Computer Numerical Control

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Understanding CNC

Have you ever asked yourself how machines in a factory know exactly when to stop making the parts they’re supposed to make? Well, this is all because of Computer Numerical Control (CNC). But to understand CNC, you have to know what Numerical Control (NC) is.

HISTORY

NC machines were first introduced after the 2nd world war as mass production became the trend. These machines were given a set of instructions in punched cards. However, these machines were hard-wired and their parameters were difficult to change.

These NC machines still required a great deal of human intervention. To illustrate this point, try to take a look at a drill press. A lot of actions have to be taken in order to manufacture a product. The process is actually so complicated that a person has to do something almost every step of the production process. This created an avenue for errors to take place as the likelihood of fatigue increased with the quantity growth.

CNC then came into the picture when computers were introduced. Punched cards were replaced by floppy disks, cables, and other software transfer media. This made it easier to manage and edit data.

Production and manufacturing were revolutionized by the increased automation of CNC machines. These machines allowed a degree of added control over the quality and consistency of the components that were manufactured without any additional strain on the operators. This reduced the frequency of errors and allowed the operators time to perform additional tasks. Furthermore, this automation allowed a greater degree of flexibility in the way components are held in the manufacturing process.

With the advent of Computer Aided Manufacturing (CAM), even programming CNC machines is a snap. These programs actually take the bulk of the programming process to make the operation less tedious. However, to be an effective programmer of CNC machines, you have to know what the machine you’re working on will be doing. That is why machinists are often the best people for the job.

The ease that the machines provide is hinged heavily on the quality of the machine. Low-cost CNC machines oftentimes have many functions that have to be manually activated. High-cost machines, however, are almost fully automated. The operator only has to load or unload workpieces. Once the cycle has been initiated, the operator just has to sit back and watch for any malfunctions. The stress on the operator is so low that some even complain of boredom in the middle of a cycle.

CODING

The programming language that CNC uses is called a G-Code. These codes actually position the parts and do the work. To be able to have a machine work properly, you have to input the correct variables such as axes, reference points, the machine accessories, and whatnot. Every machine has a different set of variables so you have to be careful to take note of the differences.

Aside from the G-Code, logical commands or parametric programming can be used to make the process more time-efficient. This type of programming language shortens lengthy programs with incremental passes. A loop can also be programmed thereby removing the need for coding repetitions.

Because of these features, parametric programming is more efficient than CAM. It allows users to directly and efficiently make performance adjustments. It also allows extensions to the functionality of the machine it is running on.

And that makes CNC.

The CNC Family

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You might have not heard of the CNC before, or what it does, or how it makes lofty manufacturing operations a lot easier. However, CNC machining is dubbed as one of the most important factors of most production processes. The common tasks CNCs machines usually perform are drilling holes, tool changing, cooling and lubrication of separate factory machines at the same time.

Let’s start with a brief introduction. CNC stands for Computer Numerical Control and it has been around since the early 1970’s. Before it was christened CNC, it was called NC, for Numerical Control. When computers were introduced during 1070’s, the name changed. It has stroked almost all manufacturing forms in almost all stages of production. CNC machines either substitute some existing manufacturing processes or combine work with them.

A CNC program is just any other set of instructions. It’s written like a sentence and the order of operation is chronological. The machine will then execute that set of instructions step-by-step. A special series of CNC words/codes are used to relay what the machine is supposed to do. CNC codes begin with letter addresses (like S for spindle speed, and X, Y & Z for common linear axis motions).

When certain codes are arranged together in a coherent method, this group of CNC codes create a “command” that is like a sentence. A common CNC machine will only be needing around 40-50 words/codes to program different commands. See, it’s not very difficult to learn.

Although CNC sounds very independent and do-it-all, there are a few words that you need to know to fully understand CNC operations.

THE CAM

CAM stands for Computer Aided Manufacturing. It simplifies the programming processes which are new, and added to the CNC program regularly. Of course, the easy applications can be programmed with only the simplest machines around: the pen, paper and calculator. However, more complex programs are vital regularly. It is when composing these programs become much more tricky and (worse) tedious.

The CAM is a program that runs on a computer that aids the CNC programmer with the programming. It also works hand-in-hand with the CAD (Computer Aided Design) design drawing (those designs engineers compose/nurture). With the CAM helping, redefinition of the work-piece configuration is not needed. What the CNC programmer is left to do is just to specify the machine operations to be executed and the CAM system will compose the CNC program automatically. Thanks to CAM, programming tediousness will not be a problem to the CNC programmer again.

