1

ISE 2214- Manufacturing Processes Laboratory

Laboratory Report

SB-A Switch Box - Assembly

Austin Hayes, Jane Hanger, Tyler Hunt

CRN: 13984

January 30, 2012

2

Table of Contents

Introduction………………………………………………………………………..3

Equipment………………………………………………………………………....4

Procedure………………………………………………………………………...5-7

Presentation of Results…………………………………………………………..8-9

Discussion of Results……………………………………………………………..10

Conclusions……………………………………………………………………….11

3

Introduction

The purpose of the Switch-Box Assembly Laboratory is to become familiar with product assembly and basic assembly line concepts. Five different assembly line configurations are investigated in order to highlight the five important objectives for assembly lines, which are to maximize throughput and minimize reject, work-in-process, line imbalance, and idle time.

4

Equipment

Assembly Line Components:

Long counter top with five mounted assembly blocks for each switch box assembly station on the line

Phillips Screwdriver Bins holding Switch Box components for assembly Test Unit Passing Inspection Box Rejection Box

Switch Box Components:

Wire Assembly( Red, Black, and Blue) 3/8-IN. Nylon Grommet 9/16-IN. Nut Spacer Lamp Assembly ½-IN. Nut SPST Switch Face Plate SPST Toggle Switch Box Screw Box Cover Box

Measurement and Recording Instruments:

Clipboards Stopwatches Pens

Procedure

5

The procedure for this lab consisted of the demonstration of the assembly process by assembling a switch box in both a paced and un-paced line by completing five different assembly line experiments. In each experiment five students were designated as line operators in charge of completing different designated tasks at their workstation in the assembly line process. For each line operator on the assembly line a task time recorder was assigned to observe and measure the time it took for the designated task to be completed. Also when an item moved from station five off the assembly line the task time recorder for that station recorded whether it was accepted or rejected. The procedure for assembling the switch box as well as how each task is denoted is summarized in the Task List for Switch Box – Item NO. 2214-001(Table 1).

Table 1. Task List for Switch Box – Item NO. 2214-001

Task Description Items Tools

a Install switch in box Switch, face plate, 1/2-in. nut, box

–

b Install lamp ass’y in box Lamp ass’y, spacer, 9/16-in. nut

–

c Insert grommet in box Nylon grommet –

d Attach wire ass’y C to lamp ass’y and run through grommet

Wire ass’y C (RD) –

e Attach wire ass’y B to switch and run through grommet

Wire ass’y B (BK) –

f Attach wire ass’y A between switch and lamp ass’y

Wire ass’y A (BL) –

g Attach box cover Box cover, box screw (4) Phillips screwdriver

h Test

- electrical (light must come on).

- assembly: both switch and lamp secure; two screws used for box cover.

– Test unit

6

In the first three experiments a paced line was used, meaning each station had exactly the same amount of time, the cycle time, to complete their assigned tasks, before each item advanced down the line simultaneously. The lab instructor paced the line, and was in control of starting and stopping the assembly line operation for a set number of cycles. The setup of the paced assembly line is shown in Figure 1.

Figure 1. Paced Lines Experimental Setup

In experiments four and five an un-paced line was used, meaning the stations operated independently of one another and items moved immediately upon completion of the assigned task. Buffer queues, spaces between two stations on the line, were added in order to account for the temporary storage of a station’s completed items due to the discrepancies in time for total task completion at each station. For the un-paced line two additional students are added to the assembly line setup, one to record the times at which an item moved from the input queue onto the assembly line at station one, and one to record the departures times for items that left station five. This setup is shown in Figure 2.

7

Figure 2. Un-Paced Lines Experimental Setup

The characteristics of operation of each experimental assembly line performed are summarized in Table 2.

Table 2. Assembly Line Operation Experiments

Experiment Line Type

Buffer Capacity

Cycle Time, C

Task 1 Task 2 Task 3 Task 4 Task 5

1 Paced - 1: 45 A, B C,D E,F G H

2 Paced - 1:00 A B,C D,E,F G H

3 Paced - 0:15 A B,C D,E,F G H

4 Unpaced 3 - A B,C D,E,F G H

5 Unpaced 3 - C A B D,E,F,G H

8

Presentation of Results

Experiment # Cycle time, C Total # of cycles, C

TOT

Total time, T # of rejects

1

2

3

4

5

Experiment

#

Observations of bj (total task time at station j), j =

1 2 3 4 5

1

2

3

4

5

9

Average task times bj in seconds at each station per experiment:

Experiment Task 1 Task 2 Task 3 Task 4 Task 5

12345

Experiment (pph) R(%) WIP(items) B D(%)12345

Calculations:

Experiment 1(Paced Calculations) –

= 1/C =

R = # Rejects/Ctot =

WIP = Average Work-in-Process Level = M =

B = Line Imbalance = ( j = 1M (b-bj)2/M )1/2 =

D = Idle time percentage = [(M x C) – Ttot] / (M x C) =

Experiment 4(Unpaced Calculations) –

Total time (T) =

= (Number of Departed Items) x (60/T) =

R = #Rejects/#Departed Items =

WIP = [0T w(t) ]/T=

B = Line Imbalance = ( j = 1M (b-bj)2/M )1/2 =

D = Idle time percentage = [(M x Bmax) – Ttot] / (M x Bmax) =

10

Discussion of Results

1.) Which of the paced line experiments (1,2, or 3) do you feel had the best line performance?

2.) Which of the un-paced line experiments (4,5) do you feel had the best line performance?

3.) Compare the best paced line configuration to the best un-paced line configuration. Which of these do you feel is better?

4.) Where did starving and blocking occur in Experiment 4? Experiment 5? Why do you think this occurred in each case?

5.) Based upon the experiments performed, describe some conditions under which you feel a paced line would be preferred over an un-paced line.

11

Conclusions