Calculating Throughput and Output

After you have added all the processes and paths that you need to the product synchronization, you can calculate the planned throughput percentage, planned output percentage, and planned scrap percentage for all the processes that are included in the product synchronization. You calculate these values when you click the Save and Calculate button on the Manage Product Synchronizations form. To view the product synchronization and the calculation results, print the Product Synchronization Results report (RF30L704).

The product synchronization calculation is based on a derivative method of determining the flow within a capacitated network. You enter a value called X at the start of the line. Each process processes a certain quantity of X and sends it to the next process on the path or line. The proportion of X that is carried forward to the next process is based on the percentage of yield that is defined for the process. It also depends on what rework, option, and scrap factors you have defined for the process. For example, a process with 100 percent yield and no option, rework, or scrap passes 1 (X) to the downstream processes. The amount of X that reaches the end of the line is used to calculate the final X factor. For example, if .875X (87.5 percent) of the product reaches the end of the line, then the X factor is calculated like this: 1 ÷ .875 = 1.14286. This factor is then applied to the starting process to determine the associated throughput, output, and scrap percentages for each process.

The following product synchronization diagram shows an example of a main line with one rework and one option path:

You calculate throughput, output, and scrap using the following steps:

Wet the line with X number of units.

The auto mold process has a yield of 100 percent. Thus, both throughput and output remain at X.

The spray process has a throughput of X. However, because it has 5 percent scrap and 5 percent rework, a quantity of 0.05X leaves the system as scrap. 0.05X is rework. That means that the net output of the spray process to inspection is 0.95, consisting of the 0.9X net usable output from spray plus 0.05X from the spray rework path.

The inspect process has 100 percent yield; therefore, its throughput and output is 0.9X.

Forty percent of the inspect process output goes to the pack option path. You calculate the amount of inspect process output that is going through the option path like this: 0.9X × 40% = 0.36X. The remaining 0.54X of the inspect process output goes through the final process.

The following table summarizes the calculations for each process:

Process	Throughput	Output
Automold	X	X
Spray	X	0.95
Scrap	0.05 X	0.05X
Spray Rework	0.05X	0.05X
Inspect	0.9X	0.9X
Final	0.54X	0.54X
Pack Option	0.36X	0.36X

Walk through the line again, taking into account all rework and using the following conditions:
- Quantities that flow through a process a second time, because the number of rework loops is set to one, are not reworked or scrapped.
- In addition to the rework quantity, new product is now flowing through the line.
The auto mold has new product input of X plus 0.05X coming in as rework. Throughput and output for this process thus equal 1.05X.
The spray process has a throughput of 1.05X. Because 0.05X (input from rework) is not reworked or scrapped, this quantity moves on to the inspect process. The new product input of X, however, does have to go through scrap and rework. Thus, you calculate the net output of the spray process like this: 0.9X (new output to inspect) + 0.05X (new product scrap) + 0.05X (old rework from auto mold) = X.
Throughput and output for the inspect process is 0.95X (new product output from spray + old rework output of spray).
The pack option path takes 40 percent of this output. Hence, its throughput and output are both 0.38X.
The final process takes the remaining 0.57X as its throughput. Because it has a 100 percent yield, its output is 0.95X as well.
Set the output at the end of the line to 1 and solve for X.
The end of the line has as its input 0.95X. Because the quantity at the end of the line is assumed to be D_c, 0.95X equals D_c. If you set D_c to 1 and solve for X, the result is X = 1.05263. You calculate the throughput and output for each process based on this value.

The following table displays the calculated values:

Process	Path	Auto Mold	Spray	Spray Rework	Scrap Percent	Inspect	Pack	Final	End of Line
Main Path	Main	Main	Main	NA	NA	Main	NA	Main	Main
Feeder Path	NA	NA	NA	NA	NA	NA	NA	NA	NA
Rework Path	Spray Rework	NA	NA	Spray Rework	NA	NA	NA	NA	NA
Option Path	NA	NA	NA	NA	NA	NA	Pack	NA	NA
Input/ Output	NA	1.05X/ 1.05X	1.05X/1X	0.05X/ 0.05X	0.05X/0	0.95X/ 0.05X	0.38X/ 0.38X	0.57X/ 0.57X	0.95X