MES flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ISA-95 Level 3

The manufacturing operations management layer that includes MES functions such as scheduling, dispatching, execution, quality, and inventory tracking, sitting between ERP at Level 4 and control systems at Levels 0-2.

MES versus ERP

ERP plans orders, costs, and materials at the business level; MES receives released orders, dispatches work, records actual consumption and yield, and confirms results back to ERP.

Work order release flow

ERP releases a work order to MES, which converts it into sequenced operations, dispatches them to work centers and resources, captures execution events, and confirms completion back to ERP.

Takt time

Available production time divided by customer demand. It sets the required pace of production, and line balancing assigns tasks so no station's cycle time exceeds takt.

Critical ratio

(Due date minus current date) divided by remaining processing time. A value below 1 means the job is behind schedule; lower values indicate greater urgency.

Little's Law

Throughput equals work in process divided by cycle time. At constant throughput, reducing WIP proportionally shortens cycle time, which is the basis for pull and kanban design.

Schedule adherence

Orders completed on time divided by orders scheduled, multiplied by 100. It measures execution performance against the plan rather than the quality of the plan itself.

Cp and Cpk

Cp = (USL - LSL) / (6 sigma) measures potential capability. Cpk = min[(USL - mean), (mean - LSL)] / (3 sigma) penalizes processes that are off-center.

Nelson control chart rules

Signals of special-cause variation include one point beyond 3 sigma, two of three points beyond 2 sigma on the same side, and eight consecutive points on one side of the mean.

Nonconformance disposition

An authorized decision on nonconforming material: use-as-is, rework, scrap, or return to supplier. Systemic causes trigger a CAPA; MES holds block movement until disposition is recorded.

Rolled throughput yield

The product of first pass yield at each process step. It estimates the probability that a unit passes every step without rework or scrap, exposing hidden factory losses.

FEFO versus FIFO

FIFO issues the oldest stock first by receipt date. FEFO issues stock with the earliest expiration date first and is mandatory for perishable or shelf-life-controlled materials.

Genealogy in MES

The as-built record of parent-child material relationships, linking finished goods to components, lots, equipment, and operators so recalls can trace forward and backward.

Backflush consumption

Automatic component consumption based on BOM quantity when an operation completes. It reduces transactions but hides scrap and mis-consumption unless reconciled against actual usage.

Cycle counting

Counting a subset of inventory on a rotating schedule rather than a full physical inventory, targeting high-value or high-movement items more frequently to maintain accuracy.

OEE formula

Overall Equipment Effectiveness = Availability x Performance x Quality. Availability = run time / planned production time; Performance = (ideal cycle time x count) / run time; Quality = good count / total count.

Six big losses

Breakdowns, setup and adjustments, minor stops, reduced speed, process defects, and startup rejects. Each maps to availability, performance, or quality loss in the OEE waterfall.

MTBF and MTTR

Mean time between failures = operating time / number of failures. Mean time to repair = repair time / number of repairs. Availability from these equals MTBF / (MTBF + MTTR).

Predictive maintenance

Condition-based maintenance triggered by measured indicators such as vibration, thermography, or oil analysis, rather than by calendar intervals or usage counts as in preventive maintenance.

OPC UA

An interoperability standard for plant-floor data exchange that provides an information model, security, and TCP-based transport, commonly used to connect MES and SCADA to equipment.

ISA-95 B2MML

An XML schema implementing ISA-95 message definitions for exchanging schedules, work orders, material confirmations, and related transactions between ERP and MES.

Idempotent interface

An interface designed so that retrying the same message does not create duplicate transactions. Essential for reliable ERP-to-MES integration where network retries are expected.

Time synchronization

Aligning clocks across PLCs, MES servers, and historians using NTP or PTP so that events are ordered correctly in audit trails, genealogy, and downtime analysis.

Configuration over customization

Using configurable workflows and master data instead of custom code. This keeps upgrades feasible, bounds validation scope, and reduces long-term maintenance cost.

MES environment promotion

A controlled path from development to test/validation to production, with documented migration of configuration and master data and approval at each gate.

Role-based access control

Assigning permissions by job role, separating configuration, production execution, and quality disposition duties so no single user can both execute and approve critical records.

21 CFR Part 11

FDA regulation for electronic records and signatures in regulated records, requiring audit trails, access control, signature integrity, and signatures linked to their records.

ALCOA+ data integrity

Records must be attributable, legible, contemporaneous, original, and accurate, plus complete, consistent, enduring, and available. The framework for GMP data integrity assessment.

GAMP 5 software categories

Category 3 covers configurable standard software, category 4 covers configured products, and category 5 covers custom code. Validation effort scales with category and risk.

Validation lifecycle

URS, risk assessment, installation qualification, operational qualification, performance qualification, traceability matrix, validation summary report, and periodic review after release.

OEE waterfall

A decomposition of losses from planned production time to run time to net run time to fully productive time, showing availability, performance, and quality losses separately.

Pareto analysis

Ranking downtime or defect causes by frequency or impact to identify the few causes responsible for most loss, prioritizing improvement work where it yields the greatest return.