MES in vehicle manufacturing - Traceability

One of vehicle’s key features which differs it from normal products is, it transports people in public area, so it’s absolutely important to consider its safety.

To make sure vehicle safety, government released lots of laws and policy, among which callback management is one key method.

To achieve callback, car makers must build relationship between vehicle and key parts(such as engine, transmission, air bag, wheel, etc.) in MES, which is mapped as link of VIN number and key part serial numbers. Besides that, sales system will also record link of VIN number and customer.

So when one batch of key parts are found with quality issue, we can trace back in MES, to get the VIN number list which are assembled with this batch of parts, and get customer list from sales system to notify.

This article will introduce the whole process of callback, and how to do traceability in MES with examples.

 

1.    Real case of callback process

Takata is a famous air bag builder, but from year 2015, it is reported out serious quality issues of its products, in some cases, expanded air bag will bring additional damage to passenger.

So lots of vehicles assembled with these air bags are called back, detail steps are:

1)       Takata queries and list out all serial numbers of air bags, and send them to car makers.

2)       Car makers query and find out which vehicles have assembled with these air bags, and also find out customer information of these vehicles, and send them to car dealers.

3)       Car dealers notify customers to drive their cars to change air bags, and send new serial number back to car maker, who will update the traceability data into their system accordingly.

 

2.    Usage of metal 2D barcode

Normally for vehicles, traceability of parts is done in Final Assembly Shop, by scanning part barcode labels.

As for assembly of engine and transmission, barcode labels are also used, but for machining, metal 2D barcode are more often used for traceability.

Due to limitation of bad environment conditions(oil/water/heat), barcode labels will be damaged easily, then they’ll be hard to identify.

So engine maker will require vendor of raw part to mark metal 2D barcode in outside, and after engine is lifted on, another metal 2D barcode will be marked representing engine itself.

Marking operations are done by specific laser marking machines, and marked barcodes are identified by specific devices, such as products of COGNEX.

For paper barcode, 1D or 2D, they are formed with square blocks; but for metal 2D barcode, they are formed with circle pits.

The identification device is basically an image device, which take a photo, then process image with OCR algorithm, to get valid characters from it.

Identification devices can be connected to MES clients via ports of USB or RS232, or connect to PLC via Industrial Bus such as Profinet/Profibus, and then connect to MES via OPC.

 

3.    Link of VIN number and engine number

Engine is heart of a vehicle, to make sure safety of a vehicle, vehicle builder must make sure VIN number is aligned with engine number.

Except for recording the link in Database, it’s also required to mark VIN number outside of engine.

The detail process:

1)       When vehicle comes through PBS Out, MES sends VIN number to conveyor PLC and marking device of Engine Assembly Line, and print out assembly sheet with VIN barcode in it.

2)       In Engine Lift on station, worker scans VIN barcode of assembly sheet by sequence, then PLC will validate it with information it received, if pass then lift on the engine.

3)       In Marking station, worker scans VIN barcode, and operates Laser Marking device to mark VIN barcode.

4)       PLC writes VIN number, engine number into RFID Tag, which is plugged into engine pallet.

5)       When engine pallet comes to vehicle chassis line, PLC will compare 2 VIN numbers: one is form RFID attached to vehicle, one is from RFID of pallet. If they’re same then continue to build.

 

4.    Software management

Vehicle software such as ECU(Engine Control Unit) are not physical parts, so it cannot be called back as them.

But sometimes car makers will inform customers to update software in car dealers, the method is quite similar as callback.

For MES, software are some kind of special parts – virtual parts, which version is similar to part’s serial number or batch number. So within vehicle’s traceability system, not only serial numbers of physical parts are included, but also key software’s versions are recorded.

For car makers, by trace software version, they can also check if customers have hacked software, if so then they can identify it in car deals during running diagnostic software.