The problem with traditional commissioning
In a conventional automation project, PLC software is written, tested briefly in isolation, then brought to the machine on day one of physical commissioning. That's the first time the control logic runs against real hardware — and it's almost always the first time you discover the bugs.
PLC programs are complex. A welding cell with six robots, 200 interlocks, and integrated safety logic might take weeks to debug on the floor. Engineers, mechanical fitters, and the customer are all standing idle. The daily cost of delayed commissioning — floor space, contractor time, equipment standing — often runs to five figures. And those bugs could have been caught months earlier.
The core problem: Traditional commissioning validates the software at exactly the worst moment — when the hardware is built, delivered, and everything is waiting on it to work.
What virtual commissioning actually is
Virtual commissioning is the practice of running real PLC software against a 3D simulation model of the machine — before the physical hardware exists.
The key word is "real." The PLC program is not simulated, approximated, or abstracted. It runs in the actual PLC environment (or a software emulator like Siemens PLC Sim Advanced) and communicates with the simulation model over standard industrial protocols — OPC UA, TwinCAT ADS, or PROFINET. The simulation responds exactly as the physical machine would: it moves robot axes, activates sensors, returns encoder values. From the PLC's perspective, it is talking to a real machine.
Bugs found in virtual commissioning are bugs in the real code — not artefacts of a test bench. When the physical machine arrives, the software is already validated.
How it works: the technical setup
A virtual commissioning environment has three components connected in real-time:
PLC / Software PLC
Runs the real program. Siemens TIA Portal + PLC Sim Advanced, Beckhoff TwinCAT, or B&R Automation Studio
Communication protocol
OPC UA (universal), TwinCAT ADS (Beckhoff), PLC Sim Advanced (Siemens), or shared memory
3D simulation model
Visual Components model of the machine — robots, conveyors, grippers, sensors. Acts as the physical machine for the PLC
The simulation model is built from CAD data, robot datasheets, and mechanical design drawings. All robot models from major brands (ABB, KUKA, Fanuc, Universal Robots, Yaskawa) are available in the Visual Components library of 1,000+ certified models. Custom fixtures, conveyors, and grippers are modelled parametrically or imported from STEP files.
What you can test in the virtual environment
Once the PLC and simulation are connected, the full commissioning scope can be tested virtually:
- Sequence logic: Does the control program step through the correct states in the correct order?
- Interlocks and safety logic: Do safety doors, E-stops, and light curtains trigger the correct machine responses?
- Robot reach and collision: Does every programmed position fall within the working envelope? Are there interference points between robots?
- Cycle time: Does the cell meet the target cycle time under normal conditions and under fault recovery?
- Error handling: Do all fault states resolve correctly and restart sequences safely?
- HMI logic: Do operator panel inputs trigger the correct machine responses?
Bugs are found, fixed, and retested in the virtual environment — without stopping real hardware, without waiting for mechanical fitters, without incurring on-site costs.
Virtual commissioning vs simulation alone
| Capability | 3D simulation (no PLC link) | Virtual commissioning |
|---|---|---|
| Layout and reach analysis | ✓ Full capability | ✓ Full capability |
| Cycle time estimation | ✓ From model logic | ✓ From real PLC timing |
| Tests real PLC code | ✗ Not applicable | ✓ Real program running |
| Validates interlocks and safety logic | ✗ Not applicable | ✓ Full sequence testing |
| Error state and recovery testing | ✗ Not applicable | ✓ All fault states testable |
| Finds PLC software bugs | ✗ Not applicable | ✓ Primary purpose |
| Requires PLC program to exist | ✗ Not needed | ✓ Required |
The two methods are complementary. 3D simulation without PLC integration is used earlier in the project — during design — to check layouts, verify reach, and estimate cycle times. Virtual commissioning happens later, once the PLC program exists. Both run in a single Visual Components model; the design-phase model becomes the commissioning environment when the code is ready.
When VC makes sense — and when it doesn't
The financial case depends on the cost of physical commissioning bugs versus the cost of building the virtual model:
- Strong VC candidates: Multi-robot cells with complex interlock logic. Projects with tight go-live deadlines. Machines with Siemens Safety Integrated or PILZ safety. First-of-a-type machines where the program has never run before. Sites with restricted access windows for physical commissioning.
- Borderline: Single-robot cells with simple sequence logic, short physical commissioning windows, accessible machines.
- Probably not needed: Standalone machines with no PLC integration. Systems where the program is a direct copy of a fully proven previous project.
Rule of thumb: If two days of delayed physical commissioning costs more than the VC model build, the ROI is positive. For most multi-robot cells that's true.
The SimulateFirst approach
We build the 3D Visual Components model in parallel with the PLC software development phase — so both are ready at the same time and integration testing starts before hardware delivery.
We connect to the PLC using whichever protocol matches the platform: OPC UA for platform-neutral integration, TwinCAT ADS for Beckhoff systems, PLC Sim Advanced for Siemens TIA Portal projects with no physical PLC required. All robot models from the Visual Components library are available, and custom mechanisms are modelled from your CAD.
After the virtual commissioning phase you receive: the complete 3D model, all signal mappings, a test report documenting every scenario run, and — optionally — offline robot programs ready for direct upload to the robot controller.
Need virtual commissioning on your next project?
We run VC in parallel with your PLC development phase. No delays — the model is ready when the code is ready.
