A Hermle C42U with an iTNC 530 SP6 can establish the datum between two existing bores by probing both bore centers and calculating their midpoint with Q parameters. This avoids forcing a four-bore probing cycle into a two-bore setup and makes the coordinate transformation easier to verify.
Separate datum setup from rotary-axis alignment
In the reported setup, the workpiece was tilted to A=-90. Probing two Z points and aligning the C axis worked; the remaining problem was setting a datum from two pre-machined bores.
Treat these as separate operations: first establish the workpiece orientation, then measure the bore centers and calculate the required datum. Confirm from the drawing that the datum is actually the midpoint between those bores. A two-point midpoint calculation cannot establish a different design relationship without additional geometry.
Choose the two-bore method
| Method | Use | Constraint |
|---|---|---|
| Probe both bores and calculate with Q parameters | Preferred for a reusable program | Operators must understand the variables, so document each parameter and result. |
| Cycle 418 with duplicated coordinates | Temporary workaround | Enter bore 1 again as bore 3 and bore 2 again as bore 4. This uses a four-bore cycle for geometry it was not designed to represent. |
| Angle measurement and PRESET correction | Alternative when measuring in the tilted state | The evidence mentions Cycle 403 or parameter-based angle compensation, but does not provide the required cycle arguments. |
Calculate the datum with Q parameters
- Probe the center of the first finished bore and store its measured coordinates in clearly labeled Q parameters.
- Probe the center of the second finished bore and store those coordinates separately.
- Calculate the midpoint only in the axes required by the drawing:
Xdatum=(X1+X2)/2andYdatum=(Y1+Y2)/2. - Transfer the calculated result to the intended PRESET or datum mechanism. Use the machine's validated program structure; the evidence does not identify specific Q numbers or PRESET fields.
- Add comments identifying the two measured bores, coordinate values, calculated midpoint, and destination datum so another operator can audit the sequence without changing the arithmetic.
If the datum requires the line between the bores to define orientation as well as position, retain the measured angle and apply it through the validated orientation or PRESET workflow. Do not silently treat the midpoint calculation as an angular correction.
Diagnose the apparent second coordinate system
The observed symptom was a change in displayed axis values when manual 3D-ROT was switched between ACTIVE and INACTIVE, even with the displayed angles entered as zero. That establishes that the two states were not coordinate-equivalent; it does not by itself prove a hardware fault.
A kinematic or swivel-geometry error was proposed as one possible cause. The cited service approach includes checking X, Y, Z, A, and C geometry, remeasuring the machine's 3D rotation behavior, and adapting kinematics in the PLC around MP 7530.0 and following entries. Treat this as service-level work, not an operator-side parameter change, because the evidence supplies neither the machine data nor the calibration procedure.
Escalate to qualified Hermle service or trained maintenance personnel if the coordinate jump remains after the active datum and transformation states are restored. Kinematics should also be reverified after head removal or replacement of mechanical locating components because reassembly can change the machine geometry.
Verify before machining the four bores
- Return to a known datum and transformation state, then confirm which PRESET is active.
- With the intended tilted setup active, re-probe both bore centers and compare the calculated midpoint with the drawing requirement.
- Toggle manual 3D-ROT only as a diagnostic check. At zero entered angles, record any coordinate-value change rather than compensating for it inside the workpiece program.
- Repeat the measurement sequence and confirm that the same datum is produced within the process tolerance defined for the job.
- Perform a safe position check over all four bores before boring. Stop and investigate if the measured centers, calculated datum, or transformation state is inconsistent.
FAQ
How do I set an iTNC 530 datum from two bores?
Probe both bore centers, store their coordinates in labeled Q parameters, and calculate Xdatum=(X1+X2)/2 and Ydatum=(Y1+Y2)/2. Use that result only if the drawing defines the midpoint as the datum.
Can Cycle 418 be used with only two bores?
A reported workaround duplicates bore 1 as bore 3 and bore 2 as bore 4. Use this only as a temporary method; a documented Q-parameter midpoint calculation represents the two-bore geometry more clearly.
Why do axis values change when iTNC 530 3D-ROT is toggled?
A change between ACTIVE and INACTIVE at zero entered angles shows that the coordinate states are not equivalent. Verify the active PRESET and transformations first; if the change persists, have qualified personnel check the C42U swivel geometry and kinematics.
