This section was originally included as part of the CNC instructions. In order to get new users directly into the actual operation of the computer and CNC machine, we have created this separate file. I hope you will read it before operating your CNC system, because I think it will be helpful for you to understand where I was coming from when I wrote these instructions.
Back in the day all sorts of ideas were being tried to simplify the mass production of machined parts. Many manufacturers were using hydraulic power and came up with some interesting systems. The method of choice before NC (back then they were called Numerical Control (NC) because the storage device was a one-inch wide paper tape) was a tracing system that duplicated parts by tracing them with a hydraulic system controlled by a really neat valve controlled by a stylus that the operator would move like a probe and the machine would duplicate their movements. Gigantic machines were built around this idea for the aircraft industry.
Hydraulic CNC systems?
It was only natural that this was the group of manufacturers would be the first to try this new field, and did they ever come up with some weird systems! You also have to realize that electronics were pretty crude during that same time period. My first NC machine was a Cinematic manufactured by Cincinnati machine tool. It had ball lead screws driven by hydraulic motors and was fairly reliable and quite popular at the time. Tool changers were still in their infancy. I ran it until it was so out-dated that I gave it away when it still ran. Another interesting point is this machine had a “wire wrapped” control with few circuit boards. If a recent graduate of electronic engineering had ever looked into the control enclosure, I’m sure his first comment would be, “impossible.”
I thought I bought a telephone company
My first machine that was controlled by electronics turned out to be a disaster. I bought it used and it came with a stack of manuals 18 inches high. I never dreamed I was going to have to look at every page, but I did. When I opened the control and looked inside, I thought I had bought a telephone company. I believe there were 120 individual circuit boards and thousands of individual transistors. It was manufactured by Edlund. We used to call it a “Deadlund.” I wasted more time and money on that machine than I care to admit, and I felt relived as it was loaded on a truck for its final journey to the junkyard.
Problems with no memory storage
The way this machine stored memory was interesting. At this time there weren’t any memory storage devices invented for commercial use. What this control did was feed a single block of code (a block of code contained the instructions the machine needed to make a single move) into a very long piece of Ni-chrome wire. The high resistance of the wire would delay the signal long enough so the signal could be amplified at the other end and sent back on the same wire without interference. The signal would then bounce back and fourth until the machine had moved to a location that corresponded to that block of code. Back to top
Sometimes I can be persistently stupid
New machines were thousands of dollars more than I could afford and not that reliable either. I remember a friend who had a three-year-old machine that cost over $100,000 that needed service. The first thing the technician said was, “I didn’t think they had any of these old bastards still running.” You can imagine how my friend felt when he made that $2500 payment each month.
You’d think I would have learned by then, but I can be persistently stupid at times. My next disaster was a MOOG milling machine. It used a Bridgeport base and didn’t have leadscrews. It was entirely controlled by hydraulics. Movement was controlled by thin plates that moved with the machine slides with accurate holes located at every inch. Pins about 0.187″ (5 mm) would engage the proper hole and then another plate with holes spaced at 0.200″ would come into play, and the last 0.200″ relied on a single turn of a lead screw. The machine finally arrived at a position within a 0.001″ of accuracy. I didn’t realize it when I bought it, but I was horrified to find that this thing worked like a player piano. The one-inch wide paper tape wasn’t read with switching devices like other machines. It actually was more like a valve that allowed or prevented air to get to cylinders that controlled hydraulic valves. When it read a block of tape (around 10 lines of holes of 8 holes each) the SOB sounded like a steam engine. I chalked that one off to having more balls than brains; however, we actually made more parts with it than we did with the Deadlund.