THE DNC SYSTEM

DNC stands for Distributive Numerical Control. It is a computer that is connected with one or more CNC machines, forming a network. When a program is manually composed and ready to be loaded to the CNC control, it is being typed right into the control. However, this is like using the CNC machine as a luxurious keyboard.

Moreover, if the CNC program is achieved with the help of CAM, it is already in text form and ready to be loaded to the CNC control. The DNC simply distributes the CNC program to more than one CNC machine. Lately, the newest controls are more advanced in terms of networking capabilities and can be networked with, say, the Ethernet.

If it’s your first time to read and learn about the CNC, it may sound so mighty and ubiquitous. It’s about time you learn they also need help from some programming friends such as the CAM and the DNC. No man is an island; but hey, neither are CNC machines.

People You Will Need When You Already Have A CNC Machine

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If you think that you will just sit back and relax when you have a CNC machine in your shop, think again. CNC may help you speed up your operations and even make them more efficient. However, CNC is not a “wonder robot” which will make you disregard all your employees and expect your shop to run on auto-pilot.

Though you will need more people without the CNC technology, you will need only three very, very skilled people. Call these people your friends, your team, whatever. In the long run, they might be just all you need to keep the shop in good shape.

THE PROGRAMMER

The first person is the CNC programmer. S/he is like the "playmaker". S/he will create the programs that the CNC machines are intended to execute. Since the programs are in the form of CNC codes fabricated like sentences, he should have mastered these codes because they work like a different language. The regular CNC machine can use up to 50 codes, so that’s like learning 50 new words for the newbie.

Also, the programmer should have at least and engineering or machining degree. Remember that the CNC machine will only execute WHAT IT IS PROGRAMMED TO DO. If the program is wrong, the whole operation goes down the drain with it. Moreover,s/he should also be flexible and have a fast turn-around because a CNC machine is often used to machine a huge selection of different work-pieces.

THE OPERATOR

The second person that you need is the CNC operator. S/he will simply recheck the programs loaded to the machine and push the right buttons to get the work done. However, thinking that a CNC operator can have little or NO SKILL AT ALL is wrong. A CNC machine operator must have at least basic machining skills and s/he should have undergone some form of training to run a CNC machine.

These machines can produce very intricate motions, making it possible to make shapes that cannot be created on conventional machine tools. So, the operator should foresee this complexity and know how to cruise with it. The skills that an operator must have though, are lesser compared to the operators of conventional machine tools.

THE TECHNICIAN

The third person that will need is the CNC technician. Although this may still be the programmer, it’s more convenient to always have a technical expert on-call because in the long run, you may have more than one CNC machine and you may need to prioritize over the other in case both gets crippled at the same time. Just like the programmer, the technician should also be flexible and articulate. CNC offers a lot of complexity when it’s running right, how much more if it’s behaving badly?

So, if you are having job openings for positions that need to be handling a CNC machine, ask the applicants first to do a demo for you and make sure that during the demo, they know what they’re doing. An exam may also do wonders too. If they have no experience with any kind of CNC machine, it is advisable that you encourage them to take short courses on CNC.

Eighty-hour courses are available online and hey, it’s better than nothing. Experts even encourage employers to hire CNC machinists who have finished AND PASSED the National Occupational Competency Testing Institute (NOCTI) assessment just so they could be sure that their CNC machines will go to good hands. After all, a CNC machine is still an asset.

Programming 101: CNC

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After World War II, people realized that they have to manufacture goods at a faster rate and at a lower cost. Hence, mass production trending came to be. Those events led to the development of the Numerical Control (NC) machines which in turn led to the Computer Numerical Control (CNC).

HOW TO PROGRAM A CNC MACHINE

CNC programming uses a code similar in structure to BASIC. So, if you know how to construct a simple counting program, chances are, you already know what a G-Code looks like. However, there a few other things you have to consider before you start encoding instructions.

The first thing that you have to do is to assign values for each of the variables. These variables include the programmable motion directions (axes), and the reference point for the axes. The values that you assign to these variables dictate the movement of the machine.

The next thing that you have to do is to take into account the accessories of the machine. Many machines have accessories that are designed to enhance the capabilities of the basic device. However, using these accessories requires you to include them in the coding system. This means that if you want a more efficient machine, you will have to know the machine inside out.

READING CODES

After those steps, you have to create a subprogram that will deal with the math. This step will then allow your machine to compute the necessary variables and effectively operate without stopping to ask the operator what the limitations are.

