Models not matching prints

[drafting3]

I want to get everyone's feedback on this issue.

 

I was given a project, a one off, of a large aluminum ring (34" OD). This was delivered to me from another shop which had already done the turning work. My job is to mill out some notches that blend in with the OD. The other shop is a manual-only shop, so they work from prints. I requested a solid model, which I programmed from.

 

I realize something isn't right, so I investigate. The prints show an OD 0.100" larger than the model. Everything else on the model is correct.

 

Does this happen often? How do you handle errors between print/model? Does one supersede the other?

[rrichard]

    _{Yes it does with my people, what I've noticed is all the revisions they do on the run with the drawings, and never change the model. I always go with the drawing and revisions and sometimes call the customer. So I have to modify the solid or just make a new one from the drawing.}

_{Nothing easy anymore.}

_Later

[drafting3]

    _{Yes it does with my people, what I've noticed is all the revisions they do on the run with the drawings, and never change the model. I always go with the drawing and revisions and sometimes call the customer. So I have to modify the solid or just make a new one from the drawing.}

_{Nothing easy anymore.}

_Later

 

Well that blows... The drawing was obviously done in SW or Inventor, so why wouldn't they change the model to directly update the print? Isn't that one of the huge benefits to using parametric modeling programs?

[Guyinthedesert]

95% of our work, if I get a model, it's reference only and the paper print takes precedence. And No, the supplied reference models are never right.

 

The other 5% are reduced dimension drawings, and the model takes precedence, however it needs to be spelled out in black and white that you go by the model.

[htm01]

always the print.we have a customer that draws in solidworks and then outputs a dwg and does the print in autocad.

when they give a model they tell us "at your own risk"

[Colin Gilchrist]

At Boeing, the model always takes precedence over a paper drawing.

[bd41612]

I've run into this too.  From my past experience, the print was the contractual document tied in with the PO.  However, if you contact the customer they may say that the model is king.  After all the part model they supplied is what fits into their assembly.  The best practice is to question the confliction.  Someone will be glad you did.  BTW I "love" limited dimension drawings with supplied models, there are always things you will find that are wrong.

[Oscar R.]

Very common to see these print to model deviations. Some customers will use print as master, others model as master, some will use both with limited dimension drawings. Sometimes the print will specify which one is the master.

 

I'm in the habit of checking my customer models to the print 100% regardless. That way at least I know if there's a discrepancy.

 

If there's no one at your shop that can tell you for sure which to go with, the safest thing to do in any case of doubt is to ask the customer.

[RonC.]

Very common to see these print to model deviations. Some customers will use print as master, others model as master, some will use both with limited dimension drawings. Sometimes the print will specify which one is the master.

 

I'm in the habit of checking my customer models to the print 100% regardless. That way at least I know if there's a discrepancy.

 

If there's no one at your shop that can tell you for sure which to go with, the safest thing to do in any case of doubt is to ask the customer.

Same here , 

[djstedman]

Its very rare to NOT see errors between the model and the print, for us at least we let our customers know up front that unless otherwise specified in writing all work will be done per B/P, this didn't used to be the case and we had one customer that would specify to use the model for any dimensions that weren't on the print.. all it did was cause total confusion and tons of ambiguity over what was ok vs. what wasn't..

[Oppiz]

In Inventor it warns you if you try to change the print without changing the model. We used to have a problem with one of are designers taking shortcuts and not updating model. That person is not longer in the engineering dept..

[MATT Q]

I dimension the model just like the print to find any errors and I find a lot.  But most of our customer's prints state model is king so I will take screen shots of the cad and then highlight the print and send them a document (excel) with all the errors.  Most of the time they say the drafters messed up.

[Guest]

always the print.we have a customer that draws in solidworks and then outputs a dwg and does the print in autocad.

when they give a model they tell us "at your own risk"

Model should be king no matter what. If it's not, why bother.

 

"Use at your own risk". That says it all right there. They know they have $#!+  for "engineers" and are saying it without saying it.

[Oscar R.]

Model should be king no matter what. If it's not, why bother.

