THE 2010 ASME STUDENT MECHANISM AND ROBOT DESIGN COMPETITION
More details here: https://forum.solidworks.com/message/143698#143698
Archive for the ‘Product Design’ Category
Let’s Go Design in 3D
02/17/20102D drafting methods are not able to relay the quality and quantity of design information because 2D methods will always rely on human interpretation or visualization skills to interact with a 2D design. This is always difficult for non design staff and almost impossible for computer systems to extract this kind of information, because computers do not have the ability to interpret.
As a result, many human errors can occur with traditional 2D design methods. In the past problems such as component collisions, incorrect quantities or parts that don’t fit, would happen because a designer who works in only 2D is forced to hold much of the information mentally.
Reducing human error by using the 3D modeling design methods minimizes the need for re-work because the design quality is greatly improved. Using 3D design modeling greatly improves design quality because it is a more complete process than 2D design. One most important thing about 3d CAD design is that people can have view of the model from all possible dimensions. It is a highly detailed drawing of what your concept will look like as a finished product.
Whether you’re designing a new innovative product, creating technical manuals, or requesting quotes from suppliers, 3D CAD design is extremely powerful. But when a 3D CAD design is transformed into a physical 3D print or job shops’ product prototypes, there is no substitute for the tactile and visual feedback a physical model provides to all participants in the design process.
Mechanical Designers usually share their work space with drafters or other engineering technicians in quiet, well-lighted surroundings separated from production areas. Working from drawings, sketches, planning sheets, and other engineering and shop data, tool designers must visualize the Design, do the panning, document and verify every step of the way.
Because of reductions in defense spending, jobs for mechanical engineering type work will decrease; however, the employment of mechanical engineers is expected to grow about as fast as the average for all occupations through this year due to the demand for new and more complex industrial machinery and tools resulting from the development of more sophisticated automated production processes.
The use of 3D modeling technology is essential when you want to develop a superior product. Such a product will not be influenced by human interpretation. Furthermore, it will look like the final model.
APPLICATION OF DOCUMENT AND CHANGE CONTROLS TO DESIGN
12/01/2009The design control system has to be concerned with the creation and revision of documents, as well as the management of finished documents. Additional mechanisms are required to provide needed flexibility while preserving the integrity of design documentation. These additional mechanisms are embodied in the procedures for review and approval of various documents.
It is important that the design change procedures always include re-verifying and re-validating the design. Fortunately, most design changes occur early in the design process, prior to extensive design validation. Thus, for most design changes, a simple inspection is all that is required. The later in the development cycle that the change occurs, the more important the validation review becomes. There are numerous cases when seemingly innocuous design changes made late in the design phase or following release of the design to market have had disastrous consequences.
The quality assurance model
11/30/2009Introduction
This International Standard is one of three International Standards dealing with quality system requirements that can be used for external quality assurance purposes. The quality assurance models, set out in the three International Standards listed below; represent three distinct forms of quality system requirements suitable for the purpose of a supplier demonstrating its capability, and for the assessment of the capability of a supplier by external parties.
a) IS0 9001, Quality systems- Model for quality assurance in design, development, production, installation and servicing for use when conformance to specified requirements is to be assured by the supplier during design, development, production, installation and servicing.
b) IS0 9002, Quality systems -Model for quality assurance in production, installation and servicing for use when conformance to specified requirements is to be assured by the supplier during production, installation and servicing.
c) IS0 9003, Quality systems -Model for quality assurance in final inspection and test for use when conformance to specified requirements is to be assured by the supplier solely at final inspection and test. It is emphasized that the quality system requirements specified in this International Standard, IS0 9002 and IS0 9003 are complementary (not alternative) to the technical (product) specified requirements. They specify requirements which determine what elements quality systems have to encompass, but it is not the purpose of these International Standards to enforce uniformity of quality systems. They are generic and independent of any specific industry or economic sector. The design and implementation of a quality system will be influenced by the varying needs of an organization, its particular objectives, the products and services supplied, and the processes and specific practices employed. It is intended that these International Standards will be adopted in their present form, but on occasions they may need to be tailored by adding or deleting certain quality system requirements for specific contractual situations. IS0 9000-l provides guidance on such tailoring as well as on selection of the appropriate quality assurance model, viz. IS0 9001, IS0 9002 or IS0 9003.
Concurrent engineering, the name of the game.
