Question

A UD. Ergonomic Chairs engaged in the used wood craft industry in the form of making chairs, wanting to know the efficiency of making these chairs. In the manufacturing process the operator works for 8 hours / day. While the amount of production is 30 seats / day. The settlement operations are as follows:

Operation	Description	Preliminary Operation	Time (minutes)
1	Measure wood for the legs	-	2
2	Cut wood according to size	1	3
3	Smooth the cut wood	2	4
4	Measure wood for the holder	-	3
5	Cut according to the size of the holder	4	4
6	Smooth the cut off holder	5	4
7	Assemble the stand with the legs	3,6	5
8	Provide the backrest for the assembly	7	6
9	Painting	8	7
10	Drying	9	10

From the data above, determine the preliminary diagram, cycle time, work station, work station efficiency and trajectory efficiency of making the chair using the Kilbridge-Wester Heuristic method and Ranked Positional Weight (RPW).

Answer 1

Ans:  

Preliminary/Precedence Diagram:

By using Kilbridge and Wester's Method (KWM):

Based on the data given assuing the Cycle Time (Tc) = 10 mins.

Work Station	Operations	Time for each operations (Te) in minutes	Ts = Sum (Te) at stations in minutes
1	1	2	5
	4	3
2	2	4	7
	5	3
3	3	4	8
	6	4
4	7	5	5
5	8	6	6
6	9	7	7
7	10	10	10

By using Ranked Positional Weights Method (RPW):

Operation	RPW	Time for each operations (Te) in minutes	Immediate Preliminary Operations
4	39	3	-
1	37	2	-
5	36	4	4
2	35	3	1
3	32	4	2
6	32	4	5
7	28	5	3,6
8	23	6	7
9	17	7	8
10	10	10	9

Operations assigning to the Work Stations:

Work Station	Operation	Time for each operations (Te) in minutes	Ts = Sum (Te) at stations in minutes
1	4	3	9
	1	2
	5	4
2	2	3	7
	3	4
3	6	4	9
	7	5
4	8	6	6
5	9	7	7
6	10	10	10

Production Rate (Rc): It is measured by using the formula.

Rc = Assumed station time / maximum operated station time

= 10/9 = 1.11 units/min

Work Station Efficiency (E):

E = [(Number of stations*max operated station time)-remaining station count] / [Number of stations * max operated station time]

E = [(6*9) –5] / [6*9] = 0.90740741 = 90.7%