Datasheet

Thursday, 17 July 2003 MiniProject: Design Aspects Colin K McCord
EEE512J2 – Electronic Product Design Page 24 Chapter 4: Project Planning and Management
diagram is a diagrammatical representation of the sequence of work elements as defined by the precedence
constraints.
The following list of work elements could describe the production of the ECG monitor for a line with a
production rate of 60 units/hr. At a line efficiency of 100%, the value of the cycle rate is 1.0 min (i.e. the ideal
cycle time is 1 min). Note: this is an example of line-balancing, values are crude approximations designed to
demonstrate the method; in the real-world it is important to carry out work measured (timing of each element)
and know exactly how many items need to be produced per hour.
Work
Element
Element Description T
e
Predecessors
1 Check PCB board (e.g. broken tracks, etc…) 0.2 …
2 Assemble plug to power cord 0.4 …
3 Populate PCB board 0.7 1
4 Test PCB board 0.1 1,3
5 Assemble PCB board to ABS plastic case 0.3 4
6 Wire power cord to transformer (via power switch and mains lamp) 0.11 2,5
7 Assemble metal cage for electrostatic protection 0.4 …
8 Insert rechargeable battery 0.11 7
9 Assemble the rear panel slide control 0.3 4
10 Attach cover 0.38 6,8,9
11 Testing 0.5 10
12 Place in bay for packing. 0.12 11
1
0.2
3
0.7
4
0.1
5
0.3
9
0.3
2
0.4
6
0.11
10
0.38
7
0.4
8
0.11
11
0.5
12
0.12
Figure 4.4a. Precedence Diagram
Note: T
C
= Ideal cycle time = theoretical cycle time.
T
e
= time associated with a work element.
n = No of work stations on assembly line.
d = Balancing loss
≅ Balancing delay.
Step 1: Calculate ranked positional weight (RPN) for each work element by summing the elements T
e
with
all T
e
’s of elements that follow it in the precedence diagram.
W
e
RPM T
e
RPM Calculation
1 2.71 0.2 0.2 + 0.7 + 0.1 + 0.3 + 0.3 + 0.11 + 0.38 + 0.5 + 0.12
2 1.51 0.4 0.4 + 0.11 + 0.38 + 0.5 + 0.12
3 2.51 0.7 0.7 + 0.1 + 0.3 + 0.3 + 0.11 + 0.38 + 0.5 + 0.12
4 1.81 0.1 0.1 + 0.3 + 0.3 + 0.11 + 0.38 + 0.5 + 0.12