Shigeo Shingo described Process Industrial Engineering in his Book
"A Study of the Toyota Production System From an Industrial Engineering View Point"
The chapter is titled "Improving Process"
The purpose of industrial engineering is maximizing production efficiency in a production process or system. The general purpose of industrial engineering is increasing efficiency or productivity in engineering processes, operations and systems. It has the responsibility of determining the production quantity that can be produced from a facility within a specified time. F.W. Taylor termed the department initially as "Elementary Rate Fixing Department." The department determines the production rate after doing all improvements in all elements of production/engineering processes.
Industrial engineering is real time engineering carried out inside an operating system as response to data being created in the production, distribution and service processes. Basic product design and development and Process Planning are carried out in major project mode and put their design and plans into operations mode. Industrial engineering is engineering carried out in operations activity of the enterprise making changes as required to improve productivity and provide cost competitiveness maintaining quality of the product and comfort, safety and health of employees.
Improvement of the process has to be done before improving individual operations can be attempted.
Process is flow of material (input into the process) through operations resulting in change of shape etc. in the desired direction. The operation breakup and the selection of operations has to be improved first before investigating how the operation is being carried out using specific machines, tools and operators.
Process Chart - Gilbreth
Process chart as a productivity improvement visualization aid was first proposed by Frank Gilbreth. ASME standardized it later with five operations with specified symbols.Processing operation
Inspection operation
Transport operation
Temporary delay on the shop floor, and
Permanent Storage in designated store
The Japanese standard uses slightly separate symbols
In the book chapter, Shingo focuses on five operations
Processing operation
Inspection operation
Transport operation
Two types of delay operations - Process delay, Lot delay
Process Improvement
Process improvement has two major steps.
The first step is to improve the product design through product redesign. This is termed as "Product Industrial Engineering" and it is design efficiency engineering using value engineering, design for manufacture, design for assembly, and design optimization techniques. It is important to highlight that industrial engineering uses updated technical or engineering knowledge, creative thinking to solve productivity problems or opportunities and productivity analysis, value analysis and cost analysis to identify productivity improvement opportunities. Industrial engineering researchers and practitioners have developed certain methods, techniques and concepts which help in increasing productivity of product designs and process designs or plans.
The second improves the engineering process or manufacturing process through process analysis and operation analysis. This second activity is termed "Process Industrial Engineering." Process industrial engineering utilizes methods and techniques that include, process analysis, operation analysis, methods efficiency engineering, machine work study, method study, motion studies (human effort study), production process or method optimization and variability reduction methods. Both process industrial engineering and product industrial engineering suggestion have to be cleared as economically feasible under engineering economic analysis.
ECRS Method of Process Improvement
Eliminate the operation – sometimes it is found to be not necessary or sometimes it can be eliminated due to improvement of earlier operation.Combine operations with earlier one or latter one.
Rearrange the sequence of operations
Split or Divide Operations
Shingo Method of Process Improvement
Shingo discusses important fundamental issues related to five operations recorded in process charts.
Processing operation
Inspection operation
Transport operation
Process delay
Lot delay
Processing Operations Analysis
Two alternatives to improve production operations
1. Manufacturing or Production operations can be improved by introducing alternative production methods which are more efficient, productive and less costly.
2. The production operation can be improved by modifying process parameters, like temperatures, tool materials, cutting speed, feed, depth of cut, heat treatment time etc.
https://www.fanuc.eu/bg/en/industrial-applications/cnc-grinding
Examples in the book
Manufacturing operations can be improved by alternatives related to proper melting or forging temperatures, cutting speeds or tool selection.
Examples related to vacuum molding, plating and plastic resin drying are given in the book.
Eliminating Flashing in Castings (Die)
Flashing in die castings occurs due to escape of air.
Removing the air in mould with a vacuum pump eliminated flashing.
Removing Foam in High-Speed Plating
Spraying or showering the surface to be painted resulted in a 75% reduction.
Drying Plastic Resin
Letting the resin dry a little at a time by allowing it to float to the surface resulted in a 75% reduction of electric power consumption.
Analysis of Inspection Operations
Inspection also is carried out using inspection or measuring instruments, gauges and some inspections are automatic and some are manual. Hence machine work study and man work study (motion study) are used in improving inspection operation also.Shingo classified inspection as judgment inspection and informative inspection. He said normal or traditional inspection is judgment inspection.
It separates good and defective items.
Rework done on defective items if possible
Informative inspection asks for process improvement. It is like medical examination that leads to treatment. What Shingo suggests can be termed "Preventive Inspection" similar to preventive maintenance. Poka-Yoke devices are an examples of preventive maintenance.
100% Inspection to Assure Zero Defects
Statistical Process Control (SPC) is sampling based informative inspection.
