Part Numbers can be funny and frustrating things when really they should be inconsequential. Over many years of working as an employee or a consultant to various companies in many different industries I have been amazed at the Part Number 'systems' that companies have tried to use. Part Numbers within a company are used to assign a unique 'identity' to different items tracked within the company. HERE is a Wikipedia talking about Part Numbers if you want to know more about what they are generally. The reason that I am bringing this up is because I have seen P/N's become a source of money wasting time and confusion and I want to put my opinion out there with some examples of what I have seen. I am only going to address the topic of Part Numbers in this post and not the Descriptions. Part Descriptions is an entire topic all by itself.
Significant vs. Insignificant Part Numbers
The first schism in the Part Number philosophy/religion debate is over how P/N's should be assigned to things. Some folks believe that a Part Number should have some unique significance built into it - or intelligence - to describe what the thing is that has the Part Number. In other words by looking at the P/N one should be able to have an idea of what the item is. In this case the P/N really becomes the description of the particular part (or assembly) and usually each digit in the Part Number has a particular meaning. On the other side of the battle field is the army of people that say that a Part Number should just be a number, any number, that is just unique to an item and doesn't tell you anything about what the part is. These two approaches are usually referred to as Significant Part Numbers and Insignificant Part Numbers. Part Numbers are assigned to things as unique identifiers for tracking purposes and referencing records etc... The only stipulation when giving something a part number is that it be unique and never reused.
Insignificant Part Number Systems
Everything has a name and a number associated with it within a company, even the employees. Have you ever cared what the employee number is of a co-worker? Probably not, you are more likely to care about their name. The same logic follows when talking about part numbers in an Insignificant Part Numbering System. The number a particular part has isn't important in an Insignificant Part numbering system, but the description (or name) is. That's the thinking with non significant part numbers.
In a Insignificant Part Numbering System numbers are assigned in any order with any part number being assigned to any part or assembly. Numbers are usually assigned in numerical order by a specialized computer program like a Product Life Cycle Management (PLM) system of some kind but I have even worked at companies that used MS Excel to issue and track part numbers. Back in the old days before computers I would even write the numbers in a log book. No matter how it's done the important thing is that any part or assembly can have any number assigned to it and if someone wants to know what something is they will have no idea from looking at just the part number.
In an Insignificant Part Numbering System you can 'create' or 'pull' as many part numbers as you want when you set out to design or specify something and give each item any number in any order because the number isn't related to the thing that you are designing. Issuing or pulling large 'blocks' of numbers is a common practice when starting out with a new design or especially if you have employees working off site who may not have access to the companies part number database. For example in cases like that you can allocate 500 numbers and assign them to all the things that you are creating. If the first thing that you assign a Part Number to is a flat washer and the second number is assigned to a resistor, all is well in an Insignificant Part Number system. The part or thing that gets the number doesn't matter at all to which part number it is given.
Significant Part Number Systems
Significant Part Numbers are numbers that are assigned to a part or assembly based on what that part or assembly is or other things about the part like where it is used. With Significant Part Numbers you have to know what the thing is that you are assigning the number to before you create the number. In fact the Part Number is actually created by the part that you are assigning it to based on things like what the part is, where it's used, where it's stored in the warehouse, what product it is used in or even when the part was designed.
Significant Part Numbers are much more complicated and usually much longer than Insignificant Part Numbers. Companies that use Significant Part Numbers usually have rules and procedures for creating the part numbers and frequently the creation of the numbers is done by one department within the company, usually Document Control. Significant Part Number Systems are sometimes referred to as Intelligent Part Number Systems.
An example of a Significant Part Number might be a number that has one digit, a dash, three digits, dash and 4 digits like this: 0-123-4567. In this case the first digit might be the product so the 0 might be coffee grinder for example. The next three digits might be a code for screws, a motor, a power cord something else. The last 4 digits might be just numbers issued insignificantly to make it unique or they might have some meaning and significance as well, sometimes the date the part was created. The point here is that the number is describing what the part is and in many cases it's describing a lot more. In order to create a part number you have to know what the thing is so you can 'build' the Part Number.
Differences of Each System
As I mentioned above I have worked with and used both Significant and Insignificant Part Number Systems and I have seen a lot of things happen with each. Here are some of the things that I have experienced in no particular order.
