Tài liệu Wts_3_performance

Performance Rating Work and Time Studies Vietnamese German University Dr.-Ing. Marlene Helfert 2016 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 1 Performance rating Contents Performance rating Standard performance Influences on performance Scales of rating  Westinghouse system  Synthetic rating  Speed rating  Objective rating  REFA performance rating » REFA performance rating criteria » Rating scales » Evaluation of performance rates Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 2 Performance rating Motivation Situation Workers differ in their performance rates:  Worker A assembles 12 components per hour,  Worker B assembles only 10 components per hour under the same conditions. Problem How can a performance standard be determined (standard performance = 100 %), that can be used for production and operation scheduling and also be met by all workers? Solution Observation of the activities including assessment of the workers performance. Schlick 2005 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 3 Performance rating Purpose The purpose of performance rating is to determine, from the time actually taken by the operator being observed, the standard time that can be maintained by the average qualified worker and that can be used as a realistic basis for planning, control, and incentive plans. Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 4 Performance rating Definition Performance rating adjusts the mean observed time 𝑡𝑖 for each element performed during the study to the basic time 𝑡𝑔 that would be required by a qualified operator to perform the same work: 𝐿 𝑡𝑔 = 𝑡 100 𝑖 where the performance factor L is expressed as a percentage. If the analyst decides that the operation being observed is being performed with less effective speed than the concept of standard, the analyst will use a factor of less than 100 (e.g. 80 or 90). If the analyst decides that the effective rate of working is above standard, it has a factor greater than 100 (e.g. 115 or 120). Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 5 Performance rating Definition The performance factor 𝐿 indicates the ratio of the actually observed productivity to a standard productivity. Example  Observed time 𝑡𝑖 = 12 min per unit  Rated performance 𝐿 = 120 %  Normal time 𝑡𝑔 = 120 ∙ 12 100 = 14,4 min per unit So in this case the worker is performing very well. He or she is faster than average, so the normal time of an average worker would be higher than that of the observed worker. REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 6 Standard performance Standard performance is the rate of output that qualified workers in a well-designed work environment will naturally achieve without undue fatigue or overexertion during a typical working day or shift, provided that they know and adhere to the specified method and are motivated to apply themselves to their work. This performance is denoted as 100 on the standard rating and performance scales. Characteristics are e.g. a work execution that appears flowing, harmonious, natural and balanced. Standard performance features a performance range, not a fixed point. Salvendy 2001 REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 7 Influences on performance Effects on work execution Work environment  Process design  Ergonomic design  Tools and resources  Task to be performed Disposition of the worker  Mood  Fatigue  Circadian rhythm REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 8 Influences on performance Factors that affect the work performance Outside the worker’s control  Variations in the quality or other characteristics of the material used, although they may be within the prescribed tolerance limits  Changes in the operating efficiency of equipment within the useful life  Minor and unavoidable changes in methods or conditions of operations  Variations in the mental attention necessary for the performance of certain elements  Changes in climatic and other surrounding conditions such as light and temperature. Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 9 Influences on performance Factors that affect the work performance Within the worker’s control  Acceptable variations in the quality of the product  Variations due to his or her ability  Variations due to attitude of mind, especially the operator’s attitude to the organization To do a fair job of rating, the time study analyst must evaluate the job in terms of the factors that affect the rate of working. Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 10 Influences on performance Requirements for measuring performance The working system is designed optimally, the work conditions (prescribed working method, environmental conditions, tools) allow work execution in accordance with standard performance. The operator is suitable at the required level (physically and mentally), trained (controlled, smooth workflow) and wellinstructed. The work execution is not affected by environmental influences or other circumstances. The workflow can be influenced by the work execution. In case of only limited influenceable workflows the result of performance assessment depends largely on the experience of the investigator. The workflow is doubtlessly observable by the observer. REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 11 Scales of rating There are several scales of rating in use, among the most common are: Westinghouse system Synthetic rating Speed rating Objective rating REFA performance rating Salvendy 2001 REFA 2013 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 12 Westinghouse system Westinghouse system One of the oldest rating systems, developed by Westinghouse Electric Corporation Wide application, especially on short-cycle, repetitive operation where performance rating of the entire study takes place Applicable only for manually performed elements. All machine-controlled elements are rated 100. Four factors in evaluating performance Skill Effort Environmental condition Consistency The overall performance factor rating is obtained by adding the sum of the equivalent numerical values of the four factors. Niebel 1992 Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 13 Westinghouse system Westinghouse system Please find the performance factor for a worker, who works with good skill (C1), excellent effort (B1), good condition, and good consistency. economicsdiscussion.net Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 14 Westinghouse system Westinghouse system Please find the performance factor for a worker, who works with good skill (C1), excellent effort (B1), good condition, and good consistency. Good Skill (Cl) = + 0.06 Excellent Effort (Bl) = + 0.10 Good Condition = + 0.02 Good Consistency = + 0.01 _____________________________ Sum = + 0.19 L = 119 % The algebraic sum indicates that the worker is 19 percent above average. If the worker gets negative algebraic sum, he is considered to be below average. economicsdiscussion.net Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 15 Westinghouse system Westinghouse performance-rating plan Developed in 1949 by Westinghouse Electric Corporation In addition to using the operator-related physical attributes, the relationship between physical attributes and the basic divisions of work is evaluated The characteristics and attributes considered are Dexterity Effectiveness Physical application These three major classifications are assigned nine attributes that carry numerical weights. Appropriate for either cycle rating or overall study rating Both of the Westinghouse rating techniques demand considerable training to differentiate the levels of each attribute. Salvendy 2001 Niebel and Freivalds 1999 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 16 Westinghouse system Westinghouse performance-rating plan Niebel 1992 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 17 Synthetic rating Developed in 1946 by Morrow Eliminates judgment of the time study observer, therefore giving more consistent results The procedure determines a performance factor for representative effort elements of the work cycle by comparing actual elemental observed times and fundamental motion data gained from PTS. L= PTS value for the element Average actual time value for the same element This rating factor is then used for all other effort elements of the method. L = 60 = 1,03 = 103 % 58 A worker needs an average of 58 seconds for a task. According to an MTM-analysis, this task needs 60 seconds. Can you calculate the performance factor? Salvendy 2001 economicsdiscussion.net Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 18 Speed rating In speed rating, the speed of the movements of a worker is the only factor to be considered. One of the most widely used rating systems The time study engineer observes the speed of the movements of the worker against a standard expected pace and notes the relationship between them as the rating factor. L= Workers speed Speed expected from the worker The analyst must be familiar with the work being studied and should undergo a comprehensive training program prior to conducting independent studies. L= 8 parts per hour 7,5 parts per hour A worker produces 8 parts per hour, while an average worker produces only 7,5 parts. Can you calculate the performance factor? = 1,07 = 107 % Niebel 1992 Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 19 Objective rating Developed by Mundel and Danner (1994) In objective rating, speed of movements and job difficulty are rated separately and the two factors are combined into a single value by multiplication. Firstly the pace is rated by comparison with a standard pace independent of job difficulty, then a second factor showing its relative difficulty is assigned. Factors influencing the difficulty adjustment are Amount of body used Foot pedals Bimanualness Eye–hand coordination Handling or sensory requirements Weight handled or resistance encountered A numerical value for each of the six factors is assigned, and the sum of these constitutes the difficulty factor. Salvendy 2001 Dr.-Ing. Marlene Helfert | Work and Time Studies | 2016 | 20