It should also be noted that I’m sure that these early NC machines were the best that could be designed with what was available, and the solutions that they came up with were quite ingenious at the time. I’m looking back at it from a slightly humorous position and in no way infer that the designers of that era weren’t up to the task. They just didn’t have the tools to work with that we do today. Back to top
The course is set
At this time, CNC machines could only cut straight paths, and as soon as the electronics were available to store just a small amount of memory the new rage became “look-ahead” control systems. This meant the cutting tools wouldn’t create machining problems when they hesitated as the next block of information was read. Stepper motors were used for a short period to drive the lead screws; however, within a few short years the entire industry switched to DC motors. Encoders or resolvers were used to keep track of position. The DC motors controlled by fast computers and working in unison with accurate ball lead screws created a system that was very close to where we are today; however, they were slower and very expensive. Today, servo drives use AC motors controlled by varying the frequency to the windings, eliminating the brushes needed with DC motors. The latest innovation is linear motors that can move machine slides at incredible speeds. Back to top
A new way of thinking
The marvelous part of the CNC revolution wasn’t just the fact that it was eliminating workers from sometimes very strenuous and boring jobs; it was that there was finally a method of cranking these handles in unison to do things that the best machinist in the world couldn’t accomplish. By moving screws on the X- and Y-axes in unison, you could machine tapers, circles and, in fact, any shape you wanted. This allowed engineers to design parts with the shapes that they wanted, not just shapes that were possible to machine using the old methods. Machines that cost many thousands of dollars suddenly became scrap iron. These new CNC machines didn’t care if they were cutting a complex shape or a straight line. Whether the tolerance was tight or not the machine was always “right on,” and the tools determined the tolerances. Back to top
Ball lead screws—the missing ingredient
The lead screws used on these machines should be mentioned. They are the interface between the computers and the mechanics. The problem of backlash was solved with “ball lead screws.” These screws have re-circulating balls that roll in a groove ground into a shaft at a pitch of two tenths of an inch. The pitch on these screws has increased over the years to achieve speeds over 1000 inches (25 meters) per minute. At a pitch of .200² (5 mm), a lead screw would have to turn at 5000 RPM to accomplish this speed, which is why ball lead screws have as high as one inch in pitch. Even more amazing was the fact that they improved the accuracy as they increased the pitch. You can make a .0001² (.0025 mm) correction on a good CNC lathe. Think about that. A slide will accelerate to a speed of over 1000 inches a minute in less than a second, move a short distance and decelerate, stop and still be accurate to one ten thousandth of an inch. The ball screws must be very precise, because a lead screw would be useless if it had any backlash (the amount you have to rotate a lead screw before the slide moves).
Ball lead screws are very difficult to make, which makes them quite expensive—several thousand dollars for each axis. The people who solved the lead screw problem should be commended as much as the electronic geniuses who came up with the computer controls. At Sherline, we have CNC machines that have been running over ten years and still don’t have any noticeable backlash. Back to top
Carbide insert tooling changed the entire machine tool industry
At the same time, carbide insert tooling became available and took the market over like a storm. I don’t think I could have ever convinced a machinist in the fifties that some day he would be taking 0.300″ cuts on cold rolled steel at a cutting speed around 400 to 600 fpm (200 meters/min) using a 40 hp lathe at 0.020″ (.5 mm) feed rate for each revolution with little carbide tools made using powdered metal technology and held in place with little screws and still be able to get marvelous finishes on gummy old cold rolled at the same time. They do, and we at Sherline do all these things that give our customers a lot of bang for the buck. The consumers of products that manufacture using this technology benefit as much as the manufactures that use them.
Because lathes could also produce these types of moves, the large and expensive form tools were on there way out. This may not seem significant, but by generating rather than forming shapes, these shapes could be far more precise, and at the same time machines didn’t have to be so massive to prevent tools from chattering. Hand scraped ways were replaced by frictionless, ingenious slides that lasted for years with little maintenance. Because there is always the possibility of a crash, machines are no longer built where the headstock is an integral part of the base casting, and in most cases they can be realigned if one of these disastrous events should happen. Back to top
Why I love CNC robots
In closing this section, I firmly believe that these machines that we call CNC are the robots of the future and I truly love them. They have allowed me, Joe Martin the designer, to design the parts that I’ve always wanted to design without dumping my problems on Joe Martin the machinist, who must produce parts for Joe Martin the businessman, who can supply you, the customer, a fairly priced quality product and at the same time allow Joe Martin the owner a reasonable profit to buy more of these marvelous CNC machines, of course. And so it goes.
