英文资料翻译题目CNCCNCCNC stands for Computerized Numerical Control and has been around since the early1970s. prior to this, it was called NC,for numerical control. 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 youll be working in manufacturing, its likely that youll be dealing with CNC on a regular basis.Before CNCWhile there are exceptions to this statement,CNC machines typically replace (or work in conjunction with) some existing manufacturing processes. Take one of the simplest manufacturing processes,drilling holes,for example.A drill press can of course be used to machine holes. 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 pulleys), and 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 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 workpieces must be machined, as quantities grow, so does the likelihood for fatigue due to the tediousness of the operation. And do note that weve 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 style of machine that CNC is replacing as the conventional machine.)By comparison, the CNC equivalent for a drill press (possibly a CNC machining center or CNC drilling & tapping center) can be programmed to perform this operation in a much more automatic fashion. Everything that the drill press operator was doing manually will now be done by the CNC machine, including:placing the drill in the spindle, activating the spindle,positioning the workpiece under the drill, machining the hole, and turning off the spindle.How CNC worksAs 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, some of the specific programmable functions.Motion controlAll CNC machine types share this commonalty: 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 imply a CNC machines 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 axes would position then 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 named X,Y,and Z. Common rotary names are A,B,and C. There are related to the coordinate system.Programmable accessoriesA CNC machine wouldnt 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(machining centers).Automatic tool changerMost machining centers can hold many tools in a tool magazine. When required, the required tool can be automatically placed in 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.CoolantMany 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. A CNC program is nothing more than another kind of instruction set. Its 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. CNC words begin with letter address(like F for feedrate,S for spindle speed,and X,Y,and Z for axis motion). When placed together in a logical method, a group of CNC wo