The Problem with Reporting Basic Dimensions
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- Опубликовано: 16 сен 2024
- Basic Dimensions are theoretically exact dimensions that define the ideal exact location and orientation of surfaces and features of size. We are frequently asked whether these basic dimensions should be recorded on an inspection report. In this video, we explain why you should not.
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Great information. I report XY locations of features if someone asks for it, with the caveat that it has nothing to do with the drawing requirements. I agree that the final requirements for the drawing are whatever the feature control frames indicate.
Thanks for the comment! We definitely support and encourage supplying any additional requested information that aids in manufacturing and quality control.
Heya! Love your videos Mr. Odell! I never really understand why some customers want the XY locations; my boss seems to think that they just wanna make sure we’re doing the math correctly 🤷🏻♀️ this seems plausible, but then there are customers who then don’t understand why there isn’t a “tolerance” listed for the basic or why we just put 999.99 when we do list the “tolerance” with the XY.
Do you have any insight on why people want to have the locations?
The extension of this question is how to report position outside of its tolerance zone but within tolerance due to MMC/MMB.
The short answer to that is it depends on the company and their quality department. There are many ways to break down how it is relayed in the quality data report. For examples i would highly suggest checking out the ASME Y14.45 Standard.
thank you for the explanation
Glad it was helpful!
The concern with reporting actual XY location with orientation/form error is valid, but a CMM report without this information is useless to the guys on the shop floor. They need to know how to shift to correct/mitigate error. You should be able to output the average XY location as a reference dimension. This is the biggest piece of information a guy on the floor needs for TP. Recommending this information to be withheld is setting people up for failure.
Thanks for the comment Ken, we definitely agree with you. The ASME Y14.5 outlines the bare minimum requirements to deem a feature with in tolerance. We recognize that a pass/fail on a position for a feature gives the floor zero information when it comes to mitigating error. This is why we say in the video that we highly encourage adding additional information to the report along side the position deviation that explains the location of the extremes of that feature, and possibly the orientation deviation as well. This might look very different depending on the software used.
Hello May friend
Pela-se, Im starting projects and I have doubts regarding the use of the basic dimension. Coul you please explain to me Its function is? Is it considered in dimesnion repoting?
Tks
Thanks for the question! Basic dimensions are not considered in dimension reporting. They are only there to define perfect locations, orientations, and profiles of the surfaces of the part. The tolerances in the feature control frames are what get ultimately reported. However, when the geometric tolerances are reported, often times the x,y, and z values of error are also reported within the reported tolerance to assist manufacturing.
Since you've drawn a symmetry plane on the top view, shouldn't you have omitted the "bottom" holes base dimension of "1.000"? It's basically duplicated.
You're right, we could have easily omitted this 1" dimension, or even dimensioned 2" between each hole, and omitted both 1" dimensions. Sometimes additional clarity never hurts if you have the room for it!
The culture that you are teaching your students is 100% incorrect. Without reporting XYZ coordinates to Manufacturing, you are not only creating confusion, you are not giving them the information to adjust the feature, you are also not a tool of value, you also allow escape, plus stop spindles. So as far as QC in manufacturing, you basically cost for zero value added. I think I’m todays world of QC, it has turned into a “I only check the part like the draftsman says” however, not only are design and draftsmen completely incompetent to manufacturing, they also don’t know how a manufacturer is going to competitively manufacture the part. What if -A- is the last feature finished for example? Our job is to manufacture a finished part that meets the customers requirements per the print. At that time you can leave out your “Basic” with no tolerance ideology. If basics didn’t mean anything to a feature and don’t need to be reported, then you also wouldn’t have a CAD model. It’s time that QC, Design Engineers and ASME clarify with each other that if they want there parts for $1000 per part or $50 per part.
Thanks for the comment, we do our best to follow the ASME Y14.5 standard that outlines the requirements that need to be followed when this standard is listed on a drawing. Reporting that the total deviation remains with in tolerance is how the position of a feature is verified to be with in spec. However, I completely agree that more information is required for manufacturing to gain a better idea on corrections that need to be made. Simply ballooning and reporting a basic dimension could lead to confusion depending on how that 2D measurement is taken. This is why we say in the video that we highly encourage adding additional information to the report with the position deviation that explains the location of the extremes of that feature, and possibly the orientation deviation as well. This might look very different depending on the software used.
"Plus stop sindles" dudes forsure a machinist haha.
@@Gdandtbasics can you provide exact location or page to look up the standard.
This is not a new concept and they are very correct. It seems like you’re caught up on the wording of reporting and who it’s being reported to. What is being discussed isn’t really for the manufacturing side, it’s for the final reporting and customer side.
You sound like a machinist and you SHOULD be informed of deviations in the XYZ but it’s completely meaningless to report Basic dimensions to the customer who provided the print with basic and position dimensions and wants the part. If the part meets the position callout, that’s how they know that the part will work with whatever they’re using it for.
Towards the end of the video (where he’s marking up the slide) it shows you why on the customers end the part will meet their needs even if there are deviations. It’s along the same lines of LMC and MMC and even just the existence of a tolerance, would you argue with those concepts too?
Just think about where/when these types of dimensions are used, they will be used with certain mating parts and allow “imperfect” parts to work with other parts perfectly.
I can totally understand your frustrations if indeed you are a machinist, you drop off your first piece or your in process, your part fails and you’re only handed a CMM report with a position which tells you as the machinist NOTHING about where you drifted off. You definitely need to know XYZ in order to adjust and if you have inspectors doing what I just mentioned then THEY are the asshole lol.
When they’re talking about the reporting side, it’s really not for reporting to production, it’s for reporting to the customer side.