Cummins, the world’s largest independent manufacturer of diesel engines, builds over 62,000 engines for customers in Europe, Middle East, Africa and the Far East in 2006, and employs 1,000 people. There are more than 2,000 possible engine variants and Cummins recently decided to upgrade a large part of their assembly and pressure test process. Engines had previously been transported through the manufacturing process by a combination of overhead chain conveyor, powered floor conveyor and an Automated Guided Vehicle (AGV) system. This was all replaced by an Electric Monorail System (EMS) using PROFIBUS during a two week shutdown in 2006.
The EMS comprises 600 metres of overhead monorail, 50 carriers, 14 switchpoints, 3 lift units, 1 rotate unit, 34 assembly stations and 4 pressure test stations. There are a number of PROFIBUS DP networks in the system, providing communication to RFID devices, HMI operator panels, maintenance touch panels, carrier controllers and distributed I/O. These networks are also used to interface between the S7-317DP PLC’s which control the system. All fifty carriers have a Moby data tag attached to store an engine’s build attributes and to determine its route through the system. At each of the assembly and test stations there is a read/write device which communicates the engine data and operational status back to one of the PLC’s controlling the system.
There are three production pressure test lanes and one repair test lane. Each carrier has an onboard controller which constantly reads an encoded rail to determine its position in the system. Status and Command words are received and sent to each carrier from the PLC again via PROFIBUS DP. There are also six colour touch panel HMI’s on the line, used for pressure test control and display and for maintenance functions such as alarms and manual functions.
In the year since the system was installed, production rates have increased from 220 engines per day to 350 engines per day. The system was designed and built by Cleveland Systems Engineering Limited in co-operation with Trackfit Engineering Services, who designed and installed the supporting steelwork and mechanical elements.