How to judge whether the tuning accuracy of the self-locking tuning screw meets the requirements?
The core of judging whether the tuning accuracy of the self-locking tuning screw meets the requirements lies in three dimensions: parameter measurement, function verification and comparison standard, focusing on the matching degree between the position stability and displacement error after tuning and the preset value. It needs to be verified by combining special tools with actual working conditions to avoid deviation caused by single index judgment.
First, the basic dimension: verify the displacement accuracy by measuring tools.
The core of tuning accuracy is "deviation between actual displacement and theoretical tuning value", which needs to be directly detected by high-precision measuring tools to ensure that the displacement error is controlled within the allowable range of design.
Selection of measuring tools with adaptive accuracy: Select tools according to the tuning accuracy requirements of screws (such as 0.01mm and 0.1mm). When the accuracy requirements are high (such as aviation and precision instruments), use micrometer (accuracy 0.001mm) and digital depth gauge (accuracy 0.005 mm); Calipers (accuracy 0.02mm) can be used in ordinary scenes. When measuring, the tool should be calibrated to zero to avoid the error of the tool itself affecting the result.
Multi-point measurement, calculation of displacement deviation: after tuning, mark 3-4 evenly distributed measuring points (such as the edge of the component and the periphery of the positioning hole) on the connected part corresponding to the screw, measure the position data before and after tuning respectively, and calculate the actual displacement value of each point. For example, the design requires the tuning displacement to be 0.5 mm. If the measurement result is 0.48-0.52mm, and the deviation of each point is ≤±0.02mm, it meets the accuracy requirements. If the deviation of a certain point exceeds ±0.05mm, it needs to be re-tuned and re-measured.
Check the smoothness of thread fit: during the tuning process, when turning the screw with hands or tools, you need to feel whether the thread fit is smooth, and there is no jamming or tooth jumping. If there is obvious resistance fluctuation during rotation or slight rebound after tuning (for example, the displacement is reduced by more than 0.03mm after loosening the tool), it means that there may be collision or interference of locking structure in the thread, which will affect the stability of tuning accuracy and need to be re-tested after replacing the screw.
Second, the functional dimension: verify the locking stability after tuning.
The tuning accuracy requires not only "accurate adjustment" but also "stable locking". It is necessary to verify whether the locked position remains stable and there is no parameter drift through simulation test.
Static locking test: After tuning and locking, let it stand for 24 hours (or the time required by the design) and measure the position of the connected piece again. If the displacement change after standing is ≤0.01mm (high-precision scene) or ≤0.05mm (ordinary scene), the locking is stable; If the displacement change exceeds the allowable value, it may be that the locking structure is not fully activated (such as insufficient torque) or there is stress release in the connector, which needs to be re-tightened and re-measured.
Dynamic simulation test: For scenes with vibration and impact requirements (such as automobiles and aviation), it is necessary to simulate the actual working conditions (such as vibration frequency of 10-500Hz and impact acceleration of 10-50G) by shaking table or impact testing machine, and then measure the position deviation again after the test. For example, after the simulated engine vibration test, the displacement deviation of the screws of automobile engine parts should be ≤0.03mm, otherwise the fitting accuracy of the parts will be affected, and the tuning parameters should be re-optimized.
Third, the standard dimension: compared with the design requirements and industry norms.
Judging whether the accuracy is qualified or not should be based on clear standards, with reference to the requirements of design documents and general specifications of the industry as the core, so as to avoid subjective judgment.
Check the accuracy indexes of design documents: the design drawings or product manuals usually specify the requirements for tuning accuracy, such as "displacement error ≤±0.02mm" and "preload deviation ≤ 5%", so it is necessary to compare the actual measured data with these indexes one by one. For example, the design of the tuning screw of a precision instrument requires a pre-tightening force of 5±0.25N・m. If the actual measured value is 4.7N・m or 5.3N・m, it is beyond the deviation range and needs to be re-tuned after adjusting the torque.
Follow the general precision standards of the industry: if the design documents are not explicitly required, please refer to the industry standards, such as the precision regulations for precision screws in the mechanical industry standard GB/T 3098.1-2010 Fasteners Mechanical Properties Bolts, Screws and Studs, or the aviation field HB 6200-2018 General Specification for Self-locking Screws for Aviation. For example, the self-locking tuning screw for aviation usually requires a position deviation of ≤±0.01mm after tuning, and there is no displacement change in the environment of-50℃ to 150℃ after locking.
Fourth, auxiliary dimension: observe the actual application effect
In some scenes, whether the tuning accuracy is qualified or not can be indirectly judged by the actual functional performance of the connected parts, which is especially suitable for assembly scenes that cannot be directly measured.
Check the mating clearance of components: If screws are used to adjust the clearance of components (such as bearing end cover and gear box), the clearance value should be measured with a feeler gauge after tuning to ensure that the clearance meets the design requirements (such as 0.05-0.1mm). For example, if the measured clearance of the tuning screw of the bearing end cover is 0.12mm, which exceeds the design upper limit, it means that the tuning accuracy is insufficient, and the screw needs to be fine-tuned until the clearance reaches the standard.
Test equipment operation parameters: If screws are used to adjust equipment parameters (such as radar antenna angle and sensor position), the equipment needs to be started after tuning to check whether the core parameters are normal. For example, the tuning screw of radar antenna needs to measure the signal gain and phase error of the antenna after tuning. If the parameters are within the design allowable range (such as phase error ≤ 1), the tuning accuracy is qualified; If the parameters are abnormal, it is necessary to reversely check whether the tuning position of the screw is deviated.
To sum up, judging the tuning accuracy of the self-locking tuning screw needs the combination of "measured data+functional verification+standard comparison", and the qualification of a single dimension does not mean the overall standard, especially in high-precision application scenarios, multi-dimensional cross-validation is needed to ensure that it not only meets the requirements of displacement accuracy, but also remains stable in actual working conditions, so as to avoid equipment failure caused by insufficient accuracy.
