Miscellaneous again Flashcards
Give two reasons for using ergonomic simulations with computer manikins
- Evaluation of user interfaces
- Evaluation of concept for manual assembly
Mention four different standards for geometry exchange and what type of geometry data they can handle
- IGES - Mathematical description
- STL - Triangulated format
- VRML - Triangulated format
- JT - Both mathematical and triangulated
- Step - Mathematical description
Describe the concepts of Component based and feature based assembly modeling
Component based assembly modeling:
- The position of the part in the assembly is determined by specifying its position and orientation in the global or relative coordinates
Feature based assembly modeling:
- Associates form features on different parts
- handles restrictions on form, position, orientation etc between mating form features
Mention two advantages of using off-line programming
- Avoid costly mistakes with real machines
- Faster more efficient programming
- Possibility to make new programs without stopping the production
What are the three types of modeling components in a multi-body system dynamic simulation?
- Rigid bodies
- Constraints (joints, motions)
- Forces (gravity, spring/dampers, friction etc.)
What are the industrial benefits of using parameterization to reuse engineering knowledge?
Shorter time - means more iterations, i.e. more design solutions can be evaluated
More iterations means better products because:
- Larger amount of design considered and evaluated in concept phase
- Knowledge related to lifecycle aspects (design for: assembly, manufacturing, serviceability, environment..) can be integrated in detail design phase
- Synthesis - analysis loops can be shortened - verification feedback instant
The Method of Influence Coefficients can be used to perform Monte Carlo variation simulations on non-rigid parts. How does it work?
- When doing a Monte Carlo variation simulation more than 1000 iterations have to be done
- To do this with traditional FE methods would take too long time
- Therefore, a FE solver is used to create a linearized model of the assembly
- The linearized model is then used in the simulations
- This gives a very large reduction of the simulation time (~a factor 1000)
- If the locators or support points are moved, a new linearization has to be done
Describe how the Z-buffer algorithm for depth sorting of object drawn on a computer screen works
- Initiate video memory and a Z-buffer for each pixel on the screen
depth [ x, y ] = ∞, refresh[ x, y ] = I_background - Polygons are rendered in an arbitrary sequence
- For each pixel: check if the z-coordinate of the current polygon is less than the stored one (use the plane equation for the polygon)
- In that case the video memory is updated for the pixel
- When all polygons are checked the screen is updated with the color closest to the observer
Mention three benefits of using virtual product models in the product realization process
- Minimizing the need for costly physical prototypes
- Finding problems as early as possible in the development process (easier and cheaper to fix)
- Faster development process with efficient tools (time to market)
Geometry models, created in a CAD-system, are used by a number of different functions (departments etc.) within the product development process. Describe some problems related to this
- Different functions uses different software requiring different file formats: problem with file conversion
- Problem with access to the right models
What type of geometry representation is usually used in a digital mockup (DMU)
Triangulated surface model
Mention four essential tasks for a PDM-system (product-data-management (hantering av data & info om produkter))
- Capture information at the source
- Organize information
- Run the information flow - when, where, what, to whom
- Search and re-use information
Mention four different types of geometrical models and what they are used for
- The original CAD-model
—Defines the geometry of the product - Mechanical model
—View of the product as a mechanical system
—Used by design to evaluate mechanical behaviour - Visual model
—View of the products appearance
—Used by design, management, marketing etc. to view the products appearance - Ergonomic model
—View of the products ergonomic properties
Used by design, manufacture, service etc. to evaluate different ergonomic properties of the product
What does perceived geometrical quality depend on?
- Visual sensitivity
—geometrical form
—split-line placement - Geometrical sensitivity (locator placement)
—Tolerances/distributions
Describe four different aspects that has to be considered when designing for injection molding
- Assign proper draft angles, rule of thumb: 1 deg. per inch cavity depth
- Wall thickness should be uniform, e.g. coring out could be used to avoid thick walls
- Compensate for shrinkage
- Locate parting line, ejector pins and gate appropriately
- Avoid sharp corners and small corner radiuses, gives stress concentration and hinders a
streamlined flow for the molten plastics
