Engineering and IT Insight: What’s the best manufacturing operations management systems design?
Some of the most frequently asked manufacturing IT questions deal with MOM systems and architectures. MOM is short for manufacturing operations management and includes the functions of MES (manufacturing execution systems), LIMS (laboratory information management systems), WMS (warehouse management systems), tank farm management systems, and AMS (asset management systems). The functions of MOM are defined in the ANSI/ISA 95 standards, and these standards have served as the basis for most new MOM implementations. ANSI/ISA 95 defines the tasks that a MOM can perform, but not the architecture of a MOM solution. MOM architectures are defined by vendors and by their applications suites.
One important point for an IT group to consider is that MOM implementations differ from centralized ERP implementations. In the centralized ERP model there is strong pressure to make all sites look the same, from the viewpoint of the business process used to run the site. This is because localization (the activity of defining local rules that differ at each site) is expensive and difficult to implement. The ERP model of standardization cannot be carried down to MOM systems. Sites that produce the same products often have different equipment layouts, operating rules, regulatory rules, and personnel environments and, therefore, require different MOM configurations. Sites that produce different products will vary even more in MOM configurations.
For these reasons MOM systems generally are considered site- or area-level systems, with workflows, recipes, resource definitions, and production optimization rules that are highly customized for each site. MOM systems usually become mission critical, so they also have high availability and second-to-subsecond response time requirements. This means that MOM systems have usually been located on-site with local customization support. MOM systems can provide well-documented operational benefits in yield improvements, defect reductions, and business-level integration, but they are often hard to economically justify because of the perceived requirement for on-site servers and support.
There is an alternative to on-site servers and support. MOM systems can be decentralized or centralized. The classical model has been decentralized, with servers located within a site running local MOM applications. On-site systems remove the problem of offsite communication failures and help provide the required high availability and local configuration control. The decentralized model requires local server rooms and an IT infrastructure that is hard to justify and maintain at small sites. Many small sites may never get any MOM systems to support their operations because of the inability to support the servers and applications.
Centralized MOM systems provide an alternative that should be considered for medium-to-small sites. In the centralized MOM model a geographically centralized small server farm is used. The server farm hosts VMs (virtual machines) for each site and is connected through a corporate WAN to each site. With dedicated VMs for each site and moderate speed WAN connections, the centralized system can usually meet the response time requirements. The MOM server farm can be centrally managed and supported, often without requiring a physical presence. A centralized support staff can provide the customization and configuration that each site needs, also often provided without requiring an on-site presence. This model works well in areas and countries that do not have a pervasive power and communication infrastructure or that do not have the local IT and MOM resources available for full-time support.
The communication link between the server farm and the sites can be a problem for a decentralized MOM implementation. No one wants to shut down a site because someone outside the site cut the connecting communication line. This is the backhoe-Bob syndrome: if Bob’s backhoe cuts the main phone/Internet line to the plant, the plant still must operate. There is a solution to this communication problem with which we are all familiar: smartphones and pad or tablet computers.
Smartphones and pad computers usually have two communication channels available, 3G (or 4G) and Wi-Fi. This built-in redundancy, combined with mobility, provides a great tool for MOM services. Normal communication would be provided through a site’s Wi-Fi network. In the case of Internet or intranet communication failure, the devices can convert to 3G/4G communication, using the same pad or phone (PAP) applications. When sites lose the corporate connection, 3G/4G connections often remain because these are provided through different connections.
PAPs also have other features that make them suitable for MOM interfaces. Most PAPs have cameras that can be used as barcode scanners. They have local Wi-Fi connections that can connect to wireless printers and have text messaging for notifications from MOM applications. PAPs also include browsers, and many MOM systems support browser user interfaces (UIs). Small mobile devices are the ideal MOM interface device.
PAPs also provide a third level of redundancy, if the MOM applications can send commands and receive responses using text messages. Text messages do not require a 3G/4G connection, just a normal cell phone connection. A MOM system can be configured to provide time critical information for mission critical processes using text messages. If normal communications are out but phone service remains, then the site can continue to operate, even if the MOM system is remotely located.
MOM systems provide significant benefits for those who have implemented them. The addition of PAPs (phones and pads) as interface devices with centralized MOM server farms means that medium and small sites will also gain these benefits. Encourage your MOM vendors to support mobile device interfaces. These are usually browser interfaces that work in the small screen size of a smartphone or small pad computer. Marry centralized MOM systems with PAPs to bring manufacturing operations management support to all of your sites, large and small.
– Dennis Brandl is president of BR+L Consulting in Cary, NC, www.brlconsulting.com. His firm focuses on manufacturing IT. Contact him at firstname.lastname@example.org. Edited by Mark T. Hoske, Control Engineering, www.controleng.com.
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