1. Product Definition and Scope of Application
This Microvan Assembly Line system serves as core final assembly equipment for the Commercial Vehicle Final Assembly Line sector. It is specifically positioned for Mixed-Model Production (MMP) scenarios on Bread Van Production Lines, covering the manufacturing of microvans (commonly referred to as “bread vans” due to their boxy, loaf-like silhouette), light buses, and similar commercial van-type vehicles. The microvan assembly line covers the complete process chain—including interior sub-assembly and loading, chassis modular mating, powertrain integration, final assembly and commissioning, and End-of-Line (EOL) testing—forming a full-sequence manufacturing closed loop from Body-in-White (BIW) to finished vehicle roll-off.
In terms of platform compatibility, this production line is built upon the Flexible Common Line design concept. Through modular process layouts and standardized interface definitions, it achieves mixed-model assembly on a single line for two major technical routes: traditional Internal Combustion Engine (ICE) and Battery Electric Vehicle (BEV). Specifically, the line is compatible with two BIW structural forms—Monocoque and Body-on-Frame—and supports various powertrain layout schemes including Front-engine Front-wheel-drive (FF), Front-engine Rear-wheel-drive (FR), and electric Rear-wheel-drive / dual-motor All-Wheel-Drive. To address the differentiated assembly requirements of different powertrain platforms—such as engine-transmission assemblies, exhaust systems, and fuel lines for ICE models, versus traction battery packs, e-axles, high-voltage harnesses, and thermal management systems for EV models—the line utilizes Reconfigurable Fixtures, programmable switching of multi-spindle tightening systems, and RFID body identification with PLC automatic routing control. This enables automatic identification and adaptive matching of process parameters for different models within the conveying cycle, achieving Zero Changeover Downtime.
Furthermore, the production line is designed with expandable compatibility for multiple Wheelbases and variant types (e.g., low-roof/high-roof, blind-window/glazed-window, passenger/cargo versions). Through Adjustable Datums and Quick-Change Pallets, it ensures that a single line can simultaneously meet the common-line production requirements for microvans (wheelbase approx. 2500–3000 mm) up to light buses (wheelbase approx. 3000–3800 mm). This effectively supports OEMs’ Order-Driven Mixed-Scheduling strategies across multiple market segments, maximizing line utilization and Return on Investment (ROI).
2. System Architecture
This bread van assembly line consists of four functional sections. Body transfer between sections is achieved through transfer mechanisms.
2.1 Interior Assembly Section
Utilizes a floor drag chain or skid conveyor system. The body moves at a fixed cycle time. Workstation spacing is set according to assembly content, typically 6–8 m per station. Each station is equipped with a pneumatic stopper; after operation is completed, the worker triggers a release signal.
The main operations completed in this section are:
- Instrument Panel Sub-assembly & Installation: After HVAC ducts, wire harness connections, and infotainment head unit pre-installation are completed on an offline sub-assembly bench, the instrument panel assembly is lifted into the body by an assist manipulator or KBK hoist. Locating holes are docked with the body’s instrument panel cross member.
- Wire Harness Routing: The vehicle wire harness is routed through side wall holes and floor channels according to the predetermined path. At the docking station, connections with the instrument panel harness and chassis harness are completed, followed by a continuity test.
- Interior Trim Assembly: Headliners, A/B/C pillar trims, and side wall interior panels are fixed using a clip + screw method. Some models are equipped with overhead grab handles, sun visors, and rearview mirror bases.
- Weatherstrip Installation: Weatherstrips for the front doors, sliding doors, and tailgate are embedded into the sheet metal flanges using rolling or manual tapping methods.
2.2 Chassis Assembly Section
Non-unibody bodies are equipped with a frame conveyor line to complete the pre-assembly of the front axle, rear axle, suspension system, and powertrain (engine/motor + transmission/reducer). Unibody bodies use an Electric Monorail System (EMS) for underbody component assembly while the body is suspended.
Key processes include:
- Powertrain Pre-assembly: The engine/motor and transmission/reducer are docked on a sub-assembly pallet. After applying grease to the input shaft splines, they are pushed together, and connecting bolts are pre-tightened in a diagonal sequence.
- Suspension & Axle Installation: The front MacPherson suspension or front axle assembly is fixed to the frame/subframe using torque-controlled tightening machines. The rear leaf spring or coil spring suspension is selected and installed according to specifications.
