What are the specific methods for quality verification of automobile door checking fixture?

The quality verification of automobile door inspection fixture is the key link to ensure that the inspection fixture can accurately detect the size, shape and position tolerance and assembly relationship of the door, and its performance needs to be verified from different dimensions by various methods. The following are specific quality verification methods:

A, design drawings compliance verification

Drawing check

Check whether the overall structure, positioning elements (such as locating pins and supporting blocks), clamping devices and measuring datum (such as datum plane and datum hole) of the fixture are consistent with the drawings according to the design drawings of the fixture (including 3D model and 2D engineering drawings).

Focus on verifying whether the dimension tolerance and material grade of key functional parts (such as detection pin, stop gauge and profile template) meet the design requirements (for example, the diameter tolerance of positioning pin should be controlled within ±0.01mm).

BOM list check

Check whether the parts of the checking fixture (such as standard parts, non-standard parts and identification plates) are completely matched with the bill of materials (BOM), so as to avoid missing and mispacking (such as whether the model and quantity of screws are correct).

Second, the geometric accuracy verification

Coordinate system calibration

Based on the design datum of fixture (usually consistent with the coordinate system of automobile body, such as X, Y and Z datum), the coordinate system of fixture is established by using CMM to ensure that the coordinate system error is ≤ 0.02 mm..

Key dimension measurement

Use CMM to detect the deviation between the actual size of positioning element, measuring surface and detecting hole and the theoretical value, for example:

The positioning degree of the positioning pin (such as the deviation of X and Y coordinates relative to the benchmark) shall be ≤ 0.02 mm;

The flatness of the top surface of the support block shall be ≤ 0.05mm/1000mm;

The profile of the detection surface (such as the simulated door mounting surface) shall be ≤ 0.03mm..

Verification of form and position tolerance

To verify the form and position tolerances such as parallelism (such as the parallelism between the clamping device and the positioning surface) and verticality (such as the verticality between the guide column and the reference plane) of the fixture, it is usually required to be ≤ 0.02 mm/m..

III. Functional Verification (Detection Effectiveness)

Simulated assembly test

Use standard samples (calibrated qualified doors or door simulators) for assembly test:

Check whether the door can be put into the inspection fixture smoothly and whether the positioning is reliable (no looseness or interference);

Whether the clamping device can effectively fix the door and the clamping force is moderate (avoiding deformation).

Stop gauge detection

For the key hole positions (such as hinge mounting hole and lock hole) of the car door, use the detection pins (general gauge and stop gauge) equipped with the fixture to verify:

The general gauge should be able to be inserted into the hole smoothly, and the check gauge should not be inserted (or the insertion depth should be less than ≤2mm), so as to ensure that the hole size is within the acceptable range (for example, the hole with φ 8 0.05mm, the general gauge φ8.05mm and the check gauge φ7.95mm).

Profile and clearance verification

Use the plug gauge to detect the gap between the door and the simulated surface of the fixture (such as the edge of the door frame and the simulated surface of the glass guide groove), and verify whether the fixture can reflect the actual assembly gap (if the required gap is less than or equal to 1mm, the plug gauge is judged to be qualified if it can pass 1 mm and cannot pass 0.8mm).

The section template (simulating the key section shape of the car door) is attached to the car door surface, and the maximum clearance between the template and the car door is measured by a feeler gauge, so as to verify the detection ability of the fixture for profile (such as the maximum clearance ≤0.5mm).

Auxiliary measuring tool verification

Check whether the installation position of measuring tools such as dial indicator and dial indicator on the fixture is correct, and whether the measurement repeatability error is ≤0.01mm after zeroing (the same position is measured for many times, and the deviation should be within the allowable range).

Fourth, material and process performance verification

Material verification

Check the material certificates (such as material test sheet) of the main structure of the fixture (such as cast iron and aluminum alloy) and wear-resistant parts (such as Cr12 hardened steel for locating pins) to ensure that they meet the design requirements (such as hardness reaching HRC58-62).

Check the temperature resistance and wear resistance of non-metallic parts (such as rubber support blocks) to avoid the influence of material aging on the detection accuracy.

Surface treatment verification

Check whether the surface coating (such as spray painting and chrome plating) of the fixture is uniform, without shedding, and whether the rust-proof performance is up to standard (it can be verified by salt spray test, which usually requires no rust for 48 hours).

V. Verification of Stability and Durability

Repeatability test

For the same standard sample, repeat the installation and inspection for 5-10 times, record the measurement results (such as gap value and hole position deviation) each time, calculate the standard deviation, and require the repeatability error to be ≤0.02mm (to ensure the stability of the fixture accuracy).

Fatigue test

Carry out opening, closing and plugging tests for moving parts such as clamping devices and locating pins for many times (for example, 1000 times) to check whether there is looseness, deformation or wear. After the test, the deviation of key dimensions should still be within the allowable range.

VI. Identification and Security Verification

Identification clarity

Check whether the datum marks (such as "X0, Y0, Z0"), coordinate axis direction, inspection point number, operation instructions, etc. on the fixture are clear and accurate, and conform to industry standards (such as ISO standards).

Security check

Verify whether the clamping device has anti-loosening design (such as self-locking nut), whether the movable parts (such as turnover mechanism) have safety limit, and whether the edges are chamfered (to avoid scratching the operator).

Through the above methods, the design compliance, accuracy reliability and detection effectiveness of the automobile door checking fixture can be fully verified, so as to ensure that it can accurately identify the size deviation of the automobile door and provide guarantee for the automobile assembly quality.