Question

Calculate Lead Time

Williams Optical Inc. is considering a new lean product cell. The present manufacturing approach produces a product in four separate steps. The production batch sizes are 73 units. The process time for each step is as follows:

Process Step 1	6	minutes
Process Step 2	8	minutes
Process Step 3	5	minutes
Process Step 4	4	minutes

The time required to move each batch between steps is 10 minutes. In addition, the time to move raw materials to Process Step 1 is also 10 minutes, and the time to move completed units from Process Step 4 to finished goods inventory is 10 minutes.

The new lean layout will allow the company to reduce the batch sizes from 73 units to 4 units. The time required to move each batch between steps and the inventory locations will be reduced to 2 minutes. The processing time in each step will stay the same.

Determine the value-added, non-value-added, and total lead times, and the value-added ratio under the present and proposed production approaches. If required, round percentages to one decimal place.

	Present Approach		Proposed Approach
Value-added time		min		min
Non-value-added time		min		min
Total lead time		min		min
Value-added ratio (as a percent)		%		%

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Answer 1

Ans:

Present Approach

Valued added time = 6+8+5+4 = 23 min

Non Value Added time=Total Within batch wait time + Move time
={Total time required for the four steps* (Batch-1)} + Move time

Non-Value Added Time = Value Added Time * (Batch size -1) + move time between each step

={6+8+5+4)*(73-1)} +10*5=23*72 +50=1706

Total lead time = 23+1706 = 1729 min

Value added ratio = Value added time / Total lead time = 23/1729= 1.33%

Proposed Approach

Valued added time = 6+8+5+4 = 23 min

Non-Value Added time

Non Value Added time=Total Within batch wait time + Move time
={Total time required for the four steps* (Batch-1)} + Move time

={6+8+5+4 )(4-1)} +5*2=23*3 +10=79

Total lead time = 23+79 = 102 min

Value added ratio = Value added time / Total lead time = 23/102 =22.5490 %=22.55% If rounded off

	Present Approach		Proposed Approach
Value-added time	23	min	23	min
Non-value-added time	1729	min	79	min
Total lead time	1729	min	102	min
Value-added ratio (as a percent)	1.3	%	22.5	%