A skeletal trailer from design to the amount of output sold to consumers is a tedious and lengthy process. In general, the basic processing process of the skeletal trailer is divided into the following main processes, namely stamping, welding, painting, and assembly. These are the four well-known automobile processes, and they are also suitable for skeletal semi-trailers. Next, the production process of the skeletal trailer is introduced in four sections.

1. Stamping process

The stamping workshop is responsible for the manufacture of various parts of the skeletal trailers, and performs cutting, punching, blanking, bending, stretching, and overturning processes on the main beams, frame and other parts. It is the first step in the production of skeletal semi-trailers , which is to process metal sheets into parts with specific shapes through special molds. The steel coil purchased from the steel mill is cut into a specific material flakes shape after being punched by the blanking pattern die . The size and shape of the material flakes is calculated by the engineer through Auto-Form and other software analysis and calculations, and professional drawings are made according to the shape, which are cut by the plasma flame cutting machine with reference to the drawings. This shape must be economical (saving materials) on the one hand, and on the other hand, it is necessary to ensure the forming of accessory.

1）Before the start of the production process, the steel coil raw materials purchased from the steel mill need to be inspected to confirm that its quality meets the standards

2）The material suitable for the main beam is selected from the steel material, and the components of the main beam are include upper wing plate, lower wing plate and web beam. First cut the web in the middle of the beam, pick out the material and place it on the plasma flame cutting machine, and cut out the appropriate size according to the size of the drawing and the configuration requirements. Then cut the upper and lower wing panels, which also need to be cut as required. Note that the device thicknesses of the upper wing, lower wing and web are different.

3）Correction. Hang an upper flange (the one above the beam) place on the correction table, bend it into a certain shape, and then hang a straight bottom flange (the one under the beam) place on the correction table.

4）Forming. The upper and bottom flange and between the piece of the web place on the correction table, adjust the distance of plate, and maintain the level and stability.

2. Welding process

The welding workshop is responsible for the team welding of the frame and body. The welding of the frame and the body is the most vital process in the production of the skeletal semi-trailer. The type of semi-trailer depends on the type of semi-trailer body. The weight of the semi-trailer and the type of goods to be transported determine the length, width and height of the semi-trailer body and the structural strength that needs to be designed. The length, width, height and structural strength of the body are all determined by the semi-trailer body. The production equipment on site is mainly have   automotive arc-submerge machine, CNC plasma cutting machine, team mould, chain turning machine and other equipment. After each welding is completed, the worker must carefully check the welding condition. After the body welding is completed, the welding condition must be further checked . After confirming that there is no problem with the welding, the next step can be carried out.

1）Use a welding torch to perform spot welding in the gap between the wing plate and the beam web to achieve a stable effect. In this way, the main beam is basically formed, but it is not stable enough, and it needs to be welded with a submerged arc welding machine.

2）The fixed beam is hoisted to the automotive arc-submerge machine table, and the gap between the wing plate and the beam web is welded twice by submerged arc welding, so that the welded beam is stronger. To this step, the beam is formed.

3）Welding the frame. Put the formed two beams on the frame assembly table and adjust the spacing between the beams. Weld the front and rear cross beams , and perform group welding on the vehicle longitudinal beams and cross beams. The purpose of this step is to fix the frame, make it stable, and shape the frame.

4）Welding of side beams and other accessories.

5）Assembly welding of frame suspension and traction plate. Note that cross welding is not allowed between the reinforcing plate of the lower wing plate and the king pin plate, and the two ends need to be left 20mm without welding. The suspension connecting plate is bent at the edge of the front bracket, which can effectively reduce the force transmitted from the suspension bracket to the longitudinal beam and avoid the force concentration of the longitudinal beam.

6）The frame is overturned and welded, and the frame bottom plate is welded together. There is a special chain turning machine for the frame turning, which can be hoisted and welded.

7）Install the king pin plate, king pin, channel steel, clamp beam, bottom beam , suspension , tool box , tail device and support plate of various parts .

3. Painting process

Object of an aspect of the coating is to prevent corrosion of the body, on the other hand to the vehicle body with a beautiful in appearance . The paint shop is responsible for the coating protection and decoration of the exterior of the car body. The equipment used mainly includes high-purity air purification spray room, automatic lifting platform polishing room, automatic drying room, automatic sanding room and other equipment. Due to the complex structure of the semi-trailer body, manual spraying is used for painting and spraying operations.

1) Before spraying, it is necessary to sand the skeletal trailer body as a whole to remove the residual welding slag and weld on the formed frame to make it beautiful and smooth.

2) Spray primer. In the modern market, the electrophoretic primer is mostly used. The electrophoretic coating process generally consists of four main processes: handle before coating, electrophoretic coating, cleaning after electrophoresis, and drying of electrophoretic coating film . The function of this step is to make the car body flat and smooth, and at the same time play a role in preventing rust and corrosion. Primer is also called anti-rust paint. Its main function is to prevent rust of metal car body and protect the steel. At the same time, it can improve the adhesion of substrate and color paint. It is a very important part of car paint. After spraying, it needs to be dried. The primer color is usually fixed iron red, zinc gray, gray, white, zinc gray and so on .

3) Spray finish. After the drying is finished, apply a top coat to the whole car, and electrostatic spray on the spray paint. Then use a temperature of 200 degrees to dry.Generally, there are ordinary paint, metallic paint, pearl paint and several top coats. The colors of the top coats are also diverse. The colors and attributes can be determined according to the preferences of consumers. Note: The primer and face paint color is not as easy holidays when otherwise construction.

4) After the topcoat is spray,it needs to be dried, and then the whole vehicle is inspected.

4. Assembly process

The assembly workshop is responsible for the installation of tires and axles, the installation and commissioning of electrical circuits, and accessories for interior and exterior decoration of the body. Assemble the semi-trailer body, tires and interior parts together to form a fully usable car .

1）Assemble axles, tires, nameplates, indicator lights, etc. and other accessories.

2）Assemble the electrical circuit and debug after the assembly is completed to ensure its availability.

3）Measure whether the spread of axles and the distance of wheel are appropriate. The spread of axles and wheelbase dimensions of the semi-trailer directly affect the overall dimensions, total mass, throughput rate, driving stability and other performance of the vehicle. Technicians need to ensure its accuracy and minimize errors.

4）Vin number(chassis number) and name plate. The semi-trailer has its own special large frame number coding machine, supporting the signal access of the production line to realize the automatic marking of automobile VIN number.

5）Vehicle inspection and storage. The vehicle can only be put into the warehouse after the certification test and compliance test of the whole vehicle export global regulations have reached the standard.