In the light truck assembly line, the assembly of the frame involves the following steps:

1. **Frame Assembly**: The frame is the core of the light truck chassis, including the assembly of the longitudinal beams and crossbeams. The production processes involved in frame assembly include roll forming, CNC flanging, plasma cutting, etc.

2. **Frame Wiring Harness and Brake Line Layout**: The frame wiring harness is an important connection part of the entire vehicle chassis, which needs to be laid from the front to the rear of the vehicle. The brake lines are designed inside the frame belly and connected with brakes, ABS, etc., to achieve the braking effect of the entire vehicle.

3. **Front and Rear Axle Sub-assembly and Assembly**: The front and rear axles include components such as brake assemblies and shock absorber assemblies. These components are combined on a sub-assembly platform, hoisted onto the line as a whole, and secured with pins to the required torque.

4. **Engine Installation**: The engine is pre-assembled on a sub-assembly line, then hoisted onto the frame line from above, lowered to the position on the frame crossbeam for assembly and fixed, and connected with the transmission and driveshaft.

5. **Frame Flipping**: After the frame assembly is basically completed, the frame assembly needs to be flipped to its normal posture, which is generally operated by a frame flipping machine.

6. **Minor Component Assembly**: This includes the assembly of components such as the steering mechanism, steering system, air conditioning pipes, fuel tank system, driveshaft, body locking mechanism, flipping mechanism, and mudguards.

These steps together ensure the accurate assembly of the frame in the light truck assembly line and the final assembly of the entire vehicle.