Design for Manufacture Flashcards
List three possible causes for manufacturing inconsistency in the diameter of a steel shaft.
Machine misalignments, tool wear, loose jig, material property variations, poorly controlled thermal environment.
What does the variable z refer to in the context of quality control?
The number of standard deviations from the mean metric value that are acceptable for consumption.
What values of z should be aimed for?
Between 4 and 7.5.
Name a manufacturing philosophy spawned out of the desire to aspire to z=6.
Six sigma process capability.
How can asymmetrically distributed part defects be avoided?
By regularly checking tool wear and machine settings.
How is z defined?
z = t/sigma, where sigma is the standard deviation of the part metric and t is the (one-sided) tolerance magnitude.
How is the process capability measure, Cp, defined?
Cp = t/3*sigma.
For what value of Cp is a process ‘capable’?
1.33
What is an unbiased estimator for the standard deviation of a sample?
sigma = sqrt(sum( (x - \bar{x})^2 )/ (N-1) )
What is the purpose of the ‘House of Quality’ design method?
Converting customer requirements into engineering requirements.
How would you produce a House of Quality design table?
List customer requirements to the left of the table. Weight them. List engineering requirements to the right of the table. Record weak, strong, and very strong relationships between these requirements and the customer’s desires using numbers. Compute scores for each engineering requirement by multiplying the customer requirement weights by their associated relationship scores. This results in a ranking of engineering requirements.
What is a product’s ‘footprint’?
Essentially its brand.
List five types of artefact order that a manufacturer might handle.
Engineer-to-Order: Designed and built to customer specifications.
Make-to-Order: Artefact is based on a standard design, but production is linked to the customer order and specifications.
Assemble-to-Order: Product is built to customer specification from a stock of existing components.
Make-to-Stock: Product is built against a sales forecast, then sold to customers from stock.
Ship-to-Stock: Similar to make-to-stock, but the stock is held by a retailer rather than the manufacturer.
What is a module?
A module is a complete, integrated, product subassembly that can easily be inserted into a broader assembly.
What are the advantages of modular units?
They are easy to maintain/replace, there is quality control over their assembly (making it easier to localize assembly faults), and they are sealed-for-life.
What are the disadvantages of modular units?
Small defects in modules cannot repaired (replacing them may also be expensive), and often they must be high-volume in order to offset associated design and manufacturing costs.
What is platform design?
When the members of a product family use a common set of modules or components that are designed in-house.
What are the advantages of platform design?
It is easier to manage inventory (since there are fewer parts), developments costs are reduced (since design work is not repeated), quality is increased (since design work can be focused on fewer components), greater product variety can be achieved (since components can be mixed and matched), and there is global standardization (which is convenient and reduces expense).
How can product mass and volume be minimized?
By designing integrated products with as few interfaces as possible.
How can assembly complexity be minimized?
By producing a modular design that has standardized part interfaces.
List the advantages of modular design.
- Ease of maintenance
- Dividing labour is easier
- Makes it easier to test a design
- Allows technologies to be easily integrated
- Enables platform design
How might the recyclability of a product be affected by modularity?
High-level disassembly is easier, but low-level disassembly is harder. Remanufacturing becomes possible with modules (i.e. re-using the entire module).
List six quality-management tools.
BS 7000 Design Management Systems ISO 9000 Quality Assurance Total Quality Management Six-sigma Lean manufacturing Poka-yoke
What six areas does the BS 7000 provide advice on?
Managing innovation, managing the design of manufactured products, managing service design, managing design in construction, managing inclusive design.
