MES in vehicle manufacturing - Vehicle Identification

This article introduces the methods of identifying vehicles during manufacturing.

There’re 5 types of material used to identify vehicles:

1) Ultra high frequency RFID Tag, mostly used in vehicle manufacturing.

2) High frequency RFID Tag, mostly used in manufacturing of engine and transmission.

3) Screw/Bolt RFID Tag, mostly used in machining of engine and transmission.

4) Metal 2D barcode, mostly used in machining of engine and transmission.

5) Paper barcode label, mostly used in vehicle manufacturing.

Details are mentioned as below.

1. Ultra High Frequency RFID TAG

Ultra High Frequency RFID Tag is referring to RFID Tag which works in frequency range of: 65 - 868 MHz(Europe), and 902 - 928 MHz(North America). 

RFID is short of Radio Frequency Identification.

Tag is the material used to store data.

RFID related devices include: 

1) Tag, used to store data.

2) Antenna, used to expand covering area of radio frequency signal.

3) Reader, used to write data to Tag, and read data from Tag, and send energy to activate Tag.

4) Communication module, used to transfer data between Tag and PLC data block.

5) PLC or PC as data receiver.

6) Other devices, such as cable, connector.

Diagram 2.3-1 shows relationship between RFID related devices:

 

Diagram 2.3-1: Relationship of RFID related devices

The advantage of Ultra High Frequency RFID is its high range of identification area, which can reach a couple of meters.

In vehicle assembly shop, a typical station has 6 meters, and vehicle is moving slowly during reading, Ultra High Frequency RFID can support such requirement from distance and angle.

Now let me introduce some working scenarios.

Scenario 1: Merge station of Welding Shop

When vehicle’s sub-assembled parts come from Front Cabinet/Front Floor/End Floor, and move forward into merge station, PLC will download new Work Order and VIN number of new vehicle, together with information such as model type, color, vehicle attributes, and then PLC writes data into RFID Tag.

Scenario 2: Quality Check station

There will be a RFID station before Quality Check, and another RFID station after Quality Check, after receiving data from PLC and RFID Tag, MES will know the vehicle list which have already passed previous RFID station, but not yet passed later RFID station, so in Quality Check station, MES will display this list, and operator can pick one from it.

Scenario 3:: Material trigger station in Assembly Shop

Normally there will be a RFID station in PBS OUT, so when vehicle passed this station, MES will broadcast vehicle number to logistics handling/execution system, to trigger the pull of material for assembly lines.

2. High Frequency RFID TAG

High frequency RFID works in 13.56 MHz, its read/write distance is less than 0.2 meter.

Due to this limitation, the application of RFID should match with below conditions:

1) Tag should be holding still during reading/writing.

2) Tag should be near Reader as close as possible.

Such technology is used in assembly of engine and transmission quite a lot, because their manufacturing process can match with these 2 conditions.

For example, when the engine comes to an assembly station, it will be holding still on the pallet, and RFID Reader is installed just below pallet, and RFID Tag is plugged into pallet just above Reader.

The feature of this type of RFID makes it quite different to identify an engine than the way to identify a vehicle.

1) Uses High Frequency RFID.

2) A Reader is installed in each station, while in vehicle assembly Readers are only installed in line head and line end stations.

Since each station has installed RFID Reader, it’s reasonable to store process data into RFID Tag as much as possible, so we can read and write RFID Tag directly, without interacting with MES for each station.

For example, Siemens High Frequency RFID Tag can store up to 54KB data, then we can store lots of data into it, such as product master data, lift on data, BOM, key working command, key process parameters, assembled part Serial Numbers, traceability data, repair data, so a Tag can be regarded as a working manual and also as an assembly dataset.

3. Screw/Bolt RFID TAG

The key part of an RFID Tag is its data storage chip, which can be packed and installed with many ways.

Some Tags are packed with magnet together, so we can stick it at top of vehicle; So Tags are packed as coin-thick plate, so we can plug it into pallet.

Here introduces screw form Tag, such as Siemens RF630T, this Tag is packed with a M6 screw and a 64B data chip, can be installed into M6 holes. Balluff’s screw form RFID Tag can store data up to 64KB.

This kind of Tag can be used in 2 typical scenarios.

Scenario 1: machining of engine and transmission.

In Machining Shop, we don’t have pallet, the mechanical parts are moved between stations by robots, so we can only install Tag into mechanical parts, and move together with it.

Scenario 2: Assembly of engine and transmission.

Although we do have pallet in assembly, but some company want to keep key manufacturing data in RFID Tag, and ship it to customers as part of product, so in the future if we need to repair it, we can read original manufacturing data from RFID Tag.

4. Metal 2D barcode

In machining shop of engine and transmission, to avoid infection of bad environment, normally laser marking is used to generate 2D barcode in surface of metal part.

The machine used to generate metal 2D barcode is called laser marker, it consists of laser transmitter, control module, positioning module, communication module.

Metal 2D barcode cannot be identified by normal handhold barcode scanner, it needs specific device for identification, it consists of photo taking, image processing, OCR, and communication modules.

5. Barcode label

Barcode labels have been used in MES field all the time, especially in vehicle manufacturing.

Barcode labels have these outstanding advantages:

1) Very cheap.

2) Can be read by man eyes.

3) Don’t require interaction with backend system(PC regards scanner as keyboard device).

Now let me introduce 2 typical scenarios.

Scenario 1: Assembly sheet printing

When vehicle passed through PBS, MES will trigger all sub-assembly line printers to print out assembly sheet of each line, the sheet includes lots of barcode labels, such as of VIN number, model type, key station part numbers. When vehicle comes to assembly station, operator will scan labels of part on stack, and also of label of part in sheet, then MES will validate if they are matched or not.

Scenario 2: Error Proofing.

When a vehicle is started assembly, MES will print out an Error Proofing sheet, which is a list of barcode labels, each label is the parameter string of each key Error Proofing station. When vehicle comes to Error Proofing station, operator scans Error Proofing label, and then device PLC gets parameters from label.