Even though this doesn’t do the subject justice I thought you might find that interesting. It’s always wise to see at least a brief history of a subject before becoming part of it, even if it’s only statistical. Back to top
Here is something I wrote in my book, Making Money the Old Fashioned Way, that you may find interesting:
“THE NEW MANAGERS
CNC machines allow a smart worker to produce more work than ever. Rather than eliminating the need for intelligent workers, these machines require organizational skills that few managers have. The machines they control are very complex, and the employees who can control these machines are equally as valuable to a company as that of standard managers. In the past managers were considered people managers. The managers who control these machines are robot managers. When you consider how important these machines have become to the quality and efficiency of manufacturing a product, the group of workers that controls these machines will soon be equal to the managing staff of any company in prestige and wages. Today’s management still hasn’t grasped this concept, but soon they will be forced to accept this condition when they find their million dollar machines operating at half speed.”
This CNC class is open to those willing to work hard
In order to make the following instructions more interesting for me to write and you to read I’m approaching the teaching of CNC programming the same as I would as if I were teaching a small class of students. The students who attend these specialized classes later in life have various reasons and expectations for being there, and I’m trying to address the whole class as I write. When I take off on a tangent I’m addressing individual students with a different background who I visualize sitting in the class and answering a question that I believe may be asked in a similar class, so please bear with me. I don’t want any of my students left behind. Back to top
Enjoy the flight
In many of the coming examples I also describe the movement of the spindle as an aircraft that you’re riding in. This may seem “far out there,” but CNC milling is a 3D world, and if you try to describe these movements in the movement of the table slides you’ll soon not know whether you are coming or going. You have to visualize the work staying still while the cutter moves. Again, bear with me and enjoy the flight. Back to top
A different way of learning
Long ago I became aware of the success rate of people who, when left alone with their video recorder and an instruction manual, failed to pass the test and had to stay up late to turn on their recorder to record a show they wanted to save. From their own statistics you would think manufacturers would have attempted to teach in a different manner, but they don’t. The products get more complex, making the instructions more complex, and the poor consumers of these products are at a loss. I don’t teach using these methods because they obviously don’t work. With my instruction you won’t be sure if you’re reading a novel or an instruction manual, but I’m sure you’ll be able to program and make a part when you get to the end.
The first instructions I completely wrote for my tools (I had written instructions about radio control equipment and rules for RC events in the past) were how to cut a screw thread using a rather crude device I designed (but which works well) for a Sherline lathe. I was surprised how few calls on how to use it came in after I sold my first 200, because it is a bit of a complicated thing to do. I then started to wonder if anyone was using it, and you’ll never know how relieved I was when a customer came in with a bunch of parts that he made with threads on them.
I knew I was on to something and have always written in this style ever since because it works. It had to work because at that time I was the only one at my company who could answer questions of this type, and I didn’t have the time. The fact that I’m a self taught person probably has something to do with it. I even went on to write a couple of books in this style that were well received. Back to top
A new challenge
I remember getting a call from Sears about my folksy style of writing that didn’t follow Sears’ instruction guidelines about the screw cutting attachment. I asked him how many calls they had received about how to cut threads using it. He answered, “None.” I asked him who there could answer a technical question of this type. He answered, “Nobody.” I said, “With this being the case, don’t you think you should leave well enough alone?” I never heard from him again. Right now, I’m looking at these instructions as one of the biggest challenges I’ve ever taken on as an author, and I don’t plan to fail. The average instruction manual written on this subject is two to three hundred pages of very technical reading. You’ll never crack a smile reading one of these manuals. I’ll do it in less than fifty.
The only students I hired who learned CNC had good teachers, not good training manuals. In fact, I can’t think of any employee in the last 30 years that I’ve ever hired who learned CNC programming and how to run these complex machines on his own. You will! I had to learn on my own because I was so broke after I bought my first NC I was out of choices. I learned by staying up late, working my ass off and making costly mistakes. I would have given my left you-know-what if I had something like this to read rather than reading the junk written by professors trying to prove how smart they were to other professors rather than attempting to teach their own students. Back to top
Sherline customers want to build components
I saw the customer who was going to read these instructions as a person who wasn’t particularly interested in computers or gadgets and was only interested in making parts. I believed they were curious about CNC and wanted to learn about it without spending too much money. They probably haven’t tried to learn how to do something this complicated in the last 20 years. Remember that CNC is a new way of doing and thinking about the machining process, and I believe I’ll help get your brain in tune with what you are about to learn with my ramblings. Back to top
Learning while you work
A student of this class could be already working at the trade. Words of advice for this group: You can’t afford to have idle thoughts as you load parts on machines that other people set up and wrote the programs for unless you are satisfied to load parts for the rest of your life.
