Where does the car need to use the checking fixture?

In the production and assembly process, many parts and assemblies of automobile need to be controlled by checking tools to ensure that the dimensional accuracy, shape and position tolerance and assembly matching meet the design requirements. The following are the main parts of the car that need to use the checking fixture, which are classified according to the types of parts:

First, the body structure

The car body is the basic frame of the car, and its dimensional accuracy directly affects the assembly and safety of the whole car, so it needs to be strictly controlled by checking tools:

Body panels: such as door panels, engine hoods, trunk lids, fenders, etc. The checking fixture mainly detects the profile, edge size, lap gap with adjacent parts (such as the gap between door and fender ≤1mm) and punching hole position (such as the position of mounting hole).

Body frame parts: including front longitudinal beam, rear longitudinal beam, sill beam, upright post (A-pillar/B-pillar/C-pillar), etc. The fixture mainly detects the position accuracy of key connecting holes (such as the coaxiality of bolt holes) and the flatness of welding surface (to avoid deformation after welding).

Body assembly: such as side wall assembly and floor assembly, the fixture should simulate the coordinate system of the whole vehicle, and detect the overall size of the assembly (such as wheelbase deviation) and the assembly position of each subassembly (such as the verticality between the column and the floor).

Second, the chassis system

Chassis components directly affect the driving performance and safety, and the checking fixture is used to ensure the connection accuracy and movement coordination;

Suspension components: such as control arm, steering knuckle, and shock absorber mounting seat. The fixture detects the position of key holes (such as ball pin mounting holes), the tolerance of shaft diameter (such as cylindricity of bushing mounting shaft), and the angular deviation of welding bracket.

Braking system: the flatness of the mounting surface of the brake disc and caliper (which affects the braking effect) and the alignment of the hole position of the brake pipeline need to be verified by checking tools.

Steering system: the length tolerance of the steering tie rod and the coordinates of the installation hole of the steering column, and the checking fixture ensures that it matches the assembly of the steering wheel and steering gear.

III. Interior and exterior ornaments

Internal and external ornaments are related to appearance quality and user experience, and the fixture focuses on dimensional accuracy and assembly aesthetics;

Interior trim:

Center console and instrument panel: detect the fit with the car body, the position accuracy of functional holes (such as air conditioning outlet and multimedia interface), the clearance and height difference with peripheral parts (such as steering wheel and door trim).

Seat assembly: detect the parallelism of the seat slide rail, the matching between the mounting hole and the body floor, and the reference position of the seat back angle adjustment.

Door trim panel: detect the fit with the door sheet metal, the position of the armrest mounting hole, and the outline size of the storage compartment.

Exterior decoration:

Bumper (front/rear): Check the butt edge gap with the car body (such as the gap with the fender ≤1.5mm), the fog lamp installation hole position and the flatness of the radar installation surface.

Window glass and sealing strip: Check the matching gap between the glass and the door frame and the section size of the sealing strip (to ensure sealing performance).

Rear-view mirror and door handle: Check the position of the mounting base (to avoid interference with the car body) and the flatness of the appearance surface (without protrusion or depression).

Iv. Powertrain and accessories

The accuracy of power system components affects the efficiency and reliability of power transmission, and the fixture is used for key dimension control;

Engine components: the coaxiality of the main bearing hole of the cylinder block, the position of the valve seat hole of the cylinder head and the flatness of the sealing surface of the oil pan.

Gearbox components: position accuracy of bearing hole of shell, working stroke reference of shift fork, shaft diameter tolerance of input/output shaft.

Air intake and exhaust system: the flatness of the flange surface of the intake manifold (to ensure sealing with the engine) and the position of the hanging hole of the exhaust pipe (to avoid vibration interference).

V. Electronic and Electrical Devices

Automobile electronic components should be accurately matched with mechanical structure, and the fixture should ensure installation and function realization;

Instrument panel: detect the parallelism with the installation reference plane of the center console and the flatness of the display screen (to avoid reflection or visual deviation).

Harness assembly: Check the mounting hole position of the harness fixing buckle (to ensure matching with the body fixing point) and the size of the locating pin of the plug (to prevent wrong insertion).

Sensors: such as reversing radar, the angle of the installation surface of the camera (to ensure the accurate detection range), and the positioning benchmark of millimeter wave radar.

Six, special functional parts

Airbag: detect the tear line position of the airbag cover plate (to ensure accurate deployment during blasting) and the accuracy of the connecting hole position between the mounting base and the car body.

Charging interface (new energy vehicle): Check the positioning size of the interface seat (to ensure the smooth insertion of the charging gun) and the flatness of the sealing surface (to prevent water leakage).

The application of checking fixture runs through the whole process of automobile production, from incoming inspection of single parts, inter-process inspection to final inspection after assembly. Its core function is to reduce assembly problems caused by dimensional deviation through standardized inspection means, and finally ensure the consistency of vehicle quality. The fixture design of different parts will be optimized according to their materials (metal/plastic), structural complexity and functional requirements.