SINUMERIK CNC Collision Simulation: Profikinematik vs Real-PRO

Overview

Collision control is the most safety-critical function in any CNC machining workflow. On Siemens SINUMERIK controls, the on-controller kinematic monitor handles real-time protection, but the off-line simulation environment determines whether collisions are caught before the part is ever loaded. Two simulation philosophies dominate the SINUMERIK CAM ecosystem: kinematic reconstruction in Proficam / Profikinematik (the "Profi"-line of CAM-simulation utilities) and NC-block-true replay in Real-PRO, often combined with ChekT-it B4 and the controller's own Virtual-NC HMI. This reference documents the architectural differences, the PFR-file workflow, retraction-plane-change monitoring, and the decision matrix an integrator should apply before commissioning a 5-axis cell.

Why Off-Line Simulation Is Not Optional

A 5-axis SINUMERIK program (e.g. SINUMERIK 840D sl with TCPC / ROT / MEAS transformations) carries more degrees of freedom than a 3-axis program. The CAM system emits a sequence of linear blocks (G1) that the controller interprets against a kinematic chain. Small rounding errors in the post-processor propagate through the inverse kinematics and can drive the tool shank into the fixture or the table trunnion. Field experience shows that the visual line of motion on the CAM screen is not a guarantee of safe motion on the real machine. Collision simulation must therefore replay the actual NC program, with the actual tool table, the actual machine zero offsets and the actual kinematic model.

Architectural Models: Profikinematik vs Real-PRO

The decisive engineering distinction is the data origin. Real-PRO sources its NV archive, cycle definitions, and machine data directly from the SINUMERIK, so the simulation is bit-equivalent to the runtime behaviour up to the limits of the kinematic solver. Profikinematik re-derives the motion from CAM-internal data; a passing Profikinematik simulation is therefore a necessary but not sufficient condition for collision-free runtime.

ChekT-it B4 and Virtual-NC Integration

The ChekT-it B4 workflow uses Virtual-NC, a Windows-hosted HMI that mirrors the SINUMERIK operator interface. Operators launch the simulation against the same program, tool table, zero offsets, and kinematic model that the real control will see. The procedure:

1. Export the active NV archive (NV-NCK, NV-PLC, NV-DRIVE, NV-COM, NV-MM) from the controller through the SINUMERIK HMI's commissioning menu or via sc; in SINUMERIK Operate.
2. Import the archive into the Virtual-NC HMI; the same user-interface dialogs are exercised, so cycle parameters and protection zones are loaded identically.
3. Run the NC program under the HMI in single-block or rapid-feed mode; observe the 3D window and the axis-actual-value trace.
4. Any collision, protection-zone violation or kinematic-limit alarm reported by Virtual-NC will be raised identically on the real control.

Because Virtual-NC consumes the same NC variables ($AA_IM[X], $VA_POS[X], $AC_BLOCKNO) as the real kernel, simulation results are deterministic across the simulation host and the controller.

PFR File Management for Profisimulation

The .PFR file is the Postprocessor-File-Runtime artefact emitted by the CAM system. It binds the CAM-internal toolpath to the post-processor configuration and the kinematic descriptor used by Profisimulation. Failure to refresh the PFR file after any of the following changes produces a simulation that is silently out of date:

• Post-processor revision (new build, new vendor release).
• Machine kinematic descriptor (e.g. head change from SWIVEL to TCARR).
• Tool-table update on the controller side.
• Controller firmware upgrade that changes the NC language dialect.
• Changes to protection-zone or software-limit settings in machine data.

Retraction Programming on Inclined Planes

Multi-axis work frequently requires the tool to retract along the tool vector from an inclined surface, change the working plane (PLANE SPATIAL, PLANE PROJECTED, PLANE EULER), and re-engage. The critical sub-second window between lift and re-engage is where most 5-axis collisions originate. Profikinematik/Proficam reaches its limits here because:

1. The CAM-internal toolpath uses a simplified representation of the rotary-axis interpolation; the actual control may add transition arcs via SOFT, BRISK, COMPCAD or spline interpolation.
2. The travel limits ($MA_SW_LIMIT_MINUS, $MA_SW_LIMIT_PLUS) and the working-area monitoring (MD20150 family) are evaluated by the SINUMERIK on the post-interpolated positions; a CAM-side check that does not honour these exactly is unsafe.
3. For swivelled heads, the vector to a stationary fixture is rotated by the kinematic transformation; the rotation is correct on the controller and may be approximated in Profisimulation.

Real-PRO, sourcing its data from the controller, inherits the same kinematic and software-limit evaluation. Travel-limit monitoring during retraction from oblique planes is therefore authoritative in Real-PRO and indicative in Profikinematik.

