MES in vehicle manufacturing - Andon Calls

Andon system is used in vehicle plants widely, when issues are found in lineside, workers can trigger calls with rope or button, and the call can be notified by audio/light/screen.

Andon is the realization of 2 key management concepts:

1)       Put quality first, line-stop is allowed to expose and resolve lineside issues.

2)       Put line side assembly first, any other resource such as employees from quality/maintenance/process/material handling should assist lineside workers and machines, because assembly line’s efficiency defines plant’s efficiency.

This article will introduce some key elements of Andon system.

 

1.   Call

Grouped by call type, Andon Calls can be categoried as Quality Call, Material Call, Equipment Call, Conveyor Call.

Quality Call refers to situation of quality issues are found in lineside, which cannot be resolved by worker himself, so worker pulls a rope or presses a button to trigger a call for help. For this call, sender is worker, receiver is line leader and quality engineer.

Material Call refers to situation of material shortage, so worker presses material call button. For this call, sender is worker, receiver is material handler. Normally each button will be mapped to specific material, and it will be integrated to logistics execution system.

Equipment Call refers to situation of machine warning or machine error, which is trigger by equipment controller automatically. For this call, sender is equipment PLC, receiver is equipment engineer.

Conveyor Call refers to situation of conveyor line issues(such as stop, error, starve, blocked), which is trigger by conveyor controller. For this call, sender is conveyor PLC, receiver is line leader and equipment engineer.

 

2.   Notifications

Andon system will provide multiple notification forms such as audio, light, screen.

Normally in working stations we will install stack light with 1 or 3 colors. For 1 color case, it usually uses yellow light, and if Call is triggered, it will flash light to notify. For 3 color case, normally it will use color of read/yellow/green, usually it’s used in key stations such as Error Proofing stations, green light means normal, yellow light means warning, red light means error. Stack light is integrated to conveyor PLC, which can act within 100ms.

In vehicle’s Final Assembly Shop, there’re lots of workers and machines, and engineers will support multiple lines, so engineers might not see the stack light at lineside. So audio notification system is also installed for broadcasting, which includes players + amplifiers + speakers. The players are integrated into PLC, and can act within seconds, and can play pre-record mp3 audio files.

Besides that, larger LCD/LED screens are also used to show words/tables/diagrams as another form of notification. Large screen can be integrated into PC as external displayer, in this PC, SCADA software such as WINCC/FTVIEW/CIMPLICITY will be installed, to show information such as Call status, equipment state, planned quantity, actual quantity, buffer data, shop layout.

 

3.   Escalation

Calls have different level such as information, warning, error.

Information level includes case of shift change, when Call occurred, there’s no any exception in lineside.

Warning level includes case of Material Call, Equipment Call, line starve, line blocked. When Call occurred, the line is not normal but it’s still working.

Error level includes cases of machine fault, line fault, line stopped. When Call occurred, it should be handled immediately.

The same Call such as Rope Call, can be referred to different level, there’s an escalation mechanism behind it.

For example in Welding Shop, at moment of Pulling Rope, it will be defined as Warning level, and if it’s not responsed within 10 seconds, then it will be escalated to Error level.

And in Assembly Shop, all stations have definition of 70% position, 90% position, 100% position. At moment of Pulling Rope, if vehicle has arrived 70% position, then the Call will be defined as Warning level; if 70% position is passed, then define Call as Error level; if 90% position is passed and the Call is not resolved then line will be stopped.

When Call is escalated, the notification of audio/light/screen is also changed, for example stack light flashes yellow as warning, flashes red as error.

 

4.   Line stop management

In vehicle’s Final Assembly Shop, all stations are lined to conveyor line.

So if one station can not complete assembly job in time, then it require to stop whole line, which means Andon system need to integrate to Conveyor PLC.

Normally Andon system will send these signals to conveyor PLC: line-stop signal, 0% position signal, 70% position signal, 90% position signal.

Andon system has its own PLC, which can communicate with conveyor PLC via industrial field coupler.

For conveyor PLC, after it received signal from Andon PLC, it will check with other information such as line status, safety status, to decide whether to stop the line or not.

 

5.   Shift management

Normally we will setup shift management in Andon system as well, even it has only 1 shift.

Because in plant, there’re lots of indexes related to shift, such as planned quantity, actual quantity, stopped time, call time. These indexes are assigned to shift, and should be reset on shift startup. Some indexes are collecting data from conveyor PLC, so Andon system must send shift change signal to conveyor PLC, so that conveyor PLC can reset all counters and timers accordingly.

Besides that, when shift is changed, Andon system can notify workers and mangers with flashing lights and music.