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THE OPEN MANUFACTURING LANGUAGE
OML—An Internet of Manufacturing
Solution for PCB Assembly
BY MICHAEL FORD AND DAN BAILEY
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For years, the PCB manufacturing industry has needed a robust real-time, comprehensive shop-floor
communication standard that would include detailed bidirectional machine-to-machine communication as
well as shop-floor to IT computerization communication. Now, engineers at the Valor Division of Mentor
Graphics have introduced a real solution: the Open Manufacturing Language (OML), an open communications
standard managed through a community of industry members and designed to support the evolving Internet
of Manufacturing. OML makes vendor/platform-independent data accessible across the entire shop-floor,
opening up the potential for Industry 4.0 and Smart Factory 1.0 solutions. This paper describes the basics of
OML, as well as real-world uses and values to which it can be applied.
WHAT IS THE OPEN MANUFACTURING LANGUAGE?
The driver behind OML has been the strong demand from the industry to provide a standard language on
which the Internet of Manufacturing for the PCB assembly industry can be based. Unlike previous standards,
OML features bidirectional data flows, supporting shop-floor data collection as well as process control, all
through a single standard format, language, and protocol. The specification of the OML standard is available
free of charge to OML community members (www.OMLcommunity.com).
OML development is based on many years of PCB assembly
shop-floor communication experience, where information
from production processes has been gathered in real time
and applied to real-world manufacturing shop-floor
solutions such as finite production planning, Lean material
management, quality management, and full materials and
production traceability.
As a result, the OML standard represents a high degree of
value from the start and can be put to use immediately. Any
creator or consumer of OML data will require the development and support of only one standard interface,
compared to the pre-OML situation of needing many different interfaces. Development costs and lead-time
for PCB assembly shop-floor projects, including advanced manufacturing computerization, can be reduced
significantly using OML. This improved efficiency enables manufacturers to evolve to meet their customers’
demands. OML will continue to be developed by the community to ensure that it meets expectations in the
industry and continues to enable a true Internet of Manufacturing environment.
WHO BENEFITS FROM OML?
OEM MANUFACTURERS
Large manufacturing companies continuously run internal improvement projects that focus on individual
aspects of the shop-floor operation. They try to keep a balance between in-house manufacturing and services
procured from EMS companies. The key to success for OEM manufacturers is to retain competitiveness within
the operation. Internal production offers the advantage of having a vertical management and operational
structure from design through manufacturing, so that design can be optimized for the manufacturing
capability; however, manufacturing also can be setup and optimized according to the needs of the products
to be built. With a common supply-chain and engineering flow, the main variables to consider then become
planning around the growing number of products and variants that are made at each site, as well as material
flows to support all of the many changeovers required on the SMT machines as lot sizes become smaller.
Three key goals for an OEM manufacturing business are productivity, material turns, and quality management
to protect the brand. The management and improvement of each of these metrics are driven by collection of
data from the shop-floor. The current production status of completions, as well as measured performance
statistics, has to be known so that upcoming production jobs can be planned for, modeled, and scheduled
effectively.
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The current practice of pushing materials out from the warehouse to the shop-floor as full kits for the series of
upcoming work-orders on each line becomes unmanageable in high-mix environments. A pull system based
on actual materials consumption and spoilage can reduce the investment in needless bloated stock on the
shop-floor and in the warehouse. Accurate visibility of inventory by ERP eliminates internal shortages, which
means buffer stocks can be further reduced. Active quality management is driven by the immediate visibility
of test performance and repair issues. These three initiatives are all driven by information. Some of this
information is used in parallel by common productivity analysis and material management as well as quality
control, with data overlapping between these different uses.
Information traditionally has been gathered haphazardly, using different standards, protocols, and
methodologies, which causes delays and a significant unwelcome workload for data and production
operators. The use of OML provides the opportunity to gather all such data and convert it into a single
standard, which can be exchanged between production, engineering, and IT “big data” systems with ease,
providing the opportunity for enhanced control and management of the production operation as well as
performance enhancement.
