Intro
In the manufacturing industry, there are a lot of different nomenclature, jargon, & company specific terms that make it challenging to communicate across companies or even sometimes teams. This is especially true when it comes to handling manufactured parts & components. The traceability terms “serial number”, “lot code”, & “part number” get thrown around, sometimes with little regard to their precise definitions. Today, we will go over how these terms are properly used for identification and how we use them at Serial.
Serial Number
Serial numbers are unique identifiers with a 1-to-1 relationship with a part. For example, every car has a VIN (Vehicle Identification Number) that is unique to that vehicle, therefore, a VIN is a type of serial number. They usually are assigned programmatically, such that the serial number itself encodes lots of information about the something it is identifying (if you want to learn more about creating and managing serial numbers, check out this blog post on the topic).
Once you have associated a serial number with something, you can then track that something across your manufacturing line (with a barcode or sticker indicating the serial number) and even once it has been delivered to customers (which can help you manage warranty). Then if an issue arises in the field, serialization combined with a good data storage solution makes it simpler to root cause the issue, and even preemptively address it (i.e. swapping known defective equipment) for other serial numbers with similar characteristics.
For example, in the above serial number lookup page, not only do I know the date of manufacture right from the serial number (2023/12/12), but I can also use the Serial Database to look up all the testing history for this given serial number.
When should you serialize a part?
In general terms, serial numbers should be given to any part that will be either a) used by/sold to a customer, as having one will help you greatly with quality control & improving service or b) is a high value part of an assembly. The definition of “high value” depends on the nature of your organization, but a good rule of thumb is if you are measuring the functional performance of a part, then it should be serialized (i.e. a plastic o-ring should not be serialized, but a PCB with functional performance requirements should be).
Lot Code
Lot codes (also known as lot numbers) are unique identifiers with a 1-to-many relationship, usually bought, used, or sold together. Some typical examples of parts that would use lot codes are: nuts & bolts, tires, and chemicals. Typically, the usage of lot codes reflects the fact that the item was manufactured in a batch, as well as the expectation of little variance between individual members of a batch (as an aside: typically when a batch is purchased, the statistical distribution is included with its sale, and should be checked as part of your manufacturing process, trust nobody!). Lot codes are very common in industries with lots of batch manufacturing, such as pharmaceuticals & food processing. This is the case because each individual item (such as a pill or package of food) will have little or no individual information, but information about its batch is very important when meeting compliance requirements or doing quality control. Typically, a user can find the lot code either machine etched into the product or on a sticker attached to the product.
When should you use a lot code?
Unlike serial numbers, where giving a serial number to low value parts can introduce frustrating overhead to your operations, being liberal with assigning lot codes can add clarity to your manufacturing stack at very little cost. With that in mind, anything that is either produced in batches (such as plastic molds or liquid products) or purchased in batches (such as mechanical parts such as nuts, bolts or fasteners, or a simple electronic components like resistors) should be noted as a batch in your MES, because when you find a defect, there is a very high likelihood you will discover that defect is spread among a single batch, rather than across batches.
For example, pulling from the prior example, here we can see this lot coded battery stores its date information and the fact that it came in the first batch of the day, as well as the tests that were run against it when it was linked to (i.e. assembled with) its parent drone.
Part Number
As opposed to serial numbers & lot codes, part numbers (often referred to as PN, P/N or part #) are an identifier for a particular part design, not an individual unit, which may have serial or lot number.
The purpose of part numbers is to contain the design requirements (i.e. include all metadata for a given part). This is the basis for the specifications a part should be built to: 2D drawings, CAD, revisions, or materials. For example, some component (like a temperature sensor) might be open to the air with a part number suffix “O”, have a duct connected to the sensor with the suffix “D”, or might require a special probe, denoted with the suffix “P”. Here the part number indicates to the user and operator what kind of part needs to be used or built.
When should you use a part number?
Part numbers should ideally be a ubiquitous part of your design and manufacturing processes, communicating the design engineer’s intent for the product to the manufacturing engineer. With that in mind, anything that you manufacture, whether it is a final product or part of a sub assembly, should have a part number. As well, whenever a design changes, that new revision should be given a new part number, ideally marked in such a way that it is clearly a new revision of an existing part number. Once you do this, part numbers will then simply exist as a property of your serial & lot numbers, which will provide you more granularity when slicing your manufacturing data.
Going back to our prior example, we see that our drone has a part number of DRN-2980, which we can easily look up to find out what kind of drone it is, what its vibration plate screw torque should be (which we can leverage in work instructions) and whether is has a rear gimbal screw.
Summary
To review the traceability terms:
- Serial Number: A unique identifier for a single part, that can be used to track the lifecycle of that part.
- Lot Code: A unique identifier for a batch of parts, that can also be used to track that batch's life cycle, which may be across several parent serial numbers.
- Part Number: A name/identifier for a design of part, that ideally gives employees & customers information about that kind of part.
Thank you for reading, we will be back next week with a deeper dive into using part numbers to improve your work instructions.
