The secret is:
They actual become the identifier of the manufactured part!
I have never seen so much attention paid to something that is so incredibly simple.
I am so tired of seeing article after article written by some self proclaimed pundit sitting in some ivory tower that has an opinion on how we should do our engineering. These MSMEs, PHDs and InfoTech PLM managers have never checked out a part number, modeled an assembly, created the documentation or parts list, released it into the system, investigated problems, done a revision, etc and now are in charge of our engineering system? Virtually having no applicable knowledge. They have no professional experience on any 3D CAD system. Yet, they are telling those of us that work everyday designing functional parts how we should do it. Sadly, the industry leaders listen to them along with the major MCAD vendors, making our engineering world more convoluted and chaotic.
PART NUMBERS are truly too simple to complicate.
In engineering we are not defining a PART number we are defining drawing or document number. They do not become actual part numbers until the parts are made. But for this article we will use part numbers and know that there is always a drawing or document.
Note: We have to define engineering documents: The Drawing, the 3D Model and the AID (Associated Information Document) delivered as a package and the obscure PMI.
Why do we use part numbers?
Because part names are so ambiguous.
I always reference Boeing. How many supports, stringers, hat sections and frames do we have in an airplane? Can you imagine the confusion?
So some bright fellow a century or so ago said:
Well, let’s just use unique numbers!”
As a draftsman at Boeing and many other companies for that matter, I would check out a part number. There was no rhyme or reason. Just the next number. We may check out a block of numbers. Now these would not become important until the release of the drawing.
The drawing was released into the system in the beginning as a blue print and available at blueprint counters. Soon, Boeing moved to microfiche and we would go to the microfiche center and look through boxes of cards.
How did they organize these blue prints and microfiche?
Yes, very good, they did it in numerical order.
But there was no significance of the number. You could have a secondary structure bracket and the next number would be a placard for payloads.
Once in a while there would be part numbers especially defined for the group.
When the drawing was released to Document Control this would put the basic requirements for setting this part into motion. It would be sent to purchasing. They would review the part and send it to the appropriate manufacturing department or supplier to procure a quote resulting in an order for a number of parts.
When I start a part numbering system for a company. I start with two letters that define the company. I also define each of the company products with unique set of top model numbers.
But let’s not get wrapped up in numbers.
What do the numbers represent in engineering!!
Yes, you have been paying attention: Drawings or Documents
Now all drawings include in what assembly the part is used, what is called the "Used On". When you would get a rejection tag denoting a problem with the engineering from liaison, you would review the assemblies and trace down the parts you wanted to investigate. There are many common parts that come out of a bin and will not have a used on, mostly fasteners. We would look at the PL (Part List). If you see BOM (Bill of Materials) you were probably working with AutoCAD or a CAD program that came on the market after AutoCAD. It was basically an architectural package and that is what they call a Part List. Bizarre? Only to a few.
Part List or BOM?
We have to do a bit of an aside here so as to not fall in the trap of “Part numbers are all about engineering”. Of course, after the manufacturing of the part the part number now represents the actual parts themselves. We have special part mark instructions, print, stamp, bag and tag, etc. Yes we have to have part numbers to order the broken widget in our dish washers. After the drawing was used to make the blueprint and delivered to manufacturing it was put in a vault and may never be seen again. That is the funny part of part numbers. Once the project is done so is the part number as they relate to engineering. Hmm who has a bunch of active drawing numbers for a 57 Chevy???
So they are only important until they are delivered to manufacturing and put into a format, probably by planning, where they will never need the drawing again. When the project is complete you, will hopefully never see the drawing again.
Yes, I know if there is a problem or error with the part the drawing is checked out and revised. Lots of this goes on in engineering. Murphy is always hanging around causing problems.
There are a few drawings that handle many different configurations and were constantly being updated. But they were all assemblies. But most part drawings are put away never to be seen again. But once in a while parts can be modified for new products or a design modification. A small change here and a small change there. These are controlled by the dash (-) number. There may be many dash numbers involved with an inseparable assembly like a weldment or any other assembly that is permanently fastened (riveted or bonded) or have permanent fasteners like clinch nuts, studs, etc. A sheet metal assembly: 123456-1 Bracket Assy is made up of 123456-2 Bracket + cinch nuts + studs, etc.
