MES in vehicle manufacturing - Quality Management

Quality management is a key function of MES.

This article will introduce some specific functions of quality management in vehicle manufacturing.

1. Defect management

In quality management module, defects are configured as master data.

Scientific definition of defects helps operators to input defects quickly, and it also helps to generate defect analysis report with more values.

Here introduces 2 types of defect definition.

Type 1: grouped by class, such as class level 1/class level2/defect, or shop/line/station/defect.

Type 2: grouped by coordinates. For quality check station, we can load a component picture into system, and system will split it into lots of areas with horizontal and vertical coordinates. When defects are found, operator click the according position of the picture, then MES will find its mapped coordinate and store it into system.

Type 2 is mostly used for appearance check.

Based on the data recorded by coordinates, MES can generate report to highlight the defect density of each area, and then we can adjust our process to improve quality accordingly.

 

Diagram 2.4-1: Input defect based on coordinates

2. Quality route

In vehicle manufacturing, MES is highly integrated with automation systems, even the manual quality check result should interact with conveyor line.

The so-called quality route means to decide vehicle’s route based on quality status. Here we have 3 scenarios.

scenario 1: vehicle quality route.

As shown in diagram 2.4-2:

1) When vehicle comes to quality check station, operator input defect, and then choose a repair lane, the data will be saved into MES. If no defect found, then vehicle will be marked with default lane.

2) When vehicle comes to turn table, PLC identifies vehicle, and then request to get lane number from MES, and then transfer vehicle accordingly: via default lane to next station, or via repair lane to repair area.

 

Diagram 2.4-2: Vehicle quality route

Scenario 2: engine quality route.

Consider that engine is standing still in any assembly station, so we can install RFID reader in any key assembly stations and turn tables.

So in any assembly station or quality check station, operator can input defects, and PLC will write quality status and route number into RFID Tag; when vehicle comes to turn table, PLC reads route number from RFID Tag, and then move engine forward accordingly.

Scenario: product audit.

Normally for audit, we pick audit target based on specific rate, and we don’t want operators to know whether a product requires audit or not.

So, based on audit rate, we can decide which product require audit when generating Work Orders, and write the audit mark into RFID Tag.

When vehicle comes to turn table before audit, PLC reads audit mark from RFID Tag, and then move vehicle accordingly.

3. Quality Gate

Normally we setup Quality Gate after a set of key manufacturing process, such as vehicle’s lift off station of welding/painting/final assembly, and engine’s lift off station of inner line/outer line.

From point of view of quality control, Quality Gate will check if a product has completed process of current area, if yes then allow it to move forward to next process.

Quality Gate will check below quality data if possible:

1) If quality status is good.

2) If completed all key stations.

3) If short build or over build any component.

4) If failed in any test stations.

5) If failed in any audit station.

6) If any defect not cleared.

Based on the check result of Quality Gate, MES will work with PLC, to decide vehicle’s direction, for example: lift up Gate bar so vehicle can drive to parking lot, or lock Gate bar and alarm operator to drive vehicle back to repair area. Its logic is:

1) PLC identify vehicle by RFID.

2) MES check its quality result, and show it together with defects(if have) in TV.

3) MES transfers quality status to PLC, PLC turn on traffic light, and lift up or lock the Gate bar accordingly.

Refer to diagram 2.4-3.

 

Diagram 2.4-3: Quality Gate and Quality bar