Computer-aided design is the use of computers to aid in the creation, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, to create a database for manufacturing. CAD output is in the form of electronic files for print, machining, or other manufacturing operations; the term CADD is used. Its use in designing electronic systems is known as electronic design automation. In mechanical design it is known as mechanical design automation or computer-aided drafting, which includes the process of creating a technical drawing with the use of computer software. CAD software for mechanical design uses either vector-based graphics to depict the objects of traditional drafting, or may produce raster graphics showing the overall appearance of designed objects. However, it involves more than just shapes; as in the manual drafting of technical and engineering drawings, the output of CAD must convey information, such as materials, processes and tolerances, according to application-specific conventions.
CAD may be used to design figures in two-dimensional space. CAD is an important industrial art extensively used in many applications, including automotive and aerospace industries and architectural design and many more. CAD is widely used to produce computer animation for special effects in movies and technical manuals called DCC digital content creation; the modern ubiquity and power of computers means that perfume bottles and shampoo dispensers are designed using techniques unheard of by engineers of the 1960s. Because of its enormous economic importance, CAD has been a major driving force for research in computational geometry, computer graphics, discrete differential geometry; the design of geometric models for object shapes, in particular, is called computer-aided geometric design. Starting around the mid 1960s, with the IBM Drafting System, computer-aided design systems began to provide more capability than just an ability to reproduce manual drafting with electronic drafting, the cost-benefit for companies to switch to CAD became apparent.
The benefits of CAD systems over manual drafting are the capabilities one takes for granted from computer systems today. CAD provided the designer with the ability to perform engineering calculations. During this transition, calculations were still performed either by hand or by those individuals who could run computer programs. CAD was a revolutionary change in the engineering industry, where draftsmen and engineering roles begin to merge, it did not eliminate departments, as much as it merged departments and empowered draftsman and engineers. CAD is an example of the pervasive effect. Current computer-aided design software packages range from 2D vector-based drafting systems to 3D solid and surface modelers. Modern CAD packages can frequently allow rotations in three dimensions, allowing viewing of a designed object from any desired angle from the inside looking out; some CAD software is capable of dynamic mathematical modeling. CAD technology is used in the design of tools and machinery and in the drafting and design of all types of buildings, from small residential types to the largest commercial and industrial structures.
CAD is used for detailed engineering of 3D models or 2D drawings of physical components, but it is used throughout the engineering process from conceptual design and layout of products, through strength and dynamic analysis of assemblies to definition of manufacturing methods of components. It can be used to design objects such as jewelry, appliances, etc. Furthermore, many CAD applications now offer advanced rendering and animation capabilities so engineers can better visualize their product designs. 4D BIM is a type of virtual construction engineering simulation incorporating time or schedule related information for project management. CAD has become an important technology within the scope of computer-aided technologies, with benefits such as lower product development costs and a shortened design cycle. CAD enables designers to layout and develop work on screen, print it out and save it for future editing, saving time on their drawings. Computer-aided design is one of the many tools used by engineers and designers and is used in many ways depending on the profession of the user and the type of software in question.
CAD is one part of the whole digital product development activity within the product lifecycle management processes, as such is used together with other tools, which are either integrated modules or stand-alone products, such as: Computer-aided engineering and finite element analysis Computer-aided manufacturing including instructions to computer numerical control machines Photorealistic rendering and motion simulation. Document management and revision control using product data management. CAD is used for the accurate creation of photo simulations that are required in the preparation of environmental impact reports, in which computer-aided designs of intended buildings are superimposed into photographs of existing environments to represent what that locale will be like, where the proposed facilities are allowed to be built. Pote
3D scanning is the process of analyzing a real-world object or environment to collect data on its shape and its appearance. The collected data can be used to construct digital 3D models. A 3D scanner can be based on many different technologies, each with its own limitations and costs. Many limitations in the kind of objects that can be digitised are still present. For example, optical technology may encounter many difficulties with shiny, reflective or transparent objects. For example, industrial computed tomography scanning and structured-light 3D scanners can be used to construct digital 3D models, without destructive testing. Collected 3D data is useful for a wide variety of applications; these devices are used extensively by the entertainment industry in the production of movies and video games, including virtual reality. Other common applications of this technology include augmented reality, motion capture, gesture recognition, industrial design and prosthetics, reverse engineering and prototyping, quality control/inspection and the digitization of cultural artifacts.
The purpose of a 3D scanner is to create a 3D model. This 3D model consists of a point cloud of geometric samples on the surface of the subject; these points can be used to extrapolate the shape of the subject. If colour information is collected at each point the colours on the surface of the subject can be determined. 3D scanners share several traits with cameras. Like most cameras, they have a cone-like field of view, like cameras, they can only collect information about surfaces that are not obscured. While a camera collects colour information about surfaces within its field of view, a 3D scanner collects distance information about surfaces within its field of view; the "picture" produced by a 3D scanner describes the distance to a surface at each point in the picture. This allows the three dimensional position of each point in the picture to be identified. For most situations, a single scan will not produce a complete model of the subject. Multiple scans hundreds, from many different directions are required to obtain information about all sides of the subject.
These scans have to be brought into a common reference system, a process, called alignment or registration, merged to create a complete 3D model. This whole process, going from the single range map to the whole model, is known as the 3D scanning pipeline. There are a variety of technologies for digitally acquiring the shape of a 3D object. A well established classification divides them into two types: non-contact. Non-contact solutions can be further divided into two main categories and passive. There are a variety of technologies. Contact 3D scanners probe the subject through physical touch, while the object is in contact with or resting on a precision flat surface plate and polished to a specific maximum of surface roughness. Where the object to be scanned is not flat or can not rest stably on a flat surface, it is supported and held in place by a fixture; the scanner mechanism may have three different forms: A carriage system with rigid arms held in perpendicular relationship and each axis gliding along a track.
