Online Encyclopedia
Industrial and manufacturing engineering
In industrial and manufacturing engineering, engineering principles are utilized to produce an end product. This end product can be a chemical compound or mixture such as soap, gasoline or petrol, or/and assembly of products from different manufacturing processes to produce some as complex as an automobile or an airplane.
There are a number of things engineers do to make products more manufacturable.
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Value engineering
One is called "value engineering." Value engineering is based on the proposition that in any complex product, 80% of the customers need 20% of the features. By focusing product development, one can produce a superior product at a lower cost for the major part of a market. When a customer needs more features, sell them as options. This approach is valuable in complex electromagnetic products such as computer printers, in which the engineering is a major product cost.
To reduce a project's engineering and design costs, it is frequently "factored" into subassemblies that are designed and developed once and reused in many slightly different products. For example, a typical tape-player has a precision injection-molded tape-deck produced, assembled and tested by a small factory, and sold to numerous larger companies as a subassembly. The tooling and design expense for the tape deck is shared over many products that can look quite different. All that the other products need to have are the necessary mounting holes and electrical interface.
Quality Assurance/Quality Control
There are two quotes which define quality these are as follows:
"Quality is never an accident; it is always the result of an intelligent effort" John Ruskin. (Author 1819 - 1900)
"Quality is free. It is not a gift, but it is free. What costs money are the un-quality things - all actions that involve not doing the job right first time" Philip B. Cosby (Author of "Quality is free - The art of making quality certain")
What Is Quality "The degree of excellence achieved in meeting those conditions that influence the characteristics of a product which makes that product acceptable to a specific consumer"
Quality Control = "The operational techniques and activities employed to measure and regulate the characteristics of an item in order to meet the specified requirements"
Quality Assurance = " All those planned and systematic actions, which are necessary to provide confidence in the achievement of the required quality"
Quality Assurance/Quality Control. Part 1.
Quality Assurance/Control has been around for many years, although the phrase Quality Assurance is a relatively new title, and has become well known over the last few decades in line with the developments in manufacturing and construction.
It really all started during the stone age, just think of the dire consequences if the tool or weapon which the stone age man made failed, then he either did not eat or have a fire to keep himself and his family warm.
Eventually, a system of trade evolved which meant people had to rely on the manufacturer to supply his needs and of course this eventually lead to the saying of ‘Caveat Emptor’, literal translation of this is, - let him beware – (more to the point, let the buyer beware (he alone is responsible if he is disappointed)).
The pyramids as we all know, were built some 5,000 years ago, in those days quality was taken very seriously indeed and if you were the supervisor you had to ensure your product was correct the first time, and the reason for this ‘ASSURANCE’ was, if the work did not conform to the specifications then the supervisor was executed, now that is what I call ensuring good QA.
These people had to be good at their jobs when you think of the tools they had to work with, the pyramid at Gaza which were constructed about 2,700 BC, consider the four 230.5 metre sides are similar to within 0.2 metres, this is +/- 0.044 percent tolerance. An even greater achievement, the four sides are square to each other to within 3.5 arc seconds and 5.5 arc seconds of the correct compass settings.
To emphasise the previous statement, about the supervisor being executed, this is even happening in this day and age.
The following is a summary of an item, which was reported in a Newspaper in China during 1993.
“Refrigerators are among the most sought after consumer items in China at a factory in Beijing the products had a reputation for failure.
For years, factory workers complained that many component parts did not meet the required specifications and the end product did not function as required. Complaining workers quoted the plant manager as stating, “Ship it.” Some customers who had waited for up to five years for their appliances were outraged.
One Monday morning as 500 working looked on, 18 people – including the Plant Manager, QUALITY MANAGER, the Engineering Managers and their top staff were taken out to a rice paddy outside the factory and unceremoniously shot to death for committing unpardonable crimes against the people of China.”
This really makes you reflect on the step you are now about to take in choosing your vocation as a Quality Assurance/Quality Control Engineer.
If any of you wish to change your minds and look towards a much safer career, (such as Mercenary Soldier, a Christian Teacher in Iraq/Iran or some other safe employment) I am sure that the rest of us will understand.
A form of QC or inspection is shown in some of the wall paintings dated around 1450 BC at Thebes in Egypt which illustrates stone cutting and measurements being taken, this shows the profession we have chosen is a long and prestigious one. (Albeit at times thankless).
Over the years QA/QC developed into a requirement in just about every trade around, but not all that evident, until we now come to the period of the Middle Ages it was during this time the control of quality through Livery Companies and Craft Guilds came to the fore, during this stage these Guilds sought to control the product standards and craft skills.
Since this early period a steady evaluation in quality management, control, policy and practices have improved mainly through the needs of the military markets.
One of the earliest appointments to, what you could call QA/QC or inspection, was William Wrotham, as Keeper of the King’s Ports and Galleys, his duties included the supervision of ship building and repairs, during the reign of King John in 1214.