EMS MANUFACTURERS
The perspective for electronic manufacturing services (EMS) companies is a little different. Their essential
priority is cost-effectiveness, running the production lines for customers’ products with as little cost and risk
as possible. The focus is online level performance rather than site-level because there are no crossovers
between products made for different customers. EMS manufacturers want to avoid needless costs for the
single product being produced or for the small and limited number of products that are made on each
production line. The productivity and capability of the line’s SMT program efficiency, line balance, testing
time, and the first-pass yield are all important metrics.
As SMT and related machines have grown more complex over recent years, the time when an operator could
just look at a machine or line and see whether there is inefficiency have long since passed. Different elements
within machines now work together simultaneously, with different modules, heads, and lanes. Any issue with
individual operations can result in a “chaos theory” effect to the rest of the machine or line. Advanced
computerized solutions are needed so that inspection machines can be used to assess the performance of the
assembly operation, highlighting the need for process adjustment that would improve the reliability of the
operation.
The solutions that are important to EMS companies are those that have a significant effect on first-pass yield
and raw productivity of the lines. These solutions are often provided by different machines from different
suppliers, each with different communication capabilities. Using the OML standard allows all of the machines
to share a common communication backbone and language so that advanced computerized solutions can be
realized by each line and deployed across the entire factory. OML enables EMS companies to manage and
control optimized production lines for their customers, and by so doing, provide a direct measurement of
production cost, which in turn helps to improve EMS business strategies.
MACHINE VENDORS
A third perspective is from the machine vendors. For many years, customers aware of the data that could be
obtained from automated production processes have been demanding that machine vendors release more
ways to make relevant data available. The machines from different vendors have their own platforms, all of
which have different specialist technology that has driven different ways of communication. On the
information consumer side also, customers of these machines have requested that different kinds of
information be provided in different ways. This has put a significant strain on the machine vendors to provide,
not only information, but also the first steps toward solutions.
In many cases, the solutions have benefited those vendors who made partnerships, such as between
inspection machine vendors and placement machine vendors, that excluded other vendors. The OML
standard allows all vendors to produce data and solutions based on a single common data format, bringing
the opportunity for customers’ requests to be satisfied with the minimum amount of work, cost, and time.
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HOW OML FITS INTO A MODERN FACTORY
The OML Internet of Manufacturing standard defines the different types and content of data, and it provides
the common backbone infrastructure for communication. The extent to which OML can be applied in a
factory spans from even the lowliest of processes on the shop-floor to the largest enterprise IT systems and
production support infrastructures. OML simplifies the integration of IT systems with factory equipment and
processes, allowing the use of a rich variety of reliable, real-time data. This removes a critical barrier—the
expense of development and support to create the multitude of interfaces required for each of the enterprise
systems.
A key attribute of OML is the ability not only to collect and exchange data between processes and systems,
but also to allow control of processes and even entire lines through commands from computerized systems.
OML allows the shop-floor to be automatically controlled and “fine-tuned” to react quickly to sudden
changes, while maintaining the highest levels of productivity and quality. Manufacturing data from one site
can then be exported through the cloud and combined with data from other sites to provide a continuous
health check on global manufacturing.
For the developers of software solutions and system integration, OML provides key advantages, while
minimizing risks to the operation. Offline development or simulation of new application code is possible in
advance of deployment. Any new production process that creates OML data, or any new consumer of OML
data, can be developed and tested against the known standard, so that all issues can be resolved reliably in
advance before joining the newly developed module to the main backbone. For example, deployment lead-
time and operational downtime would be reduced when new automation is added to the factory.
As well as the addition of simple processes, complex uses of data can be streamlined with the OML standard.
Where there are many individual uses of the same manufacturing process data, the use of OML avoids
conflicts. For example, certain pieces of information may be normalized in different ways or even be excluded
according to the needs of the first application each time a new application or use of the data is added, which
potentially affects all existing applications and systems, causing unexpected system issues and failures.
OML provdes a common data language between all systems, avoiding the need for changes and reducing the
risk of these post-development integration side effects. It also makes sure that every user of the data sees the
exact same view of the data, all normalized in the same way. This enables different areas of production and
support operations to work together with a common view of any issues or requirements that may arise,
avoiding operational conflict. The OML standard also allows support for the protection of sensitive data, such
as customer- or business-specific data elements that should not be openly available.