But Shingo says even it is not sufficient to assure zero defects.
To assure zero defects we need to inspect every item but at low cost per item.
Shingo’s Suggestions Regarding Informative Inspections
Self Inspection
Successive Inspection
Enhanced Self Inspection – Inspection enhanced with devices - poka-yoke
Example 2.4 – Vacuum Cleaner Packing
Cleaner along with attachments and leaflets to be packed.
When a leaflet is taken from the pile, a limit switch is operated.
When attachments are taken from the container, a limit switch is operated.
Then only, the full package is allowed to be sealed.
Principle
The purpose of inspection is prevention of the defect.
Quality can be assured when it is built in at the process and when inspection provides immediate and accurate feedback at the source to prevent the defective item to go further.
Self Inspection
It provides the most immediate feedback to the operator.
He can improve the process and also rework on the item.
Disadvantage inherent.
There is potential for lack of objectivity.
He may accept items that ought to be rejected.
Successive Inspection
The operator inspects the item for any defect in the previous operation before processing it.Shingo says, when this was introduced defects dropped to 0.016% in Moriguchi Electric Company in television production
Inspection enhanced by Poka Yoke
Human operation and inspection can still make errors unintentionally.Poka Yoke will take care of such errors.
Ex: Left and right covers are to be made from similar components with a hole in different places.
The press was fitted with a poka yoke which does right cover pressing only when the hole is in proper place.
Source Inspection
This is answering the question: What is the source of the defect in the process/operation?
Two types proposed.
Vertical
Horizontal
Source Inspection – Vertical, Horizontal
Vertical source inspection traces problems back through the process flow to identify and control conditions external to the operation that affect quality.
Horizontal source inspection identifies and controls conditions within an operation that affect quality.
Poka-yoke Inspection Methods
Poka-yoke achieves 100% inspection through mechanical or physical control.Poka-yoke can either be used as a control or a warning.
As a control it stops the process so the problem can be corrected.
As a warning, a buzzer or flashing lamp alerts the worker to a problem that is occurring.
Three types of control poka-yoke
Contact method - identify defects by whether or not contact is established between the device and some feature of the product's shape or dimension
Fixed value method - determines whether a given number of movements have been made
Motion step method - determines whether the established steps or motions of a procedure are followed
Choosing/Designing Poka Yoke
First decide stage of inspection – Self or Successive
Second – Type of regulation
Control or warning.
Third decide Error Sensing type – Contact, fixed number or motion step
Analysis of Transport Operations
Transport within the plant is a cost that does not add value.Hence real improvement of the process eliminates the transport function as much as possible.
This involves improving the layout of process.
Ex – 7. Transport Improvement
Tokai Iron Works – process layout - presses, bending machines, embossing
Layout Change: Flow based layout.
A 60 cm wide belt conveyor with ten presses on either side.
WIP reduced. Production time shortened. Delays disappeared.
200% increase in productivity.
Principle
Only after opportunities for layout improvement have been exhausted should the unavoidable transport work that remains be improved through mechanization.
Improvement of Flow - Eliminating Delays - Temporary and Permanent
Eliminating - Storage Operations (Delay)
Process Delay – Permanent storage – Whole lot is waiting
Lot Delays – Temporary storage – One item is being processed. Other items in the lot waiting.
Another classification is storage on the factory floor and storage in a controlled store.
Eliminating - Storage Operations (Delay)
There are three types of accumulations between processes:
Evening the flow storage- E storage - resulting from unbalanced flow between processes (engineering)
Cushion for production problems storage - C storage - buffer or cushion stock to avoid delay in subsequent processes due to machine breakdowns or rejects (control)
Safety for Demand Increase storage - S storage - safety stock; overproduction beyond what is required for current control purposes
Eliminating E-Storage
E-storage is due to engineering/planning/design of the production-distribution systemThis can be eliminated through leveling quantities, which refers to balancing flow between high and low capacity processes and synchronization.
Leveling would mean running high-capacity machines at less than 100% capacity, in order to match flow with lower capacity machines that are already running at 100% on short interval basis. The alternative to be run the whole plant a capacity equal to the period demand. This is followed in TPS.
At Toyota, the quantity to be produced is determined solely by order requirements (Takt time).
Principle
Presence of high capacity machines should not be used to justify large lot processing and resulting inventory.
Process capacity should serve customer requirements/production requirements and should not determine them
Synchronization.
The lots especially one piece lot is processed without delay in a flow.It is efficient production scheduling that ensures that once quantities are leveled (output is matched), inventories do not pile at any stage due to scheduling conflicts.
Synchronize the entire process flow.
Eliminating C storage - Cushion
Cushion stocks compensate for:
machine breakdowns,defective products,
downtime for tool and die changes and
sudden changes in production scheduling.
