MES and Production Tracking

What is an MES?

A Manufacturing Execution System executes the production plan at the shop-floor level. Where ERP plans what to build and when, MES manages the actual execution: releasing work orders to the floor, tracking progress against each operation, recording operator inputs, capturing quality data at process steps, and closing jobs with actual time and material usage.

The ISA-95 standard (also published as IEC 62264) defines MES as operating at Level 3 of the industrial automation hierarchy — above the control layer (PLCs, SCADA) and below business systems (ERP). In practice, the boundaries are blurry and many small shops call various combinations of work order tracking, machine monitoring and quality forms "MES."

How MES differs from ERP

ERP and MES solve different problems at different time horizons:

Many small manufacturers have ERP but no MES. They manage the gap with paper travellers, whiteboards, or spreadsheets updated after the shift. This works up to a point — but it means job costing is always estimated, not actual, and quality issues are caught at the end of a run rather than in real time.

Core MES functions

The MESA International framework (MES Functionalities and MRP to MES Data Flow) defines 11 functions of MES. The ones most relevant to small manufacturers:

• Work order management — releasing work orders to the floor, sequencing operations, tracking status.
• Labour tracking — recording actual operator time against each work order and operation.
• Material tracking — recording lot/serial numbers consumed at each step; building a production genealogy record.
• Quality management at process steps — in-process inspection forms, SPC data collection, first-article inspection records.
• Performance analysis (OEE) — calculating availability, performance and quality metrics from actual production data.
• Electronic work instructions — delivering the correct procedure, drawing revision and tooling list to the operator at the correct workstation.
• Dispatch and sequencing — showing the operator queue: what to build next, in what order.

Shop-floor data collection methods

Before selecting any software, decide how you will collect data from the floor. Each method has a different cost, accuracy profile and operator burden:

Machine monitoring for small shops

Machine monitoring — automatically capturing machine state (running, idle, faulted) and cycle counts — has become accessible for small shops through low-cost IIoT hardware. The data feeds OEE calculations and downtime reports without requiring operator input.

There are two broad approaches:

• Hardware sensor approach (machine-agnostic): A current transformer or power meter clips onto the machine's supply to detect running vs idle. Simple, works on almost any machine, does not integrate with the machine controller. Cannot distinguish part type or cycle count without additional sensors.
• Machine controller integration (OPC-UA, MTConnect, Fanuc FOCAS, Siemens DNC): Connects directly to the CNC controller or PLC to extract cycle counts, program names, tool data and alarms. More data, but requires machine compatibility and sometimes a gateway device.

For a shop with 5–20 CNC machines, a cloud-based machine monitoring service typically costs $50–$200 per machine per month plus hardware. Many vendors offer a free trial on 1–2 machines so you can validate the data quality before committing.

Paperless work instructions

Electronic work instructions (EWI) replace paper travellers and binder-bound SOPs with digital documents delivered to the workstation. Benefits: automatic revision control (operators always see the current revision), embedded images and video, mandatory sign-off before proceeding, and a digital audit trail.

For small manufacturers, EWI software ranges from purpose-built MES modules to simple tools built on SharePoint, Microsoft Teams or tablet-based PDF delivery. The right choice depends on:

• How frequently your procedures change (high change rate = stronger case for proper EWI software)
• Regulatory requirements (ISO 9001, AS9100, ITAR, FDA 21 CFR Part 11 all have document control requirements)
• Whether you need operator confirmation of each step captured as a record

Does a small shop need a full MES?

Probably not a full MES — at least not at first. A full MES implementation for a 50-person shop can run $100,000–$500,000 in software, hardware and implementation. For most small manufacturers, the right progression is:

1. Start with your ERP's shop-floor module. If you have manufacturing ERP, it almost certainly has work order tracking, labour entry and basic job costing. Use it fully before buying separate MES software.
2. Add machine monitoring if OEE data is valuable. A low-cost IIoT sensor on your bottleneck machines can deliver machine utilisation data for $100–$200/month per machine, with no ERP integration needed initially.
3. Add electronic work instructions if revision control is a problem. This can be as simple as a controlled SharePoint folder or a dedicated EWI tool — the choice depends on your compliance needs.
4. Consider a purpose-built MES only when your ERP's shop-floor module is genuinely limiting you — typically when you need real-time operator dispatch queues, complex genealogy/traceability, or multi-step in-process quality checks at scale.