Predetermined Time Systems Chapter 26 Predetermined Time Systems

Methods To Set Time Standards Estimation Estimated times Historical records Historical times Methods to set time standards Work measure-ment techniques Direct time studies Engineered standards Pre-determined time systems Standard data systems Work sampling Proportions of work activities

Predetermined Time Systems Frank and Lillian Gilbreth broke work into therbligs (elements). The next step is to assign time values to the elements. Times for elements are added to obtain a total time. Independence and additivity are assumed. PTS are based on the concept that there are basic, universal units of work with standard amounts of time.

Methods-Time Measurements Developed in 1946 Simplified versions are available. A training course is required for using the system correctly.

MTM-1 10 categories of movements Times in TMUs (Time Measurement Units) 1 TMU = 0.000 010 h = 0.000 600 min = 0.036 s Times are for an experienced worker working at a normal pace. No allowances are included in the times. Takes ~ 2,000 cycles to make MTM standard time.

Reach 5 cases: Parameterized by distance (inches) knuckle-to-knuckle Reach to an object in a fixed location or in the other hand. Reach to a single object whose general location is known. Reach to an object jumbled with others in a group (requires search & select). Reach to a very small object or where accurate grasp is required (visual control). Reach to an indefinite location (minimum mental control). Parameterized by distance (inches) knuckle-to-knuckle Must consider shoulder, body movement (body assist) acceleration, deceleration

Move Hand usually holding something. 3 cases: Parameterized by Move object to the other hand or against stop (little control). Move object to an approximate or indefinite location (some control). Move object to an exact location (control). Parameterized by distance object weight Variation: Crank parameterized by diameter

Turn A movement that rotates the hand, wrist, and forearm about the long axis of the forearm. Time depends on degrees of turn, weight of the object, and resistance against turn.

Apply Pressure Application of force without resultant movement.

Grasp Pickup grasp Regrasp Transfer grasp Jumbled grasp Contact, sliding, or hook grasp

Position Aligning, orienting, or engaging one object with another Position times vary with: Amount of pressure needed to fit Symmetry of the object Ease of handling

Disengage Breaking contact between one object and another Times vary with: Class of fit Ease of handling Care in handling

Release Relinquishing control of an object by the hand or fingers Two types: Simple opening of the fingers Contact release

Other Motions Body, leg, and foot motions Eye motions Combined motions e.g., Regrasp during Move time is greater of two times Limited motions accuracy required for one motion limits accuracy of simultaneous motion requires continuation of limited motion after limiting motion is completed

MTM Form

MTM-2 Takes about 40% of the time of MTM-1 to analyze a task. Has only 37 times in all. Key categories are GET and PUT. Provides decision trees to determine case. User estimates distance and uses time from table. Includes 7 other motions.

MTM-2 Analysis

MTM-2 Exercise

MTM-3 Takes about 15% of the time of MTM-1 to analyze a task. Has only 10 times. Key categories are HANDLE and TRANSPORT. Provides decision trees to determine case. User estimates distance (< 6 in. or > 6 in.) and uses time from table. Includes 2 other motions.

MTM-3 Analysis

MOST Work Measurement System Based on observation that the majority of activities are associated with a limited number of motion sequences. Significantly reduces time required to perform an analysis. 4 sequence models.

General Move Sequence Model

MODAPTS Based on the concept that the body member used is the key variable. All body movements are multiples of a MOD (1 MOD = .129 s).

Comments about PTS In theory, PTS can accurately predict task times. Evidence shows reality and theory don’t agree. One problem is that analyst judgment is required. Most managements are not concerned with a great deal of accuracy. Managements are concerned with cost of analysis.