Okay, Okay we don’t do drawings any more. So now what do the part numbers represent?
What do you mean, Joe, we don't do drawings? Of course we do drawings!!
The times have been changing for awhile. In 1982 we, uh actually I, started working in 3D. That is when Model Based Definition started. Yes we were doing Model Based Definition long before some Johnny come Lately thought of it in the late 1990's. The 3D model was used only to create the drawing in the beginning.
The 1980's - 3D CAD - The Beginning
No, no, no!! It did not all start with PLM!!!
We now had a 3D model and in those days until probably the late 1990’s an AID (Associated Information Document). These were drawing like documents, but were generated from the 3D model. No, we didn't do any drawing, just 3D modeling! EGAD!!
The Death of the Drawing
These AIDs (drawings) would be handled just like before, sent to document control, where they would be turned in to prints. We would send these AIDs (drawings) to manufacturing as a print. This was prior to CNC. As CNC showed up we would send the 3D wire frame with the printed AID (drawing) for what was called 2.5 axis machining. In the late 1980’s surfacing was well in place and we were now commonly providing the IGES 3D surface model for CNC including the printed AID (drawing) for reference to manufacturing. Things even got easier with when solid modeling showed up on the PC in 1995. Solid modeling and the AID made engineering design and documentation so simple! (What? Simple? Just look at the mess today!)
The 1990's - 3D CAD/CAM Moves to the PC!!
This, of course, went on until we could get the AID into the form of a PDF. This did not become popular until the late 1990’s. So now we were sending the 3D model in a native and/or neutral 3D format with the AID as a PDF in an email.
Something happened during the release of the PDF. Catia 5 came out for the PC. It came out with the concept of PLM. They probably looked at currently delivering the 3D model with the printed AID and came to the conclusion this was very costly. Of course, PDF was around the corner. Who knows when Catia made PDF a standard printer? Many companies bought an Adobe Acrobat, but soon free PDF printers started showing up. Most of the mid-range 3D CAD jumped on the PDF band wagon instantly, soon adding the ability to generate the regular PDF and later the 3D PDF directly from the program. The high end programs were always lagging. They had a bit of a more captured audience.
The necessity to maintain a synchronized model and drawing and deliverery of the print became a horrible burden on the PLM system. This problem spawned the most idiotic and convoluted engineering deliverable to replace the AID (drawing).
Good Gawd Joe, what the hell has this got to do with part numbers?
Sadly, the PMI is a native file.
PMI vs AID
Instead of sending out the 3D Model and an AID (with any level of detail) as a PDF to manufacturing that is in stone. The companies are dealing with handling the native CAD file and trying to deliver them to the supplier. These are actually emailed!!!
Handling of a native CAD file is much different than delivering a dumb model. Boeing today sends out a Catia 5 native PMI file. You have to have a seat of the same version of Catia 5 or Enovia to read these files. Yes, there are 3rd party readers and translators that are available and have to be kept up to date to read latest version of Catia 5. Now, if you use those, you have to have a 3rd party validation program to assure the Catia 5 part is the same at the part you are machining. It is shocking no one sees the complications this causes and how it opens the door for Murphy to just stroll in!!!
So Dassault has put Boeing and any other Catia 5 user in a place where the optimum is that all have the same version of Catia 5 to be compatible!!! Can you imagine a system devised by the Fox to protect the Chickens? Very clever those French!!
I have worked with Boeing and Catia for over 30 years. Dassault is responsible for keeping Boeing one of the most ignorant and isolated manufacturing companies. Their lack of interoperability is beyond belief.
Nothing makes me angrier than watching a company the size and reputation of Boeing an Icon in engineering standards so easily manipulated!!!
This has caused a huge problem with those that need to import PMI. Here is a solution for importing Catia 5, NX, Creo and Solidworks files with PMI?
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