 

"Use at your own risk". That says it all right there. They know they have $#!+  for "engineers" and are saying it without saying it.

I agree 100%.

MBD was supposed to be the way of the future, but somewhere along the line companies got lazy about keeping their models and prints matching in the transition and here we are today with shops having to do double the work just to verify that the part is being made as intended.

[htm01]

 

Model should be king no matter what. If it's not, why bother.

 

"Use at your own risk". That says it all right there. They know they have $#!+  for "engineers" and are saying it without saying it.

otherwise they say they will not provide model

[Newbeeee™]

I agree 100%.

MBD was supposed to be the way of the future, but somewhere along the line companies got lazy about keeping their models and prints matching in the transition and here we are today with shops having to do double the work just to verify that the part is being made as intended.

Yup. Lack of education on the cad jockey's part.

They don't  understand how to make things and how important their modelling is.

Correct models can save a ton of time or cost a ton of money!

[?Mark]

"THE CATIA SOLID SERVES AS THE SOLE DEFINITION FOR BASIC FORM, LOCATION,

ORIENTATION, AND DIMENSIONAL CHARACTERISTICS OF ALL UNDIMENSIONED PART FEATURES"

 

All aerospace work follow this. And yes, model features that are dimensioned on the print very often do NOT match the model. lol

[Patternmaker706]

Our engineering dept says 3d modes are not for manufacturing... The drawing is the "legal" document. I usually end up making my own models anyway.

[Newbeeee™]

Our engineering dept says 3d modes are not for manufacturing... The drawing is the "legal" document. I usually end up making my own models anyway.

Out of interest, what did they say when you spend time making models, and effectively costing the company double?

Because it is pretty indefensible.

Just curious.

[Robert Ouellette]

I have a job in house right now that is like that. drawing says one thing cad model says something else. on the drawing it says only dimensions on print are critical. all dimensions not on print are to be taken from model. but the model does not match print. not even close. what do you do then? I was told how did you get a model that does not match the print? um you gave it to me. totally lost. does not accept any responsibility at all. we ended up scrapping one part and having to remake it on their dime. had to change the model to match the print and remake it. we can never win.

[Patternmaker706]

Engineering makes models of our finished parts. The pattern to make an impeller casting may require up to 10 different components. I have to model each one of those. The drafters don't even make modes that are easy to draft or add machine stock. You would think engineering and manufacturing would be more integrated but it's just not a perfect world. They use NX, I use Solid works.

[Guest]

Our engineering dept says 3d modes are not for manufacturing... The drawing is the "legal" document. I usually end up making my own models anyway.

That is just pathetic. Double the work because some lazy @$$ cartoonist doesn't know how to do his/her job.

[Jason B.]

As a part designer (and CNC programmer) I ALWAYS put on my prints "CAD model is controlling document"  This is how I have seen it the majority of the time in my 22 years doing this. How would you even begin to cut a core block for a mold or cavity block without the 3D file anyway? (unless it's super basic) Sure, you can redesign it. But again, unless it's super basic, you won't get very far very fast. Most parametric designers HATE changing the part model simply beacuse parametric modeling programs hate change unless it's also basic and simple. Thus the problems of un-updated part files. These "designers" give good designers a bad name. (like lazy @$$ cartoonists )

Bottom line is.... always check the print for the notes that say wether the print or the CAD file is the controlling document, and go by that.

[within a thou]

Model should always be bible. Prints should be used a references for tolerances and hole call outs. I just ran into this today Bored hole with a .005" tolerance all drawn the same .100 bigger on all 4 parts that stack together to make the asembly. A simple call to the customer and we were told follow the print. Hope the guy making the pins catches it as well otherwise they are going to have a bit of trouble assembling this thing and it will be assembled and tested in front of their customer that they are making this machine for. Just hope my boss sent a email to reconfirm what  was said on the phone.

[MIL-TFP-41]

Biggest issue I come across is say a pocket is 1 inch square. Paper print has a tolerance of +.000 -.030

Model is drawn at 1 inch. Programmer does not catch this....part is cut & its on the edge of nothing or scrap....