11/29/2009Although the waterfall model is a useful tool for introducing design controls, its usefulness in practice is limited. The model does apply to the development of some simpler devices. However, for more complex structures or devices, a concurrent engineering model is more representative of the design processes in use in the industry and is key to success in any industry, where design and manufacturing come together “and stay together” from concept to finished parts, systems, and vehicles, reporting from both the manufacturing and engineering perspectives.
In a traditional waterfall development scenario, the engineering department completes the product design and formally transfers the design to production. Subsequently, other departments or organizations develop processes to manufacture and service the product. Historically, there has frequently been a divergence between the intent of the designer and the reality of the factory floor, resulting in such undesirable outcomes as low manufacturing yields, rework or redesign of the product, or unexpectedly high cost to service the product.
One benefit of concurrent engineering is the involvement of production and service personnel throughout the design process, assuring the mutual optimization of the characteristics of a device and its related processes. While the primary motivations of concurrent engineering are shorter development time and reduced production cost, the practical result is often improved product quality.
SHEET METAL
11/29/2009Article contents:
Sheet metal drawings and fabrication
Characteristics of sheet metal bends
VERY VERY VERY…EXTENSIVE.
von Mises and Tresca Stress Criteria comparison
10/24/2009The maximum shear stress criterion is more conservative than the von Mises stress criterion since the hexagon representing the shear stress criterion is enclosed within the ellipse representing the von Mises stress criterion. For a condition of pure shear, von Mises stress criterion predicts failure at (0.577*yield strength) whereas the shear stress criterion predicts failure at 0.5 yield strength. Actual torsion tests used to develop pure shear have shown that the von Mises stress criterion gives more accurate results than the maximum shear stress theory.
Maximum von Mises Stress Criterion
10/24/2009The maximum von Mises stress criterion is based on the von Mises-Hencky theory, also known as the Shear-energy theory or the Maximum distortion energy theory.
In terms of the principal stresses s1, s2, and s3, the von Mises stress is expressed as:
svonMises = {[(s1 - s2)2 + (s2 - s3)2 + (s1 - s3)2]/2}(1/2)
The theory states that a ductile material starts to yield at a location when the von Mises stress becomes equal to the stress limit. In most cases, the yield strength is used as the stress limit. However, the software allows you to use the ultimate tensile or set your own stress limit.
svonMises ≥ slimit
Yield strength is a temperature-dependent property. This specified value of the yield strength should consider the temperature of the component. The factor of safety at a location is calculated from:
Factor of Safety (FOS) = slimit / svonMises
What is Meshing?
10/21/2009Finite Element Analysis (FEA) provides a reliable numerical technique for analyzing engineering designs. The process starts with the creation of a geometric model. Then, the program subdivides the model into small pieces of simple shapes (elements) connected at common points (nodes). The representation of a given region by a set of elements (i.e., discretization or mesh generation) is an important step in finite element analysis. Meshing the model is the heart of any FEA analysis. The choice of element type, number of elements, and density of elements depends on the geometry of the domain, the problem to be analyzed, and the degree of accuracy desired. Local mesh refinement tools are very important to have good mesh with gradual transitions between the mesh densities. One should have a finer mesh in the areas of high stress gradient to ensure accuracy of the solution.
What is nonlinear analysis?
10/21/2009What are the types of nonlinearities that can occur?In linear analysis, the response of a structure is directly proportional to the load. We assume that:
- the displacements and rotations are small
- stress is directly proportional to strain
- loads maintain their original directions as the structure deforms.
However any of the convenient assumptions that are made during a linear analysis may not hold good in real life situations. For example:
- A contact area may change as the load changes
- A material may no longer exhibit an elastic behavior especially after it starts to yield and flows into the plasticity region.
- The stiffness of the structure may decrease because of buckling or the material may even fracture!
- The displacements and rotations may become too large and thus there is a need to develop equations describing the equilibrium at various intervals instead of one single configuration.
The direction and magnitude of the applied force can change in large rotation problems.
What is Linear Static Analysis?
10/21/2009When loads are applied to a body, the body will deform and the effect of the loads will be transmitted throughout the body. To absorb the effect of loads, the body generates internal forces and reactions at the supports to balance the applied external loads. Linear static analysis refers to the calculation of displacements, strains, and stresses under the effect of external loads.
What is Static Analysis?
