Week 6: Process Selection

Question 1

What are the important process selection drivers(10+)?

Answer 1

• Product quantity
• Tooling costs
• Labour intensity and work patterns
• Maintenance
• Material cost and reliability
• Component form and dimensions
• Surface finish needs
• Process to component variability
• Component recycling
• Equipment costs
• Processing times
• Process supervision
• Energy consumption and other overhead costs
• Material to process compatibility
• Tolerance requirements
• Bulk treatment and surface engineering
• Process waste

Question 2

Describe PRIMA

Answer 2

PRocess selection Information MAp

1. Estimate production quantity
2. Choose material type
3. Identify technically capable processes
4. Compare costs and capabilities
5. Select the most appropriate process
6. Consider alternative designs for the component (back to 2)
7. Review the selected process against business requirements

Question 3

What is a direct cost?

Answer 3

Direct cost - spent directly on making the product, scales linearly with the quantity produced and includes materials and labour effort

Question 4

What is an indirect cost/overhead?

Answer 4

Indirect cost/overhead - all costs that cannot be directly attributed to a specific product including:

• Manufacturing: rent, rates, heat, light, etc.
• Business: research, design, development, sales, marketing, finance, legal costs

Question 5

How can costs be time categorised?

Answer 5

Capital/Fixed costs - cost of setting up the system

Yearly running cost - total expenses in operating the manufacturing system during a year

Question 6

What is depreciation?

Answer 6

Depreciation is the capital cost divided by the number of years the capital purchase remains in use

Question 7

Define bottom up costing approaches

Answer 7

In bottom up approaches the cost of the product is viewed as an aggregate of the cost of the detailed manufacturing processes

Question 8

Describe the ABC approach

Answer 8

Activity Based Costing: assignment of overheads based on all the activities that take place, very thorough

Question 9

Describe the VBC approach

Answer 9

Volume Based Costing: slightly simpler, the assignment of overheads is solely based on machining time or labour time. All small costs are added together into one aggregate figure

Question 10

Define top down approaches

Answer 10

In top down approaches the costing process is abstracted and the cost is determined without considering every detail of the manufacturing process, but rather using mathematical models, statistical models or baseline costing

Question 11

What is process capability?

Answer 11

Process capability is a measure of the acceptability of the variation of the process. The simplest measure is given by:
Cp = (UTL-LTL)/6s
where UTL is the upper tolerance limit, LTL is the lower tolerance limit and s is the standard deviation.
For one sided capability index, use Cpk which equals to the lower index