If you walk into the front office of a typical SME manufacturing business, the conversation usually revolves around the ERP. In the boardroom, the ERP is the system of record. It handles the invoices, the purchase orders, and the high-level financial health of the company.
However, if you walk out onto the shop floor at 10:30 on a Tuesday morning, the ERP is often nowhere to be seen. Instead, you see supervisors leaning over paper job cards, planners looking at custom spreadsheets, and operators checking whiteboards.
There is a fundamental disconnect in many UK factories between the systems used to plan the business and the tools used to run the shift. To fix this, we need to be clear about the roles of ERP, MRP, and MES. They are not interchangeable, and using one to do the job of another is a common cause of shop floor friction.
The ERP: The business perspective
Enterprise Resource Planning (ERP) is, at its heart, a financial tool. It is designed to track “the what” and “the how much.” It tells you that you have an order for 500 components, what you charged for them, and when they are due to be shipped.
The ERP is excellent for the Managing Director and the Finance Manager. It keeps the books clean and manages the high-level relationship between the business and its customers. But an ERP is not a shop floor tool. It operates in days and weeks, whereas a production shift operates in minutes and hours.
The MRP: The planning perspective
Material Requirements Planning (MRP) is the engine that sits behind the schedule. Its job is to calculate “the when” and “the with what.” It looks at your Bill of Materials (BOM), checks your current stock levels, and tells you when you need to order material or start a sub-assembly to hit a delivery date.
For a Production Planner, the MRP is essential. It prevents the nightmare scenario of a CNC machine sitting idle because a £2 fastener hasn’t arrived. However, MRP is a “perfect world” calculator. It assumes that if the plan says a job takes four hours, it will take four hours. It doesn’t know that Machine 3 has a coolant leak or that an operator called in sick this morning.
The MES: The shop floor reality
This is where the Manufacturing Execution System (MES) comes in. If the ERP and MRP tell you what should happen, the MES shows you what is happening right now.
A MES tracks the pulse of the factory. It records exactly when a job starts, which operator is running it, how many parts have been scrapped, and why a machine has stopped. It bridges the gap between the office and the spindle.
In many factories, this gap is currently filled by “manual MES”, human beings walking around with clipboards, chasing status updates, and manually updating spreadsheets. This creates a lag. By the time the office knows a job is behind, the shift is already over. The cost of that delay is measured in overtime, missed delivery dates, and eroded margins.
Why you cannot “plan” your way out of a shift crisis
The reason many SME manufacturers struggle to scale is that they try to use their ERP or MRP to manage the minute-by-minute reality of the shop floor.
When a tool breaks or a customer calls with an urgent “pull-in” request, an ERP cannot tell you the immediate impact on your capacity. You end up relying on the “loudest shout” method of prioritisation.
The MES provides the data to make decisions during the shift. It allows a Works Manager to see a bottleneck forming at the deburring station at 11:00 and move a person from assembly to clear it before the afternoon dispatch. That is the difference between proactive management and reactive firefighting.
Integration, not replacement
It is a mistake to think you have to choose between these systems. A well-run factory needs all three layers to work in harmony:
1. ERP handles the order and the invoice.
2. MRP ensures the materials and dates align.
3. MES executes the work and feeds real-time data back to the office.
When these systems are disconnected, you get “islands of information.” The office thinks a job is 50% complete because that is what the schedule says, while the shop floor knows it hasn’t even started because the fixture is missing. By implementing a MES, you aren’t replacing your ERP; you are finally giving it the accurate data it needs to be useful. You stop guessing your lead times and start measuring them.
See what “running the shift” actually looks like
If you are tired of the disconnect between your office plan and your shop floor reality, it is time to look beyond the ERP.
DynamxMFG provides the real-time visibility that MRP systems lack. We help SME manufacturers in CNC machining, fabrication, and assembly to see exactly what is happening on every machine, in real-time. Stop firefighting and start managing your shift with confidence.
