Finding the constraint is simple once the preliminary data previously discussed has been analyzed.
You simply look for that operation which has the lowest net output. That net output is now going to be the lines potential thruput. 100% thruput will be whatever the constraint’s net output is.
At this point, we have developed a target for the line.
You will also see that the net output of the constraint is usually much higher than the actual output that has been typically been achieved from the line. The reason for this is the effect of downtime of the non-constrained machines, which are starving or stopping the constraint from running. As you will see in the in depth analysis, this is often as much as 20 to 30 percent or even more as seen in the example below.
As you can see in this chart, I have simply extended the calculations to each machine. The Filler is the constraint to the line with a net output of 166.6 ppm. This is the target thruput for the line. 100% thruput would be achieved if the Filler was always able to run whenever it is capable of running. However, due to the malfunctions which occur on the other machines, the Filler is left idle with either no product to run or no place for its output to go. This is in effect the result of the compounding of all the machinery’s downtime.
In order for this line to produce a product, all machines have to be running at the same time. The probability of that happening is the result of compounding all of the PORs of the machines. The result is .943*.952*.946*.888*.985*.897 = .676
There is only a .676 probability that all machines will be running at the same time. When they do run they are paced by the rate of the filler at 175PPM. The result is 175PPM *.676= 118.3 Net Output for the line.
What happens when buffers are added?
By placing Buffers in the ideal places and sizing them for the longest downtime exposure we now create a condition where the buffers will protect the constraint from most malfunctions of the non-constraint machines.
In this particular example, the Net Gain in Thruput on the Total Line from 118.3 Net Output to 166.6 Net Output is increased by 41% or 48 PPM.
Examples like this one are not uncommon to find when we evaluate a customers line. If you want us to perform a free line analysis like this one for your company, reach out to our team today to request a line analysis.
Stay tuned for the next installment when we will dive deeper into what exactly a buffer is and how it can improve the thruput of your line.