CAD

Development path

CAD (Computer Aided Design) was born in the 1960s and was a research plan for interactive graphics proposed by the Massachusetts Institute of Technology. Due to the expensive hardware facilities at that time, only General Motors and Boeing Airlines Use the self-developed interactive drawing system.

In the 1970s, when the cost of small computers fell, the American industry began to use interactive drawing systems extensively.

In the 1980s, due to the application of PC, CAD (Computer Aided Design) developed rapidly, and a company specialized in CAD system development appeared. At that time, VersaCAD was a professional CAD production company. The CAD software developed was powerful, but because of its high price, it was not widely used. At that time, Autodesk (American computer software company) was a small company with only a few employees. Although the CAD system developed by it had limited functions, it was widely used in society because it can be copied for free. At the same time, due to the openness of the system, the CAD software is rapidly upgraded.

Designers started using computers for calculations very early. Some people think (Ivan Sutherland) Ivan Sutherland's Sketchpad (drawing board) developed at MIT in 1963 was a turning point. The outstanding feature of SKETCHPAD is that it allows designers to interact with the computer graphically: the design can be drawn into the computer on the cathode ray tube screen with a light pen. In fact, this is the prototype of the graphical user interface, and this interface is an indispensable feature of modern CAD.

The earliest application of CAD is in large companies in the automobile manufacturing, aerospace and electronics industries. As computers become cheaper, the range of applications has also gradually expanded.

The implementation technology of CAD has undergone many evolutions since then. At the beginning of this field, it was mainly used to produce drawings similar to hand-drawn drawings. The development of computer technology has made computers more skillful in design activities. Today, CAD is not only used for drawing and display, it is beginning to enter the more "smart" part of the designer's expertise.

With the increasing development of computer technology, performance improvement and cheaper prices, many companies have adopted three-dimensional drawing design. In the past, due to the limitation of computer performance, the drawing software could only stay in graphic design, lacking in realism, and the three-dimensional drawing broke through this limitation, making the design blueprint more materialized, and 3D drawing can also express that 2D drawings cannot be drawn. The curved surface can more fully express the designer's intention.

Development history of domestic CAD.

Chinese CAD technology originated from the secondary development based on foreign CAD platform technology. With the increasing demand for CAD applications by Chinese enterprises, many domestic CAD technology developers have made domestic enterprises truly popular by developing secondary development products based on foreign platform software. In addition to CAD, a number of truly excellent CAD developers have gradually emerged.

On the basis of secondary development, some of the top domestic CAD developers have gradually explored CAD suitable for China's development and demand model, which is more in line with the CAD products used by domestic enterprises. Their purpose is to develop the best CAD, even for Provide the best CAD technology in the world.

In addition to providing excellent CAD platform software technology in 2014, it has been actively promoting the development of domestic CAD technology. The domestic CAD alliance formed by many domestic CAD secondary developers has greatly promoted the development and growth of domestic CAD. Chinese companies provide CAD solutions that truly suit China's national conditions and application needs.

Certification

1. The introduction of the national computer-aided technology certification project is to deeply implement the spirit of the 17th National Congress of the Party on "vigorously promoting the integration of informationization and industrialization and promoting industry from big to strong", speeding up the pace of industrial and information technology personnel training, and satisfying the national The demand for industrial and information technology talents in the development of economic and social informatization, our center decided to launch the "National Computer Aided Technology Certification" project (referred to as CAXC project). The project is mainly for teachers and students of various colleges and universities, vocational and technical colleges across the country, and hopes to work in computer-aided design (CAD), computer-aided engineering (CAE), computer-aided manufacturing (CAM), computer-aided process plan (CAPP ), product data management (PDM) and other social personnel in related industries, with the aim of improving the professional skills of teachers and students and various engineering and technical personnel in colleges and universities, through professional and systematic skill course training and certification, to help students master the necessary employment Prepared knowledge and skills. The CAXC project will definitely play a positive role in improving the evaluation system of industrial and information talents and accelerating the cultivation of industrial information technology compound talents.