First study the mechanical part of the setup; things like how the part is held and the type of cutting tools used and how long they last. You have to show some initiative and start analyzing the program you are running and ask intelligent questions. Notice, I said intelligent questions. Bosses are usually smarter than you think they are, and they easily know when some when clown is pulling their chain. Don’t ever make suggestions unless you are sure you are right. A better way to make a suggestion of this type is to ask them just why the job is set up or run the way it is rather than your way. That way you’re not threatening them with your question, and they’ll appreciate a chance to teach you if you are wrong. If you find out you were wrong, it gives you a way out by saying that you were sure that they must have had a good reason. It wouldn’t hurt to let that rule work its way into your personal life.
When you start studying their programs, you’ll find them written like a story. Just like a book, the better the author, the easier the program is to read. Each tool used will have its own chapter. (In the real world of machining you’ll run few machines without automatic tool changers.) Study these chapters one at a time and watch what the machine does as the program advances. In case you didn’t realize it, I’m also instructing all you hobbyist out there on how to organize your programs and setups. Plan them like someone else is going to run the job and pick apart your own work. If you don’t, you might find yourself trying to machine your vise off the table. Back to top
Getting you into the learning mode
I also felt that people of this type would want to read something about what they are in store for before they started. I wanted my customers to understand just how difficult CNC programming can be to learn at the start and just how interesting it can be at the same time. In other words, I felt “Joe home machinist” doesn’t stand a chance unless he’s inspired to do so, and in my own way I’m trying right now to inspire you to learn how to program and use these marvelous new CNC machines. I know how easy it is for you to go back to the way you already know or forget the whole idea. I don’t want customers who think it’ll be easy to learn because they’ll be unsatisfied from the beginning and take out their anger on Sherline. Back to top
You’re about to learn how to control your robot
These aren’t instruction about operating a simple single system like a VCR, but instructions about controlling a very complicated device. You are not operators of these marvelous machines; you are masters telling your robot what to do, and you, the controller, have unlimited choices to make. I want to get this concept through to that average customer I mentioned, yet I know that only one out of five professional machinists I know seems to really understand this point. Back to top
I’m going to be a student in my own class
I was shocked at just how much I had forgotten about the process of CNC programming. I probably know as much as anybody of what you can do with CNC machines, because I own at least twenty modern machining centers, yet I haven’t really written any code in fifteen years. After thinking about it for a couple of days while unsuccessfully attempting to write a simple program I decided this is a good thing. I also decided that I’d learn this from the Linux site on my own and not use the books that were available to me. I believed that if I wrote the instructions as I learned how to program EMC myself I’d write better instructions; after all, all you have to be is one page ahead of your students to teach. Just joking, teachers. Back to top
Something for nothing
Sherline Products Inc. is not charging you for this EMC2 program, and it is free because of work done by NIST (National Institute of Science and Technology), a government funded organization. The EMC (Enhanced Machine Controller) was written by the NIST and is a very sophisticated program. We all now have the benefit of millions of dollars of programming along with the source code, if needed, simply by asking. Back to top
We all owe thanks to the EMC group
At the time this program was written it was thought that only very advanced programmers and scientists would be using a program such as this, and the average person stood little chance of making it functional. Fortunately for us, a lot of very smart people before us, donating their time, started developing a programming interface that allowed both businesses and hobbyists to take advantage of what they had done without being engineers. I’m very pleased with what they have done. This group still works together through the Internet, and help is available through Internet chat groups. Many people have donated much of their time to make this system “user friendly.” Back to top
The EMC2 program operates under the Linux operating system, which is also a free system, and it would be wise to operate it from a dedicated computer for this task. A dual boot system can lead to problems, because Microsoft code has been purposely written to be the dominant control of your computer whether you want it or not. I like the Linux concept of people working together where all have the benefit of any single person’s work. For example, these instructions will have a Sherline link placed on the EMC for all to read whether they are Sherline customers or not. It will be my donation towards a successful system available to all. I’m learning how to program EMC by using the Internet site put together by dedicated EMC users, so you can also fall back to their site for help. See www.linuxCNC.org
(Note: The following section is repeated from the instructions.)
