Draw the precedence Find the minimum, maximum and desired cycle time for the final assembly only. We assume that each worker can produce 8 final assemblies per hour and each worker works 8 hours a day. Ignore all other figures given in Question 1. (Ans. Desired cycle time: 7.5 minutes/part) Balance the line using positional weight and determine the total idle
Summary:
A car part manufacturing company currently produce a suspension assembly for Toyota Motor Corporation. Figure 1 shows the breakdown structure of the suspension assembly and Figure 2 shows the final assembly and how to fit into a car. Table 1 shows the name of components, part numbers and number of components in each suspension assembly.
Table 1. Part lists for Suspension Assembly
|
Number in Figure 1 |
Part number |
Part name |
Amount per assembly |
|
1 |
PA-T15-001 |
Shock absorber unit |
1 |
|
2 |
PA-T15-002 |
Lower insulator |
1 |
|
3 |
PA-T15-003 |
Spring bumper |
1 |
|
4 |
PA-T15-004 |
Coil spring |
1 |
|
5 |
PA-T15-005 |
Upper insulator |
1 |
|
6 |
PA-T15-006 |
Spring upper seat |
1 |
|
7 |
PA-T15-007 |
Bushing |
1 |
|
8 |
PA-T15-008 |
Suspension Support |
1 |
|
9 |
PA-T15-009 |
Washer |
1 |
|
10 |
PA-T15-010 |
Stop nut |
1 |
|
11 |
GE-001 |
Bolt |
2 |
|
12 |
GE-002 |
Nut |
5 |
As you can notice from the part number, all parts except bolts and nuts are special purpose parts only necessary for this specific suspension assembly. All parts are purchased from outside benders except the coil spring. Note that sampling inspection is conducted for all purchased parts before they are used for the final assembly.
Coil springs are produced in-house. The process to produce the coil spring in the company is as follows.
- Heating the wire: to an appropriate temperature for the winding
- Hot winding process: with a spring winding machine to align the wire into a proper
- Cutting the wire: cut the wire in an appropriate length after the winding
- Cooling process: cool down the spring immediately by plunging into
- Heat treatment: remove internal stress within the material to provide higher resilience. Usually heated in an oven and held at an appropriate temperature for a predetermined
- Grinding: the spring needs to have flat ends. The coiled spring will be placed into a jig by operators to feed into the grinding
- Shot peening: this process requires strengthening the steel to resist fatigue and cracking during its
- Coating: to prevent corrosion, the entire spring surface will be coated by dipping into a liquid rubber.
- Inspection and Transporting: the final coil spring will be inspected and transported to the final assembly work
Using the information above, answer the followings
Question . Apply line balancing with the conditions given in Table 3.
Table 3. Processes of coil springs
|
Process (department) |
Task Label |
Time (minutes) per part |
Immediate predecessors |
|
Sampling inspection for the purchased parts |
A |
3 |
-- |
|
Transport the parts to the work stations |
B |
4 |
A |
|
Coil spring manufacturing -Heating /hot winding/cutting the wire |
C |
4 |
-- |
|
Coil spring manufacturing -Cooling process |
D |
6 |
C |
|
Coil spring manufacturing -Heat treatment |
E |
3 |
D |
|
Coil spring manufacturing -Grinding |
F |
4 |
E |
|
Coil spring manufacturing -Shot peening |
G |
5 |
F |
|
Coil spring manufacturing -Coating |
H |
2 |
G |
|
Coil-spring manufacturing - Inspection |
I |
2 |
H |
|
Coil spring manufacturing – Packaging/transporting to the workstation |
J |
3 |
H |
|
Final Assembly |
K |
7 |
B,I,J |
|
Final inspection |
L |
4 |
K |
- Draw the precedence
- Find the minimum, maximum and desired cycle time for the final assembly only. We assume that each worker can produce 8 final assemblies per hour and each worker works 8 hours a day. Ignore all other figures given in Question 1. (Ans. Desired cycle time: 7.5 minutes/part)
- Balance the line using positional weight and determine the total idle
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