If lean manufacturing and quality management have made serious impacts on what is expected from ERP solutions, Simon Holloway asks: What have they done to the Manufacturing Execution Systems that run our plants?
The concept of MES was originally established by AMR in 1992 as “the execution layer of manufacturing applications, which exists between the enterprise and control system to provide visibility and control functionality.” The body formed to promote MES, MESA International, refined this definition in 1997 as: “Manufacturing execution systems deliver information that enables the optimisation of production activities from order launch to finished goods.” This still doesn’t help.
The clear thing is that MES is about the shop floor and the operations that take place on it. It is also about software that enables a manufacturer to have some sort of automatic control over those operations; be they logistic ones, quality related, manual or automated tasks. Tom Comstock, executive vice president of worldwide marketing, product management and strategy at Apriso, defined MES as: “The system that manages all the elements of manufacturing from equipment to supplier at the plant level.” He says his customers refer to his company’s product as “the portal for blue collar workers”. In that definition, it provides to this part of the workforce information about what to do next, how to do it, what setting to use and what to do if something goes wrong. This “system” can include the following support:
● Presentation of schedules – these are often derived from ERP or Advanced Planning & Scheduling systems to work centres
● Collection of production information such as time, quantity and quality
● Analysis of production information
● Control of planned and unplanned maintenance
● Quality control
● Shipping / dispatch
● Product labelling
● Product traceability
MES and ERP
So what does an MES do compared to ERP and other systems in my business? ERP can cover a multitude of functions; so can MES and some of them overlap! And to make matters worse some ERP vendors offer MES as well. Simon Pollard, VP, SAP EMEA, says: “About 4-5 years ago we (SAP) found a transition in the manufacturing market where more emphasis was being put into improvements in the shop floor than into ERP. This was because the need has shifted to getting performance at this level due to the need for greater flexibility and agility.” So there is also market pressure to gain better control of the shop floor.
So, let us look at this from a more basic level so that we can get a better idea of what is what.
At the bottom of the pyramid are the automatic data collection devices. Machine monitoring sensors and shop floor data collection (SFDC) terminals transmit production data from the factory floor through Program Logic Controllers (PLC) to the MES software. Other devices that can be used to pass data are bar code readers and RFID readers. An interface layer in the MES software based either on supervisory control and data acquisition (SCADA) or straight XML is used to collect the information. ERP sits at the top and acts as the white collar worker’s control of the business. This leaves the shop floor and it is here that MES sits. As Comstock said, it is their portal on to their world. It takes information from the machine device level and information from the ERP and displays them back in ways that are meaningful to shop floor workers.
The main difference between MES and ERP is the focus. The focus of the ERP System is the Sale and/or Purchase Order, while the focus of the MES is the actual manufacturing operations.
According to the ISA 95 model, both systems are located in different layers. MES is within Level 3 for Manufacturing Operations and Control. ERP is located in Level 4 for Business Planning and Logistics. MES, as defined by the standard, includes four major categories of manufacturing activities – production operation management, maintenance operations management, quality operations management and inventory operations management.
The standard defines other activities that are used to support all of the major activities categories, such as management of security configuration, information, documentation and regulatory compliance.
Pollard summed up the situation at most manufacturers. “What we have seen at our customers is great standardisation around the ERP layer or level 4 and also around at he machine level – level 1. It is Levels 2 and 3 – the MES levels – where customers have many different systems in place.
However about four to five years ago we found a transition in the manufacturing market where more emphasis was being put into improvements in the shop floor than into ERP.” Comstock felt that ISA- 95 has been a real help in making MES solutions become more standardised, but he felt that there had been more success in process rather than discrete manufacturing.
The Market place
There are currently more than 40 global manufacturing companies spanning many industries that are using the ISA-95 standard to define and implement their MES solutions. Forrester stated: “MES vendors are repositioning their offerings along one of two viable strategies: flexible, horizontally robust solutions or vertically tailored solutions.” Comstock described the market as being divided into three sets of players:
● Vendors who supply machinery with PLCs and SCADA, such as Siemens, Invensys Wonderware, Rockwell and Honeywell
● ERP vendors who have entered the market mainly through purchasing a pure play MES vendor, such as SAP and Infor;
● The Pure Plays – vendors who have specialised in the MES market such as Apriso and Camstar.
Comstock went on to explain that all of these solutions were now 2nd or 3rd generation; in other words MES has been around for some time!
Automotive Sector and MES
Since the turn of the century there has been a steady move by automotive OEM’s to provide one-onone marketing to its customers. What this means is a car is built to a customer’s choice of options and they can change their mind right up to the last moment. Both customer relationship management (CRM) and advanced planning and scheduling (APS) make one-on-one responsiveness possible. They help companies move from a forecast-driven world to a more pull-based one. MES needs to have bidirectional, real-time linkages to the enterprise system to be able to support this at the plant operations level.
“MES describes an area of work,” says John Woods, director of Manufacturing Floor Systems for General Motors (Detroit, MI). “A space generally critical to the operation of the plant.” That space, consisting of an integrated collection of applications, is between controls and enterprise systems.
Swanton defines MES simply as the system that knows what the order is, knows something about that order, and can electronically communicate that information to people and machines.
What OEMs and suppliers are looking for is the current state of a customer order in the build process, right down to the current status of a given device in manufacturing. Ideally, MES would communicate state information about individual production equipment and the results of that equipment’s execution cycle – against a multitude of subassemblies that constitute a customer order.
Why a MES? In the automotive sector, the planned execution of build orders is a balance among consuming assembly plants and suppliers.
Because planned execution spans assembly plant and suppliers, setting the sequence and communicating that sequence to the world is high-level function typically relegated to enterprise resource planning systems. However, within this execution process is the need to manage that sequence and recover that sequence as needed.
That’s where MES comes in; MES controls the operations that support the sequence.
So what are the vendors working on next to support you? Comstock saw that there were three keys areas of working on MES. The first he saw as extending the current platform to cover events such as maintenance of equipment. The second area was to provide support for co-ordination across plants and companies and lastly he saw the need to provide greater flexibility for making changes over time. This would cover, for instance, the ability to make changes dynamically every 2 hours as an Automotive OEM makes changes to their schedules, which impacts Automotive Tier 1 and Tier 2 production schedules. Pollard saw the need for operational best practices to be incorporated into frameworks that could be delivered through MES packages. These would expound the process excellence capabilities for the shop floor.
So the vendors appear to be lining up innovations that are based on their and their customer’s views of the market. Although they appear to be different when taken at face value, they actually are the same in that they have agreed on the need to expand the current MES platform functionality to cover best practices across the whole of today’s shop floor world, in which plants may specialise in certain stages of manufacture or are part of a much larger picture such as a car or an aircraft. They also agree that there is a need to improve performance and standardise processes on the shop floor to make islands of data a thing of the past. Long live MES!