I came across this textbook problem today, in which we are given three steps as below

Setup and Process time for the steps

The question asks, "for what batch size is step 3 (etching) the bottleneck?"

Now, I am aware that you can calculate the capacity of a process that has setup time by using the formula

Capacity for Batch Size = Batch Size / (Setup Time + (Batch Size * Processing Time) )

I did this for all three in excel and my point is, the batch size is irrelevant in this case, as the third process will always have the lowest capacity. I encountered the same question in the last problem and had the same conclusion.

Am I forgetting something here?

  • $\begingroup$ is it all of the things you have about the problem? Is it possible there may be different resources in each step? Is there any kind of complexity such as sequences depending setup time? Are there different kinds of products or not? etc. If the answer of all the above questions is no, you must accept Prof. Rubin's answer. $\endgroup$
    – A.Omidi
    Oct 17, 2021 at 19:10

1 Answer 1


The third process does not always have lowest capacity. In fact, it never does. Ask yourself the following question: for what batch size does etching take less total time (setup plus processing) than patterning takes?


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