SINAMICS DCM 6RA80 Shear Positioning via DCC: r482 and T400

1. Application Scope

A rotary shear cutter driven by a separately excited DC motor is a standard position-synchronised load in metals converting lines. The SINAMICS DCM (6RA80) converter closes the armature and field loops natively, but the position-following loop and the cut-window logic must be added on top. Two options have historically been raised for this: an external T400 technology module, or a DCC (Drive Control Chart) program running inside the SINAMICS DCM CUD (Control Unit Deck). Only the second option is supported on the 6RA80 platform. This reference covers the wiring of connector r482 (actual position value) into a DCC chart, declaration of that input as a customer parameter, and the loop build required for a rotary shear.

2. SINAMICS DCM 6RA80 Hardware and Firmware Context

The 6RA80 chassis (catalog range 6RA8081-... through 6RA8093-...) replaces the legacy SIMOREG 6RA70 product family. Each unit contains one CUD (left, standard) and optionally a second CUD (right) for redundant control. The CUD hosts the SINAMICS firmware, the DCC runtime, the parameter image, and the encoder evaluation channels.

Confirm firmware with r0018 before commissioning any DCC chart, and validate against the SINAMICS DCM Support portal. The drive-side fault diagnostics baseline is documented in FAQ for SINAMICS DCM; 6RA80 - Fault Diagnostics (V1.4, 2018).

3. Connector Inventory Relevant to a Shear

The 6RA80 exposes connector parameters that mirror BICO sources used inside the CUD. The following are typically required for a rotary shear loop:

r482 is the canonical position source for the DCC chart. It is a 32-bit connector, normalised internally by the encoder configuration in p0400/p0410. Verify the value in r482 increments correctly with hand-cranking before any closed-loop work.

4. T400 Compatibility: Hardware and Standalone Constraints

The T400 was a plug-in technology board for the SIMOREG 6RA70 product line, mounted on the back of the basic converter and operating as a co-processor that ran IEC 61131 logic with hard real-time BICO access to drive objects. The 6RA80 / SINAMICS DCM chassis is mechanically and electronically incompatible with the T400:

• Backplane: SINAMICS DCM uses DRIVE-CLiQ-based CUD signalling; T400 was designed for the SIMOREG parallel backplane connector.
• Form factor: The T400 sub-D bracket and slot keying do not match any 6RA80 mounting location.
• Firmware support: No SINAMICS DCM firmware branch recognises the T400 option module; it does not appear in the topology editor and cannot be addressed.

The only surviving T400 variant is the SRT400 standalone subrack, which can be wired into a line externally via analogue setpoints or PROFIBUS, but it is no longer a card inserted into the DC drive itself. For any retrofit starting from a 6RA70 + T400 shear line, the migration path is to:

1. Replace the 6RA70 with a 6RA80 SINAMICS DCM.
2. Port the T400 logic into a DCC chart and load it into the CUD.
3. Keep the SRT400 only if a non-drive-resident supervisory function is still required (rare).

5. DCC Programming Model in 6RA80

DCC (Drive Control Chart) is a Siemens block-diagram environment supplied with the STARTER and Startdrive commissioning toolkits. Each block is a function from the SINAMICS DCC library; charts are compiled into the CUD and execute at a fixed cycle. The base cycle for a DCC chart on the CUD is the CUD sampling time, typically 1 ms for the position-related blocks.

Available block groups (non-exhaustive, all available in the SINAMICS DCM DCC library):

(See extended table below.)

Chart cycle time, memory footprint, and number of instances are bounded by the firmware license and the CUD revision. For a single rotary shear, a 3-block-deep nested chart is well within the budget.

6. Standard Positioning Library: What Exists and What Does Not

There is no standard SINAMICS DCM positioning function block comparable to the SINAMICS S120 basic positioner (EPOS, controlled via p2625–p2649). The S120 EPOS is implemented in firmware as part of the S120 servo object; the 6RA80 is a DC-MASTER object (DCM) without that firmware module. Therefore a rotary shear position loop must be hand-built from the DCC primitives.

The required functional blocks for a shear are:

1. Position capture: read r482 through a DI-type block.
2. Reference processing: subtract the cut reference from r482 via SUB.
3. PI regulator: error (position) -> output (speed setpoint increment).
4. Limiter: clamp the speed setpoint to a maximum delta.
5. Channel coupling: sum the DCC output into the speed setpoint channel at p1155 or p1160.
6. Cut-window detection: a comparator (WIN block) on the position error to fire the shear blade.