THE BUILDING BLOCKS OF OML
TECHNOLOGY CHOICES
Many technology and design choices need to be considered when developing modern software systems,
including a huge range of programming languages, frameworks, databases, data formats, and communication
standards. As we enter the age of the Internet of Things (IoT), there is an increased focus and healthy debate
regarding how these choices affect IoT.
It is sometimes natural to make technology or design choices based mainly on recent market trends, company
preferences, or other local factors. Although making choices like this may be simpler, it is not always a good
long-term approach. Deciding on the initial development choices for OML was difficult, but the process was
made easier by using the following five criteria.
Meet Requirements—The technology has to meet the technical requirements. In particular, performance and
reliability requirements are paramount, but also factors such as cross-platform support.
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Open Support—The technology must be inclusive to individuals or companies with a wide range of
backgrounds, across the global manufacturing and software community. The technology needs to have
complete support and avoid dependency on specific expert knowledge, environments, or immature libraries.
It also avoids favoring specific platforms, companies, or hardware.
Factual Comparisons—All technology, whether new or old, must be compared based on the facts and data
available today. A newer technology might clearly provide benefits, but if unproven in real-world conditions, it
would add considerable risk.
Domain—The primary domain of OML is the factory shop-floor. The chosen technology must be a good fit for
meeting the needs of applications, equipment, and hardware within this domain.
Flexibility—Future improvements for OML cannot be predicted, but technology choices need to generally
support the evolution of the standard.
MESSAGE PROTOCOL
OML is message-based. A message is simply a parcel or packet of data exchanged across the network. Some of
the benefits of working with messages are:
• Messaging protocols can usually be clearly specified and documented, often visually using diagrams.
• Message content can be translated into other formats if needed by other systems.
• Messages can be validated in the context of sending or receiving.
• Production scenarios can be simulated, tested, or reproduced accurately by running software
components with messages.
• Messages can be stored offline for short or long periods, allowing for functionality such as reliability and
recovery to be supported.
• A clear version control and compatibility strategy can be implemented.
• Messages can be individually traced though all system components to aid troubleshooting and
debugging.
• OML messages are exchanged using a simple protocol. OML supports several communication patterns
using the protocol.
OML EVENTS
Applications can subscribe or listen to specific OML events and receive them in real-time from the factory
floor. For example, an OML event provides the current production status of equipment.
Events provide for “loosely coupled” system architectures, meaning that one part of the system is not tightly
dependant on another part. A loose coupling is generally favored because it allows the whole system to be
more flexible to change and easier to maintain.
OML events also provide reliable delivery by using an acknowledgement from applications. If an application
does not respond, OML ensures the event is not lost and is either sent again later, or in a worse case, a
recovery can be made.
OML REQUEST/RESPONSE
OML request/response messages provide OML applications with real-time control of equipment or processes
at the shop-floor. These messages are bidirectional. Control can be initiated by the OML application toward an
OML process on the shop-floor. For example, specific equipment or lines can be stopped. Control can also be
initiated from the OML shop-floor process toward an OML application. For example, the shop-floor process
can check if a specific PCB is allowed to enter specific equipment every time a PCB enters the process.
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DATA FORMATS
OML uses the JavaScript Object Notation (JSON) standard to represent each message. The use of JSON in the
software industry has rapidly increased year on year, with the format now widely used in most web-based
technology and across the Internet generally. JSON can represent the same data, using significantly less space
than XML, which means performance gains. However, like XML, JSON is still human-readable and is able to
represent complex data. JSON is easily compressed to reduce size for further efficiency. JSON is a fully open
standard, with mature future support in most major programming languages and platforms.
