Establish the first Z tool length from one repeatable physical surface. For the stated SINUMERIK 828D and ShopMill workflow, use the ground machine table, a known end gauge, and a tool in the spindle. Check the mechanical 3D probe against the same surface and gauge so that tool and probe measurements share one reference.
Separate the machine reference from the work offset
The ground table can serve as a practical measurement reference, but it is not automatically the workpiece zero or the machine datum. G54 defines a work-coordinate displacement; it should not be used as an improvised correction for an uncertain tool length. Otherwise, an error in the first tool length becomes mixed with the work offset and can explain the reported deviation of several hundredths.
A “real zero” is therefore ambiguous until its purpose is defined. For this task, define the table surface as the physical Z reference for measurement, store tool lengths consistently from that reference, and establish each workpiece zero separately with G54 or another work offset.
Establish the first tool length
- Clean the ground table, the end gauge, and the tool contact surface. Place the known end gauge on the selected table location.
- Load any suitable tool in the spindle and approach the end gauge in Z using the available tool-measurement function. Enter the known gauge height where the measurement workflow requires it. Do not derive the tool length by changing G54.
- Repeat the contact from a safe Z position. Accept the length only when repeated results are stable within the machine’s required process tolerance.
The evidence does not identify the ShopMill softkeys, measurement cycle, machine-data configuration, or the reference convention used by this specific machine builder. Do not guess those settings. If the measurement function cannot establish the value directly, obtain the machine-builder procedure before changing machine data or calibration values.
Check the 3D probe on the same reference
Place the same end gauge on the same table area and touch it with the mechanical 3D probe. Compare the indicated contact position with the reference already established using the tool and gauge. Using the same surface and gauge removes a change of physical reference from the comparison.
The cited workflow reports accuracy down to a few micrometres, but that is not a guaranteed machine specification. Confirm performance through repeated measurements; contamination, contact technique, table location, gauge condition, and probe condition can all appear as disagreement.
Verification and fault isolation
| Observation | Decision |
|---|---|
| Repeated tool contacts are stable, but G54 produces a Z error | Recheck how the work offset was established; do not compensate by altering the verified tool length. |
| Tool contacts vary on the same gauge | Clean the contact surfaces and repeat at the same table location before accepting a value. |
| Tool measurement repeats, but the 3D probe disagrees | Check the probe against the same gauge and surface; treat probe length or probe condition as unresolved until repetition confirms it. |
| No-tool probing is unavailable | Use a tool in the spindle for the initial reference workflow; the evidence confirms that the observed setup requires one. |
FAQ
How do I establish the first tool length on a SINUMERIK 828D?
Load a suitable tool, place a known end gauge on the ground table, and use the available Z tool-measurement function. Repeat the contact and keep G54 separate from the tool-length result.
Can I use the machine table as Z zero in ShopMill?
Use the ground table as a repeatable physical measurement reference. Establish the workpiece zero separately with G54 rather than treating the table reference, machine datum, and work zero as the same value.
How do I verify a mechanical 3D probe length?
Touch the same known end gauge on the same table surface used for the first tool measurement. Repeat the contact and investigate the probe or measurement setup if the comparison is not stable.