7. Wiring r482 to a DCC Chart

Procedure in the DCC editor inside STARTER:

1. Open the project and select the 6RA80 drive object.
2. Open the DCC chart (create one if none exists). The chart will be assigned to the CUD execution level.
3. Insert a DI-type block from the SINAMICS library (block name DI_F for a floating-point digital input or DI_I for integer).
4. Right-click on the input pin of the DI block.
5. Choose Interconnection to address.
6. Enter r482 as the source. Confirm the data type matches (DINT for typical encoder count).
7. Compile and download the chart to the CUD.

8. Declaring the DCC Input as a Customer Parameter

To make the position value tunable from the operator panel or the PLC, expose the DI block input as a customer parameter:

1. Right-click the input pin of the DI block and select Parameter declaration.
2. Assign a parameter number in the customer range, conventionally p95xx or a project-defined block.
3. Choose the display format (hex, decimal, engineering units).
4. Set the visibility to operator-visible if it must appear on the AOP30 or in the parameter list.
5. Compile, save to ROM on the CUD.

Customer parameter declarations survive a power cycle only if the chart is saved to non-volatile storage. Use Copy RAM to ROM in STARTER or set the CUD save bit (p0977 = 1) from the operator panel.

9. Step-by-Step: Building the Shear Position Loop in DCC

The procedure below produces a position-following shear chart that tracks a reference position, fires the cut pulse inside a window, and writes a clamped speed correction to the drive setpoint.

9.1 Block List

1. DI_F (block 1): source r482, declared as customer parameter p9500.
2. SUB: subtract the line reference (DI_F block 2, source p9501) from p9500 to produce the position error e_pos.
3. ABS: take the absolute value of e_pos for window detection.
4. WIN: window comparator, lower bound p9502, upper bound p9503; output TRUE inside the cut window.
5. PI: PI regulator, gain p9504, reset time p9505; input e_pos; output v_corr.
6. LIM: clamp v_corr to ±p9506.
7. AO_F (block 3): write v_corr to the speed setpoint channel sink (interconnect to p1155 or to a summing point).
8. DO: cut pulse output, driven by WIN and gated by a safety interlock.

9.2 PI Tuning Starting Points

For a DC motor shear cutter with armature time constant T_a in the 5–20 ms range and mechanical time constant T_m in the 30–150 ms range:

• Position loop gain K_p = 1 / (2 · T_m) for critically damped response.
• Integral reset time T_n = 4 · T_m to start; reduce by half if overshoot is observed.
• Speed clamp (±p9506) at 10 % of base speed as a safe starting point.

Use the STARTER trace function to capture r482, the PI output, and r500 simultaneously while tuning.

9.3 Cut-Window Logic

The WIN block should be configured as absolute inside band: output TRUE when ABS(e_pos) < p9502. A typical entry-exit window is 1–3 mechanical degrees for a slitter and 3–5 degrees for a rotary shear, depending on blade overlap geometry. The DO block that fires the cutter should additionally be interlocked with a hardware safety relay and a machine run permissive, not only the DCC output.

10. Commissioning Sequence

1. Topology check: Confirm CUD left and right (if dual) are visible in STARTER and the encoder module (SMC10/SMC20) reports online at the expected DRIVE-CLiQ port.
2. Motor data: Enter armature and field ratings; run the automatic motor identification (p1910 = 1 for static, +20 for rotating if permissible).
3. Encoder data: Configure p0400–p0431 for the position encoder; check r482 advances in the correct direction with hand rotation (positive count for positive direction per project convention).
4. DCC chart download: Compile, download to CUD, save to ROM.
5. Customer parameters: Set p9500–p9506 to safe initial values (PI gains at zero, window wide open, clamp at 5 % of base speed).
6. Open-loop test: Disable the regulator output; command a small speed setpoint; verify motor turns.
7. Close the position loop: Enable PI; step the reference; trace r482, v_corr, r500.
8. Cut-window test: Jog the line at low speed; observe the DO output transitions.
9. Production speed ramp: Increase line speed in 10 % steps; tune gains and clamp.
10. Save and back up: Copy RAM to ROM, export the project, archive the DCC chart source.

11. Verification and Diagnostics

After commissioning, validate the chart against these checks:

12. Troubleshooting Matrix

13. Engineering Notes

• Single CUD only: If the 6RA80 has only one CUD, plan for non-redundant operation. Dual CUD adds redundancy but doubles chart maintenance overhead.
• Cycle budget: Each DCC block consumes a fixed slice of the CUD cycle. A 30-block chart at 1 ms cycle is well within the SINAMICS DCM envelope; above 100 blocks, profile the chart with the trace tool.
• Security: Lock the DCC chart with a know-how protection password if the customer requires IP protection on the shear logic.
• Documentation: Export the DCC chart as PDF and store with the project. Many integrator disputes start from missing chart prints after a service visit.
• Spare chart binary: Always store the compiled chart on the engineering laptop and on the customer's server, not only on the CUD, because a CUD replacement will lose the chart until the next download.