Simple JSON example of OML:
{
“$type” : “ItemStartedEvent”,
“header” : {
“uuid” : “4f6dfc5a-c5c0-4d72-921f-861166854541”,
“dateTime” : “2016-01-22T14:42:02.453+0000”,
“senderAddress” : “192.168.2.1:80”,
“processId” : “ProcessId”,
“version” : “1.0.0b”,
“requestId” : “4f6dfc5a-c5c0-4d72-921f-861166854541”
},
“dateTime” : “2016-01-22T14:42:02.453+0000”,
“itemId” : “123”,
“barcodeId” : “Barcode123”,
“laneId” : “1”,
“recipeId” : “A”
}
COMMUNICATION PROTOCOL
A huge variety of technology and standards is available to allow different applications to communicate or
exchange data. Some standards are designed for specific applications, such as financial systems, social media,
chat, or voice and video transmission. Higher level standards sometimes favor or enforce the use of particular
programming languages or operating systems. A lot of this technology is powerful and widely used, and
hence they were researched and trialed as potential technologies for OML. However, some popular
technologies were unable to meet all of the criteria, such as having enough open support available for
different platforms.
The protocol chosen to exchange OML messages is the Transmission Control Protocol (TCP). OML messages
are exchanged with standard network sockets. TCP is the underlying protocol of many Internet applications.
TCP is a mature, open standard with support for creating the communication sockets available across all major
programming languages and platforms. TCP also meets the low-level performance and reliability
requirements of OML.
SOFTWARE DEVELOPMENT KITS
A software development kit (SDK) enables a software developer to work more effectively with specific
platforms and development environments. SDKs are already available for OML. For example, using the .NET
platform from Microsoft, a developer using the popular Visual Studio IDE can simply reference an OML .NET
assembly, and within a few lines of programming code, immediately start to communicate with any other
OML-based applications in the factory. SDKs are also available that support the popular Maven build system
for Java. These SDKs typically provide real working sample application code and OML simulator environments.
A good SDK will allow software developers to focus their time on building the value-added logic for their
application, safe in the knowledge that the SDK is managing the OML communication layer.
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THE INS AND OUTS OF OML SOLUTIONS
OML represents a low barrier to entry for applications that require the use of real-time data acquired from
both automated machines and manual processes. Existing solutions can be enhanced and new solutions
created, for which the return on investment can be compelling. The following are some simple examples that
illustrate the scope of the usage of the OML standard.
KPI DASHBOARDS
The role of a dashboard is to bring a continuous
summary of key points about the operation into
a single simple display that can alert even the
casual observer to issues that require attention.
The measurement of effectiveness of a
dashboard is to have accurate and timely
information. Accuracy of data has historically
been a huge challenge, at least when pushed
beyond the most simple of parameters. For
example, a count of the number of PCBs passing
through each process may be an easy parameter
to measure across the whole shop-floor through
the use of sensors and then report using a
dashboard. However, without OML, it is
exceptionally difficult for the real use of data
from each of the various machines and processes to include such things as peak and average production rate,
minimum cycle time, stop events with reason and duration, production modes such as changeovers, pass and
fails, top 10 defect list, production WIP bottlenecks, first-pass yield, repair cycle counts by PCB, etc., with like-
for-like comparison of data in different formats and protocols.
At each production process location, standard OML is typically provided by a dedicated producer application.
This makes the data available continuously to any OML application that requires it (Figure 1). Development of
the web app is simple because it only needs to work with one language, OML. The scope for the content and
analysis is huge because data can be coming from literally any production process to be capable of
supporting many useful KPIs. OML producer applications can be developed for each type of process location
using the specifications of OML. The data most often used for dashboards is a record of events so that
whenever anything happens on a machine or process, it is communicated to the OML dashboard app, from
which current status and historical trends can then be reported.
POKA-YOKE CONTROL
The principle of poka-yoke control is to ensure
that processes are not allowed to operate
where it is known that the operation is likely to
result in a defective or incomplete product
(Figure 2). The reason for the OML stop
controller to prevent the process from
operating can come from several triggers, such
as the needed materials were not set up and
verified, the machine program was not
confirmed, or a trend analysis of data from
quality-focused dashboards identified a high
risk of an issue.
OML data can be used to enforce compliance of
management practices, as well as be a part of
process setup and active quality management systems.
Figure 1: Data collection with OML to create a KPI dashboard.
