计算机辅助设计及制造英文翻译

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资料题目：计算机辅助设计与制造

CAD and CAM

The engine lathe, one of the oldest metal removal machines, has a number of

useful and highly desirable attributes. Today these lathes are used primarily in small

shops where smaller quantities rather than large production runs are encountered.

In the beginning, CAD systems were no more than a graphics editor with some

built-in design symbols. The geometry available to the user was limited to lines,

circular arcs, and the combination of them. The development of free-form curves and

surfaces, such as Coon’s patch, Bezier’s patch, and B-spline, enables a CAD systems

allow a designer to move into the third dimension. Because a three-dimensional

model contains enough information for NC cutter-path programming, the linkage

between CAD and NC can be developed. So called turnkey CAD/CAM systems were

developed based on this concept and became popular in the 1970s and 1980s.

The 1970s marked the beginning of a new era in CAD – the invention of

three-dimensional solid modeling. In the past, three-dimensional, wire-frame models

represented an object only by its bounding edges. They are ambiguous in the sense

that several interpretations might be possible for a single model. There is also no way

to find the volumetric information of a model. Solid models contain complete

information; therefore, not only can they be used to produce engineering drawing, but

engineering analysis can be performed on the same model as well. Later, many

commercial systems and research systems were developed. Quite a few of these

systems were based on the PADL and BUILD systems. Although they are powerful in

representation, many deficiencies still exist. For example, such systems have extreme

computation and resource (memory) requirements, an unconventional way of

modeling objects and a lack of tolerance capability have all hindered CAD

applications. It was not until the mid-1980s that solid modelers made their way into

the design environment. Today, their use is as common as drafting and wire-frame

model application.

CAD implementations on personal computers (PCs) have brought CAD to the

masses. This development has made CAD available and affordable. CAD originally

was a tool used only by aerospace and other major industrial corporation. The

introduction of PC CAD packages, such as AutoCAD, VersaCAD, CADKEY systems,

made small companies, even individuals, own and use CAD. By 1988, more than

100,000 PC CAD Packages had been sold. Today, PC-based solid modelers are

available and are becoming increasingly popular. Because rapid developments in

microcomputers have enabled PCs to carry the heavy computational load necessary

for solid modeling, many solid graphics user interface (GUI) , CAD systems can be

ported easily from one computer to another, most major CAD systems are able to run

on a variety of platforms. There is little difference between mainframe, workstation,

and PC-based CAD systems.

When a design has frozen, manufacturing can begin. Computers have an

important role to play in many aspects of production. Numerically controlled (NC)

machine tools need a part program to define the components being made; computer

techniques exist to assist, and in some cases virtually automate the generation of part

programs. Modern shipbuilding fabricates structures from welded steel plates that are

cut from a large steel sheet. Computer-controlled flame cutters are often used for this

task and the computer is used to calculate the optimum layout of the components to

minimize waste metal.

Printed circuit board assembly can also be improved by computer methods.

Quality is maintained by computer-controlled automatic test equipment that diagnoses

faults in a particular board and rejects defective boards from the assembly line.

Computers are used extensively to plot the artwork used to etch printed circuit boards

and also to produce part programs for NC drilling machines.

One of the most important manufacturing functions is stock and production

control. If the original design is done on a computer, obtaining lists of material

requirements is straightforward. Standard computer data processing methods are

employed to organize the work flow and order components when required.

Part geometry requires calculation of a large number of tool positions. Part

programming software is usually incorporated into a family of CAM (Computer

Aided Manufacturing) software. Some CAM software is associated with CAD

(Computer Aided Design) software into CAD/CAM stations. Then the CAM software

can use the CAD files as a source of data, which speeds up the programming process.

Part programming software is user-friendly, meaning that the programmer does

not have to know the computer programming language or its operating system. It uses

screen menus to lead the user through the programming process. Data can be entered

via the keyboard, the mouse, or the function keys. Experienced programmers can use

built-in macro capabilities and advanced techniques such as a family of parts to

become even more productive.

Programming software has a dynamic graphics database to hold the actual

machining sequences. These sequences can be viewed, edited, chained, or deleted.

The programming can be accomplished whether single cuts or CNC machine canned

cycle will be used. The software will also automatically calculate the proper feeds and

speeds to be used during the machining, create a tooling list, and define the tool path.

Programmers can use different layers to associate with each profile being

created or to construct clamps and fixtures to get a complete picture of the part setup.

The tool motion can be seen as it will occur at the machine.

Using part programming software, the programmer can easily solve

trigonometry problems to define an accurate tool path. When the program is done, the

programmer can send it from the PC to the machine via a communication channel

using built-in software with communications capability. Good part programming

software is capable of:

（1）Establishing the machining parameters and tooling for a particular

machine or job.

（2）Defining the geometry and tool path.

（3）Code generation, enabling the programmer to use standard

communications protocols or create his or her own.

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资料题目：计算机辅助设计与制造CADandCAMTheenginelathe,oneoftheoldestmetalremovalmachines,hasanumberofusefulandhighlydesirableattributes.Todaytheselathesareusedprimarilyinsmallshopswheresmallerquantitiesratherthanlargeproductionrunsareencountered.Inthebeginning,CADsystemswerenomorethanagraphicseditorwithsomebuilt-i...

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