To show you what these codes look like, here’s an example from Wikipedia:

#100=3 (bolt circle radius)
#101=10 (how many holes)
#102=0 (x position of ctr of bolthole)
#103=0 (y position of ctr of bolthole)
#104=0 (angle of first hole
Tool call,
spindle speed,and offset pickup,etc
G43 in some cases (tool length pickup)
G81(drill cycle)
call sub program
N50
G80
M30

Subprogram
N100
#105=((COS#104)*#100) (x location)
#106=((SIN#104)*#100) (y location)
x#105 y#106 (remember your G81 code is modal)
If #100 GT 360 goto N50
#100=(#100+(360/#101))
Goto 100

In the code above, the machine is a drill. The operator utilized a loop in order to keep the machine from stopping. The subprogram then governs the cycle of the machine. This code is still quite a simple code. Other machines require the inclusion of the maximum RPM in the coding.

An easier way of programming CNC machines would be the use of Computer Aided Manufacturing (CAM). This system takes on the brunt of programming so that it doesn’t seem so tedious and frustrating. It is still similar to BASIC.

Another programming enhancement that was developed was the parametric programs or the logical commands. These programs were designed to shorten lengthy codes in order to make them user friendly. However, these codes do not always use the same language with every machine. The language and sequence often varies depending on the typ of machine you will be working on.

The operator has to know what the machine can do or what it was made to do before attempting to program it. You should be able to visualize the machine doing what you want it to do.

But, you don’t have to be a math wizard or a programming genius. You just have to know what your machine does and what you want it to do.

Programming CNC Machines With G-Codes

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Ever since the industrial revolution started, the demand to create precise instruments and products is an important factor in large scale manufacturing. Belts, screws, Drills and all movable parts needed to create other products in the assembly line must all be exact and compatible, thus extra care must be taken in order to ensure that all moving parts match perfectly. Computer Numerical Controlled programming has become an extremely important part of this process.

Computer Numerical Controlled Machines are useless without any programming. CNC’s rely on pure hard codes in order to execute commands that the Machine Operator wants to do, therefore not only is it needed to learn the mechanics of the whole Computer Numerical Controlled Machine but it is also at the utmost importance that the Machine operator knows how to communicate with the machine, and that is by using G-codes.

Preparatory code/ functions or much commonly called as G-codes are functions in the Computer Numerical Control programming language. The G-codes job is to manage the position of the tool as well as control the step by step commands during the actual work. Basically the G-codes are the most important part of the Computer Numerical Control Programming algorithm.

There are other codes involved in the programming of CNC’s such as M-codes that manages the machine, T-codes for managing the tools, and F-codes for the tool feed and tool speed controls. All of these codes are created in a Computer Aided Manufacturing (CAM) software.

G codes as well as the others use the RS-274D as the recommended standard for the Computer Numerical Controlled Machines. This standard was developed by the Electronic Industry association during the 1960’s. These standards provide a basis for the creation of Computer Numerical Controlled Programs.

First designs of these standards came from punched paper tapes as the medium standard for data interchange, but now ASCII character bit patterns are the standard for the representation.

G-Codes

Lets discuss the g-codes further, as what I have said earlier G- codes constitute only a part of the Computer Numerical Control Program, in the whole programming algorithm, they are denoted by the letter G, Basically it is a code telling the machine what kinds of actions to perform in a step by step basis, examples of these actions would be rapid move, controlled feed moves that would bore holes, a work piece cut routed to a specific dimension, change a pallet, and set a tool information such as offset.

After creating each part of the codes, the algorithm is compiled in the Computer Aided Manufacturing (CAM) software. The CAM software basically use translators called post processors to output the code optimized for a certain machine type. Often times, post-processors are often used to allow users to enable further customization.

G-codes can also be used to create outputs for Computer Aided Design systems used to design printed circuit boards (PCB). Any software must be customized for each type of machine tool that it will be used to program. Some G-codes are written by hand for volume production jobs.

Some Computer Numerical Controlled machines use conversational programming. Conversational programming is an easier way to program CNC machines because it is more “user friendly” because it uses a wizard like program that hides the G-codes into plain view. Some Popular examples of this kind of CNC machines are the Southwestern Industries’ Proto TRAK, Mazak’s Mazatrol, and Mori Seiki’s CAPS conversational software.

Conclusion

With these kinds of further sophistication in programming Computer Numerical Controlled Machines, it is expected in the future that programming would be much easier for its machine operators.

Weighing Technology's Offers: The Pros and Cons of a CNC Job

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Are you good with computers and looking for a job? Well then, consider being a CNC machine operator. It’s usually easy, full-time and the name isn’t intimidating, right?