2. The urgency of developing a national computer-aided technology certification project 　Manufacturing is a pillar industry for the development of a country, and the development of the manufacturing industry determines the development of the country. In 2011, my country's export products were mainly low value-added, labor-intensive products. From the perspective of reality and development, it is imperative to turn the "World Workshop" into a "World Factory" and turn "Made in China" into "Created in China".

38% of our college students are engineering students. Although there are many graduates, they cannot meet the needs of enterprises. The CAXC project uses modern information technology, network technology, multimedia technology and other advanced educational technology to transfer the latest, most popular and practical 2DCAD/3DCAD/CAE/CAPP/CAM/PDM design management technology and skills to students. It enables students to understand the industrial product design process in a short period of time, greatly shortening the internship period of the students in the enterprise, learning to apply, and quickly designing better products for the enterprise.

The Education Management Information Center of the Ministry of Education has analyzed various certifications, combined with the development of domestic enterprises, and focused on the skills training of learners based on the actual needs of enterprises. It has changed the traditional certification model and changed the certification organization and content. Experts from the domestic business community and internationally renowned companies are invited to join, determine the certification content, and guide and manage the certification process. In order to standardize the process, the Ministry of Education has formulated implementation procedures, determined that specialized agencies and special personnel will control the entire process, and ensure the authority and seriousness of the project.

System composition

Usually based on an interactive computer system with graphics capabilities, the main equipment includes: computer host, graphics display terminal, graphics tablet, plotter, scanner, printer, tape drive, and various software.

Engineering workstation

Generally refers to a single-user interactive computer system with super minicomputer functions and three-dimensional graphics processing capabilities. It has strong computing power, uses standard graphics software, has a high-resolution display terminal, and can work on a local area network that shares resources. It has formed the most popular CAD system.

Personal computer

The pc system is inexpensive, easy to operate, and flexible to use. Since the 1980s, PC performance has been continuously renovated, hardware and software have developed rapidly, coupled with the application of graphics cards, high-resolution graphics displays, and the development of PC network technology, CAD systems composed of PCs have emerged in large numbers and have risen. trend.

Peripheral equipment

In addition to computer mainframes and general peripherals, computer-aided design mainly uses graphic input and output devices. Interactive graphics systems are particularly important for CAD. The general function of the graphics input device is to send the coordinates of the points on the plane to the computer. Common input devices include keyboards, light pens, touch screens, joysticks, trackballs, mice, graphics tablets, and digitizers. Graphic output devices are divided into soft copy and hard copy. Soft copy computer-aided design CAD shell devices refer to various graphic display devices, which are indispensable for human-computer interaction; hard copy devices are often used as auxiliary devices for graphic display, which copies the images on the screen for storage. There are three commonly used graphic displays: directed beam display, storage tube display and raster scan display. Directed beam display is the earliest application. In order to make the image clear, the electron beam must constantly redraw the graphics, so it is also called refresh display. It is easy to erase and modify the graphics and is suitable for interactive graphics. The storage tube displays the saved image without refreshing, so it can display a large amount of data, and the price is lower. The raster scanning system can provide color images, and the image information can be stored in the so-called frame buffer memory, and the resolution of the image is high.

Software

In addition to the computer's own software such as operating system and compiler, CAD mainly uses interactive graphics display software, CAD application software and data management software. Since 2014, Haochen CAD, Zhongwang CAD, etc., which have risen rapidly in China, are very compatible with AutoCAD, and they are also one of the users' choices.

The interactive graphic display software is used for window opening, editing, viewing, graphic transformation, modification, and corresponding human-computer interaction of the graphic display. CAD application software provides functions such as geometric modeling, feature calculation, and drawing to complete various specialized designs for various professional fields of machinery, advertising, architecture, and electrical. The four elements for constructing application software are: algorithm, data structure, user interface and data management. Data management software is used to store, retrieve, and process large amounts of data, including text and graphic information. For this, an engineering database system needs to be established. Compared with the general database system, it has the following characteristics: data types are more diverse, the entity relationship is complicated during the design process, the values and data structures in the library often change, and the designer's operation is mainly a real-time interactive processing.

