So now what begs the question. If you only have one sided tolerance limits should you use the range or just enter like in my case a zero for the LSL and a 100 for the USL?
First, if you had entered 0 as a LSL and 100 as USL, you should obtain the same result as entering the range of 100. Leaving the LSL field empty was the cause of the difference.
This is how Minitab responds to a
One-sided Tolerance, and is the reason for your different results. So, which method is appropriate?
This is a difficult question to answer. The AIAG MSA manual is silent on this and no other "guru" that I am aware of has spoken on it. This probably because there is no one, right answer.
Lets look a few scenarios, and I will give you my

:
- Scenario 1, Flatness: Zero is a natural boundary and there is a maximum allowable flatness specification. Presumably, there is some incentive to drive for smaller and smaller levels of flatness, thus moving farther and farther away from the USL. In this situation, you will conceivably utilize the entire tolerance spectrum. This would tend to justify what you have done. That is, using the whole range, or entering 0 as a LSL.
- Scenario 2, Minimum Hardness: I am using the example used by Minitab in the above link. In this scenario, you are not going to strive for infinite hardness. There will be practical and economical reasons for you to "hover" a safe distance above the LSL, and to not increase over time. In this scenario, it would make more sense to use the Minitab approach. (I will casually overlook the fact that you cannot enter infinity into the USL field). The same logic could apply to a maximum activation force for a push button. If you strove for zero activation force on a conventional spring-loaded design, there would no force left to reopen the switch. In this case, the Minitab approach would also make sense.
Having said that, there will probably be 10 others that will vehemently disagree with me.
