Cummins Engines have been manufacturing high quality diesel engines at their Darlington plant for over 40 years. Recently the demand from their customers has increased significantly and in order to satisfy the new production volumes Cummins decided to upgrade a large part of their engine assembly and pressure test process.
Engines had been transported through the old process by a combination of overhead chain conveyor, powered floor conveyor and an aging AGV system. This was all removed and replaced by an EMS system during Cummins two week shutdown in 2006. The EMS system comprises of 600 metres of overhead monorail, 60 carriers, 14 switchpoints, 3 lift units, 1 rotate unit, 34 assembly stations and 4 pressure test stations.
Engines travelling through the main assembly area.
All sixty carriers have a Siemens Moby RFID tag attached which stores all of the engines build attributes and also determines the engines route through the system. There are in excess of 2,000 engine variants manufactured at Darlington, all of which could potentially travel through the EMS line. Each of the assembly and test stations has a Moby RFID read/write module which communicates the engine data via a Profibus DP network back to one of the Siemens S7-317DP PLC’s controlling the system.
There are three production pressure test lanes and one repair test lane.
Each carrier has an onboard LJU controller and 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 Siemens S7-317DP PLC again using the Profibus DP network
At every assembly station there is a Siemens OP77A HMI panel. The HMI allows the operator to raise and lower the carrier hoist, offload engines to the floor, reload engines into the system and to release an engine to the next station when work is complete. When engines are offloaded or reloaded the Moby RFID tag is updated to reflect the new status of the carrier. All OP77A HMI’s and six touch panel HMI’s are connected on Profibus DP to one of the Siemens PLC controllers. The PLC’s also communicate with each other via Profibus.
The rotate unit accepts engines from one of two input lanes and delivers them to one of two pressure test lanes.
In the year since the EMS system was installed, Cummins daily production rate has increased from around 220 engines per day to the current level of 350 engines per day. Cleveland Systems´ were responsible for system design, control panel design and build, electrical installation, software design and commissioning. The steelwork and all mechanical components of the system were designed and installed by Trackfit Engineering Services of Herefordshire.
