ISE 3014, 10/17/2012

Time Study: Predetermined Time SystemWednesday Lab Section:

Challyn BentsonGrant DePhillips

Jane HangerTan Huynh

Amanda KrauthDana Krell

Jennifer Yelpo

I. INTRODUCTION

Predetermined time systems are standard data systems that use generalized micro-motions, fundamental motion time unit, and can predict consistent cycle times. In this lab, we used the Methods Time Measurements (MTM) system, which is the most common motion-time analysis in industry. Using this method, we broke down a task into small body movements to calculate the total task time. The use of predetermined time systems allows a more systematic approach of work study that can be used to predict future task performance.

To analyze a specific activity or procedure, you divide the task into several manual activities and basic elemental motions. A few of these motions include: reach, move, grasp, position and release. You begin the study by determining what body motions are required to complete the task and in what specific sequence. After analyzing these motions you can find the predetermined times of each element from the MTM Times tables. Lastly, you can sum the elemental task times to find your overall total task time.

In this lab, we investigated a prescribed valve assembly task. The objective of this lab was to identify the motions of the assembly, and develop an LH-RH chart by reading the prescribed procedure and carefully watching the assembler’s motions. A LH-RH chart shows the sequential ordering of motions performed by the left and right hands. It organizes a description, motion and TMU for each elemental task. After determining these basic elemental motions, we use the predetermined times to calculate the overall task time. In addition to those calculations and charts, we also recorded three real cycle times of the assembly by our right handed worker. The goal of this lab was to demonstrate the MTM predetermined time system, and compare the differences to the experiences we have seen in our previous labs.

II. METHODOLOGY

Lab groups were organized into sets of at least five students. In our case, we chose a group of seven. Our group consisted of one leader, one right handed worker and five time study analysts. First, we chose a group leader and set up our work place as per the figure given (Figure 1). As you can see the disposal bin, stems, washers, screws, caps, bonnets, handles, and bodies are evenly distributed around the work in a semi-circle with an approximate 10-12 inch radius. We used this distance instead of 20 inches to accommodate the space we had to perform our study. After the workplace was set up, the leader began to train the right handed worker in the prescribed method of assembling the valve. This specific procedure is shown in Figure 2. While the leader was training the worker, the five time analysts worked as a team to identify the motions, TMUs and ultimately develop an LH-RH chart depicting the assembler’s movements.

While watching the worker assemble the water valve, we divided the task into micro-motions consisting of applying pressure, moving, reaching, grasping, positioning and turning. After carefully observing the assembly process and determining the best sequence of motions, the LH-RH chart was created. Using the MTM Times tables, the TMUs for each motion were determined. After the chart was completed and the valve assembler felt well practiced and trained at the assembly procedure, we timed the worker assembling the water valve. To find an accurate value, we timed the worker assembling the valve three times with a stopwatch. We used the continuous method to time the overall task of assembling the water valve rather than trying to time each individual step of the process.

Figure 1.

Figure 2.

III. Results

Below is Chart 1, the LH-RH Chart with the motions, LH/RH descriptions, and TMU values placed in sequential order of the assembly.

Figure 1. LH/RH Chart for Predetermined Time Systems

In Table 1 are the results from the predetermined times calculated from the LH-RH chart for the motions, distances, and weight of the task completed in order to complete the assembly.

Table 1. Predicted time to Complete Assembly Task using PTS

Total TMU Time: 633.5TMU Time Converted to Seconds:

22.81s

In Table 2 are three observed cycle times in seconds that were measured for completing the assembly.

Cycle Number Cycle Time (s)

1 44.42 40.23 36.6

Average Observed Cycle Time: 40.4 s

IV. DiscussionIn this lab, there were ten different motions used to describe the action done by one of our

group members. In order to calculate the correct TMU, time measured unit, the following equations were used:

As shown in Figure 1, the TMU varies from task to task. Our completed time measurement unit is shown in Table 1, meanwhile the TMU in seconds is also shown in this table as well. As far as the data shown in Table 2, this was done by a group member in completion of a cycle. The recorded times are as follows, 44.4 seconds, 40.2 seconds, and 36.6 seconds. These three times are close in range, but showing 36.6 seconds as the fastest completed cycle time. As our group member began the first task, he then started to learn the perks and tasks of what was needed to complete the cycle, as shown getting faster times as the cycles went on. This may apply to real life situations and tasks whereas the first time learning something will always be the hardest when it is new material, but as you complete the repetitive process, it is much easier to finish and comprehend what is needed. These times were much higher than the TMU time we calculated in table 1, the predicted time to complete one cycle. After reading each task that was needed to be done from one to another, it makes sense that our calculated time is much lower than our actual observed times. Our group member had to grasp the product and all, meanwhile think ahead of the next step to be done and pause after each one, adding up more seconds between each pause and each task.

V. Conclusion