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
Mention three reasons for the increased industrial need for IT support for product development
- Shorter lead-times and product lifecycles
- Increased complexity: variants, functions, components etc.
- Collaborative product development
Mention two reasons why it is important for the designer to have knowledge about them manufacturing process
Applying guidelines for manufacturing already at the design stage leads to:
- Reduced manufacturing cost
- Shortened lead time
