Siemens SINUMERIK measurement cycle configuration

Siemens SINUMERIK Measurement Cycle: A Complete Configuration Guide from Basic Parameters to Advanced Applications

In modern CNC machining, achieving high-precision and high-efficiency automated production relies on rigorous monitoring of process reliability. One of the key steps is in machine measurement. By integrating a probe system on CNC machine tools and combining it with specific functions of the CNC control system, manufacturers can automatically detect workpiece dimensions, compensate for tool wear, and even identify clamping errors during the machining process. The Measurement Cycles of Siemens SINUMERIK 840/880 series control systems provide a powerful and flexible solution to achieve this goal. This article will provide a detailed interpretation of its core concepts, parameter definitions, configuration process, and practical applications, aiming to provide engineers and technicians with a highly operational technical guide.

The core values and principles of in machine measurement

It is crucial to understand the basic logic of in machine measurement before delving into specific parameters. Its core goal is to detect unacceptable workpiece size deviations in the early stages and automatically initiate compensation measures. These deviations may be due to tool wear, thermal expansion (such as ball screws, bed frames), or workpiece clamping tolerances.

The core of SINUMERIK measurement cycle is the principle of "in machine measurement". Unlike traditional signal transfer through PLC, this system directly processes probe signals at the NC level. The process is as follows:

Start and positioning: The control system sends a movement command to the servo circuit, and the measuring head moves towards the expected measurement point at the set speed.

Signal triggering: When the measuring head contacts the surface of the workpiece, the switch signal is immediately triggered.

Latch actual values: NCK (numerical control core) latches the actual position values of each axis within microsecond level delay and stores them in the specified R parameters.

Delete remaining travel: Once the signal is processed, the system will immediately delete the 'remaining travel' and command the axis to quickly move (G00) back to the starting position.

This direct processing method ensures extremely high measurement repeatability accuracy, up to ± 1 micron, which mainly depends on the repeatability accuracy of the machine tool and measuring head, as well as the resolution of the measurement system.

Selection and parameterization of probe types

Choosing the appropriate probe is the first step towards successful measurement. The SINUMERIK system categorizes probes into three types based on their detectable directions and defines them using the R22 parameter.

Multi directional probe (3D): can be used without limitation for all tool and workpiece measurement cycles.

Bidirectional probe: can be used for measuring workpieces on lathes. On milling machines and machining centers, it is considered a unidirectional probe for use.

Unidirectional probe: can only be used for measuring workpieces on milling machines and machining centers, and has many limitations. Before use, the M19 function must be used to position the spindle at a specific angle (such as 0 °) to ensure that the measuring ball contacts in the correct direction.

In addition, the R22 parameter is used in milling machine applications to distinguish between unidirectional and multi-directional probes through specific values (such as 101). For example, if a multi-directional probe is configured, R22 should be set as the probe number (1 to 14); If it is a unidirectional probe, set it to 100+probe number.

Definition and Logic of Core Parameters

The strength of the measurement cycle lies in its highly configurable nature. The following R parameters are the foundation of each loop and must be defined correctly before use.

R10: Bias Memory Number

In workpiece measurement, R10 is used to specify which zero offset (such as G54-G57) or tool compensation memory (TOA) to automatically store the calculated difference (the difference between the set point and the actual value) after measurement.

In zero point determination mode, R10=0 indicates no automatic writing, 1-4 corresponds to G54-G57, and 5 corresponds to G58.

R11: Experience/Average Memory

Experience values are used to suppress random deviations that do not follow trends, such as system differences between different measuring devices. R11 defines the numbering of the empirical value memory. When calculating the measurement results, the system will automatically add or subtract this empirical value. In addition, R11 is also used to define the average value storage number, which is used for floating averaging the dimensional deviations of multiple processing to smooth out random errors.

R22: Probe type/number: As described in the previous section, define the physical probe used.

R23: Measurement variant: This is the "function selector" that determines which measurement task the loop specifically executes. For example, in the turning cycle L974, R23=0 represents single point measurement to determine the zero point, R23=21 represents single point measurement, R23=22 represents single point measurement with spindle reversal (to eliminate chuck eccentricity), and R23=25 represents circumferential multi-point measurement.