This is going to be easy if you do it my way
The Linux operating system works pretty much like all the others. If you can find your way around a Mac or Windows computer, you will have no trouble navigating menus, opening, closing and copying files or saving and deleting items in Linux. The new Ubuntu version is the most Windows-like yet. When you turn on the computer, there will be four icons on the desktop. Depending on whether you have a lathe or a mill, inch or metric, choose the correct icon for your machine and double click on it. In a few seconds you’ll get the graphical interface to the EMC2. Well, that was easy. Now, after BS-ing you to death on how hard this was to do I’m going to show you how easy this can be, but only if you do it my way. Back to top
Computers have the patience of a saint
If you’ve had little computer experience, the first thing you will learn is that computers have the patience of a saint. If computers were more human they would probably like to toss their operators out the window as much as frustrated operators want to do the same to them. The only way you can keep a computer from giving you an error message is to not give it errors. The tricky part is computers don’t always tell you the error to fix or how to fix it. Computers just tell you that there is an error of a certain type. This can become maddening, and you have to know when to take a break and walk away. Things of this nature are the worst when, for the sake of your own sanity, they should be the best. In many ways, learning programming is similar to learning machining. You can’t take short cuts. If you find yourself going in the wrong direction, back up immediately. Back to top
Learn machining first
If you know little about machining and little about computers I’d suggest you first concentrate on learning about machining. How can you expect a machine tool and a computer to carry out your commands if you don’t know the commands to give? Above all, don’t start with a project so complex you don’t stand a chance in hell of succeeding. Let each simple problem solved have its own rewards in knowing you just traveled another block further down the CNC machining super highway, route EMC.
NOTE: I have written a book called Tabletop Machining that is an introduction to metalworking at the small end of the size scale. Details can be found at HERE. If you are new to machining, you will find the information in this book quite helpful. Back to top
You will be learning the CNC language of the robot world
The standard “G” code method of programming is to simply replace the manual inputs into a machine (cranking the handles) with the commands that have become industry standards. This is the method you should learn before learning any other method of programming. It is the basic way that CNC machines “talk” to other CNC machines. Even if a simpler system were available today I still wouldn’t teach it. It would be similar to teaching a language that few citizens of the world spoke. Programs written using G-codes can be read throughout the world. G-code standards came about very early in the game because this game was controlled by engineers rather that marketing people. Back to top
Contouring programs—another world
Programs that allow you to do contouring quickly become very complex. Today there are some affordable programs available for sophisticated hobbyists. These programs can create as many problems as they solve, because of the complexity of each program. Each program has to work with other programs, and each program has its own set of complex rules. If you think you can learn these programs easier than you can solve a couple of trig problems you’re in store for a rude awakening; however, if you already know how to use 3D CAD programs you could quickly find these programs very useful. It should also be stated that it is the only way available to create contoured machined shapes. Back to top
What it costs in the industrial world
The basic method that these programs work together in the industrial world and the cost of these programs is: 1) The part is designed using a modeling program ($5000 to $10,000), 2) The modeling program is converted to a CNC program (another $5000 to $6,000) and 3) the resulting code is run on a CNC machine starting at ($25,000) that makes the part. The people who can operate these systems are carefully chosen, trained and well paid. The fact is that any business has no choice except to use the program they purchased, because the programs cost so much and are so very necessary to remain competitive in today’s world. They have to spend a great deal of money to accomplish this, while the hobbyist has a choice. Back to top
Today’s low-cost programs were once complex, expensive programs
The business world understands how complex it is to implement these procedures; the hobbyist doesn’t. Because the hobbyist may be purchasing a program that cost thousands of dollars just a few short years ago for a few hundred dollars, the programs themselves haven’t become less complicated. They only cost less! In your mind you may be having visions of complex shapes being machined with little effort on your part while your two thousand-dollar investment turns out parts that the old masters of the machine trades would envy. Well my friend it’s possible, but it’s time to come down to earth and again think about the complexities of doing so. Back to top
Cutter compensation—what makes CNC work in a machining environment
I could have sneaked out the back door and only wrote instructions for a couple of simple moves without cutter compensation and let it go at that; but deep down inside, I’d have known I was cheating you out of the real benefits of CNC. I believed that if I started teaching you to use this marvelous programming tool right at the very start it will soon be second nature, and our class will leap-frog ahead of our competition with those thick boring books being taught by instructors I wouldn’t let near the least expensive CNC machine in my shop.
