CNC stands for C omputer N umerical C ontrol and has been around since the early 's. Prior to this, it was called NC, for N umerical C ontrol.
In the early 's computers were introduced to these controls, hence the name change. While people in most walks of life have never heard of this term, CNC has touched almost every form of manufacturing process in one way or another.
If you'll be working in manufacturing, it's likely that you'll be dealing with CNC on a regular basis. Take one of the simplest manufacturing processes, drilling holesfor example. A drill press can of course be used to machine holes. It's likely that almost everyone has seen some form of drill press, even if you don't work in manufacturing.
A person can place a drill in the drill chuck that is secured in the spindle of the drill press. They can then manually select the desired speed for rotation commonly by switching belt pulleysand activate the spindle. Then they manually pull on the quill lever to drive the drill into the workpiece being machined.
As you can easily see, there is a lot of manual intervention required to use a drill press to drill holes. A person is required to do something almost every step along the way! While this manual intervention may be acceptable for manufacturing companies if but a small number of holes or workpieces must be machined, as quantities grow, so does the likelihood for fatigue due to the tediousness of the operation.
And do note that we've used one of the simplest machining operations drilling for our example. There are more complicated machining operations that would require a much higher skill level and increase the potential for mistakes resulting in scrap workpieces of the person running the conventional machine tool. We commonly refer to the style of machine that CNC is replacing as the conventional machine.
Everything that the drill press operator was doing manually will now be done by the CNC machine, including: There is another article included in this web site called The Basics of CNC that explains how to program, setup, and operate CNC machines in greater detail.
Additionally, we offer a series of products aimed at helping you learn how to use CNC machines. Here we're relating how CNC works in very general terms.
As you might already have guessed, everything that an operator would be required to do with conventional machine tools is programmable with CNC machines. Once the machine is setup and running, a CNC machine is quite simple to keep running.
In fact CNC operators tend to get quite bored during lengthy production runs because there is so little to do. With some CNC machines, even the workpiece loading process has been automated. We don't mean to over-simplify here. CNC operators are commonly required to do other things related to the CNC operation like measuring workpieces and making adjustments to keep the CNC machine running good workpieces. All CNC kiesling types share this commonality: They all have two or more programmable directions of motion called axes.
An axis of motion can be linear along a straight line or rotary along a circular path. One of the first specifications that implies a CNC machine's complexity is how many axes it has. Generally speaking, the more axes, the more complex the machine. The axes of any CNC machine are required for the purpose of causing the motions needed for the manufacturing process. In the drilling example, these 3 axis would position the tool over the hole to be machined in two axes and machine the hole with the third axis.
Axes are named with letters. Common linear axis names are X, Y, and Z. Common rotary axis names are A, B, and C. A CNC machine wouldn't be very helpful if all it could only move the workpiece in two or more axes. Almost all CNC machines are programmable in several other ways. The specific CNC machine type has a lot to do with its appropriate programmable accessories.
Again, any required function will be programmable on full-blown CNC machine tools. Here are some examples for one machine type.
Think of giving any series of step-by-step instructions. A CNC program is nothing more than another kind of perforex set. It's written in sentence-like format and the control will execute it in sequential order, step by step. A special series of CNC words are used to communicate what the machine is intended to do. When placed together in a logical method, a group of CNC words make up a command that resemble a sentence. For any given CNC machine type, there will only be about words used on a regular basis.
So if you compare learning to write CNC programs to learning a foreign language having only 50 words, it shouldn't seem overly difficult to learn CNC programming. The CNC control will interpret a CNC program and activate the series of commands in sequential order.
As it reads the program, the CNC control will activate the appropriate machine functions, cause axis motion, and in general, follow the instructions given in the program.
Along with interpreting the CNC program, the CNC control has several other purposes. All current model CNC controls allow programs to be modified edited if mistakes are found. The CNC control allows special verification functions like dry run to confirm the correctness of the CNC program.
The CNC control allows certain important operator inputs to be specified separate from the program, like tool length values. In general, the CNC control allows all functions of the machine to be manipulated. For simple applications like drilling holesthe CNC program can be developed manually. That is, a programmer will sit down to write the program armed only with pencil, paper, and calculator.
Again, for simple applications, this may be the very best way to develop CNC programs. As applications get more complicated, and especially when new programs are required on a regular basis, writing programs manually becomes much more difficult.
To simplify the programming process, a computer aided manufacturing CAM system can be used. A CAM system is a software program that runs on a computer commonly a PC that helps the CNC programmer with the programming process. Generally speaking, a CAM system will take kiesling tediousness and drudgery out of programming.
In many companies the CAM system will work with the computer aided design CAD drawing developed by the company's kiesling engineering department. This eliminates the need for redefining the workpiece configuration to the CAM system. The CNC programmer will simply specify the machining operations to be performed and the CAM system will create the CNC program much like the manual programmer would have written automatically.
Once the program is developed either manually or with a CAM systemit must be loaded into the CNC control. Though the setup person could type the program right into the control, this would be like using the CNC machine as a very expensive typewriter. If the CNC program is developed with the help of a CAM system, then it is already in the form of a text file.
If the program is written manually, it can be typed into any computer using a common word processor though most companies use a special CNC text editor for this purpose. Either way, the program is in the form of a text file that can be transferred right into the CNC machine.