If you think that being a Computer Numerical Control (CNC) machine operator may be a bit out of your reach, think again. You don’t have to be a math wizard or a programming genius to get that position. But don’t jump in just yet! There are a few things that you have to know (and consider! ) before applying for the job.

The first thing that you have to understand is the abbreviation CNC. According to an online encyclopedia, CNC stands for Computer Numerical Control, and refers specifically to a computer “controller” that reads G-code instructions and drives a machine tool, a powered mechanical device typically used to fabricate components by the selective removal of material. CNC does numerically directed interpolation of a cutting tool in the work envelope of a machine. The operating parameters of the CNC can be altered via a software load program.

THE PROS

The good thing about being in this job is that the workload is actually light. Operators even complain of boredom because the cycles of CNC machines are all automated. All they have to do is initiate the sequence, sit back, watch for malfunctions, adjust the performance of each machine, and turn them off. If your boss is kind enough to let you use an MP3 player while working, then you sure are lucky.

Another good thing about this job is that job openings for this position will always rise. Technology is moving forward. CNC machining will certainly lead the demand because in CNC, a group of machines can be controlled at the same time. That is exactly what big-time companies want, right? To reduced manual overseeing and just leave it to the machines.

Advantage in this job arena is easy too. Statistics show that you will need only a high school diploma and (more importantly) an experience in CNC operations to gain an edge.

THE CONS

The thing is, when you’re in this line of work, it is repetitive. One gets bored after doing the same mechanical thing over and over again. As time withers, you will reach a point where you will breathlessly wait for the next paycheck and not actually care about the job. It’s emotionally exhausting. Furthermore, programming and operating these machines can be tedious. So, add that up to boredom and you get disproductivity.

Another thing that you should think about is the work environment. You’re going to be working in a factory. And factories are located away from town. If you’re not comfortable with being away from the hustle and bustle of the city, this might not be for you.

It can get pretty dangerous. Reports show that although most CNC operators work in a well-lit and smoothly ventilated environment, the high-power machinery poses dangers for them in the form of flying particles of metal and plastic. Also, though most modern machines produce less noise, ear plugs are still recommended by experts.

Lastly, this may not sound like a biggie, but most CNC operators are on their feet all day. They can only sit when the programs are being loaded into the computer. It’s pretty comforting that they receive salaries waaaay bigger than those salesladies.

What It Takes to be a CNC Operator

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Being a CNC operator may seem a little too easy but take a look at the requirements from companies and you'll think twice about the difficulty level of being a CNC operator.

Being a CNC operator takes a lot more than just being able to handle long hours of staring at the monitor or creating an input stack for the programs. What it means is that you have to have outstanding programming capabilities and at least basic machining knowledge.

Job Requirements

A CNC operator has to be knowledgeable about blueprint reading. This is because, basic design concepts and construction is hinged heavily on blueprints. Furthermore, the components that are being manufactured by companies that have CNC machines are based on blueprints of a whole structure. Therefore, if you do not know how to read blueprints, you won't know what to program the machine to do.

Another thing that a CNC operator has to have is familiarization with machine operations. If the operator does not know which machine tools are for which job, or how fast the machine can work, or what the rate of feed is for the machine, or even the depth of the cut needed for the operation, then you wouldn't be productive and the operation would be a failure.

The most obvious thing that an operator would have to know would be the general operating characteristics of the machine. He/she would have to know what the machine runs on—tape, network data input, or floppy. Furthermore, proper data input procedures have to be observed to lower the error ratio. A faulty data input procedure could cause the entire cycle to collapse therefore lowering the level of efficiency.

Working with CNC machines means that you will also be dealing with a lot of computer work. This means that you have to be familiar with basic computer operations. In addition to that, you will have to know how to interpret data in the program output stack.

The company's requirements and the benefits.

some companies require a lot more than what is written above. Oftentimes, they require applicants to be familiar with the system that they use. Other times, they want the applicants to have no less than five years of experience working in a factory or at least working with a CNC machine. Also, some companies require applicants to undertake a specific training program to ensure the employers that the material they are getting is worth the money they will be shelling out.

However, the benefits that can be reaped is quite solid. Salaries and insurances are often negotiable. Working hours are also a snap! All you would have to do is initiate the cycle and then sit back and occasionally check for glitches. Furthermore, these companies often takes care of their operators as there is always a shortage of skilled enough people to take hold of the position.

So, what does it take to be a CNC operator? To synthesize the requirements, you have to be amazingly determined to pass the requirements of the company you are applying for. And then, you have to be able to quickly restructure the program in case of any glitch that the computer might encounter during the process.

The benefits are solid, but passing the requirements is like surviving the gauntlet. Think about this career.