Some 450 years later in 1664 during the period when Samuel Pypes was Secretary to the Admiralty, appointments were made for overseers with direct responsibility for the construction of the ships.
These overseers were “enjoined” (now that’s a nice word which means they were to ENSURE all timbers for the building of ships shall be “of good, sound, well conditioned and in all aspects fit for His Majesty’s Service”, also the canvas “be fit for sailcloth, equal in size and goodness to the patterns in the Navy Office and sealed with the seals of the said office” also all anchors “shall be of good Spanish iron, substantially and of workmanlike wrought”).
The same as now, it was the duty of the Ships Overseer to ENSURE the ship’s carpenters were “of sober condition”.
Up until the end of the nineteenth century the first step was one of operator quality control. Under this system, one or a small number of workers, were responsible for the manufacture of an entire product, this way each worker could control the quality of his work.
These men were proud of their work and would allow nothing but the best workmanship to be passed through, but this was slow and obviously expensive, the progress from this system was as equipment became more complex groups of workmen became involved in the manufacture of one unit only, and as a result formal quality control systems were developed in the early 1900’s, (during the Industrial Revolution).
This led to a system in which large groups of men performing a similar type of work were grouped together under the supervision of a foreman who also took on the responsibility to control the quality of work manufactured.
It has taken approximately 80-90 years (in about 20 year intervals) for present day Quality Assurance to be established from inception to attainment of the present day.
During World War 1, the manufacturing process became more complex, and the introduction of large numbers of workmen being supervised by a foreman designated to ensure the quality of the work, which was being produced. This period also introduced mass production and piecework, which created quality problems as workmen could now earn more money by the production of extra products, which in turn led to bad workmanship being passed on to the assembly lines.
It was due to the large amount of bad workmanship being produced that the first full time inspectors were introduced into the large-scale modern factory. These full time inspectors were the real beginning of inspection quality control, and this was the beginning the large inspection organizations of the 1920’s and 30’s, which were separately organised from production and big enough to be headed by superintendents.
The systematic approach to quality started in Industrial Manufacture during the 1930’s, mostly in the U.S.A, when some attention was given to the cost of scrap and rework. With the impact of mass-production, which was required during the Second World War, it became necessary to introduce a more stringent form of QC which can be identified as “Statistical Quality Control”, this system came about with the realisation that Quality cannot be inspected into an item. What this entailed was to extend the inspection phase and make inspection organizations more efficient and to provide inspections with control tools, such as sampling and control charts.
This “Statistical Quality Control” had a significant contribution in that it provided a sampling inspection system rather that a 100 per cent inspection. This type of inspection however did lead to a lack of realisation to the importance of the engineering of product quality. For example, if you have a basic sampling scheme with an acceptance level of 4%, what happens is you have a ratio of 96% products released onto the market with 4% defective items – this obviously is a fair risk for any company/customer – unless you happen to be one of the 4 who lands up with one of the 4% defective items.
In the 1940’s, inspections progressed more to process control, which together became known as Quality Control. With the introduction of the Nuclear and Space industries during the 1950’s attention was focussed on design, then progressing through into the 60’s and 70’s, the true meaning of Quality Assurance really became known.
Quality Assurance covers all activities from design, development, production, installation, servicing and documentation, this introduced the rule “Fit for purpose” and “do it right first time”.
During the 1980’s, the concept of “company quality” with the focus on management and people came to the fore. It was realised if all departments approved quality with an open mind success was possible if the management administrated the quality improvement process.
The company-wide quality approach places an emphasis on three aspects :-
i. Elements such as controls, job management, adequate processes, performance and integrity
criteria, identification of records etc.
ii Competence such as knowledge, skills, experience, qualifications etc.
iii Soft elements, such as personnel integrity, confidence, organisational culture, motivation, team
spirit and quality relationships.
The quality of the outputs is at risk if any of these three aspects are deficient in any way. The approach to quality management given here is therefore not limited to the manufacturing theatre only but can be applied to any business activity, e.g.:-
i. Design work, ii. Administrative services, iii. Consulting, iv. Banking, v. Insurance, vi. Computer software, vii. Retailing, viii.Transportation, etc.
It comprises a quality improvement process, which is generic in the sense it can be applied to any of these activities and it establishes a behaviour pattern, which supports the achievement of quality.
This in turn is supported by quality management practices which can include a number of business systems and which are usually specific to the activities of the business unit concerned.
In manufacturing and construction activities, these business practices can be equated to the models for quality assurance defined by the International Standards contained in the ISO 9000 series and the specified Specifications for quality systems.
Still in the system of Company Quality the work being carried out was shop floor inspection, which did not control the major quality problems, this led to quality assurance or total quality control, which has come into being recently.
Total Quality Control is the most necessary inspection controls of all, but despite all of the statistical quality control techniques, or the quality improvements implemented, sales decrease.
