Just in time systems

MRP vs Kanban

MRP is a schedule schedule vs Kanban is production on cue = what we make right now is because someone needs it MRP is complex Kanbam is repetitive MRP is high level planning Kanban is shop level control over production

uniform loading

arrange daily production mix in the same ratio as monthly demand always have some quantities of each product steady demand on components

flexible machines

automated, general purpose machines with quick set up times

supply variability #3: quality

consistently high quality products are necessary due to small inventory quality at the source empowerment = authority given to workers to stop the production line if a problem occurs preventive: poke-yoke: devices that are designed to prevent mistakes and defects from happening part of fool proof design continuous improvement("kaizen") quality circle: team based process improvement

pull system

coordination between processes reduce variability of supply and demand to improve pull system

Supply variability #1: lot sizes

each kanban container represents the production or order lot size smallest lot size = provide many benefits - better coordination - better material handling - reduce average inventory level - reduce inventory space - avoid buildup of defective items - flexibility in reacting to problems quick set up time is crucial

push system

each workstation produces according to a schedule and pushes its completed work to the next work station traditional approach to production builds inventory

work cells

eliminate worker inefficiency = increase worker productivity operations of a number of different machines = highly utilized, multi-functional workers utilize cellular facility layout

job enlargement

expansion of the job through increasing the scope of the work designed

job enrichment

expansion of the job through increasing the worker responsibility

pull production system

improve poor coordination between processes eliminate need for large inventory each workstation requests (pulls) items from the previous workstations only when needed prevent overproduction and underproduction force coordination between processes - kanban system

before JIT systems

inventory to protect against uncertainty assembly lines push manufacturing defects long set up times suppliers treated as individual entities workers following manager instructions

supply variability #2: machine breakdowns

maintenance: to keep facilities and equipment in good working order machine downtimes are waste fix fast, but fixing is also a waste preventive maintenance needed periodic inspection and maintenance designed to avoid breakdowns

JIT system

management system that aims to improve the manufacturing or service process by eliminating waste

supply variability #4: Suppliers

need reliable suppliers for on time and frequent delivers build long term relationships single sourcing = entire family of parts provided by one supplier JIJT 2 = supplier working in the manufacturers plant

specialization

performing single or limited task

Types of waste

process - scrap over production - extra inventory inventory - storage costs product defects = interrupted fllow, lost capacity waiting time = expensive, unplanned methods = poor layout movement = material handling

Just in time manufacturing

produce only what is needed and when it is needed JIT inventory, JIT purchasing, lean manufacturing no excess inventory supply = demand

after JIT system

reduce inventory Cells pull manufacturing zero defects reduce set up times emphasize team oriented work suppliers seem as partners

time study method

sets a standard time based on timed observations of one worker over several cycles 3 Measures time necessary for a task to be completed

job rotations

shifts workers to different jobs to increase understanding of the total process

how to control supply variability

small lot sizes preventive maintenance high quality reliable suppliers

job design

specifies the contents of the job

quality circle

team based improvement

method analysis

the study of how a job is done

how to control demand variability

uniform loading

JIT not suited for

very high volume very low volume with unique products highly fluctuating demands or true make to order products

kanban system

visible production control system which authorizes the production or movement of the next batch of material only when needed kanban = japanese word for signal or visible record kanbans are NOT schedules work the same way as a fixed quantity inventory system where order quantity equals to the reorder point only inventory maintained is the amount needed to cover usage until the next order arrives

Demand variability

volume adjustment by a number of workers kanban system can absorb +/- 10% variability in demand by manipulating the number of kanbans fewer kanban = less production

key elements of JIT systems

work cells = efficiency within a process, multifunctional workers

cellular facility layout

work is moved within a cell of U shaped traditionally an assembly line is used in mass production