Auxiliary model

Commonly used CAD software, also known as 3D drawing software, is more intuitive and accurate in reflecting entities and features than 2D drawings and 2D drawing software (such as Haochen CAD).

For professional enterprises, because there are different drawing goals, there are often multiple parallel CAD systems, so it is necessary to configure a unified and cross-platform component data resource library, the standard parts library and outsourcing parts library Model data is exported to a three-dimensional configuration system in an intermediate format (such as IGS, STEP, etc.), such as mainstream Autodesk Inventor, SolidWorks, CATIA, Zhongwang 3D, Pro/E, AutoCAD, UG NX, SolidEdge, Onespace Wait. Abroad, this kind of network service is called "part library" or "data resource warehouse". Pro/E is mostly used in the aerospace industry, Catia is mostly used in the manufacture of complex products such as airplanes and automobiles, and Solidworks is used more in small and medium-sized enterprises. Among PLM users in Europe, America and Japan, the popularity of the Internet-based PLM component data resource platform LinkAble PARTcommunity (PCOM for short) is no less than the network platforms such as BLOG and SNS that we are familiar with today.

Basic technology

It mainly includes interactive technology, graphics transformation technology, surface modeling and solid modeling technology.

In computer-aided design, interactive technology is essential. Interactive CAD system means that when users use computer systems for design, people and machines can exchange information in a timely manner. With the interactive system, people can conceive, proof, and modify, and can see the display result of each operation from the graphic terminal screen at any time, which is very intuitive.

The main function of the graphic transformation is to connect the user coordinate system with the coordinate system of the graphic output device; translate, rotate, zoom, and perspective transform the graph; realize the graph transformation through matrix operation.

Computer design automation The computer's own CAD is designed to automate or semi-automate the computer's own design and development process. Research content includes functional design automation and assembly design automation, involving computer hardware description language, system-level simulation, automatic logic synthesis, logic simulation, microprogramming automation, automatic logic division, automatic layout and wiring, and corresponding interactive graphics system and engineering database system. Integrated circuit CAD is sometimes included in the scope of computer design automation.

Basic skills

First of all, it is a visual drawing software. Many commands and operations can be realized through menu options and tool buttons. And it has rich drawing and drawing auxiliary functions, such as entity drawing, key point editing, object capture, annotation, bird's-eye view display control, etc., its toolbar, menu design, dialog box, graphic open preview, information exchange, text editing, image Processing and graphic output preview bring great convenience to the user's drawing. Secondly, it is not only more mature in 2D drawing processing, but also more complete in 3D functions, which can be easily modeled and rendered.

Basic functions of 2D CAD.

Plane drawing: You can create basic graphic objects such as straight lines, circles, ellipses, circular polygons (regular polygons), splines, etc. in a variety of ways.

·Drawing auxiliary tools: Orthogonal, object capture, polar axis tracking, capture tracking and other drawing auxiliary tools are provided. The orthogonal function makes it easy for users to draw horizontal and vertical lines. Object snapping can help pick up special points on geometric objects, while the tracking function makes it easier to draw diagonal lines and locate points along different directions.

Edit graphics: CAD has powerful editing functions, you can move, copy, rotate, array, stretch, extend, trim, scale objects, etc.

·Dimensions: You can create multiple types of dimensions, and you can set the appearance of the dimensions.

·Writing text: You can easily write text at any position in the graphic and in any direction, and you can set attributes such as text font, tilt angle, and width scaling.

· Layer management function: Graphic objects are located on a certain layer, and the characteristics such as object color, line type, line width, etc. can be set.

·3D drawing: 3D solid and surface models can be created, and the solid itself can be edited.

·Network function: You can publish graphics on the network, or access AutoCAD resources through the network.

