Capacity planning and control

 

Changeovers and set-ups take an average of 10 hours and breakdown failures average 5 hours every seven days.

 

The time when the machine cannot work because it is waiting for material to be delivered from other parts of the process is 5 hours on average and during the period when the machine is running, it

averages 90 per cent of its rated  speed. 

 

Subsequently 3 per cent of the parts processed by the machine are found to be defective in some way.

Maximum time available = 7  X 24 hours = 168 hours

 

Loading time = 150 hours

 

Availability losses = 10 hours (set-ups)  + 5 hrs (breakdowns) = 15 hours

 

So, total operating time = loading time  – availability = 150 hours – 15 hours = 135 hours

 

Speed losses = 5 hours (idling) +  ((135–5) X  0.1)(10% of remaining time)  = 18 hours

 

So, net operating time = total operating  time – speed losses = 135 – 18  = 117 hours

 

Quality losses = 117 (net operating  time) × 0.03 (error rate) = 3.51  hours

 

So, valuable operating time = net operating  time – quality losses = 117 –  3.51= 113.49 hours

 

                                                    total operating time

Therefore, availability rate = a = –––––––––––––––   = 135/150 = 90%

                                                        loading time

 

net operating time 

Performance rate = p = ––––––––––––––––– = 117/135 = 86.67%

                           total operating time

 

         valuable operating time

and quality rate = q = ––––––––––––––––––––– = 113.49/ 117 = 97%

              net operating time

 

 

 OEE (a × p × q) = 75.6%

THE ALTERNATIVE CAPACITY PLANS

 

Next step is to consider the alternative methods of responding to demand fluctuations.

 

There are 3 ‘pure’ options available for coping with such variation:

 

•  ignore the fluctuations and keep activity levels constant (level capacity plan);

 

•  adjust capacity to reflect the fluctuations in demand (chase demand plan);

 

•  attempt to change demand to fit capacity availability (demand management).