Significant Part Numbers
Significant Part Numbers can take a lot of time to create and sometimes be debated within the company when they are assigned. I have witnessed long discussions at companies where the topic was what the part number for a particular item should be. Folks couldn't decide if a washer that was being used to cover a hole in a water tank should be given the P/N for hardware (nut's screws, washers) or should it be given the P/N for hydraulic components (hole plugs, pipe caps, fittings, valves) for example. "it's a flat washer but we are using it as a hole plug, what number does it get?" A group of three or four people standing around for an hour reading and discussing the companies part number system rules and procedures and trying to figure out what the P/N should be for a $2.00 part.
Some companies have assigned Significant Part Numbers for a particular product, like the 0 above for a coffee grinder that uses a electric motor for example. Only to use that motor later in a margarita mixer and a dish washer. The margarita mixes is product 1 and the dish washer is product 2 so what part number do you assign to the motor? Maybe it gets a 0 because it was first used in the coffee grinder but later used in the margarita mixer. Once you start using that motor in something other than a coffee grinder, knowing that the P/N starts with a 0 doesn't tell you where it's used.
With Significant Part Number systems you can search for and find particular types of parts from just the part number. Searching for *-54* might show you all the wire that a company has assigned part numbers to for example. This is really handy if you are designing something and need some particular wire in the design. You have to find out if the wire you want to use already exists in the company or if you need a new number. By searching on the Part Number with some wild card characters you can quickly find out if the wire you need is already released.
Insignificant Part Numbers
Insignificant Part Numbers can cause a lot of work when trying to figure out what something is when all you have is a list of P/N's in front of you. A long list of numbers that have no meaning is almost useless so with Insignificant Part Number systems you almost always have to print out part lists (Bill of Material) with descriptions of each part. Knowing a part number doesn't tell you anything about the part by definition in an Insignificant Part Numbering system so you always have to have access to the description. Most of the time that isn't a problem but sometimes, like if you are working off site it can be a problem.
With an Insignificant Part Number System you have to rely on the descriptions of the parts if you want to sort or look for a particular type of part. Like the wire example above where you could search for *-54* and see all the wire, that kind of search won't work with Insignificant Part Numbering Systems. With insignificant Part Numbers you have to search in the description field to find all the wire that the company is using. This can be OK if the description fields are all the same, like all wire used in the company has the word "wire" in the description but that isn't always the case. I have worked at companies that used the word "wire" in the description for wire and also the word "cable" for wire not to forget "conductor" for wire and even "harness" for wire. Description fields in most Part Number databases are limited to some small number of characters like 40 for example so the tendency is to abbreviate. "wire" "cable" "condt" "harnss" might all be in the descriptions so if you are looking for wire it might not be that easy to find with Insignificant Part Numbers. Only if strict discipline and rules are established for how to name things can Insignificant Part Number Systems be used successfully. In my experience I rarely see this and a lot of time can be wasted by an engineer who needs to use a $1.20 bolt in a new design but spends 2 hours searching the companies database to see if that bolt already has a part number.
Semi-Significant or Hybrid Systems
A Hybrid Part Numbering System is my personal favorite way to assign Part Numbers in a company. One way that I have seen this work well is with Class Codes. An example of this is a company that creates part and assembly classes and usually gives each class of item a number. This Significant Class Code number can be used as a prefix separated from the Insignificant Part Number by a dash. For example a three digit Class Code of 100 might be resistors and 400 might be fasteners. If you are releasing a new resistor you can search by the class code for all the resistors and see if the one you want is already released. Same for any other part that has been released and you need to add it to a new design.
Companies that really have their act together release a bunch of standard parts in bulk the first day of business. For instance release all 1/4 watt resistors of all standard values and release all screws of different head types and materials right off the bat. You don't have to buy them or stock them but there are numbers assigned to all of then so the engineering department doesn't spend a lot of time documenting and creating Part Numbers for standard off the shelf items - engineering can stay focused on engineering design in other words. If you have any questions of comments please email me at firstname.lastname@example.org and/or leave a comment.
To expand on that concept a company can not only release all the standard off the shelf common items that they believe they are going to likely use but creating a Preferred Number System of First, Second and Third choices for using parts can cut down on inventory and save money in purchasing. The concept of Preferred Numbers has been around for a long time and I don't understand why it isn't used more in Part Numbering Systems. I have only seen a system like this used once in my career and it works great in reducing inventory, speeding up design, and even making it easier to assemble products by reducing required tools and removing clutter from the assembly area.
Other Related Topics
Another puzzling question that seems to bring up debate is when to change part numbers and how you do it. Form, Fit, Function is one thing to look at and what kind of Part Numbering system you use. Does the company use revisions as well as Part Numbers to identify things? What system is used to write Engineering Change orders and how does the company document changes in the design.
I'll write more about this topic and related topics sometime soon. In the meantime feel free to contact me!