A distributive numerical control DNC system is used for this purpose. A DNC system is nothing more than a computer that is networked with one or more CNC machines. Until only recently, rather crude serial communications protocol RSc had to be used for transferring programs. Newer controls have more current communications capabilities and can be networked in more conventional ways Ethernet, etc. Regardless of methods, the CNC program must of course be loaded into the CNC machine before it can be run.
As stated, CNC has touched almost every facet of manufacturing. Many machining processes have been improved and enhanced through the use of CNC. Let's look at some of the specific fields and place the emphasis on the manufacturing processes enhanced by CNC machine usage.
Machining processes that have traditionally been done on conventional machine tools that are possible and in some cases improved with CNC machining centers include all kinds of milling face milling, contour milling, slot milling, etc. In similar fashion, all kinds of turning operations like facing, boring, turning, grooving, knurling, and threading are done on CNC turning centers.
There are all kinds of special "off-shoots" of these two machine types including CNC milling machines, CNC drill and tap centers, and CNC lathes. Grinding operations of all kinds like outside diameter OD grinding and internal diameter ID grinding are also being done on CNC grinders. CNC has even opened up a new technology when it comes to grinding. Contour grinding grinding a contour in a similar fashion to turningwhich was previously infeasible due to technology constraints is now possible almost commonplace with CNC grinders.
In manufacturing terms, fabrication commonly refers to operations that are performed on relatively thin plates. Think of a metal filing cabinet. All of the primary components are made of steel sheets. These sheets are sheared to size, holes are punched in appropriate places, and the sheets are bent formed to their final shapes.
Again, operations commonly described as fabrication operations include shearing, flame or plasma cutting, punching, laser cutting, forming, and welding. Truly, CNC is heavily involved in almost every facet of fabrication. CNC back gages are commonly used with shearing machines to control the length of the plate being sheared. CNC lasers and CNC plasma cutters are also used to bring plates to their final shapes. CNC turret punch presses can hold a variety of punch-and-die combinations and punch holes in all shapes and sizes through plates.
CNC press brakes are used to bend the plates into their final shapes. Electrical discharge machining EDM is the process of removing metal through the use of electrical sparks which burn away the cnc.
CNC EDM comes in two forms, vertical EDM and Wire EDM. Vertical EDM requires the use of an electrode commonly machined on a CNC machining center that is of the shape of the cavity to be machined into the workpiece. Picture the shape of a plastic cnc that must be machined into a mold. Wire EDM is commonly used to make punch and die combinations for dies sets used in the fabrication industry. EDM is one of the lesser known CNC operations because it is so closely related to making tooling used with other manufacturing processes.
As in the metal removal industry, CNC machines are heavily used in woodworking shops. Operations include routing similar to milling and drilling. Many woodworking machining centers are available that can hold several tools and perform several operations on the workpiece being machined. Many forms of lettering and engraving systems use CNC technology. Waterjet machining uses a high pressure water jet stream to cut through plates of material.
CNC is even used in the manufacturing of many electrical components. For example, there are CNC coil winders, and CNC terminal location and soldering machines. There is quite a shortage of skilled people to utilize CNC machines. And the shortage is growing. Everywhere I go I hear manufacturing people claiming that they cannot find skilled people. Unfortunately, it has also been my experience that pay scales have not yet reflected this shortage.
Even so, you can make a good wage and develop a rewarding career working with CNC machines. Here are some of the job titles of people working with CNC machine tools. Companies looking for people. The Optional Stop newsletter. Mike's Tech Talk column. Home Products Services Resources Links About Us Contact Us Content Index On-line Store.
And More - Feature Article: How CNC works There is another article included in this web site called The Basics of CNC that explains how to program, setup, cnc operate CNC machines in greater detail. Let's look at some of the specific programmable functions.
Motion control All CNC machine types share this commonality: Programmable accessories A CNC machine wouldn't be very helpful if all it could only perforex the workpiece in two or more axes. Machining centers Automatic tool changer Most machining centers can hold many tools in a tool magazine. When required, the required tool can be automatically placed in the spindle for machining.
Spindle speed and activation The spindle speed in revolutions per minute can be easily specified and the spindle can be turned on in a forward or reverse direction.
It can also, of course, be turned off. Coolant Many machining operations require coolant for lubrication and cooling purposes. Coolant can be turned on and off from within the machine cycle. The CNC program Think of giving any series of step-by-step instructions. The CNC control The CNC control will interpret a CNC program and activate the series of commands in sequential order.
What is a CAM system? What is a DNC system? Types of CNC machines As stated, CNC has touched almost every facet of manufacturing. In the metal removal industry: In the metal fabrication industry: In the electrical discharge machining industry: In the woodworking industry As in the metal removal industry, CNC machines are heavily used in woodworking shops.
Other types of CNC machines Many forms of lettering and engraving systems use CNC technology. Job opportunities related to CNC There is quite a shortage of skilled people to utilize CNC machines. Working for manufacturing companies: CNC helpers CNC tool setters CNC operators CNC setup people CNC programmers CAM system programmers CNC maintenance personnel Working for companies that sell CNC machines CNC service technicians CNC applications engineers CNC instructors Working for schools CNC instructors.
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