Bonus is explained as when the hole gets bigger there's more room for the mating part to be able to assemble. It's a 1 for 1 relationship. A micron bigger than the minimum hole size converts into a micron bigger in position.
You also have datum shift in the callout. Same general idea that as the datum surface varies more tolerance is allowed. However, it's not a one for one relationship and not for the faint of heart.
I'd throw the question back at them. Why did they design a part specifying material modifiers if they don't understand how those modifiers work?
It's been the same issue for the as long as GD&T has existed. There is not a company wide push for effective GD&T training and followup support. Design, Manufacturing and Quality Control all have to be brought in at the same time with pretty much the same training. Even Engineers fresh out of college have never been exposed to it, mostly because the people creating the curriculum have never been exposed to it.
I deal with these same problems, I am sure just like other programmers do every day. it is SO frustrating to have to explain to a "design engineer" exactly what he put on a print really means. it is amazing to me how the engineering profession has gotten to this point. it does not matter, fresh out of college or 20 years of "experience" most I deal with are sorely under informed about GD&T.
In the XactMeasure position report label, the value in the column labeled BONUS depends on whether it is on the considered feature row or a row containing a datum feature referenced LMB/MMB. The value in the BONUS column for a considered feature is simply the bonus tolerance gained from the feature's departure in size from its LMC or MMC. The value in the BONUS column for a datum feature is the remainder of the "bonus tolerance" after what has been used up (what you see as the datum feature's MEAS value). The "bonus tolerance" for the datum feature is the departure in size from its LMC or MMC coupled with any previously specified geometric tolerance assigned to the datum feature with respect to datums defined in the FCF with higher precedence.
Since you see a BONUS value of 0.0000 for your datum features, they used all the bonus that they had (through datum shift) and the amount that they had is shown in the MEAS column. For example, in FCFLOC3, datum feature CIR_B had a total of .0021 bonus that is obtained from its departure from MMC size and its orientation allowance back to datum A (if previously defined).
For FCFLOC3, your considered feature CIR_24 did not fall in its allowed position tolerance zone even after datum shift was applied. The Summary label shows the measured position in the shifted coordinate system. Make sure that you have an orientation tolerance assigned to B with respect to [A] and a position tolerance assigned to C with respect to [A|B(M)] somewhere above in your program to ensure you're getting the max allowable datum shift.
One note, you should be evaluating these feature control frames simultaneously as they share a datum reference frame.
I like how they fixed that though with Geometric Tolerancing. Now instead of having to do them all together in one big a** grouping, you can just setup the SIM EVAL at the end and it keeps them all in numerical order but puts the SIM EVAL name next to the FCF.
bfire85 I couldn't agree more. The new style is much cleaner. I'm finding it awkward to adjust older programs that were setup with report comments compensating for the old design but it's all part of the process of continuous improvement.
