A2 Processes & Layouts Flashcards
Demands placed on modern manufacturing systems
Increase in product variety
Decrease in product quantity (esp. in HVM)
Increase in customer expectations
Reduction in time to market
New/better materials
Global production
Aims of good plant layout
Organise factory for simplicity to improve throughput & efficiency
Locate equipment within a department
Locate departments & facilities within a site
Reduce overhead cost for production
Criteria for good plant layout
Maximise: flexibility of machines/layout, use of volume (quantity), coordination between departments, visibility of people & machines, accessibility of machines, security & safety
Minimise: distance & handling of parts, discomfort of workers
Efficient & smooth process flow
Identification of workers
Advantages of good plant layout
Minimise process cost & time
Reduce movement & handling
Improve effectiveness of all work processes
Simplify supervision & control
Accommodate changes readily
Maximise output via effective use of space & resources
Encourage morale of workforce
2 types of process layout & types of production typically used in each
Process (batch/job), product (flow production)
Process layout A&D
A: Flexible use of equipment & workforce, low investment cost, specialised supervision
D: Large volume of WIP, complexity in planning/control, long production time, higher skill level required in workforce
Product layout A&D
A: Operations arranged in planned sequence, less material handling, much reduced WIP, short production time, simplified planning/control/supervision, lower worker skill level
D: Lower flexibility, production pace determined by slowest operation, breakdown of 1 machine leads to production stoppage, mundane repetitive tasks, expensive automation
Group technology
Manufacturing concept that takes advantage of similarities (geometry, process) among parts
Cellular manufacturing
Using several machine cells that can produce different parts with similarities
GT & Cellular manufacturing As
Standard part design
Minimise design duplicaiton
Estimate cost of new products easily
Tools & jigs standardised due to part families
Reduce part flow/movement/WIP
GT & Cellular manufacturing Ds
Difficult to schedule jobs to large variety
FMS (flexible manufacturing systems)
Extension of GT & cellular manufacturing to encompass whole factory
FMS As
Produce parts randomly at low unit cost & in small batch sizes e.g. 1
Reduced direct labour & inventories
Improved productivity with high MUR (machine utilisation rate)
Reduced production lead time
Reduced WIP
CIM (computer integrated manufacturing)
Extension of FMS to encompass whole manufacturing organisaiton
CIM As
Responsive to shorter product life cycle & changing product demand
Uniformity through better process control
Better use of resources
Better control of planning & scheduling & manufacturing
CIM Ds
Expensive
Long periods of introduction
Benefits not immediately visible
Lead to fundamental organisational changes
Examples of job production
Low tech - hairdressing, tailoring
High tech - bridges, ship building
Batch production
Seasonal/limited edition products
Flow production
Mass produced goods e.g. cars, household goods, food products
Job production
Task handled by single/group of workers
Resources allocated for duration of project
1-off project, no expectation of identical repeat order
Cost of production includes design, production, tooling, admin cost & all overheads
Batch production
Specific production quantity with set time intervals
Expect future orders
Orders & amount of stock determine production quantity
Cost of production spread over whole batch
Flow production
Continual orders of near identical products
At each production stage - same timing of operations, equipment provided
Cost of production spread over long period of production
Process planning
Function within manufacturing facility that determines which processes are used to convert parts form initial to final form based on engineering designs
Process plan then generated & used by schedules & machine operators
Info on process plan
Features to manufacture
Tools/machines to use
Manufacturing time of each feautre
Main steps in process planning
Geometry analysis, raw material selection, process selection, process detailing
Setup, fixture planning & design
Process plan analysis & evaluation
What is variant CAPP?
Computer aided process planning
Assume similar parts have similar process plans
Software identifies similar parts, retrieves them & edits plans to suit requirements of each part
GT used
Only modifies existing plans
What is generative CAPP?
Computer aided process planning
Automatic synthesis of a plan for a new part rather than human decision making
Plan made using info from manufacturing process database
Same procedure as variant CAPP but quicker, generates completely new plans
Workflow
Sequence of tasks/arrangement of processes a product undergoes as it’s made
Each product has flowed through a sequence of production processes having work performed on it
Precedence diagrams
Illustrate workflow required to make a product & identifies manufacturing lead time
Manufacturing lead time
Total manufacturing time from start to finish incl. processing, setup, waiting & idle time
Relationship chart
Analyses plant layout in manufacturing organisation to best locate machines/departments based on criteria such as general material flow & safety
Travel charts
Quantitatively illustrate pattern & amount of part movement between departments/machines to identify critical path of production process
Line balancing
Balance operations at various stages of a flow line to ensure even loading on each stage, spread tasks evenly across workstations, minimise job complexity/errors/bottlenecks/machines used
Line balancing As
Precedence requirements achieved, idle time reduced, production capacity & rate improved
How to achieve line balancing
Rearrange manufacturing processes assigned to which workstations so total time at each workstation is equal
Work Content
All work completed on line/total production time for 1 unit/batch, made up of service & repositioning time
Service time
Time spend processing e.g. drilling
Repositioning time
moving parts/tools/people
Cycle time
Service + repositioning time
Time between products being finished when line is running
Production rate
amount of products produced per unit time to meet demand
Line efficiency
ratio between actual operating time & ideal operating time - working time available
Measures typical time lost due to unexpected machine breakdowns, power cuts
Value derived from experience of similar lines
Balancing efficiency
ratio between total work content & total available service time - accounts for idle time
Why difference between ideal no. of workstations required & actual no.?
time wasted positioning parts & imperfect balancing so actual time available to work is shorter so more workers required to meet production rate