The major problem, which led to the decrease in sales was, the specifications did not include the most important factor, “What the customer required”.
The major characteristics, which had been ignored during the search to improve manufacture and overall business performance were:-
i. Reliability ii Maintainability. iii Safety
Because the most important factor had been ignored i.e. “What the customer required”, this needed to be corrected and a few refinements had to be introduced:-
i. Marketing had to carry out their work properly and define the customer’s specifications.
ii Specifications had to be defined to conform to these requirements.
iii Conformance to specifications i.e. drawings, standards and other relevant documents, were
introduced during manufacturing, planning and control.
iv Management have to confirm all operators are equal to the work imposed on them, and
holidays, celebrations and disputes did not affect any of the quality levels.
v. Inspections and tests were carried out, and all components and materials, bought in or
otherwise, conformed to the specifications, and the measuring equipment was accurate, this
is the responsibility of the QA/QC department.
vi Any complaints received from the customers were timorously and satisfactorily dealt with.
vii Feedback from the user/customer is used to review designs.
If the original specification does not reflect the correct quality requirements, quality cannot be inspected or manufactured into the product.
e.g. All parameters for a pressure vessel should include, not only the material and dimensions,
but operating, environmental, safety, reliability and maintainability requirements.
To conclude, the above forms the basis from which the philosophy of Quality Assurance has evolved, and the achievement of quality or the “fitness-for-purpose” is “Quality Awareness” throughout the company.
It's a truism that "quality is free." Very often, it costs no more to produce a product that always works, every time it comes off the assembly line. It requires a conscious effort during engineering, but it reduces the cost of waste and rework quite a bit.
Commercial quality efforts have two foci. First, to reduce the mechanical precision needed to get good performance. Second, to control all manufacturing operations to assure that every part and assembly are within tolerance.
Statistical process controls on manufacturing usually proceed by randomly sampling and testing a fraction of the output. Variances of critical tolerances are continuously tracked, and manufacturing processes are corrected before bad parts can be produced.
A valuable process to perform on a whole consumer product is called the "shake and bake." Every so often, a whole product is mounted on a shake table in an environmental oven, and operated under increasing vibration, temperatures and humidity until it fails. This finds many unanticipated weaknesses in a product. Another related technique is to operate samples of products till they fail. Generally the data is used to drive engineering and manufacturing process improvements. Often quite simple changes can dramatically improve product service, such as changing to mold-resistant paint, or adding lock-washed placement to the training for new assembly personnel.
Many organizations use statistical process control to bring the organization to Six Sigma levels of quality. In a six sigma organization, every item that creates customer value or disasstisfaction is controlled to assure that the total number of failures are beyond the sixth sigma of likelihood in a normal distribution of customers - setting a standard for failure of fewer than four parts in one million. Items controlled often include clerical tasks such as order-entry, as well as conventional manufacturing tasks.
Producibility
Another engineering discipline is "producibility." Quite frequently, manufactured products have unnecessary precision, production operations or parts. Simple redesign can eliminate these, lowering costs and increasing manufacturability, reliability and profits.
For example, Russian liquid-fuel rocket motors are intentionally designed to permit ugly (though leak-free) welding, to eliminate grinding and finishing operations that do not help the motor function better.
Some Japanese disk brakes have parts toleranced to three millimeters, an easy-to-meet precision. When combined with crude statistical process controls, this assures that less than one in a million parts will fail to fit.
Many vehicle manufacturers have active programs to reduce the numbers and types of fasteners in their product, to reduce inventory, tooling and assembly costs.
Another producibility technique is "near net shape" forming. Often a premium forming process can eliminate hundreds of low-precision machining or drilling steps. Precision transfer stamping can quickly produce hundreds of high quality parts from generic rolls of steel and aluminum. Die casting is used to produce metal parts from aluminum or sturdy tin alloys (they're often about as strong as mild steels). Plastic injection molding is a powerful technique, especially if the part's special properties are supplemented with inserts of brass or steel.
When a product incorporates a computer, it replaces many parts with software that fits into a single light-weight, low-power memory part or microcontroller. As computers grow faster, digital signal processing software is beginning to replace many analog electronic circuits for audio and sometimes radio frequency processing.
On some printed circuit boards (itself a producibility technique), the conductors are intentionally sized to act as delay lines, resistors and inductors to reduce the parts count. An important recent innovation was to eliminate the leads of "surface mounted" components. At one stroke, this eliminated the need to drill most holes in a printed cricuit board, as well as clip off the leads after soldering.
In Japan (the land where manufacturing engineers are most valued), it is a standard process to design printed circuit boards of inexpensive phenolic resin and paper, and reduce the number of copper layers to one or two to lower costs without harming specifications.
See also
- List of industrial engineers
- Institute of Industrial Engineers
- Value engineering
- Reverse engineering
- List of production topics