Jim Connett, on August 06, 2024, 09:05 AM
MES Modeling: Monolithic or Modular Flows?
One could argue that the most important model to develop, control, and protect is the process flow. A well-defined process flow is a key component of an MES and – in the end – is critical to financial success. Flows ensure the material is processed on the correct tools as it transforms from raw material to sellable units. Without a process flow, the benefit of an MES could be in question.
A process flow is generally defined as:
(…) a list of one-to-many steps sequentially organized in a logical order so that a material assigned to that flow will exit the flow with the intended result. A flow can be defined to represent a logical area, a process sequence, or a general action.
Process flows are also called routes or sequences or – in some cases (like in this article), just flows. We’ve already detailed the importance of process flows, so let’s address a rather common question regarding the implementation of process flows: As flows are created, what is a better end-goal: a single monolithic process flow with hundreds of steps or a modular approach where smaller modular flows are chained together (a flow of flows)?
The Monolithic View
Monolithic flows represent a single flow containing all required steps in a sequential order such that the completion of the final step in the process flow will result in a finished product or component. When process flows are initially modeled in an MES, the natural tendency exists to create monolithic flows. This tendency may be fueled by equal parts logic and convenience. A company’s MES may not be able to configure flows of flows (we’ll discuss this later), so monolithic flows may be the only option. A company’s processes may be limited such that a monolithic flow is most appealing. Regardless of the reason, monolithic flows are prolific in today’s MESs.
Here are a few benefits realized when using monolithic flows:
- More manageable across a small number of products, especially if process capabilities and context information feed into the step context to allow for runtime customization of the material being made
- Easier to audit for problems because monolithic flows quickly become “known” through their use and application
- More streamlined implementation processes (especially early on in an MES implementation)
- Easier to implement in high-volume, low-product mix settings
Here are a few concerns that may exist with this approach:
- Potential adverse impact of small changes to accommodate evolving product definitions and differences that invite risk and complexity
- Difficult to define, implement, and/or monitor meaningful KPIs because, logically and functionally, a monolithic flow is one large series of processes
The Modular View
The modular flow approach is common in high-product-mix manufacturing. This methodology breaks the overall process flow into “modules” that represent smaller parts of the process flow. These smaller parts are chained together to represent the product's entire process flow – essentially, a flow of flows.
Some of the benefits of this approach are:
- Natural KPI points are created where one smaller flow stops and another smaller flow begins. For example: “On average, process flow A for product XYZ takes this many minutes, whereas process B flow, the next process flow for the product, takes this many minutes”
- Provides logical data collection and aggregation points
- Allow for easier-to-understand blocks that can be used more widely to evaluate costing, raw material usage, cycle times, etc.
- Makes process flows reusable for repetitive steps and sequences
The modular approach is not without its drawbacks:
- Changes made to a widely used module (a module that is used across many product lines) could have unintended impacts on a broad array of diverse products or sub-products
- Off-flow processes could be impacted, specifically in systems where automated route and step assignments occur at the start or end of these off-flow sequences
- Managing modules in a process flow can be a tedious and time-consuming task
It’s worth noting that the way a process is modeled is NOT an either-or proposition. It can be (and often is) a both-and implementation. It is completely reasonable to see business processes and goals calling for a hybrid approach where some processes/products are modeled monolithically (one process flow representing all steps for the product) while others are more modular (smaller defined process flows containing process steps, and these process flows are linked together to form the product’s flow).
Selecting the Best MES Modeling Approach
After a cursory evaluation of some of the benefits and pitfalls of each approach, the answer to the question posed at the beginning is, oddly enough, YES. The path forward really comes down to how much effort can be given to manage process flows as a company’s product portfolio grows and investments are made into the tools necessary to manage the MES model. Secondarily, the MES must support modular flow chaining, otherwise, the only option is a monolithic approach (although, there are some ways we at SYSTEMA can help navigate around these constraints).
Committing to Effective MES Modeling Strategies
Well-defined and manageable flows are a critical component to the performance of the MES and the end product being produced. Both approaches above are separate methods to accomplish the same targeted outcome, yet each has its benefits and drawbacks for managing the product definition and process flow. Whatever paradigm is chosen, be prepared to invest time and energy into managing and maintaining the flows. SYSTEMA has over 30 years of MES modeling experience and has seen both types of implementations work successfully. We are ready and able to help work through the benefits and challenges of each approach.
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