10/21/2009When loads are applied to a body, the body will deform and the effect of the loads will be transmitted throughout the body. To absorb the effect of loads, the body generates internal forces and reactions at the supports to balance the applied external loads. Linear static analysis refers to the calculation of displacements, strains, and stresses under the effect of external loads based on two basic assumptions:
Static Assumption All loads are applied slowly and gradually until they reach their full magnitudes. After reaching their full magnitudes, loads will remain constant (time-invariant). This assumption allows us to disregard insignificant inertial and damping forces due to negligibly small accelerations and velocities. Time-invariant loads that induce considerable inertial and/or damping forces may warrant dynamic analysis. Dynamic loads change with time and, in many cases, induce considerable inertial and damping forces that cannot be neglected.
Linearity Assumption The relationship between loads and induced responses is linear. If you double the magnitude of loads, for example, the response of the model (displacements, strains, and stresses), will also double. You can assume that the linearity assumption is valid if:
- All the materials in the model comply with Hook’s law, that is stress is directly proportional to strain.
- The induced displacements are small enough to ignore the change in stiffness caused by loading.
- Boundary conditions do not vary during the application of loads. Loads must be constant in magnitude, direction, and distribution. They should not change while the model is deforming.
What is Conduction?
10/21/2009Thermal energy transfers from one point to another through the interaction between the atoms or molecules of the matter. Conduction occurs in solids, liquids, and gasses. For example, a hot cup of coffee on your desk will eventually cool down to the room-temperature mainly by conduction from the coffee directly to the air and through the body of the cup. There is no bulk motion of matter when heat transfers by conduction.
What is Convection?
10/21/2009Convection is the heat transfer mode in which heat transfers between a solid face and an adjacent moving fluid (or gas). Convection involves the combined effects of conduction and the moving fluid. The fluid particles act as carriers of thermal energy. The rate of heat exchange between the fluid of temperature Tf and the face of a solid of area A and temperature Ts can be expressed as:
Q convection= hA(Ts-Tf)
where h is the convection heat transfer coefficient, Tf is the temperature of the fluid away from the face of the solid. The units of h are: W/m2.°C or Btu/s.in2.°F Convection processes can be divided into two main classes:
Free (Natural) Convection The motion of the fluid adjacent to a solid face is caused by the buoyancy forces induced by changes in the density of the fluid due to the presence of the solid. When a hot plate is left to cool down in the air, the particles of air adjacent to the face of the plate get warmer, their density decreases and hence they move.
Forced Convection An external means such as a fan or a pump is used to accelerate the flow of the fluid over the face of the solid. The rapid motion of the fluid particles over the face of the solid maximizes the temperature gradient and results in increasing the rate of heat exchange.
What is Radiation?
10/21/2009Thermal radiation is the thermal energy emitted by bodies in the form of electromagnetic waves because of their temperature. All bodies with temperatures above the absolute zero emit thermal energy. Because electromagnetic waves travel in a vacuum, no medium is necessary for radiation to take place. The thermal energy of the sun reaches earth by radiation. Because electromagnetic waves travel at the speed of light, radiation is the fastest heat transfer mechanism.
What is a steady state thermal analysis?
10/21/2009In this type of analysis, we are only interested in the thermal conditions of the body when it reaches thermal equilibrium, but we are not interested in the time it takes to reach this status. The temperature of each point in the model will remain unchanged until a change occurs in the system. At equilibrium, the thermal energy entering the system is equal to the thermal energy leaving it. Generally, the only material property that is needed for steady state analysis is the thermal conductivity.
What is a transient thermal analysis?
10/21/2009In this type of analysis, we are interested in knowing the thermal status of the model at different instances of time. A thermos designer, for example, knows that the temperature of the fluid inside will eventually be equal to the room temperature (steady state), but he or she is interested in finding out the temperature of the fluid as a function of time. In addition to the thermal conductivity (only material property needed for steady-state thermal analysis), we also need to specify density, specific heat, initial temperature profile, and the period of time for which solutions are desired.
Flat Pattern.
10/21/2009A flat layout of a formed sheet metal part which can be bent to make the finished part without trimming after forming.
For sheet metal definitions visit:
convex curve
10/21/2009A change in the angle of inclination of a belt conveyor where the center of the curve is below the conveyor.
Concentrated load capacity (CLC).
10/21/2009A capacity rating of a vehicle, axle-load, or livestock scale, specified by the manufacturer, defining the maximum load concentration for which the weigh bridge is designed. In the case of vehicle and axle-load scales, it is the maximum axle-load concentration (for a group of two axles with a center line spaced 4 feet apart and an axle widthof 8 feet) for which the weigh bridge is designed asspecified by the manufacturer. The concentrated load capacity rating is for both test and use.
3dcadware
fredvierheller
bob92003
Deepak Gupta