MÜGE BAŞARAN 030090704 3nd WEEK

OVERALL EQUIPMENT  EFFICIENCY/ ‘’effectiveness of production’’

Old definition:

OEE stands for Overall Equipment Efficiency and is the primary measure of production effectiveness. It can be used for value stream or individual work station performance evaluation. Good value stream OEE is one of the key precursors to the implementation of Lean and is the product of three important operational parameters. These are: Equipment availability, quality yield, cycle-time performance. To calculate OEE, you will need five parameters. First is the planned production time for the line. Second is the unplanned line downtime. Third is the line cycle time, or cycle time, of the bottleneck. Fourth is the total production including scrap, and fifth is the total amount of salable product.

(How to Implement Lean Manufacturing, Lonnie Wilson; Page:61)

New definition:

Manufacturing companies are in business to make money, and they make money by adding value to materials to make products the customers want. Most companies use machines to add value to the products. To add value effectively, it is important to run the machines effectively, with as little waste as possible. Overall equipment effectiveness is a measurement used in TPM to indicate how effectively machines are running. What do we mean by overall equipment effectiveness? Many people are familiar with the idea of "efficiency," which usually reflects the quantity of parts a machine or a person can produce in a certain time. OEE is different from efficiency in several ways.

A machines’s overall effectiveness includes more than the quantity of parts it can produce in a shift. When we measure overall equipment effectiveness, we account for efficiency as one factor:

·                     Performance: a comparison of the actual output whit that the machine should be producing in the same time

In addition to performance, however, OEE includes two other factors:

·                     Availability: a comparison of the potential operating time and the time in which the machine is actually making products.

·                     Quality: a comparison of the number of products made and the number of products that meet the customer’s specifications.

When you multiply performance availability, and quality, you get the overall equipment effectiveness, which is expressed as a percentage. OEE gives a complete picture of the machine’s ‘’health’’_ not just how fast it can make parts, but how much the potential output was limited due to lost availability of poor quality.

Unlike some uses of the efficiency measure, OEE monitors the machine or process that adds the value, not the operator’s productivity. When we measure OEE, we look at how well the equipment or process is working.

Measuring OEE is not an approach for criticizing people. It is strictly about improving the equipment or process. Used as an impartial daily snapshot of equipment conditions, OEE promotes openness in information sharing and a no-blame approach in handling equipment-related issues.

OEE is a measure of overall equipment efficiency, and a higher value indicates an overall better condition than a lower value. Study of each of the factors involved in the calculation of the OFF provides a clue about how to improve the equipment condition and increase its OEE. Figure 6-1 illustrates the formula for OEE calculation .

 ( Matthew P. Stephens , Productivity and Reliability-Based Maintenance Management, pg.161)

(OEE for operators: overall equipment effectiveness, created by Productivity development team,pg.4,5)

ELECTROPOLISHING/ ‘’surface quality improving method’’

Old definition:

Electropolishing is a electrochemical process by which surface material is removed by anodic dissolution. Sometimes referred to as reverse plating, electropolishing actually removes surface material beginning with high points within the microscopic surface texture. By removing these points, the electropolishing process will improve the surface finish, leaving a smoother and more reflective surface. Electropolishing delivers a smoother, more reflective surface that reduces product adhesion and imporves surface cleanability. This porcess improves the near surface chemistry of the material, and promotes to the formation of an improved corrosion-resistant surface layer.

(O. G. Palana, Engineering Chemistry, p.162)

New definition:

Ectropolishing is defined as a process of anodic dissolution of metals or alloys in an appropriate solution resulting in production of improved morphology and geometry of the surface and a shiny, bright and smooth appearance. Technical advantages of the electropolishing include a reduction in coefficient of friction. An increase in the magnetic susceptibility of some magnetic materials, an increase in corrosion resistance and excellent reflectance in addition electropolishing is widely used in the metallography for the microscopic investigation of crystallographic structure of metals and alloys. Elettropolishing as an anode process, is similar to electromachining however there are significant differences between them. ha. instance, eleetropolishing is usually carried out from unstirred, concentrated acidic solutions as electrolytes, at lower current densities, and with the electrode separations of at least  1cm. The quality or electropolished surfaces depends on electrochemical conditions including ;fluidic polarization. electrolyte composition and microgeometry. It is determined by the appearance. measurements of profiles with optical profilometers and also using microscopic techniques. In terms of the surface roughness, the two types of electropolishing are distinguished. The first. commonly called anodic levelling or smoothing, refers to the elimination of the surface roughness with a height of more than 1 micrometer . The second type is called anodic brightening and is referred to the elimination of surface roughness less than 1 micrometer. However this distinguishing between the smoothing and brightening is a very approximate simplification, since there is no simple relationship between measurements ao profile and brightness.

(Konstantin Ivanovich Popov,Stojan S. Djokić,Branimir N. Grgur, Fundamental aspects of electrometallurgy , pg.226)

ELASTOMER  FRICTION/ ‘’mechanical material property’’

Old definition is not found

New definition:

Friction and abrasion are two properties of major importance when consider elastomeric components for dynamic applications. Dynamic seals, for example, can undergo abrasion when sliding over dry surface where friction is correspondingly high.

The friction coefficient of an elastomer depends on a number of factors, such as its geometric shape and composition, temperature, pressure, rubbing seed and surface finish of both the elastomeric part and the material with which it is in contact.

High friction can be harmful because it generates heat, which can cause degredation of the elastomer. The friction can be markedly decreased, by using a suitable lubricant or by chemical treatment of the elastomer surface (section 2.11). Rubber compounds with ‘’self- contained’’ lubricants may also be used where continuous presence of a lubricant is suspect and where minimal friction is essential.

