1. Single Geometric Error Measurement
Definition: Single geometric error measurement evaluates each independent geometric error of a gear separately, including profile error, cumulative pitch error, pitch deviation, tooth alignment error, and radial runout of the gear circle.
Measurement Methods:
Absolute Measurement Method: Installs the measured gear and a circular grating length sensor coaxially. During measurement, when the inductive probe contacts one tooth surface and reaches a predetermined position, the sensor sends a counting start signal. By calculating the number of electrical pulses generated by the circular grating when the probe reaches the predetermined position on the next tooth surface, the electrical pulse count equivalent to the actual pitch is obtained, which is then processed by the computer to determine pitch deviation and cumulative error.
Relative Measurement Method: Uses two inductive length sensor probes with a distance equivalent to one theoretical pitch. This distance is compared with all other actual pitches tooth by tooth. The measured differences are processed by an electronic computer to determine pitch deviation and cumulative error.
Generating Method: Simulates the theoretical involute trajectory using a base circle disk to compare with the actual profile error. Measurement tools include single-disk involute measuring instruments and universal involute measuring instruments.
Coordinate Method: Based on theoretical equations, calculates profile deviations using a grating system and computer. There are two types: rectangular coordinate method and normal development angle coordinate method. The rectangular coordinate method utilizes X and Y directional grating measurement systems to measure the coordinates (x, y) of each point on the tooth profile, suitable for measuring large gear profiles. The normal development angle coordinate method is specifically for involute tooth profiles, measuring the developed angle (ϕ) of the gear's rotation using a circular grating and the corresponding developed arc length (ρ) on the base circle using a linear grating system. The computer calculates the theoretical arc length and compares it with the actual measured value to record the profile error curve.
Profile Measurement:
Pitch Measurement:
Tooth Alignment Measurement: Detects errors in the tooth profile along the axial direction of the gear, based on the principle that a helical gear rotates one revolution, and the contact point moves one lead along the axis. Measurement methods include the lead method and the base circle helix angle method. The lead method determines the theoretical lead by adjusting the inclination angle of a sine bar. When the carriage moves axially, the sine bar drives the circular disk and the measured gear to rotate, causing the measuring head to make a theoretical helical motion relative to the gear, thereby measuring the tooth alignment error. The base circle helix angle method is an extended function of involute measuring instruments. During measurement, a measuring head with a spherical or conical tip is used, positioned at the mid-height of the tooth.
2. Comprehensive Error Measurement
Definition: Comprehensive error measurement evaluates the overall transmission accuracy of a gear by engaging the measured gear with a high-precision (at least two grades higher) measuring gear (or measuring worm) for transmission.
Measurement Methods:
Double-Flank Measurement: Uses a measuring gear to engage tightly with the measured gear on both flanks for rotation. The maximum variation in center distance over one revolution of the measured gear represents its radial comprehensive error. The measurement tool is a gear double-flank inspection instrument.
Single-Flank Measurement: Uses a measuring gear to engage with the measured gear at the nominal center distance for single-flank rotation. The angular error represents the tangential comprehensive error of the measured gear. Measurement tools include gear single-flank inspection instruments and gear single-flank overall error measuring instruments.
Applications: Comprehensive measurement is also commonly used to inspect the contact pattern and noise of gear pairs. For bevel gears, comprehensive measurement is generally the primary method, focusing on inspecting the contact pattern of the gear pair, while also measuring radial and tangential comprehensive errors and noise.
3. On-Machine Measurement
Definition: On-machine measurement integrates gear measurement devices into gear processing machines, allowing gear measurement to be performed directly on the machine. Measurement results are used to adjust and correct machine parameters in a timely manner to improve gear processing quality.
Characteristics:
High Precision and Speed: Demands high precision and speed in gear measurement.
Openness: Requires good openness of the gear measurement system for easy integration with the gear processing system, enabling automated or even intelligent gear processing and measurement.
Real-Time Feedback: On-machine measurement provides real-time feedback on error information during the processing, facilitating timely adjustment of processing parameters to enhance processing accuracy and efficiency.