·Data exchange: Provide a variety of graphics and image data exchange formats and corresponding commands.

2D to 3D

solprof command: Create a contour image of a three-dimensional solid in paper space.

solview command: Use the orthogonal projection method to create a layout viewport to generate multi-faceted and sectional views of 3D solids and volume objects.

soldraw command: Generate outline and section views in the viewport created with the solview command.

How to use the soldraw command and the solprof command and the difference:

The soldraw command needs to be used in conjunction with the solview command. You can only generate outline and cross-sectional views in viewports created with the solview command.

The solprof command can be used alone, that is, it can be used on any view in the paper space, and can create a contour image of a three-dimensional solid.

Secondary development

CAD allows users to customize menus and toolbars. It can use embedded languages Autolisp, Visual Lisp, VBA, ADS, ARX, etc. for secondary development. It can also load running scripts to achieve functions that the system itself does not have, such as three-dimensional automatic rotation.

The tutorial on "Secondary Development of AutoCAD .NET" introduces its secondary development method and the mixed development method of various development methods.

User Interface

The CAD system is an interactive software package. The user interacts with the graphics software package through the interface. Users can communicate with the CAD software package in a variety of ways, that is, in addition to the four basic input controls of keyboard input, on-screen menu, mouse, and digital instrument, they also adopt the advanced user interface (AdvancedUserInterface), that is, a window-like interface. . The second line in the upper part of the CAD software windows such as AutoCAD, Haochen, Zhongwang and so on is the menu bar (MenuBar). The user can select a menu item in the menu bar by moving the cursor, and a drop-down menu appears. The menu item in the drop-down menu will be a certain type of command or sub-menu item. Select the submenu item to further select its subcommands. In addition to the menu, you can also display some function control bars in the CAD window. These function bars are toolbars. A toolbar is a collection of commands of a certain type, and its control operations are similar to those of menu items.

Function key

F1: Get help

F2: Switch between drawing window and text window

F3: Control whether to automatically capture objects

F4: Digitizer control

F5: Isometric plane switching

F6: Control the display of coordinates on the status line

F7: Grid display mode control

F8: Orthogonal mode control

F9: Grid snap mode control

F10: Polar axis mode control

F11: Object tracking control

Combination function keys

Ctrl+B: Grid capture mode control (F9)

Ctrl+P: print

Ctrl+C: Copy the selected objects to the clipboard

Ctrl+F: Control whether to achieve automatic object capture (F3)

Ctrl+G: Grid display mode control (F7)

Ctrl+J: Repeat the previous command

Ctrl+K: Hyperlink

Ctrl+N: New graphic file

Ctrl+M: Open the options dialog

Ctrl+L: Turn on orthogonal mode

Ctrl+0: full screen display

Common shortcut keys

Different shortcut keys in the CAD version are different.

*You can customize shortcut keys through Tools->Customize->Edit program parameters (acad.pgp(P)) in the menu bar.

A arc

AA measuring area perimeter

AL alignment (only blocks can be aligned, multiple linear objects must be combined into blocks first)

AR array

AP loading application

ATE edit properties

B Create block

BR is broken at a point to break up a whole line

C round

CO copy

CLOSE

COL color

CHA rectangular chamfer

CTRL+1 feature panel

CTRL+2 Open the image explorer

CTRL+N New

CTRL+O open

CTRL+0 full screen

CTRL+P print

CTRL+Y to restore the undo step of U command

CTRL+Z to restore the one-step operation of U command undo

DLI line annotation [2]

DAL align callout

DRA radius callout

DDI diameter label

DAN angle label

DCE Center Mark Center Mark

DOR point labeling Coordinate labeling

DBA baseline annotation

DCO continuous labeling

DOV replaces labeling system variables

D Dimension style manager

DO ring command

DIV equal parts

DT single line text

DI query distance (distance between two points, angle to xy plane, x-axis increment, y-axis increment, z-axis increment)