The abrasive wear, fatigue wear and frictional wear of rubber are all generated on the rigid matrix surface in relative motion, which are dependent on the roughness of the rigid matrix surface to a great extent. However, the abrasive and fatigue wear frequently occurs on the smooth surfaces with high frictional coefficient. So far as the severity of wear, the abrasive wear and frictional wear are most serious, but fatigue wear is less. Friction mechanism for the tree types of wear as shown in the figure

3.2 is an important characteristic of rubber wear.

Elastomers are usually formulated to have high friction coefficients against a wide variety of counterfaces but the friction coefficient ran be very low in some cases. Friction coefficients for some common elastomers against hardened stainless steel are quite high. On the other hand, in water, the coefficient of polyurethane against most other solids is less than 0.2. The slippery nature of this elastomer became apparent when these materials came into vogue In the 70's for floor finishes. They produced a very abrasion resistant surface, but when wet they were a safety hazard. Their use as tires and floor toppings has almost ceased but they are now used for seals and wear parts in pumps where their slipperiness and abrasion resistance have a synergistic effect.

·                     The coefficient of friction of many elastomers against other solids is often I or more, but the use environment may significantly alter the friction characteristics.

The high friction of elastomers is thought by some to arise from the conformability of these materials to the counterface — there are more junctions. There is not agreement on the mechanism of high friction of elastomers but a plausible explanation could be obtained from the adhesion model where the shear strength of elastomer Cs) is

(Khairi Nagdi ,Rubber as an engineering material: guideline for users, pg. 29)

(Si-Wei Zhang, Tribology of elastomers, pg. 38)

(K. C. Ludema,Raymond George Bayer,ASTM Committee G-2 on Erosion and Wear, Tribological modeling for mechanical designers, pg.113)

QUALITY-ASSURANCE INSPECTION/ ‘’quality menagement’’

Old definition:

The technique of quality-assurance inspection is the measuring of the various quality characteristics generated in a production process or inherent in the material.This type of inspection can be a check made on each piece produced or a check made on a statistical sample of the lot.The inspection may be a mechanical or electronic measurement or visual inspection the result of which are compared with standards.

The inspection can be performed be the operator or worker making the part or component by a second person who is responsible for measuring only or performed entirely by computer-controlled measurement.

The inspection assures that the products being produced meet the standards of quality and quality levels which have been previously established.

(Feigenbaum A.V.,Total Quality Control Third Edition,p. 281)

New definition:

Quality assurance is the application of planned systematic quality activities to ensure that the project will employ all processes needed to meet requirements identified during quality planning.

•             Quality assurance addresses the program; it is the combined set of activities that the project team will perform to meet project objectives. Quality control addresses the outcomes; it is about monitoring performance and doing something about the results.

•             Defining quality assurance activities is the fourth step in a seven-step quality journey that provides a general framework for quality management.

•             Quality assurance activities are based on specifications and operational definitions. They include identified resources and responsible entities.

•             Metrics are the means of measurement that link requirements, specifications, assurance activities, and the metrics themselves.

•             The quality assurance plan lists all assurance activities in one place to assist in managing project quality.

•             Preparing a quality assurance plan is the fifth step in the quality journey.

Quality audits are structured reviews of the quality system. They may he scheduled or random and conducted by internal or external elements.

Inspection plays a significant role in quality management, but it is a role that is different from that in the traditional approach to quality. Products must be inspected at the end of a process to ensure that they conform to specification. Products must be checked before they are delivered to the paying customer. In the traditional approach to quality, as explained earlier, this end-of-process inspection was the principal focus. Results of the inspection allowed delivery of the product or required rework or discard of the defective items. In the contemporary view of quality, inspection plays a very broad role across and throughout the process. Small, frequent inspections ensure that the process is performing as planned, with the result being fewer nonconforming products at the end of the process. In-process inspection may reveal deficiencies that can be corrected before they cause costly scrap and rework. Inspections may include several kinds of activities, such as:

• Measuring physical characteristics of products

• Examining products Icy completeness or correct assembly

 • Testing products for performance

(Kenneth Rose, Project quality management: why, what and how, pg.65-68)

FIRST-PASS YIELD/ ‘’quality control’’

Old definition:

This is the number of units that make it through your final test station without incident-usually expressed as a percent. In other words, of 100 units submitted for final test, 99 units pass and one unit fails. This is a first-pass yield of 99 percent. Any unit that gets to the end of the line and requires rework of any kind is a failure. Each failure should be recorded and the failure mode defined for further analysis, such as a Pareto analysis of all failures. This will facilitate identification of the most critical areas that are causing the failures and the ones needing attention first. Obviously, first-pass yields should be measured after final product burn in, if there is one, so that failures after burn in will be included in the analysis and resolution process.

(Buckley R.L., Winning in high competitive manufacturing environment, p.179)

New definition:

First pass yield is the percent of finished product or service units that meet all quality-related specifications at a critical test point in the process. This metric assesses the yield that results from the first time through the process, before any rework, and it is calculated as the percent of output that meets target-grade specifications after the first time through the process.

First-pass yield is the proportion of units that, on average, go through a process the first time without defects. The first-pass yield is calculated as follows: 

The first-pass yield indicates the ability of the process to produce conforming output that satisfied customer requirements, while at the same time providing insight into the level of rework inherent in the process.

 (Advanced performance improvement in health care: principles and methods ,Donald E. Lighter,Pg.278,298)