Eliminate Cushion Storage
Prevent machine breakdowns:Determining the cause of machine failure at the time it occurs, even if it means shutting down the line temporarily.
Total Productive Maintenance movement.
Zero Defect Movement.
Total quality management.
Use better inspection processes:
Self Inspection.
Successive Inspection.
Enhancement to inspection through Poka Yoke
Eliminate Lengthy setups and tool changes
Implement SMED to eliminate long set-up times and tool changes
Running smaller batch sizes to allow for quick changes in production plans
Absorb Change in Production Plan
Running smaller batch sizes allows for quick changes in production plans without disturbing flow production to significant extent.
Eliminating Safety (S) storage
Safety stock is kept not to take care of any predicted problem but to provide additional securityIt may guard against delivery delays, scheduling errors, indefinite production schedules, etc.
Ex. 10 Delivery to stores
In example 2.10 Shingo mentions a company wherein vendors supply to store and from store components are supplied to assembly line.
Shingo suggested that vendors should directly supply the day’s requirements to assembly floor and in case of any problem, components in the store can be used.
Less Need for Safety Stock Observed
That practice led to the observation that very less safety stock is needed in the store.
Shingo recommends keeping a small controlled stock that is only used when the daily or hourly scheduled delivery fails or falls behind.
In case of unexpected defects also it can be used.
The safety stock can then be replenished when the scheduled materials arrive, but the supply of materials due for the process go directly to the line, rather than normally going into storage first.
This is the essence of the just-in-time supply method.
Eliminating lot delays
While lots are processed, the entire lot, except for the one piece being processed, is in storage (is idle).The greatest reduction in production time can be achieved when transport lot sizes are reduced to just one; the piece that was just worked on.
SMED
Using SMED (single-minute exchange of dies), set up time is decreased so large lot sizes are no longer necessary to achieve machine operating efficiencies.
SMED facilitates one item lot sizes.
Layout Improvement - Flow
Transportation changes can be accomplished through flow layout and using gravity feed Chutes which result in shorter production cycles and decreases in transport man-hours.
Reducing Cycle Time
Generally, semi-processed parts are held between processes 80% of the time in a production cycle time.
It quantity leveling is used and synchronization of flow is created, the cycle time can be reduced by 80%.
By shifting to small lot sizes will further reduce cycle time.
TPS – Reduction of Delays or Storage
Methods of reducing production time delays (JIT) is the foundation of Toyota Production System.
It clearly brings down production cycle time and thereby offers small order to delivery time.
Process Improvements in Toyota
Mixed model small lot production was attempted in Toyota to compete with American manufacturers.First, inefficiencies in processing operations, inspection operations and transport operations were removed. Then storage operations were attacked and inventories eliminated. Toyota surpassed American manufacturers.
Steps in Operation Analysis - Maynard and Stegemerten
Analysis of Tolerances and Inspection Standards
Analysis of Material in Operation Analysis
Tool Related Operation Analysis - Machine, Cutting Tools, Work holding, and Accessories
Material Handling Analysis in Operations
Operation Analysis of Setups
Operation Analysis - Man and Machine Activity Charts
Operation Analysis - Plant Layout Analysis - Work station layout also
Operation Analysis - Analysis of Working Conditions and Method
Operation Analysis - Common Possibilities for Operation Improvement
Ch. 3 Improving Machine Operations - More Details
Operation may be classified as follows:Set up operations - preparation
Principal operations - performance
Margin allowances - machine breaks
Personal allowances - worker breaks
Improving Setup
SMEDImproving principal operations
The easiest way to improve principal operations is to separate the worker from the machine.
Reduce involvement of man in machine running and production.
This involves the "one worker, many process" theory.
One worker attends 5-6 machines,
The principle is that cost reduction is more important than high machine operating rates.
Machines should not unnecessarily function and produce excess inventory.
But the operable time of the machine should be high.
Whenever needed machine must be ready for production.
Autonomation
Machine detects problem and stops.Workers correct the problem.
The next step is to make the machine correct the problem
Improving margin allowances
Main operations are automated by marginal activities like removing chips, feeding materials and stocking products are still done by hand by men.They also need to be automated.
Lubrication: Consider automatic lubrication, use of oil impregnated metals etc.
Cutting oil – Consider automatic oiling or cutting without oil.
Chip removal – Consider powdering chips or automatic lubrication and chip removal.
Workshop allowances
Automate the following:Automate feeding for materials.
Automate product storage.
By adopting the SMED system, Toyota achieved dramatic reductions in setup time and inventory cost.
Adding multi-machine handling and autonomation further increased productivity.
Updated on 7 March 2020
19 October 2019
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