Critical vs Non-Critical Dimensioning 4

[MotoAce51]

Hey guys,

I am new here and I joined specifically to ask this question.

What is the standard for putting dimensions on a print? I am currently making prints for FAB parts and I dimension everything that would be needed to make a part. Here is an easy example: 1/4" thick bar that is a 2" x 4" rectangle with 1/2" radius on all four corners. So the main part of the print would indicate the part is 1/4" thick x 2" wide x 4" long and then have a 1/2" TYP. pointed to the corner radius.

Here is where the question comes in: Our new Quality Manager that was hired says we have to remove all dimensions he can't measure. He can't measure the radius on the corners so that dimension needs to be removed from the print. The 1/2" radius is not critical to the part but having a radius (instead of a point) is critical. So the critical part is just the overall dimensions (1/4" thick, 2" x 4"). What would be the correct method of noting something like this? Should I remove the radius dimension completely, like QA wants? Or can I indicate what is critical and needs to be checked, leaving the non-critical dimension as-is? What is the standard?

I use Solidworks 2012 for modeling and prints. If this is in the wrong area, please let me know. Thanks.

 

[CorBlimeyLimey]

A better forum would be forum1103

A radius should be specified, otherwise you would have no recourse if either no radius was machined, nor if one was machined too large.

 

[CADFlyer]

I see 1 of 3 solutions hopefully working out for you...

1. The SW fix is to add an "Inspection Dimension" border around important dimensions. It is a button above the dimension text box, and can be found in 'dimension value property manager' portion of the Help section. The significance of this border may vary company to company, so quality needs to make sure they define a process for the symbol.

2. Make non-important Reference by adding () around the dimension. There is a button for it as well, located in the same place as the inspection dimension. Again Quality needs to define what "reference" means.

3. Do as your manager says

The most important thing is documentation of meanings of dimension symbols. will the critical dimensions be used for 1st article, 10pc incoming inspection, 100% inspection, etc? Same with regular dimensions without any symbols (like you have now); will anyone ever verify these dimensions, maybe only on 1st article inspection? Does a refererence dimension never get checked, if so why is it on the print?
These are just some of the questions you have to ask yourself when adding different 'levels' of dimensioning. I worked for a company that implemented 4 levels of inspection dimensions, regular dimensions, and reference dimensions...all with different meanings

 

[Jboggs]

How much experience does this "Quality Manager" have? That's the craziest request I've ever heard, and I've heard a lot. Give the man a radius gauge. Problem solved.

Your drawings have several "customers" or users. Each one has their own priorities. He is only one user among many.

Seriously though, if this isn't just a "turf war" thing with him, work with him to address his needs. All he's really asking is "which features do I need to verify and which ones can I ignore?" I'm sure you can work out some system that would identify those for him. Circles, squares, ovals, colors, etc. Maybe if the radius isn't important you can just replace the dimension with a note to remove sharp corners.

Does this mean that when he acquires new measurement tools that give him more capabilities, you need to go back thru all your drawings and add the "omitted" dimensions back? Hmm...

 

[ShaggyPE]

Agree with Jboggs. That seems like a pretty crazy request at face value. As mentioned, the drawing has many customers/users. When it is being used by the machinist, how is he to know what radius to put there? Perhaps a very loose tolerance is acceptable like .125/.625. If that were the case, perhaps the QA guy could accept it without a formal measurement.

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[MadMango]

If the radius is there just to remove a sharp edge, then you could write R.50 MAX, saying you don't care how big the radius is, as long as it doesn't exceed a value and is actually there. This could be checked with a simple Go/NoGo gauge, calipers, or a 1:1 print.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[SBaugh]

For our Quality Engineers we dimension our drawings how we want (varying on Customer or Manfucaturing), but any dimensions that are to be measured we mark with either C,Q or V (Commissioning, Qualification and Verification) and make the dimension red in color, so they know what they have to measure, everything else is not their concern, only those C,Q, or V dimensions are what they look for.

Regards,

Scott Baugh, CSWP
Berry Plastics
Cad Admin\Design Engineer
GEASWUG Greater Evansville Area SWUG Leader

http://www.scottjbaugh.com

"If it's not broke, Don't fix it!"

faq731-376

 

[handleman]

Wouldn't R0 (a sharp corner) be acceptable with R.50 max?

Alternately, how about a chamfer? Easier to measure, and (depending on your fabrication method) possibly easier to machine.

-handleman, CSWP (The new, easy test)

 

[frusso110]

If the part fails because the radius is too small, whose fault is it?

 

[MotoAce51]

I will give a little more info on this. one of the parts is roughly 70% of a complete circle. One side has a flat edge and the rest is an arc. The part is completely plasma cut (programmed by us in design). If a square is drawn around it the length would be 102" and the width would be 72". The flat side is around 90" long and the radius of the arc is approx 51". As you can see this is not a small part. This has to fit inside another part that is rolled. Think of an oil barrel with a flat side. Does that change anyone's opinion?

 

[SBaugh]

Its not a matter of Size... If its a critical dimensions, and others outside of Quality are going to be reading the Drawing. Then I would leave all dimensions on the drawing and mark the Critical dimensions for Quality. If Qaulity has a problem with it... tough, they are not the only ones reading the drawing. Shouldn't matter how big or small the part is. What is important is whether or not the part fits to its cooresponding component and you can keep the cost down. People that just want their way, cost the company money... see if everyday here.

Scott Baugh, CSWP
Berry Plastics
Cad Admin\Design Engineer
GEASWUG Greater Evansville Area SWUG Leader

http://www.scottjbaugh.com

"If it's not broke, Don't fix it!"

faq731-376