Journey of a bolt (MES in vehicle manufacturing)

In this article, I will take an example of a bolt, to explain how WMS(Warehouse Management System) and MES(Manufacturing Execution System) are used and integrated.

Bolt is a class of key components, has big impact to engine quality.

Below table lists out key process control points:

Area	Station/Position	Operation	System
Warehouse	WM100	Store components in box	WMS
Kitting	WM200	Pack bolt with spring and other materials	WMS
Assembly	OP10	On assembly completed, call for material pull delivery automatically	MES à WMS
	OP20	Manual assembly, manually call for material pull delivery if necessary	MES à WMS
	OP30	Pre-tighten bolt by manually	MES
	OP40	Final tighten bolt by robot	MES

 

Below chart shows high level process:

 

Now let’s analyze it from perspective of material delivery, assembly and material pull.

 

1.       Material delivery

Delivery of bolt has 3 big steps:

1)       Receives in bolt from vendor’s cargo, unpack and inspect, and then transfer to specific storage area in warehouse, with position WM100.

2)       Transfers bolt from warehouse to kitting station WM200, here operator packs bolt with spring and other components together.

3)       Uses AGV to transfer packed bolt to assembly station OP20.

To match with such requirement, we need to set below BOM info in WMS:

Material	Description	Stock No	Position
BT0010	Bolt xxx	10	WM100
BT0010	Bolt xxx	20	WM200
BT0010	Bolt xxx	30	OP20

 

2.       Assembly

Assembly of this bolt includes 3 stations:

1)       In OP20, operator put bolt into right position. In this example, we have quantity 4 of this bolt.

2)       In OP30, operator uses torque gun to pre-tight the bolts. If the station has been configured with 8 torque guns, and here we only need to user gun 1-4.

3)       In OP40, robot will final tight all bolt, with sequence of 1-4-3-2.

Then the assembly BOM should be:

Station	Material	Quantity
OP20	Bolt xxx	4
OP30	Bolt xxx	0
OP40	Bolt xxx	0

When engine arrives at station OP20, stack light of bolt will turn on, until operator picked 4 times, then stack light will turn off.

 

The torque gun error proofing is configured in MES:

Station	Gun#1 clicks	Gun#2 clicks	Gun#3 clicks	Gun#4 clicks	Gun#5 clicks	Gun#6 clicks	Gun#7 clicks	Gun#8 clicks	Sequence
OP30	1	1	1	1	0	0	0	0	00000000
OP40	1	1	1	1	0	0	0	0	14320000

In OP30, after gun 1/2/3/4 has completed tightening, error proofing of the gun is completed; when all 4 guns has completed tighten, then the error proofing of this station is completed, then PLC allows engine to leave.

In OP40, robot will tighten bolts with sequence of 1-4-3-2.

 

3.       Material Pull

In this example we have 2 layers of material pull: 1) assembly to pull from kitting; 2) kitting to pull from warehouse.

When assembly of OP10 is completed, MES will generate a travel record, and sync it to WMS, WMS will alert operator of WM200 to do kitting before engine comes to OP20.

When assembly of OP20 is completed, and if operator finds he doesn’t have enough material for next engine, then he can call for material with push button, the call message will be transferred to kitting area via WMS.

The logic of kitting area pull: each time AGV delivers material to assembly area, WMS will decrease material number of bolt in WM200, when the number is less than safe storage number, then WMS will send the pull message to mobile device of warehouse delivery operators, so they can deliver it from warehouse accordingly.