Figure 2: Poka-yoke execution using the bidirectional OML standard.
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SUPPLY CHAIN
Looking at the process setup stage in more detail,
OML can be used to record the events associated
with the setup of materials. The assignment of
materials to unique feeder IDs, as well as the
staging of the feeders on to the SMT machines in
the positions designated by the machine program,
can all be recorded by the OML material
verification controller by collecting all of the
appropriate OML events. After the completion of
the material setup, information about the
consumption of materials and any spoilage can be
read from the machine, then fed to ERP.
This information can be used by a factory-wide
computerization system to supply materials to the
various machines and processes when needed,
rather than pushing all materials out in advance.
The reduction in the need for advance materials is
possible through the visibility of the actual
material consumption and spoilage for each reel, automatically ensuring the accurate inventory record of
physical stock against the ERP database and eliminating unexpected internal shortages.
MATERIAL TRACEABILITY
As an extension to the previous example, the
setup confirmation of materials, plus the gathering
of material consumption data from the machines,
provides the opportunity for materials traceability.
An OML trace adapter service can collect
information into a database to create a clear
record of material allocation that has been used,
on a lot, job, or work-order basis.
Adding the reading of a unique serial number
from each PCB as it enters each process, the
information can be refined to provide more exact
traceability for each PCB. The OML trace adaptor
service can easily put together event records for
each PCB as it passes through each of the shop-
floor production processes to create a complete
product build record of materials used.
ROUTING CONTROL
The use of a unique PCB-ID when read at each
process can also be used by another OML control
for routing. A primary function is to confirm that,
as each PCB arrives at each process, the process
has been correctly set up and the process is the
correct next process for the operation of that PCB.
This prevents the omission of a process or even
the duplication of processes. The routing control
can also be used to manage repair loops so that
any PCBs that have failed a test process cannot
Figure 3: Material verification and inventory management-based
on OML.
Figure 4: OML-based material traceability.
Figure 5: Bidirectional control for routing enforcement.
OML—An Internet of Manufacturing Solution for PCB Assembly
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2-16 TECH13980
pass to the next planned operation until they have been inspected, repaired, and retested. Routing control
can use the same bidirectional capabilities as poka-yoke to enforce the routing decisions.
In addition to the control of the routing itself, OML routing can be used to monitor and report the number of
PCBs between processes, as well as record the times for which each PCB has been in any process or has been
between processes. Analysis can be perfomed on the shop-floor product flow to expose any bottlenecks,
which can be a key indicator on the OML dashboard.
CLOSED-LOOP LINE CONTROL
A final example of the many more applications for
which OML can be used is closed-loop control on a
production line. Information can be taken using
OML from an automated inspection process and can
then be analyzed by an OML closed-loop analysis
solution. For example, if an inspection was made on
each PCB by an automated visual inspection (AOI)
machine, the drift of placements made as measured
by their x and y position, as well as rotation, can be
calculated as a trend, and processed through a
6-Sigma algorithm to identify at what point the
trend is out of control such that a defect might soon
be made.
The result of the analysis could be a message on the
OML dashboard to say that attention is needed. Or, the OML interface can again be used to communicate back
to the SMT machine that has been identified as being the cause of the drift to automatically modify program
parameters and compensate for the trend, which allows production to continue without risk of defect.
CONCLUSION
These examples are merely a handful of applications of OML seen already on the PCB assembly shop-floor.
Until the public introduction of OML, they have been available only to those with a specific set of machines or
a significant installation of third-party software that provides custom machine-interface connections. OML
now offers the opportunity for any operation with a competent software development team to create
computerization systems such as those suggested by Industry 4.0 and Smart Factory 1.0. OML is the standard
behind the Internet of Manufacturing for PCB assembly production.
GET YOUR OML NOW!
The specification of the OML standard is available to anyone free of charge when registering on the OML
community website at www.OMLcommunity.com. End customers, machine vendors, and anyone with an
interest are encouraged to register as a member of the community, which, as it grows, will create more OML
resources, experiences, and ideas for the community to share.
Figure 6: Closed-loop line control using OML.