I. First, clarify the accuracy standards for a qualified hole system.
The accuracy of the hole system in a 3D welding table includes three core indicators: hole diameter size accuracy, hole center distance position accuracy, and fit accuracy. The qualified standards for different specifications are unified as follows:
1. Hole Diameter Tolerance: The hole diameter tolerance for the D16 series (Φ16 hole) and D28 series (Φ28 hole) is D10 grade, and the tolerance for the matching locking pin is h7 grade, ensuring proper fit and accurate positioning without wobbling.
2. Hole Center Distance Position Error: For the D16 series (hole spacing 50mm) and D28 series (hole spacing 100mm), the center distance error between adjacent holes must be ≤ ±0.05mm. The cumulative center distance error between any two holes must be ≤ ±0.1mm/2000mm to meet the usage requirements.
3. Geometric Tolerance Requirements: The perpendicularity error of the axis of all holes to the table surface must be ≤0.05mm, ensuring that the positioning pin is perpendicular to the table surface after installation and that the positioning angle is accurate.
II. Professional Testing Methods (Precise Judgment) When professional measurement conditions are available, the following methods can be used for precise testing:
1. Coordinate Measuring Machine (CMM) Method (Recommended): Fix the welding table onto the CMM workbench. Select multiple holes at different positions on the table and measure the actual diameter of each hole, the center distance between any two holes, and the perpendicularity of the hole axis to the table. Compare the measurement results with the above standards. If all are within the tolerance range, the measurement is considered合格 (qualified). This method achieves micron-level accuracy and is the mainstream method for factory inspection.
2. Vernier Caliper + Micrometer Quick Measurement: Directly measure the diameter of multiple holes with calipers and refer to the D10 tolerance table to determine if the dimensions are合格 (qualified). Then, use calipers to measure the center distance between adjacent holes and diagonally opposite holes. After multiple measurements, take the average value and check if the deviation exceeds the allowable range of ±0.05mm.
3. Fit Test Method: Insert the matching standard locking pin into any hole. A qualified product inserts smoothly without jamming and removes easily without sticking. Simultaneously, there is no significant wobbling after the locking pin is installed, and the fit clearance is uniform, indicating that the hole diameter tolerance and hole roundness meet the requirements.
III. Simple On-Site Identification Methods (Without Professional Equipment) If professional measuring tools are unavailable, two simple methods can be used for quick judgment:
1. Interchangeability Test: Randomly select multiple positioning modules and install them onto holes at different positions on the table. If all modules can be installed smoothly and securely, without any instances of individual holes not fitting or significant wobbling after installation, it indicates that the hole system accuracy is consistent and meets the requirements.
2. Positioning Repeatability Test: Repeatedly disassemble and reassemble the same standard workpiece 10 times. After each disassembly and reassembly, use a dial indicator to measure the deviation of the workpiece's positioning reference surface. If the deviation is consistently ≤0.05mm, it indicates that the hole system positioning accuracy is qualified.