Such systems work best with simple convex curved surfaces. An articulated arm with rigid bones and high precision angular sensors; the location of the end of the arm involves complex math calculating the wrist rotation angle and hinge angle of each joint. This is ideal for probing into interior spaces with a small mouth opening. A combination of both methods may be used, such as an articulated arm suspended from a traveling carriage, for mapping large objects with interior cavities or overlapping surfaces. A CMM is an example of a contact 3D scanner, it is used in manufacturing and can be precise. The disadvantage of CMMs though, is. Thus, the act of scanning the object might damage it; this fact is significant when scanning delicate or valuable objects such as historical artifacts. The other disadvantage of CMMs is that they are slow compared to the other scanning methods. Physically moving the arm that the probe is mounted on can be slow and the fastest CMMs can only operate on a few hundred hertz.
In contrast, an optical system like a laser scanner can operate from 10 to 500 kHz. Other examples are the hand driven touch probes used to digitise clay models in computer animation industry. Active scanners emit some kind of radiation or light and detect its reflection or radiation passing through object in order to probe an object or environment. Possible types of emissions used include ultrasound or x-ray; the time-of-flight 3D laser scanner is an active scanner. At the heart of this type of scanner is a time-of-flight laser range finder; the laser range finder finds the distance of a surface by timing the round-trip time of a pulse of light. A laser is used to emit a pulse of light and the amount of time before the reflected light is seen by a detector is measured. Since the speed of light c is known, the round-trip time determines the travel distance of the light, twice the distance between the scanner and the surface. If t is the round-trip time distance is equal to c ⋅ t / 2; the accuracy of a time-of-flight 3D laser scanner depends on how we can measure the t time: 3.3 p
Engineering tolerance is the permissible limit or limits of variation in: a physical dimension. Dimensions, properties, or conditions may have some variation without affecting functioning of systems, structures, etc. A variation beyond the tolerance is said rejected, or exceeding the tolerance. A primary concern is to determine how wide the tolerances may be without affecting other factors or the outcome of a process; this can be by the use of scientific principles, engineering knowledge, professional experience. Experimental investigation is useful to investigate the effects of tolerances: Design of experiments, formal engineering evaluations, etc. A good set of engineering tolerances in a specification, by itself, does not imply that compliance with those tolerances will be achieved. Actual production of any product involves some inherent variation of output. Measurement error and statistical uncertainty are present in all measurements. With a normal distribution, the tails of measured values may extend well beyond plus and minus three standard deviations from the process average.
Appreciable portions of one tails might extend beyond the specified tolerance. The process capability of systems and products needs to be compatible with the specified engineering tolerances. Process controls must be in place and an effective Quality management system, such as Total Quality Management, needs to keep actual production within the desired tolerances. A process capability index is used to indicate the relationship between tolerances and actual measured production; the choice of tolerances is affected by the intended statistical sampling plan and its characteristics such as the Acceptable Quality Level. This relates to the question of whether tolerances must be rigid or whether some small percentage of being out-of-tolerance may sometimes be acceptable. Genichi Taguchi and others have suggested that traditional two-sided tolerancing is analogous to "goal posts" in a football game: It implies that all data within those tolerances are acceptable; the alternative is that the best product has a measurement, on target.
There is an increasing loss, a function of the deviation or variability from the target value of any design parameter. The greater the deviation from target, the greater is the loss; this is described as the Taguchi loss function or quality loss function, it is the key principle of an alternative system called inertial tolerancing. Research and development work conducted by M. Pillet and colleagues at the Savoy University has resulted in industry-specific adoption; the publishing of the French standard NFX 04-008 has allowed further consideration by the manufacturing community. Dimensional tolerance is related to, but different from fit in mechanical engineering, a designed-in clearance or interference between two parts. Tolerances are assigned to parts for manufacturing purposes. No machine can hold dimensions to the nominal value, so there must be acceptable degrees of variation. If a part is manufactured, but has dimensions that are out of tolerance, it is not a usable part according to the design intent.
Tolerances can be applied to any dimension. The used terms are: Basic size The nominal diameter of the shaft and the hole; this is, in general, the same for both components. Lower deviation The difference between the minimum possible component size and the basic size. Upper deviation The difference between the basic size. Fundamental deviation The minimum difference in size between a component and the basic size; this is identical to the lower deviation for holes. If the fundamental deviation is greater than zero, the bolt will always be smaller than the basic size and the hole will always be wider. Fundamental deviation is a form of allowance, rather than tolerance. International Tolerance grade This is a standardised measure of the maximum difference in size between the component and the basic size. For example, if a shaft with a nominal diameter of 10 mm is to have a sliding fit within a hole, the shaft might be specified with a tolerance range from 9.964 to 10 mm and the hole might be specified with a tolerance range from 10.04 mm to 10.076 mm.
This would provide a clearance fit of somewhere between 0.04 0.112 mm. In this case the size of the tolerance range for both the shaft and hole is chosen to be the same, meaning that both components have the same International Tolerance grade but this need not be the case in general; when no other tolerances are provided, the machining industry uses the following standard tolerances: When designing mechanical components, a system of standardized tolerances called International Tolerance grades are used. The standard tolerances are divided into two categories: shaft, they are labelled with a let