Reporting BASIC Dims

[[To...]]

I'm curious as to how many of you are required to show actuals of BASIC dimensions on your inspection reports. What excuses do you get for why?

[[Ma...]]

We are not reporting those values.

I would say they are theoretical values, which are controling another evaluation. For example you have to report line profile on specific place, so used basic dimension is useless to report.

But since we are using Inspect now it can make a sense to report it due possible usage of RPS.

[[Cr...]]

Funny you ask this. I just got done adding actuals for basics on a program. I'm starting to see more customers demand them. One of our customers stated they caught a company manipulating true position values, so they now require the actuals for basics to see if the math lines up. I also have encountered people at companies that don't understand what a basic dimension is. 

[[Ma...]]

Like Craig, I see people demanding them but I don’t think those people understand blueprint reading or GD&T. I’m dealing with right now where a radius is defined by a X location (basic) and a size (basic) but both are controlled by a profile callout. They want the basics reported to +/- 0.50 but the profile to 0.400. 
 

They don’t understand it.

[[Ja...]]

I don't mean to ruffle any feathers - This is just my point of view. I can understand the hesitation to supply the basics if you're dealing with people who don't understand how GD&T works. It forces you to take time to explain to them how it does and like most everybody, we're probably all pretty busy and it slows us down. It can be a pain, but it is an opportunity for us to help people learn something new. For me personally, I love doing that.

When I first came here, all programs that were written by my predecessors didn't report the basics. The machinists are really happy that I include them on the reports now. They have more confidence in the results because it's easier for them to verify that what's on the report is accurate. Almost none of the machinists question the findings now. It also helps them tweak their machines to get the process closer to nominal. Most people (some could care less) have a natural desire to make good product.

We are a global OEM, but we still do get audited (by companies/agencies I can't mention) and they like seeing the basics reported as well because then they know we're being straight with them, not trying to pull something over.

It's so easy to report. Just go to "Resources/Characteristics Settings Editor/Additional Report" and turn it on for the characteristics you desire. Then go to  "Resources/Characteristics Settings Editor/Transfer Tolerances From The Enhanced Report Option To PiWeb" and turn it off for the ones you don't want tolerances assigned to. Other than that, there's no extra programming involved.

Edited 23 hours ago

[[Ri...]]

I report them and the vast majority of our aerospace partners want them reported for the last 30 years of my career.

My argument for basics, as an example I will use a true position (TP).

If you report a TP value, whether accepted or OOT, you have no data to determine what to do. (Unless you report coordinates of the TP and in many cases differ due to the construct of a TP).

The majority of our partners (partners I have worked with) want the Basics for stack up analysis.

I can calculate any TP with accuracy from Basic value analysis and provide direct feedback for engineering departments.

It's a Win-Win.

[[Ch...]]

ok I'll chime in - how about the people that want the basics reported out separately, even thought they are clear and exact in the position results already ??

 

I'm willing to do it usually if the person is not that knowledgeable about GDT etc.

 

 

[[Ze...]]

The problem with reporting basic dims is what tolerance do you apply? They have none. Another problem is that depending on how the basics are applied to the drawing, they may or may not represent an actual value related to a datum. People will daisy chain basics hole to hole, etc. that don't represent the actual value to the datums called out. 

[[Lu...]]

What I typically do is put the basic dimensions on the report, but remove the tolerance and put a comment on there for what dimension that basic dimension is referencing, I believe this not only makes it easier on me in the long run (before people would often ask me why I'm leaving dimensions that are "easy to get" off the report) and it also will explain that these dimensions are references for a different dimension which can help in teaching people what a basic dimension is. Typically I put something like "REF for TP DIM XX"  (which means "Reference for True position Dimension XX", in the "XX" I would put the dimension number it goes to) It also helps the programmers to know which way to adjust.

Though, before I knew anything about GD&T I was told to follow the tolerance block for what tolerance to put on basic dimensions. Makes me facepalm every time I open an old program lol

[[Ja...]]

I typically have the basics reported as well. The actual data may not be transferred to our final inspection sheets that we supply to our customers but we do have the data saved in case we or they need to review something in more detail. It's also been said in this thread already but I find it really valuable to record basic dimensions on features for our in-process programs for our machinists on the floor so they can dial their programs in and make as good of parts as possible, it's easy enough to add them in and they are useful for making adjustments and proving CMM accuracy and repeatability to the occasional skeptic. Sometimes it isn't super clear what basics should be toleranced as but usually you can find constraints on the print through profile callouts, positional callouts, etc. that get you close to what the intent should be.

Where I have had some pushback on whether to report basics or not is when I am performing full first article inspections. One of our customers is kind of old school and doesn't like basic dimensions reported and I was told in more delicate terms that reporting them showed my ignorance of what a basic is when it comes to GD&T. Okay, that's fine and the customer is king (even when they are more of a court jester) and we make the parts to their print so I have no problem not providing that info to them per their preference, but I do keep it for my own records.