Automated Precision Assembly & Inspection Station

A complete industrial control and data pipeline: an Allen-Bradley-style PLC owns machine safety and sequencing, an Aerotech-style three axis stage handles precision positioning, a C#/WPF supervisory application orchestrates the cycle, and every part is traceable in SQL with OEE reporting.

The point of the project is the architecture, not hardware ownership. The load-bearing claim is:

Safety and sequencing live in the PLC. Precision positioning lives in the motion controller. The supervisory application coordinates and records, and it never owns safety.

Architecture

The HMI speaks genuine OPC UA over TCP to a separate process running a real fixed-period scan engine. The supervisory application cannot tell it is talking to a simulator, which is the whole point of the seam.

Safety argument

Station.Core can request a clamp, but the PLC decides. The clamp rung is:

XIC(C_ClampRequest) XIC(S_MotionPermissive) XIC(I_PartPresent) OTE(O_ClampSolenoid);

Losing the permissive drops the solenoid on the very next scan without the supervisory request changing at all. The E-stop latch is set on first scan and on any chain break, and clears only when the chain is restored and a reset is issued, so the machine is never self-starting after a power cycle. Recovering from an emergency stop forces a return to Offline and a full re-home; a recoverable fault only returns to Idle.

Layout

Station.sln
  src/
    Station.Core/      domain, StationStateMachine, CycleOrchestrator, driver interfaces
    Station.Plc/       OpcUaPlcDriver: session, subscriptions, tag map
    Station.Motion/    trapezoidal profiles, coordinated moves, simulated stage and metrology
    Station.Data/      schema.sql, seed.sql, Dapper repositories, OeeCalculator
    Station.Hmi/       WPF + MVVM dashboard (entry point)
  sim/
    SoftPlc/           scan engine + safety chain + OPC UA server
    ladder/            ladder.L5X (Studio 5000 import format, 16 rungs)
    aeroscript/        home.ascript, inspect.ascript (Automation1)
  tests/
    Station.Core.Tests/  SoftPlc.Tests/  Station.Motion.Tests/  Station.Data.Tests/
    Station.Plc.IntegrationTests/   live OPC UA session against a hosted soft PLC
    Station.EndToEnd.Tests/         full production runs across every layer

Running it

Requires the .NET 8 SDK. Nothing else needs installing: the database is SQLite and the PLC and stage are simulated.

dotnet build Station.sln
dotnet test  Station.sln

dotnet run --project sim/SoftPlc          # terminal 1: the controller
dotnet run --project src/Station.Hmi      # terminal 2: the supervisory application

The soft PLC console is interactive when attached to a terminal:

key	action
e	toggle the emergency stop
l	toggle the light curtain
g	toggle the guard door
r	safety reset
s / x	cycle start / stop pushbuttons

The HMI connects automatically on start. Pick an operator and recipe, set a part count, press Start, then break the light curtain from the PLC console and watch motion halt, the permissive lamp drop and the station latch out.

Verifying the data

SELECT c.PartSerial, c.CycleTimeMs, c.Passed, m.FeatureName,
       m.CommandedX, m.ActualX, m.FollowingErrorMm, m.MeasuredMm, m.NominalMm
FROM   Cycles c JOIN Measurements m ON m.CycleId = c.CycleId
ORDER BY c.CompletedAt DESC;

Measurements stores commanded and actual stage position, which is what makes the position accuracy figure real rather than decorative.

OEE is the genuine three factor product computed in OeeCalculator from StateHistory and Cycles: Availability (run time / planned time) x Performance (ideal cycle time x count / run time) x Quality (good / total). Time in Offline is excluded from planned production; time in Faulted and EmergencyStopped counts as downtime.