Data Integrity Across the CAM → Post → Control Chain

A frequent commissioning finding is that a CAM system emits a program that simulates green on Profikinematik but alarms on the first block on the machine. The root causes observed in the field are:

For the full SINUMERIK alarm catalogue and reset strategies, consult the SINUMERIK 840D sl Diagnostics Manual and the List Manual (NCK alarms/messages).

NC-Block Simulation Methodology (Recommended)

The procedure that the integrator should follow on a 5-axis cell:

1. Author in CAM. Generate the toolpath, apply the standard .KIT (cutter) and TOA (tool-offset) data, and emit the post-processed program.
2. Regenerate PFR. The CAM-side PFR is used only for visual review; it is not the input to safety-relevant simulation.
3. Export NV archive. Pull NV_NCK, NV_PLC, NV_COM, NV_DRIVE from the SINUMERIK in service mode.
4. Re-simulate in Real-PRO / Virtual-NC. Drive the post-processed program through the controller-mirror solver, with the live tool table and protection zones.
5. Run the controller dry-cycle. With DRY_RUN enabled, FEEDRATE OVERRIDE at 0 %, and the doors open, dry-run the program on the actual control. Compare the axis-trace against the Real-PRO trace.
6. Sign-off. Only after the three traces (Profikinematik, Real-PRO, dry-run) agree, and the operator has visually confirmed clearance at the slowest feed, is the program released for production.

Selection Criteria: When Each Tool Is Appropriate

Pricing vs Functional Justification

The price delta between Profikinematik and Real-PRO is substantial, often 3-5x per seat. The decision is therefore a risk-based one, not a feature-based one. A useful ratio is:

Risk-adjusted cost of a single collision > (Real-PRO licence cost + PFR/Real-PRO integration hours)

For a 5-axis cell machining turbine blades, blisks, or medical implants, a single collision typically costs more than the entire Real-PRO licence fleet. For a 3-axis jobbing shop, the Profikinematik investment is amortised quickly and the residual risk is low. The two halves of the market are therefore rational.

Commissioning Checklist

1. Verify the controller is on a firmware version supported by the Real-PRO build. Reference the SINUMERIK support portal for the current compatibility list.
2. Configure the post-processor to emit the same language dialect (ISO dialect mode 0/1/2/3) as the controller's MD20150.
3. Align the cutter table between CAM and controller, including STC (sign-of-cutter), TCO (tool-correction-orientation), and the shank geometry.
4. Establish a signed-off PFR-regeneration procedure and store the PFR in revision control.
5. Perform the three-trace sign-off (Profikinematik, Real-PRO, dry-run) on the first article of every new part-number family.
6. Document the residual collision risk for the operator; do not let marketing claim "zero collision" without qualification.

Verification Procedures After a Simulation Change

After any of post-processor update, PFR regeneration, controller firmware change, or new tool family:

1. Re-run the part in Real-PRO with the new artefacts.
2. Re-run a dry-cycle on the controller with DRY_RUN and feed-override at 0 %.
3. Compare the $AA_IM traces block-by-block; deltas larger than 1 µm require a four-eyes review before release.
4. Spot-check with a single slow-feed cut (G1 F100) on a soft material witness before releasing to the operator.

Edge Cases and Field-Proven Caveats

• Multiple kinematic chains in the same program. When the part uses both a head swivel and a table swivel in different sections, only a controller-mirror solver evaluates both chains correctly against the active $TC_CARR35[n] data.
• Non-linear kinematic descriptors. If the OEM has implemented a non-standard kinematic (MD62571 $MCS_KIN_SUPPRESS_ALARM_MASK), confirm the Real-PRO kinematic descriptor matches; otherwise the simulation will be optimistic on the linear range and pessimistic on the non-linear range.
• Compressed G-code. Programs compressed by the controller's COMPBLOCK are not the same as the original program. Replay the compressed file, not the original, when verifying production output.
• Tool-measurement cycles. CYCLE971, CYCLE972, and CYCLE982 emit motion that is not always visible in the CAM toolpath. Real-PRO replays them; Profikinematik often does not.
• Synchronised actions. Programs that use IDS=... synchronised actions or ASUP routines must be simulated with the PLC-side timers loaded into Virtual-NC; otherwise motion-coupled-with-PLC events are missed.

Comparison with Native SINUMERIK 3D Simulation

Modern SINUMERIK Operate releases ship with a built-in 3D simulation that decodes the same NC language the controller executes. For shops that do not invest in a third-party CAM-side simulation, this in-HMI simulation is the right baseline. It is, however, limited by the HMI's rendering performance and by the fact that it does not import the CAM-internal geometry (the workpiece blank, fixtures, clamps). For final sign-off on a 5-axis cell, supplement the HMI simulation with a CAM-side solver that can show the full part, fixture, and machine envelope.

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