- Steering System Assembly: The steering gear, steering column, and drive shaft are installed sequentially. The intermediate shaft universal joints are aligned and locked.
- Exhaust System / Battery Pack Lifting: ICE vehicles are equipped with mufflers, three-way catalytic converters, and exhaust piping. EV models are equipped with a traction battery pack, which is lifted into position beneath the chassis by a KBK lifting system (rated capacity 0.5–2 t). After guiding with locating pins, it is locked to standard torque.
2.3 Mating and Final Assembly Section
The chassis and body are docked at the mating station. The mating station uses a hydraulic lifting mechanism to raise the chassis (or powertrain + suspension assembly) up to the body. Four sets of locating pins ensure X/Y centering accuracy of ±1 mm. Connecting bolts are tightened synchronously using multi-spindle electric torque wrenches. Torque values are collected in real-time, bound to the Vehicle Identification Number (VIN), and stored in a local database.
After mating, the vehicle enters a dual-plate chain conveyor line, where the following operations are completed sequentially:
- Tire Tightening: Five-spindle or single-spindle tire tightening machines are used, with tightening torque of 80–180 N·m and angle control of ±5°.
- Seat Installation: Front and rear seat assemblies are manually carried or transported by assist arms into the vehicle. The sliding rails are docked with floor nuts and locked.
- Door Adjustment: After installing the front doors, sliding doors, and tailgate, adjustments are made via hinge shims and strikers to ensure gap and flushness meet tolerance requirements.
- Fluid Filling: Brake fluid is filled using a vacuum filling machine (vacuum degree ≤ –0.08 MPa). Coolant is filled by quantitative filling. Refrigerant is charged by a recovery/filling all-in-one machine according to standard quantities.
- Glass Gluing & Installation: After automatic gluing by a robot or manual gluing, the front windshield is pressed onto the body using a suction cup tooling. Curing time meets the off-line strength requirements.
2.4 Inspection and Off-line Section
- Four-Wheel Alignment: Toe, camber, caster, and kingpin inclination angles are measured. Data is automatically judged and stored.
- Headlight Testing: Low beam/high beam illumination, optical axis deviation, and cut-off line angle are measured.
- Brake Testing: Pneumatic/hydraulic system leakage test and four-wheel braking force distribution test.
- Chassis Dynamometer Test: Speedometer calibration and abnormal noise monitoring.
- Water Leak Test: Simulates a heavy rain environment with spray intensity of 12–20 mm/min for 8–15 min to check body sealing performance.
- OBD / Insulation Test: For ICE vehicles, engine fault codes are read via OBD. For EVs, high-voltage system insulation resistance is tested (≥500 Ω/V).
3. Main Technical Parameters
| Item | Parameter |
|---|---|
| Production Cycle Time | 15–30 min/unit (adjustable) |
| Annual Capacity | 3,000–5,000 units (single shift, 250 working days/year) |
| Conveying Method | Floor drag chain / plate chain / EMS suspension |
| Chain Pitch | 250 mm |
| Drive Power | 3–7.5 kW (inverter control) |
| Workstation Spacing | 6–8 m |
| Load Capacity | 0.6–3.5 t (depending on vehicle configuration) |
| Travel Speed | 2.0–8.0 m/min (inverter stepless speed regulation) |
| Mating Alignment Accuracy | ±1 mm |
| Tightening Torque Accuracy | ±3% |
4. Flexible Design
The commercial vehicle assembly line adopts a modular structure. Controlled by PLC programs and an RFID body identification system, this microvan production line supports mixed-model production. Models with different wheelbases, roof heights, and powertrain types can be assembled in order on the same line without stopping for changeovers. Workshop fixtures (racks, pallets, lifting tools) are classified and designed by vehicle family. Switching is completed via quick-plug mechanisms during changeovers, with switching time controlled within 15 minutes.
5. Safety and Environmental Protection
- The conveyor line is equipped with chain break detection, chain jam protection, and audible-visual alarm devices.
- Oil collection pits and drainage systems are set up in underground pit areas.
- Emergency stop pull-cord switches are installed at workstations at intervals not exceeding 15 m.
- Noise levels at high-noise equipment operation points are ≤85 dB(A).
6. Delivery Scope
This project is executed as a turnkey project. The delivery scope includes process layout drawings, equipment design and manufacturing, installation and commissioning, operation training, and warranty maintenance. The warranty period is 12 months from the date of final acceptance.