If you take the effort to learn this method of programming at the start along with a little simple trig, you’ll find it well worth the effort. Cutter offsets are the way you control size with modern CNC machines. When you start making more complex parts and you don’t use cutter comp you’ll have to change the basic numbers of your programs to make a part on size. Sounds simple enough until you find that every time you correct a number here you end up screwing up another number there. Take my thirty-five years of experience in dealing with CNC and accept this cutter offset stuff as a fact. Back to top
I can’t help anyone who isn’t willing to work hard
Back in ancient times the great mathematician Euclid told a Pharaoh who wanted to learn geometry the easy way that Pharaohs had to walk down the same road as scholars to education. In a sense I’m also stating to you that you will have to learn programming the same way as I’m about to, and at this time I’m only a couple of pages ahead of you. I am certain that if I sat by the phone and answered questions twenty-four hours a day, and I don’t plan to, I couldn’t help those who aren’t willing to put forth the effort it takes on their own to learn to work with these marvelous tools. Back to top
This road that you are beginning to travel can become one of the most interesting roads you have every traveled; however, you must take the time to gather the facts that can make a trip so interesting. Instead of seeing great ancient cites on this road we’ll be gaining the knowledge that will make our next stop even more interesting and more complex. We’ll study a little and then apply these rules to your machine. We will first make simple moves that become more and more complex and at the same time more interesting as we travel on. Eventually we will reach Martinsville, a city on this road, where you will have so many choices as to the direction to travel that you’ll be leaving me and heading out on your own to design and build things that you never thought possible in the past. The rules and facts that you will learn on this road will allow you to have a machine at your control that home machinists a few short years ago couldn’t dream of. Take the time to enjoy this trip because you’re on a road with no end if you have set your goals correctly. Back to top
You may want to consider a CAD program in the future
I’m going to close this section off by inserting something I wrote about learning and using AutoCad®. The ease with which many of the programming problems can be solved has to be mentioned at this time; however, I wouldn’t recommend dropping what you are doing. From what I understand there are several excellent programs available at very reasonable cost, but I don’t want to recommend any particular program. Back to top
The following paragraph is from the book Tabletop Machining. It covers some comments about learning to use a CAD program.
The first task I took on to learn the program was to lay out and design a set of bevel gears that could be cut on a Sherline mill using a rotary table mounted on an angle plate. By drawing the cross sectional view accurately, the angles needed to cut this gear could be taken directly off the drawing without using a trig table or a calculator. I was beginning to see the light.
I’m getting pretty good at using the program now and it has put a lot of the fun back in designing for me. Looking over my partner Carl’s shoulder at an assembly designed by computer was of no help for me, and I would need a standard full size or larger layout to design with. I’ve since found that doing the design totally myself, it has become the perfect way for me to work. I love the program. It has become the perfect program for a designer and manufacturer like myself and has made me more productive than ever.
I’m fascinated with the program because it does a drawing without errors when used properly. The program eliminates much of the boredom of adding and subtracting numbers as you go. Accuracy isn’t attained by the precision of your lines but rather by the accuracy of the information the program is given. Angles are not derived from a protractor and using divider points but from calculations by a computer to as many decimal places as needed.
I learned drafting in high school back in the fifty’s. My problem was I was a “slob” when it came to drafting a pretty drawing. My numbers and views would be correct, but my lettering and lines weren’t neat enough. Things have changed now with the aid of this program and my lettering is just as good as the best. I can no longer spill blobs of ink on an almost completed drawing and have to start over. I can change my mind as much as I want without irritating anyone. I’m a happy man.”