DED Edit Labeling Command

E (erase) delete

EDGESURF draws a boundary curve

EL ellipse

ELEV Set object height and thickness

EX extension

EXT stretch (face)

EXP output files in other formats

F Draw connection arc

G object combination

H hatch

HELIX draws a spiral

HI blanking

I Insert block

OI is inserted into the object, hope to be IO

IMP input file

IN intersection

J Merging point Main line use

L straight line

LT Line Manager

LA layer

LTS linear scale

LI displays information about selected objects

LW line width setting

LEN elongated

LE leader label

LOFT

M mobile

MA characteristics matching

ML multi-line

MT multiline text

MI mirror

MIRROR3D three-dimensional mirror

MIRRTEXT system variable

ME fixed distance equal division

MLE edit and modify multileader

N New

O offset

OS sketch settings

OP options

PU clean up trash

PL draw polylines

PLAN Plan View Command View → 3D View → Plan View

PE Edit Multiline

PO point

POL regular polygon drawing

PER draws a vertical line

PAR draw parallel lines

PICKFIRST controls whether the object is selected before the command is issued (select first and then execute) or after

REG Create Area Drawing → Boundary → Pick Point → Left click on the center of the area boundary to be created

REDO redo

RO rotation

Rotate3d three-dimensional rotation

RE regeneration

REV draws a rotating surface

REC rectangle drawing

RULESURF draws a ruled surface. Set in the southeast view, draw a cylindrical surface between two circles

S Stretch Local zoom

SE sketch settings

SL cut

SU difference set

SC zoom

ST Text Style Dialog

SO area filling

SPL spline curve

SHIFT+CTRL+S save

SWEEP overview

SHA coloring

STATUS displays graphical status

SURFTAB1 sets the system variable of the number of translation surface segments (controls the number of mesh segments of the first selected edge and the edge opposite to the first edge. If the first edge is up and down, then the number of mesh segments is Left and right. The larger the value setting, the denser the number of grid segments.)

SURFTAB2 sets the system variable for the number of translation surface segments (controls the number of mesh segments for the third and fourth edges)

T Multiline text

TO Customize the user interface or toolbar

TX single line text

TOL marked geometric tolerance

TK tracking can specify a series of temporary points, each point is offset from the previous point.

TRACE draw constant width lines

TABSURF draw translation surface Set in the southeast view, translate the SPL spline along a straight line

U Undo the previous step command You can undo the N step command until the state at the beginning of drawing

UNI union

UCSICON opens the coordinate system

UN Graphical Units Dialog

V View Manager

VPOINT reset viewpoint

W write block

WI mask

X decomposition

XL construction line

Z window zoom

Z+E show full image

%%D degree

%%C diameter

%%P positive and negative

%%O underlined

%%U underline

%%178 square

Domestic innovation function

In CAD design, the most common dealings are drawings. Whether the drawings can be displayed quickly and accurately has a very significant impact on the user experience of CAD software.

With their own understanding of users, domestic CAD has gradually developed more practical and innovative functions in CAD design, such as automatic layers, area tables, object broken lines, block broken lines, equal point capture, statistical summation, incremental text copy 1. The conversion of CAD tables to EXCEL can solve some problems that designers cannot solve with basic functions in the design and drawing, and further improve the operation efficiency.

CAD software has become increasingly mature, personal design efficiency has been relatively high, and the room for improvement has been limited. However, various problems such as mistakes, omissions, and deficiencies will occur when multi-person and multi-professional collaborative drawing, and improving the overall design efficiency has become the focus of design units. Therefore, some domestic CAD has launched a collaborative design function based on two-dimensional drawings, which can not only realize multi-person multi-professional collaborative drawing, but also perform drawing version management, historical version backtracking, and view drawing changes, which can minimize the occurrence of errors and information. More thorough communication can reduce a lot of time that was previously required to communicate through language and text, and efficiency has also been significantly improved.

In the future, what other innovative features of domestic CAD will make users shine, which will bring convenience to everyone's design work, we will wait and see.