Standard Data Systems (SDS)

Transcription

1 Standard Data Systems (SDS) Chapter 15 Sections: 1. Standard Data System Introduction 2. Using a Standard Data System (SDS) 3. The SDS Database 4. Analysis of Machine-Controlled Element Times Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

2 Standard Data System Defined A SDS is a database of normal time values, usually organized by work elements, that can be used to establish time standards for tasks composed of work elements similar to those in the database. Normal times in the database are usually compiled from previous direct time studies (direct time study, PMTS,work sampling and historical data). Using a standard data system, time standards can be established before the job is running. Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

3 When a SDS is Most Suitable in work situations (Important of SDS) Similarity in tasks With many similar tasks, it is more efficient to use a SDS than direct time study Large number of standards to be set More productive than direct time study Need to set standards before production Direct time study requires observation of actual task to set standard, SDS does not Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

4 PMTS and SDS Compared Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

5 Using a Standard Data System The analyst engineer should consider the following steps in order to determine a time standard for new task by SDS: 1. Analyze the new task and divide into work elements. The analyst should be make distinguish between work elements: Setup elements (machine setup time) versus Production elements (one unit or two units per cycle). Regular elements (activity occurs once or greater/cycle) versus irregular elements (activity occurs less than one/cycle) Internal elements (activities during machine time) versus external elements (activities outside machine time) 2. Access database to determine normal times for the work elements: Using database (direct time study, PMTS, and work sampling) to get a normal time for each type of work elements.

6 Using a Standard Data System (Cont.) The analyst engineer should consider the following steps in order to determine a time standard for new task by SDS: 3. Add element normal times to obtain the task normal times for all work elements (e.g., setup and production cycle). 4. Compute standard times for setup and production cycle by adding appropriate allowances. T std =T n (1+A pfd ), no machine cycle

7 Using a Standard Data System (Cont.) T std =T nw (1+A pfd ) + T m (1+A m ), this equation to determine standard time for the T nw = normal time for worker, min T m = normal time for machine, min A m = Machine allowance factor for machine worker-machine system T std-su =T n-su (1+A pfd ), this equation to determine standard set-up time for the machine T std-su = standard time for setup, min T n-su = normal time for setup, min

8 SDS Database SDS Database : A catalog of normal times, organized to allow the analyst to access the values corresponding to work elements performed under various work variables. The work variables are must considered while use SDS database: Work variables - factors that affect the normal time of the element These work variables are: Worker (gender, strength, physical capability and mental abilities etc.), Worker s pace (speed, skill, experience), Method used (hand tools, equipment, hand & body motion, wok environment) Work unit (nature of work or task)

9 The SDS Database Various formats can be used in the SDS database: 1- Charts (represent the normal time dependent variable and work variables independent variables such as unit weight or dimensions etc.). One Work Variable Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. Two Work Variables

10 The SDS Database (Cont.) Various formats can be used in the SDS database: 2- Tables: is a format that lists normal time in a tabular arrangement. 3- Mathematical formulas: are often more concise of expressing the same relationships that are presented in chart and tables. (e.g., T n = d/f r ). 4- Worksheets: The worksheet is a form that indicates the steps the analyst follow in order to compute the standard time for a task. (e.g., direct time study form). 5- Computerized database and retrieval system: is the modern format of standard data system and described the data in all above mentioned techniques in excel sheet. All these process performed by the software (e.g., WorkStudy+4 software)

11 Machine Times for Machining For the worker-machine systems, the standard method often includes a machine cycle, in which the equipment runs under its own control for a certain length of time. Common machining operations: Turning Drilling Milling Machining times can be calculated or measured with great accuracy, given the machine settings (feeds and speeds) and part dimensions Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

12 Drilling Machine Drilling is a machining operation that creates a hole in a workpiece (unit), using a rotating drill bit. The usual drill bit is a twist drill The machine tool is a drill press Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

13 Drilling Machine Cutting speed of the drill machine is important to determine the time of machine. The cutting speed depends on the machine specifications and can be calculated:

14 Types of Drilling Machine (Cont.) 1- Through Hole drill machine: In this type of machine the drill bit passes through the work and exits on the opposite side.

15 Types of Drilling Machine (Cont.) 2- Blind Hole drill machine: In this type of machine the drill bit does not pass through the work (not exits on the opposite side). T m = machine time in min d = hole depth, mm (in) f r = feed rate of the drill into the work, mm/min

16 Example: Time in Drilling Machine Q1. A blind hole drill of diameter = 18.0 mm is to be drilled in an aluminum casting to a depth of 72 mm. The point angle of the drill = 118. Cutting conditions are: cutting speed = 40 m/min and feed = 0.10 mm/rev. The PFD allowance of machine is 6%. If machining time begins as soon as the drill makes contact with the work, how much time will the drilling operation take and determine the standard time for the machine. Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.