Introduce in detail: the processing flow of automobile door checking fixture.

Automobile door checking fixture is a special testing tool for testing the dimensional accuracy, contour matching and assembly relationship of doors (including door inner panel, outer panel and assembly parts), and its processing flow needs to be carried out strictly around the three core objectives of "accuracy control", "daum consistency" and "functional integrity". The following is a detailed description of the processing flow:

I. Pre-preparation: data and scheme confirmation

Before the formal processing, it is necessary to complete the design data transformation and process plan planning to ensure the accurate direction of subsequent processing:

Data reception and analysis

Receive 3D models (such as CATIA and UG formats), 2D engineering drawings (including GD&T tolerance labeling) and inspection requirements (such as key contrl points: matching gap between door and side wall, door lock installation hole position, straightness of glass guide rail, etc.) provided by customers.

Analyze the structural characteristics of the car door: distinguish stamping parts (outer panel outline), welding assembly (inner panel+stiffener) and assembly parts (including hinges, locks and other accessories), and make clear the detection range to be covered by the fixture (such as outer panel profile, inner panel hole position and assembly assembly surface).

Checking fixture design and review

3D design of checking fixture based on 3D model;

Determine the positioning standard (which is consistent with the fixture positioning in the production of the car door, usually 3 positioning points+2 auxiliary support points, such as the process hole of the inner panel and the flanging surface of the outer panel);

Design measuring components (such as locating pin for detecting hole position, profiling block for detecting contour, plug gauge groove for detecting clearance) and clamping devices (quick clamping and magnetic attraction devices to ensure the stable placement of doors);

Plan the base structure (it needs to bear the weight of the door, usually frame-type, giving consideration to rigidity and lightweight).

Organize design review: confirm the consistency of benchmark, the integrity of inspection points and the convenience of operation (such as whether there is enough space for manual loading and unloading of doors) in conjunction with customers and process departments.

Process scheme formulation

Output the Inspection Tool Processing Card, and specify the materials of each component (such as cast iron HT300 for the base, aluminum alloy 6061-T6 for the profiling block, and quenching the locating pin with 40Cr), processing equipment (high-precision machining center, coordinate grinder, etc.), accuracy requirements (such as tolerance of profiling surface ≤0.03mm, positioning hole position ≤0.01mm) and detection methods.

Second, parts processing: high-precision manufacturing of parts.

The door inspection tool is composed of multiple functional components (base, positioning component, measuring component, clamping device, etc.), and it needs to be manufactured step by step according to the principle of "high-precision machining of core components first":

1. Processing of base (bearing and reference carrier)

Material pretreatment: cast iron HT300 or welded steel structure (Q235 steel plate after welding aging treatment) is selected, and artificial aging (200℃×8h) is carried out before rough machining to eliminate internal stress and prevent deformation.

Rough machining: milling the bottom surface and top surface of the base with a gantry milling machine (5-10mm finishing allowance is reserved), drilling and tapping (used to install the threaded hole of the positioning component).

Finishing: finish milling the top surface (flatness ≤0.02mm/m) with a high-precision gantry machining center (positioning accuracy ≤0.005mm) in a constant temperature workshop (20 2℃) as the overall installation benchmark of the fixture; Milling the installation groove of positioning assembly (tolerance ±0.01mm).

2. Positioning component processing (core functional parts)

The locating component includes locating pin, supporting block and profiling locating surface, which directly determines the placement accuracy of the car door and requires the highest precision machining:

Positioning pin:

Material: 40Cr steel is quenched locally (positioning section HRC50-55) after quenching and tempering (HRC28-32), or cemented carbide (tungsten steel) is selected to improve wear resistance.

Machining: rough turning by CNC lathe → heat treatment → fine grinding of excircle by coordinate grinder (roundness ≤0.001mm, diameter tolerance+/-0.002 mm) → chamfering of the top end of wire cut machining pin (to avoid scratching the door).

Copying locating block (matching door inner panel/outer panel profile):

Material: 6061-T6 aluminum alloy (lightweight) or 45 steel (high strength), the surface is anodized (aluminum alloy) or chrome plated (steel).

