IE秒表法

•Electronic watches with a computer built into the board, generally have replaced the traditional mechanical stop watch.
NUMBER OF OBSERVATIONS
There are two approaches to determining the number of observations
NUMBER OF OBSERVATIONS
Irregular and Foreign Observations •Irregular element (exp. Breakdown) •Foreign element (exp. Customized part)
NUMBER OF OBSERVATIONS
Chapter 28
STOPWATCH TIME STUDY
Stopwatch Time study should be preceded by a methods analysis so the resulting standard is a“should take” time not a “did take” time.
Recording Techniques •Missed Readings
•Omitted Readings
•Element out of order
•Unexpected element
RATING
Normal Pace During the time study, the observer will rate the worker, that is, determine the adjustment to convert the observed time to a time that a normal, experienced worker would take
•Statistical
•Importance of Decision
NUMBER OF OBSERVATIONS
Statistical
A time study of sequential observations is a sample from a population of times. The goal is to estimate the population mean from the sample mean.
•If the observer is confused then he might stop the watch.
•Continuous is preferred over snapback.
TIMING
Three-watch system
As in the title there are three watches and it is a combination of snap back and continuous type
•The elements can also be performance rated
•If any dispute occurs then the tape can also be replayed
TIMING
One watch, continuous
•The stop watch does not stop, it is continuously run (Example)
Observed Time x Rating = Normal Time
OVERVIEW
Standard time = (Normal time) * (100/{100 – pct Allowances})
Example: Observed time = .01 hr./unit Rating = 120 % Normal time = .012 hr./unit Allowances = 10% Standard time = (.012 hr./unit * 100/90) =.0133hr./unit
OVERVIEW
Stopwatch time study is one of the two methods to establish a type I time standard.
The analyst observes one or more operators continuously and records the time taken to accomplish a task. This is called Observed Time
METHODS ANALYSIS
•After the task is broken into elements, we write the element description on the time study form with a description of its EP (End points ) or also called TP (Termination point)
•Elements make it possible to reuse the data •Elements permit different ratings for different elements(Machine time and manual time) •Elements permit consistency checks, within the study and between studies •Elements improve methods descriptions •Data collection is flexible
•As the clock never stops, there is no time omitted and workers like that
•The disadvantage is that the observer does not know how individual elements vary and the observer tries to read a moving target.
different times)
TIMING
Timing Techniques (example)
•Videotape
•One watch, continuous
•One watch, snapback
•Three watch system
•Electronic watches
TIMING
Videotape:
To minimize the differences between the sample and population means, increasing the sample size is one of the answers….
The number of sample size depends on three factors •Accuracy Desired (absolute or relative) •Confidence Desired (based on Z score) •Data Variability (use subsample to determine) Calculation formula: (See Box 28.1) -Westinghouse/ General Electric and Niebel’s approaches are in Tables 28.2 and 28.3
From a productivity standpoint, supervisors of industrial engineering department have to do job design.
•The primary reason for doing a methods analysis before doing a time study is to establish a safe, productive job.
Date of observation(Improvement curve) Person observed (Skilled…..) Person observing (Viewpoint) Machine used (Improvement curve) Tools used (Improvement curve) Part no. processed etc..
TIMING
One watch, Snapback
•As the element ends, the time is noted and the stop is reset (set back to zero).
•The advantage is that no subtraction to be done and the observer is able to see the pattern.
Time Study Sheets (from ERGO)
PREPARATION
There are basically two steps involved in Preparation 1. Methods Analysis 2. Operator Selection
METHODS ANALYSIS
TIMING
Electronic watches
•These watches can be used either the snapback or the continuos mode
•The key feature is that, when the user depresses the button, the display time is frozen while the clock continues timing.