Chapter 20 - Lean Production

Cycle Time

Actual time it takes to complete a task - use stopwatch (Component 1 in standard work procedure)

Ways to accomplish Production Leveling

- Authorizing overtime during busy period -Using finished product inventories to absorb daily ups and downs in demand -adjusting the cycle times of the production operations -producing in small batches that are enabled by setup time reduction techniques

Stops the Process

When a problem is detected in the operation of a production machine, the mechanized or automated cycle is stopped when

Acceptable quality Level (AQL)

a certain min level of fraction defects is sufficient, even satisfactory

Total Production Maintenance (TPM)

a coordinated group of activities whose objective is to minimize production losses due to equipment failures, malfunctions, and low utilization through the participation of workers at all levels of the organization

Work Cell

a group of workers and processing staton that are physically arranged in sequential order so that parts can be produced in small batches, in many cases 1 at a time

Andon Boards

a light panel positioned above a workstation or production line that is used to indicate its operating status

5S

a set of procedures that is used to organize work ares in the work environment - seiri (short) - seiton (set in order) - seiso (shine) - seiketsu (standardize) - shitsuoe (sustain)

Kanban System

based on the use of cards that authorize (1) parts production & (2) parts delivery in the plant

Kaizen

continuous improvements of production operations involving all workers (including supervisors and managers)

Continuous Flow manufacturing

denotes a just-in-time style of production operations in which work parts are processed and transported directly to the next workstation one unit at a time.

Production Leveling

distributing the changes in product mix and quantity as evenly as possible over time

Lean Production

doing more work with fewer resources --> less time, smaller space, with fewer workers and less equipment and yet achieving high quality levels

Muda

elimination of waste

Unnecessary Processing Steps

energy is being expended by the worker/machine to accomplish work that adds no value to the product *inefficient use of resources includes: wasted hand and body motions, unnecessary work elements, inappropriate hand tools, inefficient equipment, poor ergonomics, and safety hazards

Mean Time Between Failures (MTBF)

indicates the average length of time the piece of equipment runs between breakdowns

Mean Time to Repair (MTTR)

indicates the average time required to service the equipment and put it back into operation after a breakdown occurs

Jidoka

machines that are designed to stop automatically when something goes wrong - such as a defective part being processed

Setup Time Reduction for Smaller Batch sizes

reduced setup times permit for small batch sizes batches and lower work-in-process levels

Production of Defective Parts

requires a quality control system that achieves perfect first-time quality

Utilization

the amount of output of a production machine during a given time period relative to its capacity during that same period

Work Sequence

the order of work elements or operations performed by a given worker in accomplishing an assigned task (Component 2 in standard work procedure)

Poka-yoke

the prevention of errors through the use of low cost devices that detect and/or prevent them -- relieves the worker of constantly monitoring the process of errors

Standard Work in Process (WIP)

the quantity of work parts that have been started in the production sequence but are not yet completed - consisting of both parts that are being processed and those that are between processing steps (Component 3 in standard work procedure)

Operating Capability

the ratio of the actual operating speed divided by the designed speed of the machine

Take Time

the reciprocal of the demand rate for a given product or part, adjusted for the available shift time - provides a specification based on demand for the part or product

Visual Management

the status of the work situation should be evident by just looking at it -- aka visual workplace which applies this to an entire work environment (ex: kanbans)

Overproduction and Excessive Inventories

there are leftover parts that must be stored, generating an increase in costs for the warehouse, storage equipment, additional workers, other production costs, and interest payments for all of that *greatest waste of all 7 is having excess inventory

Reasons for: Unnecessary Movement of workers and materials

- Inefficient workplace layout - Inefficient play layout - Improper material-handling method - Improper spacing of production machines - Larger equipment than necessary for task - Conventional batch production

Reasons for: Workers Waiting

- Materials haven't been delivered to the workstation - Assembly line has stopped - Machine has to be repaired - Machine is being serviced by the setup crew - Machine is performing its automatic processing cycle on a work part * If this happens it means that no work is being performed

Pros to Production leveling

- greater responsiveness to changes in product demand - short lead times - smaller in-process and finished goods inventories - regularity in the workload of production workers

Reasons for production of defective parts

- incorrect machine settings - inaccurate adjustments in the setup - improper tooling

Standardized work procedures

- maintain high productivity - balance the workload - minimize the amount of work-in-process in the production sequence

Examples of production defects

- omission of processing steps - incorrectly locating a work part in a fixture - using the wrong tool - not aligning jigs and fixtures properly on the machine tool table -neglecting to add a component part in an assembly

On-time Deliveried, Zero Defects & Reliable production equipment

- parts must be delivered before stockout occur at downstream stations - control quality during production rather than relying on inspectors to discover the defects later - low work-in process leaves little room for equipment stoppages

Reasons for poor machine utilization

- poor scheduling of work - machine starved for work by upstream operation - downtime due to setups and changeovers between production batches - woeker absenteeism - low demand for type of process performed by the machine

Pull System

-the order to make and deliver parts at each workstation in the production sequence comes from the downstream station that uses those parts -downstream station calls on upstream station to replenish supply of parts when running low

3 requirements for JIT production system to work properly

1) Pull system of production control 2) Setup time reduction for smaller batch sizes 3) stable and reliable production operations

Seven forms of waste

1. Production of defective parts 2. Production of more than the number of items needed (overproduction) 3. Excessive inventories 4. Unnecessary processing steps 5. Unnecessary movement of people 6. Unnecessary transport and handling of materials 7. Workers waiting

Types of Automation Control Devices

1. a sensor to detect abnormal operation that would result in a quality defect 2. a device to count the number of parts that have been produced 3. a means to stop the machine or production line when abnormal operation is detected or the required batch quantity has been completed

3 topics of Worker Involvement

1. continuous improvement 2. visual management 3. standardized work procedures

3 Aspects of Autonomation

1. stopping the process automatically when something is wrong 2. error prevention 3. total productive maintenance

Provides an alert

This response provides an audible or visible warning signal the an error has occurred -- and on boards

Production Kanban (P-Kanban)

authorizes the upstream station to produce a batch of parts

Transport Kanban (T-Kanban)

authorizes transport of the container of parts to the downstream station

Autonomation

automation with a human touch -- the machines operate autonomously as long as they are functioning properly

Stable and reliable production operations

other requirements for successful JIT: 1) production leveling 2) on-time delivery 3) defect-free components and materials 4) reliable production equipment 5) a workforce that is capable, committed, and cooperative 6) a dependable supplier base

Push System

parts at each workstation are produced irrespective of the immediate need for those parts at its respective downstream station - pushing parts through the plant *risk:more parts get produced in the factory that it can handle, resulting in large queues of work in front of machines

Just-in-time Production System (JIT)

produces and delivers exactly the required number of each component to the downstream operation in the manufacturing sequence at the exact moment when that component is needed *main goal is to reduce inventories *must have the 3 requisites in place before it operates successfully

Workforce and Supplier Base

workers must be cooperative, committed, and cross-trained