Frank Gilbreth proposed the method of process charts to study and improve processes.
In the subsequent days, two process charts became important.
1. Operation Process Chart for study and improvement of material transformation operations and inspections.
Flow process chart shows five types of activities.
Each of these activities can be analyzed using industrial engineering methods and studies.
More activities can be added to process charts to include more items needing analysis. Energy and information are two such items which are to be added to process charts.
Shigeo Shingo explained very well how Toyota Production System emerged from the process improvement based on flow process chart. He strongly stated the fact that Toyota Production System is the excellent output from industrial engineering promoted by Japan Management Association for many years.
Read Shigeo Shingo's explanation
Toyota Production System Industrial Engineering (TPS IE) Part 1
In each activity there are machine activities and manual activities. Machine activities can be studied under machine work study (process industrial engineering) and manual activities using human effort industrial engineering (human work study).
Machine Work Study - Study Areas
Aspects of Machine to be Studied
Advanced Machine Availability
Condition of the Machine (Repair & Overhaul Need)
Improvement of the Machine
Upkeep of the machine by operator
Data Generation and Analysis
Industrial Engineering Analysis of Main Transformation Operation
2. Would the purchase of a better machine be justified?
3. Can the work be held in the machine by other means to better advantage?
4. Should a vise be used?
5. Should a jig be used?
6. Should clamps be used?
7. Is the jig design good from a motion-economy standpoint?
8. Can the part be inserted and removed quickly from the jig?
9. Would quick-acting cam-actuated tightening mechanisms be desirable on vise, jig, or clamps?
10. Can ejectors for automatically removing part when vise or jig is opened be installed?
11. Is chuck of best type for the purpose?
12. Would special jaws be better?
13. Should a multiple fixture be provided?
14. Should duplicate holding means be provided so that one may be loaded while machine is making a cut on a part held in the other?
15. Are the cutters proper?
16. Should high-seed steel or cemented carbide be used?
17. Are tools properly ground?
18. Is the necessary accuracy readily obtainable with tool and fixture equipment available?
10. Are hand tools pre-positioned ?
20. Are hand tools best suited to purpose?
21. Will ratchet, spiral, or power-driven tools save time?
22. Are all operators provided with the same tools?
23. Can a special tool be made to improve the operation?
24. If accurate work is necessary, are proper gages or other measuring instruments provided?
25. Are gages or other measuring instruments checked for accuracy from time to time?
Processing Operations Improvement - Illustrations - Shigeo Shingo's Book on IE Study of TPSExamples 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.
Gideon Halevi, Process and Operation Planning, Kluwer Academic Publishers
Industrial Engineering Analysis of Inspections
Analysis of Inspection OperationsShingo said normal 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.
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.
Enhanced Self Inspection – Inspection enhanced with devices - poka-yoke
Example – 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.
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.
It provides the most immediate feedback to the operator.
He can improve the process and also rework on the item.
There is potential for lack of objectivity.
He may accept items that ought to be rejected.
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.
This is answering the question: What is the source of the defect in the process/operation?
Two types proposed.
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.
Industrial Engineering Analysis of Transportation
Analysis of Transport OperationsTransport 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.
Only after opportunities for layout improvement have been exhausted should the unavoidable transport work that remains be improved through mechanization.
Industrial Engineering Analysis of Delays
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:
E storage - resulting from unbalanced flow between processes (engineering)
C storage - buffer or cushion stock to avoid delay in subsequent processes due to machine breakdowns or rejects (control)
S storage - safety stock; overproduction beyond what is required for current control purposes
Eliminating E-StorageE-storage is due to engineering/planning/design of the production-distribution system
This 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.
At Toyota, the quantity to be produced is determined solely by order requirements (Takt time).
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
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 - CushionCushion stocks compensate for:
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.
Eliminate Cushion Storage
Zero Defect Movement.
Total quality management.
Use better inspection processes:
Enhancement to inspection through Poka Yoke
Eliminate Cushion Storage
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
Eliminate Cushion Storage
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) storageSafety stock is kept not to take care of any predicted problem but to provide additional security
It 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.
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.
Industrial Engineering Analysis of Storage
Conventional warehouses: Simple, yet effective
As the industry continues unprecedented transformation, some of the classic approaches still hold up.
Josh Bond, Senior Editor · October 14, 2019
Improving Your Manufacturing Operations Using Warehouse Automation
June 27, 2019
Blog post written by John Hinchey, VP of Sales for Westfalia Technologies, Inc., a leading provider of logistics solutions for plants, warehouses and distribution centers.
Proposing a new framework for lean warehousing: first experimental validations
Conference Paper, 2017
Lean warehousing plays a significant role in order to achieve lower costs of logistics operations and increase flexibility and efficiency in supply chains. . This paper proposes a novel lean warehousing framework combining three well-known lean tools and presents the first outcomes of its validation campaign. It discusses the framework application to a raw material and component warehouse of an international company in the automotive sector. Results show that time savings up to 36% might be achieved in receiving, put away, and picking operations, bringing significant economic benefits in terms of labour, service level, and warehouse space.