This application uses a KUKA KR16 robot and DKP 400 two-axis positioner to generate parametric laser-cladding paths in KUKA PRC. A Siemens PLC and Beckhoff I/O control a 9 kW Laserline laser and Thermach powder feeder. The central motion problem is assigning meaningful external-axis positions while keeping the deposition tool near 90 degrees to the workpiece surface.
Define the DKP 400 Axis Roles
The DKP 400 external axes accept angular positions in degrees. One axis controls tilt and the other controls rotation. Do not assume that E1 always represents tilt or that E2 always represents rotation: the mapping depends on the configured cell.
| Item | Confirmed requirement | Engineering action |
|---|---|---|
| External-axis command | Angular value in degrees | Generate an angle for each commanded DKP axis. |
| E1/E2 assignment | Setup-dependent | Match the simulation to the physical wiring and configuration by right-clicking the DKP 400 component. |
| Base calibration | Positioner-mounted work requires an offset base | Calibrate the workpiece base as an offset base, not as a normal base. |
For the stated pipe strategy, the intended behavior is to hold one positioner axis at 90 degrees while the second axis rotates as required by the toolpath. First confirm which physical axis corresponds to E1 and E2; only then assign the fixed and continuously changing degree values.
Build the Scan-to-Toolpath Workflow
The demonstrated workflow starts with a scanned part and ends with a dry-run robot program:
- Scan the worn component and save the geometry as an STL file.
- Clean and reduce the scanned mesh before importing it into Rhino.
- Locate the scanned object's coordinate system and identify the cladding area of interest.
- Simplify the geometry, then create points and lines for the desired deposition pattern.
- Use Drape and meshBooleanSplit where needed to isolate the target pipe surface.
- Generate the toolpath in Rhino and Grasshopper, configure the robot and positioner, and perform a dry run before enabling the laser or powder feed.
Use ReduceMesh to lower imported mesh complexity. Mesh reduction also makes comparisons between the scan and isolated cladding surface easier, although the evidence does not establish a required reduction ratio.
Keep the Tool Normal to the Cladding Surface
Each path orientation must be coherent with the workpiece, process direction, robot tool, and turntable coordinate system. A visually correct model outside the simulation does not prove that the simulated robot frames are aligned. If the tool fails to remain near 90 degrees to the surface, check the complete frame chain: scanned-part coordinates, offset-base calibration, DKP axis mapping, workpiece orientation, tool calibration, and the planes used to orient the path.
Surface normals directly affect commanded tool orientation. Irregular normals in scanned geometry are a supported hypothesis for unexpected wrist motion or robot A5 limit conditions. Inspect the normals along the failing path and smooth the scan if they are inconsistent. Treat smoothing as a diagnostic correction, not proof that every A5 limit originates in the mesh.
Prevent Rotation Reversal at the Degree Boundary
A calculated rotary path can reverse direction when its angular representation crosses the degree boundary. For example, moving from 355 degrees to 5 degrees may be interpreted as a 350-degree move in the negative direction, while the desired continuous motion is from 355 degrees to 365 degrees—a 10-degree forward move.
Unwrap the rotary-axis sequence before sending it to the positioner. For every new calculated angle, select the equivalent representation that preserves the intended direction and continuity relative to the preceding command. Boundary handling requires testing because the referenced implementation was tested only with the reported setup and may contain unhandled edge cases.
Verify Geometry and Motion Before Cladding
- Confirm in the DKP 400 component that simulated E1 and E2 match the physical tilt and rotation axes.
- Verify that the workpiece uses an offset-base calibration and that its simulated location matches the real fixture.
- Display or inspect path planes and surface normals; confirm that the tool axis remains near 90 degrees to the selected cladding surface.
- Plot consecutive external-axis values and inspect boundary crossings for unintended long reverse moves.
- Run the complete path as a dry cycle and check scan-to-cladding-surface alignment, DKP direction, robot A5 limits, and tool clearance.
- Enable laser and powder operation only after the dry run reproduces the intended coordinated motion.
For segmented pipe deposition—such as cladding a 30-degree arc, skipping 60 degrees, and starting another arc—retain the segments as deliberate process regions if curve joining changes the intended gaps. The evidence confirms the desired pattern but does not establish a required KUKA PRC method for combining or sequencing those curves.
FAQ
What values do KUKA PRC external axes use for a DKP 400?
The external axes use angular values in degrees. The E1 and E2 assignments are setup-dependent, so match the DKP 400 simulation component to the physical tilt and rotation axes.
Why does a DKP rotary axis move backward from 355 to 5 degrees?
The controller or generated path can interpret that transition as a 350-degree negative move. Unwrap the target to 365 degrees when the intended motion is a 10-degree forward move, then test boundary cases in simulation and a dry run.
Why does the robot hit an A5 limit during a scanned-surface path?
Inspect the scanned surface normals because inconsistent normals can command abrupt tool orientations. Reduce and smooth the mesh, then verify the path planes and rerun the simulation; other cell or frame constraints may still cause the limit.
