PROCESS SELECTION Flashcards
What are some important drivers for manufacturing process selection?
- Product quantity
- Tooling costs
- Component form/dimensions
- Surface finish needs
- Energy consumption
- Tolerance requirements
- Material costs
Define concurrent engineering?
When design engineers work with manufacturing engineers to ensure that the product is feasible.
What are the 3 categories of manufacturing process?
Additive, subtractive, transformative
What is the general formula for cost estimation?
Cost = Direct Cost + Overheads
What are direct and overhead costs?
Direct: Spent directly on making the product. Scales linearly with quantity produced and includes materials + labour.
Overheads: Costs that cannot be attributed to a specific product. Contribue to the overall functioning of the operation. Includes: rent, heating, lighting, cleaning, research, design, sales etc
What are some reasons to undertake cost estimation?
- Manufacturing process selection
- Decide whether to buy or manufacture
- Evaluate designs
- Establish bid price of product
What are the 2 time categorisations of costs?
Capital / fixed costs: cost of setting up the system - machines, tools, equipment etc.
Yearly running costs: total expenses operating the system during a year: operators, materials, overheads, depreciation etc.
What is the formula for depreciation?
Capital cost / no. of years in use
What are the two types of cost estimation approaches?
Top down and bottom up
What are the two types of bottom up cost estimation and describe them?
Activity based costing (ABC): Assignment of overheads based on all of the activities that take place (EVERY activity is accountef for). Cost of raw materials, machine setup, material handling etc are all added up based on figures for labour cost, equipment cost, indirect labour cost etc.
Volume based costing (VBC): Simpler than ABC and more traditional.
Figures for equipment, indirect labour etc are added to give an overall manufacturing overhead (aggregate). This is then added to labour cost and raw materials to give the product cost.
What are top down cost estimation approaches?
Costing process is abstracted and cost is determined without considering every detail of the manufacturing process. Includes statistical models based on past data and regression
What is the formula for cost per product when there is one cost driver dominating?
Cost pp = Direct costs pp +
(Dominant cost driver pp * (Total overheads / dominant cost driver total))
What is Cpk?
- Capability process index
- If lower than 1, poor capablity
- If between 1 - 1.33, barely capable
- If above 1.33, capable
- Aim for 2 or above
What are the steps in process selection workflow?
- Estimate production quantity
- Choose material type
- Identify technically capable processes
- Compare costs and capabilities
- Select the most economic process (or consider alternative designs)
- Review the selected process against business requirements
