11 Assembly example and focused clamp fixture

Main example: discrete assembly station

Open TcForgeExample in TwinCAT/TcForge.sln. Its source folders combine block and type definitions by purpose:

• Assembly: MAIN, application IO structures, GVL_HW and FB_AssemblyStation.
• Actuators: reusable FB_CylinderAssembly plus feedback/output structures. Three instances operate the locating clamp, press and ejector.
• Inspection: photoelectric part/discharge sensors and analog pressure/height conditioning. The example scales INT terminal values to 0..10 bar and 0..20 mm.
• ClampCycle: the small FB_ReferenceMachine used for focused lifecycle tests.
• Simulation: the ADS bridge that runs the complete assembly station against the Python plant model.

Testing and Simulation use a source reference to TcForgeExample. The example owns these definitions once; no TcForgeReference project is needed. The main example uses the assembly station, not the small clamp-cycle fixture.

Assembly recipe

Step	Action	Completion evidence
1000	Home press and ejector	Both retracted
1002	Open locating clamp	Clamp retracted
3000	Wait for a part	Part sensor
3002	Locate part	Clamp advanced
3004	Press assembly	Press advanced
3006	Inspect assembly	Height between 9.5 and 10.5 mm
3008	Withdraw press	Press retracted
3010	Release part	Clamp retracted
3012	Eject finished part	Ejector advanced and part sensor clear
3014	Park ejector	Ejector retracted; return to READY

Pressure must remain between 5 and 8 bar and IO quality must be GOOD. Each recipe phase has a ten-second timeout. This is an example recipe, not a commissioned press process: it does not implement force control, a reject lane or safety-rated control. Failed inspection faults the sequence instead of silently passing or ejecting the part.

The press advance permissive requires a located part. Clamp motion requires the press retracted. Ejection requires a retracted press/clamp and clear discharge. Retracting the press/ejector remains possible during homing even when the locating clamp is not home. Directional permissives are checked in the reusable actuator assembly, including while movement is in progress.

MAIN maps GVL_HW.inputs into the station and copies its final outputs back. The structures are unlinked software channels until an application IO adapter maps physical terminals or a simulator. All quality values default UNKNOWN; no GOOD values or simulated feedback are hidden in the station. The Python ADS bridge supplies one coherent frame for all three cylinders, both photoeyes, and the pressure and height channels; the PLC executes this same station block.

Stop and Abort remove coil requests and wait for independent shutdown feedback. Reset is stationary and requires trusted shutdown and healthy inputs; it does not restart motion. Return a command to None before repeating it.

Focused clamp-cycle fixture

ClampCycle/FB_ReferenceMachine remains a small test composition for lifecycle, online-change and simulation regressions. The following contract describes that fixture, not the larger assembly recipe above.

Ownership and scan order

Call the machine once per cycle from a single task. The application owns all commands and every contained device. Do not call the contained blocks from other tasks or expose them as remote command targets. Remote ownership is a separate qualification item (A3/Q5).

1. Sample input/output/shutdown quality and map required conditions.
2. Consume a changed command value once. Return command to None before repeating that same command. lastResponse records acceptance or rejection; acceptance does not mean the movement has completed. Rejected/held commands do not queue latent motion.
3. Run the state machine, then each step exactly once, including inactive steps.
4. Run the actuator with the current feedback. Cancel motion when output policy inhibits the machine.
5. Apply the final quality/fault/output policy through both digital-output blocks, then publish physical command bits and aggregate status.

Use the top-level faulted field for same-scan supervision: it includes faults raised by the actuator after the state-machine call. The nested sequence and actuator snapshots describe their own cyclic evaluation. outputsInhibited indicates the machine output gate; output bits remain commands, not feedback.

Operation and recovery

Command	Application behavior
Home	Retract and require good IO quality plus exclusive retracted feedback; enter READY
Start	Advance, then retract, with quality and position requirements at each step; enter READY
Stop	Cancel the current move, then retract; enter STOPPED with outputs inhibited
Abort	Remove both coil commands immediately, wait for independent confirmed shutdown
Reset	Only while stopped, with good input/output quality, consistent position feedback, and independent shutdown confirmation; clear faults without starting movement

This application deliberately exposes no Pause/Proceed or auto-run behavior. Motion steps time out after six seconds; the actuator's five-second travel timer can fault first. Failed Stop escalates to Abort. Abort confirmation times out after two seconds and latches failed shutdown, following the framework's sequencing contract. Adapt those timings and the physical shutdown strategy for the machine.

Input or output quality loss removes coil commands in the detecting call and inhibits operation. Quality restoration alone cannot clear the latched running interlock or restart movement. Restore healthy IO, provide independent shutdown feedback, issue Reset, and issue a fresh Home before Start.

shutdownConfirmed must come from appropriate physical feedback, with shutdownQuality = GOOD. Never derive it solely from output command bits or the STOPPED enum. An actuator may retain stored energy with both coils off. This reference demonstrates control architecture and is not a safety-rated function. The IO adapter must report UNKNOWN/BAD on lost communication; a stale hardcoded GOOD value cannot establish physical channel health.

Simulation and validation

TwinCAT/Testing.plcproj lives at the common source root, allowing its compile entries and the example project to reference the same application files directly. The repository checker enforces those shared references.

FB_ReferenceMachine_Test runs the same application source as the example. Each scenario calls its machine once per actual PLC cycle. Simulated position inputs respond to observed final coil outputs; no library internals are injected. Scenarios cover unknown-quality startup, Home/Run, held Start, controlled Stop, trusted Abort feedback, input and output quality loss with explicit recovery, contradictory feedback, rejected Reset during motion, and a real timed failed Abort followed by rejected/accepted Reset.

Run the isolated test solution and export complete per-test results using the qualification workflow. Hardware commissioning must verify terminal mapping, channel diagnostics, real motion, shutdown feedback, and timing on the intended PLC. Local Usermode Runtime results do not close that hardware gate.