cnc machine lead screw production process quality inspection technology analysis
ball guide (including ball guide, roller guide) precision and reliability depends directly on the quality control of the production process, its inspection technology needs to cover the whole process from raw materials to finished product assembly, for the development of special testing program for the key process links:
First, raw materials and blank processing test
steel quality inspection
cnc machine lead screw commonly used materials for high-carbon chrome bearing steel (such as SUJ2), the need to test the material composition (carbon content 1.0%-1.1%, chromium content 1.3%-1.6%), using spectral analyzer to ensure that alloying elements Deviation ≤ 0.05%; ultrasonic flaw detection of internal defects, no ≥ φ 0.5mm inclusions or loose, to avoid cracks after heat treatment. After forging, the blanks should be subjected to hardness sampling (Brinell hardness HB200-250), and the hardness tester is used to take 3 points uniformly on the end face for measurement, and re-tempering is required when the deviation is more than ±10HB.
Blank size inspection
guide and slide blank length, width deviation needs to be controlled within ±0.5mm, using laser length gauge or coordinate measuring machine detection; datum flatness ≤ 0.1mm/100mm, through the flatness detector (eg, electronic level) measurement, to ensure that the subsequent machining allowance is uniformly distributed.
Second, raceway processing and accuracy testing
raceway grinding accuracy testing
raceway is the core of the ball guide with the surface, need to detect three key indicators:
dimensional accuracy: raceway diameter tolerance (usually g5 level, deviation - 0.005mm to - 0.012mm), the use of inductance micrometer with Dimensional accuracy: raceway diameter tolerance (usually g5 level - 0.005mm to - 0.012mm, using inductive micrometer with special probe, take 8 points in the circumferential direction to measure, to ensure that the diameter variation ≤ 0.002mm.
Shape accuracy: roundness of raceway ≤ 0.001mm, straightness ≤ 0.001mm/100mm, detected by roundness meter (e.g. Talyrond series) and laser interferometer, to avoid vibration during ball movement.
Surface quality: Roughness Ra ≤ 0.08μm, detected by white light interferometer scanning, no scratches (depth ≥ 0.005mm) or burn marks (oxidized layer revealed by acid washing method) are allowed.
Raceway positional accuracy testing
parallelism error of the double raceway ≤ 0.002mm/100mm, using a coordinate measuring machine to measure the amount of change in the center distance of the two raceways; the concentricity of the guideway and the slider raceway (after assembly) ≤ 0.003mm, through the mandrel with the percentage meter detection, to ensure that the ball and the raceway contact uniformity.
Third, the slider assembly and performance testing
Balls and return to the test
Ball diameter tolerance should be controlled within ±0.001mm, using sorting machine according to the size of the group (the difference between each group ≤ 0.0005mm), to ensure that the same group of ball and raceway clearance is consistent; return to the curve of the curve of the channel radius needs to be larger than the diameter of the ball 0.01- 0.02mm, by contouring the channel radius should be greater than 0.01- 0.02mm, by contouring the channel. 0.02mm, through the contour meter to detect the channel cross section, to avoid ball circulation stagnation.
Preload force and movement resistance detection
After assembly, the slider preload force should be detected (usually 1%-3% of the rated dynamic load), and the resistance of the slider movement should be measured by tensiometer, with the resistance fluctuation of no-load ≤ 5N; when applying the rated load (e.g., 500N), the resistance growth rate should be ≤ 20%, and there is no abnormal jamming, and the data of reciprocating movements should be recorded continuously for 10 times by the dynamic resistance tester. Reciprocating motion data should be recorded continuously for 10 times by dynamic resistance tester.
Comprehensive performance testing of finished products
Accuracy and rigidity testing
Positioning accuracy: Within 100mm stroke, the positioning error is ≤0.01mm by laser interferometer, and the repeat positioning error is ≤0.003mm.
Rigidity test: After applying radial load (e.g. 200N), measure the deflection of the guide rail ≤ 0.001mm, and measure it at the point of load and both ends by micrometer to ensure the uniformity of deformation.
Temperature stability: in the - 20 ℃ to 80 ℃ environmental chamber, the test slider movement resistance change rate ≤ 15%, to avoid temperature changes lead to gap abnormalities.
Life and reliability testing
adopts accelerated life testing machine, under the condition of 1.5 times the rated load running for 500 hours (about 1 million cycles), testing the wear of the raceway ≤ 0.001mm (through the profilometer to compare the data before and after the test), and there is no failure phenomenon such as ball crumbling and damage of the return device; vibration sensor to monitor the amplitude of ≤ 0.01mm / s, noise ≤ 0.01mm / s, vibration sensor to monitor the process of operation. 0.01mm/s, noise ≤ 60dB (measured by sound level meter).
Five, the main points of the application of detection technology
Combination of online and offline inspection: the raceway grinding process uses online laser calibrator to monitor the size in real time, and automatically stops when it is out of tolerance; finished product inspection uses an offline coordinate measuring machine to carry out a comprehensive accuracy assessment.
Environmental control: Precision inspection should be carried out in a constant temperature workshop (20℃±1℃) to avoid measurement errors caused by temperature changes (the coefficient of linear expansion of steel is about 11.5×10-⁶/℃, and the error is 0.0345mm in case of a temperature difference of 3℃ for a 1m-long guideway).
Data traceability: Each finished product needs to record the key inspection data (such as raceway diameter, preload force), through the two-dimensional code associated with the database, to facilitate the traceability of quality problems and process optimization.
The core of the quality inspection technology of ball guide is "micron-level precision control + full-process data closed-loop", which ensures its motion precision and life span in high-speed and heavy-duty environments through the strict inspection of each link of material, processing, and assembly, and provides a reliable guiding foundation for automation equipment.
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