Question

The total cycle time of an automated fiber placement (AFP) operation (sheet lamination), used to manufacture a section of the airplane fuselage, is 8 hours and 40 minutes. The setup time before the start of the operation is 10 minutes. After each layer is put down, an inspection stage is performed for 5 minutes. The AFP head requires cleaning cycle of 3 minutes every 7 layers.

1. If the part is made of 20 layers, what is the time required (in minutes) to lay down 1 layer? (40 points)

2. What is the percentage of down time for this operation? (30 points)

3. What is the total cycle time (in minutes) for making this part, if the lay down speed was doubled? (30 points)

Answer 1

Total cycle time=8 hours & 40 min = 520 min

setup time before the operation starts is = 10 min

After every layer inspection time = 5 min

After every 3 layers cleaning cycle time = 3 min

According to given data laying down of 20 layers including setup time, inspection time and cleaning time is = 520 min

To make a single part it requires 1 setup time (ST), 20 inspection stages(IS), 2 cleaning cycles(CC) and 20 lay down times(LD)

i.e 1 ST + 20 IS + 2 CC + 20 LD =520 min

10 + 20*(5) + 2*(3) + 20LD =520

20 LD = 520-116 = 404

LD = 404/20 =20.2 min

1)i.e To lay down a single layer it requires 20.2 min of time

2) Down time = 116 min (Time for which machine rests)

percentage of downtime = [(time for which machine rests)(total cycle time)] *100

= [116/520]*100 =22.3%

3) If lay down speed is increased time taken for the laydown of layers reduces

i.e if lay down speed is doubled time taken for the laydown of layers is halved.

Actual laydown time for 20 layers = 404 min

After speed is doubled laydown time for 20 layers = 404/2=202 min

Downtime for operation remains same i.e =116 min  

Now, total cycle time = 202+116 =318 min