your faithful servant. I think I'm tearing up...

Always, do the right thing...

Gaff

Encoder Woes Part II

My last post dealt with the possible failure of the servo system's encoder cable. Since it is most exposed to its environment, physical damage can happen quite easily, and will cause servo system encoder errors. The next most likely cause for Encoder Woes, is the encoder itself.

Many servo systems use optical encoders as the feedback device in their positioning and velocity closed loops. Other systems use Resolver based feedback. A resolver is a more simple device that uses sinusoidal wave forms to establish voltage references at certain positions of the resolver shaft. It is akin to a small motor, in that is has rotor and stator windings and their relative position to each other, as it spins, produces the sinusoidal wave. This "wave" is then use in an algorithm to output the feedback to servo control.

In this blog, we are concerned with an Encoder. Does it have a "pulse?" This device, the encoder, is a digital and mechanical optical feedback mechanism. Its primary component is a precision glass disk that is segmented about its outer edge with an opaque coating. This segmentation produces a number of "windows" that a light beam can shine through. The light beam is produced by an LED. This LED is mounted near the outside edge of the disk, and a receiver is mounted on the opposite side of the disk. As the disk turns, the light beam is alternately allowed to shine through the disk, and is then blocked by the opaque coating. This action produces "pulses" generated by the LED receiver module as the light energy from the LED is alternately "seen" and obscured. The number of "pulses" produced on each revolution of the encoder shaft is its resolution. There are multiple "tracks" of windows on most encoders. One such track is the index mark track. It produces only one pulse per revolution. However, the precise location of this pulse is used by the servo system to determine the encoder's (and Motor's rotor) position, relative to the motor.

Some optical encoders are low resolution, producing say, 360 pulses per revolution. Others are high resolution, these sometimes use special algorithms to produce over 1,000,000 pulses per revolution. A common resolution for servos is between 1000, and 10,000 pulses per revolution. Many servo systems have an additional algorithm that will multiply this resolution by four. This is a Quadrature circuit. With quadrature, a servo motor with 2,000 pulses per revolution (PPR), will deliver to the motion controller, 8,000 PPR. Increasing resolution, means increasing system accuracy.

Now that you have bit of general information on what an encoder does, lets concentrate on what happens when the encoder doesn't do its thing. Those encoder errors we spoke of in the last blog could be generated right at the encoder itself. A servo motor's encoder is attached directly to the end of the motor's rotor (the spinning part), and fixed to the motor's stator (motor frame).

Usually, the motor mounted encoder has some type of "industrial" connector that makes the connection to the encoder feedback cable. This "industrial" connector then connects somehow to the circuit board of the encoder inside the motor's encoder housing.

I hesitate to tell folks to open the back of a brushless servo motor. These precision motors and their encoders are assembled in "clean room" type environments and then sealed. In addition, special digital alignment tools are needed to "align" the encoder to the motor's stator (outer motor frame). If the encoder is loosened or moved in the slightest, the encoder must be realigned. Moving the encoder on a brushless servo motor, will produce system errors, and will result in your purchase of a new motor, or the expense of a servo motor repair.

Hopefully, that last paragraph instilled fear and dread in you. If you decide to open the back of a servo motor, to peek and poke around inside, don't say I didn't warn you. If you do decide to open it, your best tool will be your eyes. If at all possible, look but don't touch.

Remember, most encoder errors are due to faulty connections. Look carefully at the short interface between the "industrial" connector inside the motor and the encoder's connection header. Specifically, look at solder connections. More so, if the motor is attached to a machine with lots of vibration. That vibration can cause those solder connections to fatigue over time. The solder will not fail, it is usually the wire strands immediately adjacent to the solder that break. You might even get lucky and find the encoder's connection plug has worked its way loose. O.K., now you can use your big mitts to get in there and CAREFULLY reconnect the plug.

If all the wires prove firmly engaged and solidly connected, then perhaps the problem is with the encoder itself. Something inside the encoder has failed. Well, unless you have a very expensive alignment machine and motor specific software, you are faced with the fact that a new motor or motor repair is in your immediate future.

If you do have the afore mentioned tools and software, then why are you reading this? You probably know more about servo motors and encoders than I do. However, if you are still reading this, and would like to know why it's so darn important not to move an aligned encoder on a brushless servo motor...stay tuned for part three of Encoder Woes. Commutation explained. That's commutation, not communication.

Till next time...