MES or ERP: the question comes up in every industrial company that is equipping itself, and it hides a third. The ERP runs the company: orders, purchasing, inventory, costs, invoicing. The MES (manufacturing execution system) executes manufacturing as close as possible to the shop floor; the APS (advanced planning and scheduling) and the GPAO (production management software) plan it. None of the three has as its main purpose the commitment made to a client: the promised date, the decision to take when it slips, the record of what was agreed. This guide separates the three levels, then places the fourth.
Four verbs, four families of tools. The first two often overlap, the last two almost never.
"What did we order, buy, produce, invoice?" Customer and supplier orders, inventory, master schedule, product costs, invoicing, accounting. It sees the plant through its management flows, by the day, the week or the month. It is the transactional reference of the company.
"Where does actual manufacturing stand, and how was it done?" Order release, assignment to workstations, production data collection, work in progress, lot traceability and genealogy, quality in production, equipment performance. IBM describes it as a bridge between the company's planning systems and the production operations themselves.
"What can we make, in what order, and when?" The GPAO holds bills of materials, routings, manufacturing orders and loads, often as an ERP module. The APS calculates a feasible plan at finite capacity and schedules the shop floor under constraints, in dedicated software or built into the ERP or the MES.
"Will we keep the promised date, and who must decide if it slips?" The deal seen as a commitment: contract, delivery and acceptance milestones, risks, committees, decisions, actions, workload of the teams carrying the project, margin at completion. The client follows and approves what concerns them, without seeing your costs.
The International Society of Automation's standard sorts an industrial company's systems into five levels, from process to management. According to the ISA itself, it deals first with the interface between levels 3 and 4: exactly the boundary between the MES and the ERP.
| Level | Domain | Typical systems | What is decided there |
|---|---|---|---|
| 4 | Enterprise planning and logistics | ERP; depending on the case CRM, PLM, master planning | What to produce, for which client, with which purchases and at what cost; over a horizon of days, weeks and months |
| 3 | Manufacturing operations management | MES; CMMS for maintenance; quality and shop-floor inventory; detailed scheduling | How to execute the order, on which workstation, with what traceability; over a horizon of the shift, the hour, the minute |
| 0 to 2 | Process, measurement, control and supervision | Sensors, PLCs, SCADA | Running the machine; at the second or less |
| Outside the levels | The relationship with the client and the project's suppliers | pylotik | Keeping the promised date, arbitrating a gap, recording the decision; at the pace of the week and the committee |
The GPAO and the APS sit at the hinge of levels 4 and 3: finite-capacity planning belongs to the enterprise, detailed scheduling to the shop floor, and vendors do not all draw the boundary in the same place. The last row does not belong to the standard: it says where commitment management software sits, next to the stack and not in it. It is not one more level above the ERP, it is the relationship that links the plant to those it produces for.
The last column says where the families overlap, and what depends on the vendor.
| Need | Family | pylotik | Overlap or limit |
|---|---|---|---|
| Orders, purchasing, inventory, costs | ERP | No The project contract takes over what is ordered, invoiced and paid | The GPAO is often an ERP module |
| Bills of materials, routings, manufacturing orders | GPAO, ERP | No No management of bills of materials | Some MES also manage orders and their routings |
| Feasible plan under capacity constraints | APS | No No production scheduling | Some ERPs and MES include an APS module |
| Shop-floor execution, work in progress, machine data | MES | No | PLCs and SCADA feed the MES with data |
| Lot traceability and genealogy | MES | No | A regulatory requirement in some sectors: it stays in the MES |
| Equipment maintenance | CMMS | No It holds the maintenance contract, not the asset base | See CMMS and maintenance contract |
| Deal milestones: acceptance, delivery, commissioning | Deal-based ERP, project management | Yes Contractual milestones, amendments confirmed by the client | A deal-based ERP also tracks milestones, often those of invoicing |
| Risk of delay, options, decision with the client | Rarely the center of an ERP or an MES | Yes Risks, committees, decisions and actions with history | Reports and approval loops exist at some vendors; to be checked |
| Workload of the project teams: design, methods, commissioning | ERP, PSA | Yes Workload plan, weekly time, alerts | The load of machines and operators stays with the MES and the APS |
| Subcontractors who deliver part of the deal | ERP, on the purchasing side | Yes Linked projects and watched milestones, with the Extended Project module | The ERP keeps the purchase order and its receipt |
An SME builds packaging lines to order for food-industry manufacturers. Each deal is a project: design, procurement, manufacturing, factory acceptance with the client, delivery, commissioning at their site. A subassembly falls three days behind on the shop floor.
The MES says what happened, the APS what remains possible, the ERP what it changes for management. None says, on its own, which commitment is threatened, who must decide between rescheduling, prioritizing, informing the client or proposing an amendment, and what shared record is kept of that choice. That is what pylotik holds, on the deal's milestones, risks, decisions and actions.
Nothing flows from the MES to pylotik automatically. The project manager notes the gap and carries it into the steering, as they would today in a spreadsheet, but where the client reads it and where the decision stays attached to the milestone. If the volume of deals justifies it, a connector is defined for this specific use case.
On the side of the families, the words do not mean the same thing at every vendor. The MES and the GPAO overlap widely: as a rule, the GPAO organizes and plans production, the MES follows and steers its execution, closer to real time. Some ERPs cover part of the MES, some MES include scheduling, and an APS can live alone or in a suite. This guide describes families, not products: each function is to be checked in the documentation of the tool considered. For the ERP seen from a services company, see ERP or steering software.
The ERP runs the company: orders, purchasing, inventory, costs, invoicing, at the pace of days and weeks. The MES runs the execution of manufacturing on the shop floor: orders released, workstations, production data, traceability, at the pace of the shift and the hour. In the ISA-95 standard, the first is at level 4, the second at level 3.
The two overlap. The GPAO organizes production: bills of materials, routings, manufacturing orders, loads, often in the ERP. The MES follows and steers the execution of those orders on the shop floor, with data collection and traceability. Vendors do not all place the boundary in the same spot.
At the hinge of the ERP and the MES. The APS calculates a feasible production plan at finite capacity, then schedules the shop floor under constraints. It exists as dedicated software or as a module of an ERP or an MES.
Not by default: no standard connector exists. The pylotik connectors are optional and built to clients' needs, from the Business tier. An exchange with an MES is defined for a specific use case, for example feeding the status of an order back to a deal's milestone.
For its projects, yes: product launches, new construction works, deals for principals, maintenance contracts, with the client or the internal site that orders them. For running the shop floor, no: that is the role of the MES.
Yes. Deploying an MES at an industrial client is a project, often fixed price, with its milestones, acceptances, committees and, afterwards, its maintenance contract. See steering for integrators.
Page updated on . Sources consulted on that date; what pylotik does is described from the product in service on the same date.
A demonstration on a data set that is already filled in: a fixed-price deal and its milestones, a risk shared with the client, a committee and its decision, the workload of the project teams.