Processing:

Rough milling: the blank allowance is removed, and the finishing allowance of 0.5mm is reserved;

3D scanning calibration: the 3D model of the car door is imported into the machining center, and the workpiece coordinate system is calibrated by the probe;

High-speed finish milling: use ball-end milling cutter (diameter Φ 6-Φ 10mm) to carry out five-axis linkage machining, so as to ensure the fit (gap ≤0.02mm) between the copying surface and the door model and the surface roughness Ra ≤ 1.6μ m;

Local dressing: for details such as car door flanging and hole position, use coordinate boring machine to process positioning holes (position ≤0.01mm).

3. Processing of measuring components (testing tool installation carrier)

Measuring datum block: the datum plane used for mounting dial indicator and stop gauge, which is ground after quenching with 40Cr (flatness ≤0.005mm, parallelism ≤0.01mm).

Gap detection groove: the groove for detecting the matching gap between the door and the side wall is machined by wire cutting (the width tolerance is ±0.01mm, and the depth is consistent with the standard gap, such as 3 mm 0.05 mm).

Guide sleeve (used for detecting hole position): brass or POM material is used, and the inner hole is machined by coordinate grinder (tolerance is matched with stop gauge, such as H7/g6) to avoid wearing the door hole wall.

4. Auxiliary parts processing

Clamping device: the mounting seat of quick clamp (outsourced standard parts) is made of aluminum alloy, and the clamping block contacting with the car door is made of rubber or POM (scratch-proof).

Identification parts: the inspection point number plate and the reference mark are machined by laser engraving (acrylic material) and pasted on the corresponding positions of the inspection fixture.

Third, assembly and debugging: integrate components and verify functions.

After all parts are processed, it is necessary to ensure that the overall accuracy and detection function of the fixture meet the standard through precise assembly and multiple rounds of debugging:

1. Parts cleaning and pretreatment

All metal parts are cleaned by ultrasonic wave to remove processing oil stains, aluminum alloy parts are anodized (thickness 10-15μm), and steel parts are coated with antirust oil; Wipe the key parts such as locating pins and datum planes with anhydrous ethanol to avoid impurities from affecting the assembly accuracy.

2. Benchmark Calibration and Assembly

Leveling of the base: place the base on the marble platform, level it with a level (accuracy 0.02mm/m), and fix it by adjusting bolts at the bottom (ensure that the levelness of the top surface is ≤0.01mm/m).

Positioning component installation:

Based on the top surface of the base, use CMM to calibrate the position of the locating pin and the supporting block (coordinate deviation ≤0.005mm), and fasten them by bolts (torque is in accordance with specifications, such as M10 bolt 30-35 nm);

After installation, check the verticality (such as the verticality of the positioning pin ≤0.005mm/100mm) and flatness (the top surface of the supporting block ≤0.01mm) of the positioning component again.

Installation of measuring assembly and clamping device: fix the position according to 3D design, ensure that the distance tolerance between measuring datum and positioning datum is ≤0.01mm, and the door will not shake (clearance ≤0.03mm) after the clamping device is closed.

3. Function debugging and accuracy verification

Trial assembly of standard sample: use the "qualified door sample" provided by customers (which has reached the standard after CMM testing) for trial release and inspection:

Whether the positioning is smooth (no jamming);

Fit of copying surface (maximum clearance ≤ 0.02 mm, detected by feeler gauge);

Coordination between key hole position and locating pin (the clearance is in line with the design, such as 0.05-0.08mm).

Accuracy detection: use CMM to scan the whole fixture in full size, and focus on verification:

Coordinate deviation of positioning datum (≤ 0.005 mm);

Deviation between measuring point and 3D model (≤ 0.01 mm);

The reset accuracy of moving parts (such as clamping arms) after movement (≤0.01mm).

Repeatability test: the same door sample is repeatedly loaded and unloaded for 10 times, and the reading changes of key measuring points are recorded with a dial indicator, and the deviation should be ≤0.01mm (to ensure the detection stability).

Fourth, surface treatment and marking: improve durability and ease of use