Automotive body painting is characterized by its complex processes, numerous steps, and high coating quality requirements, making it the most representative of automotive painting technologies. Germany's newly developed rotary dip-conveyor technology and robotic cup electrostatic spraying technology are two major highlights of advancements in automotive body painting processes/technology over the past five years. To meet the needs of environmental protection and enhanced market competitiveness, new equipment and technologies are constantly being developed that are more environmentally friendly, improve coating quality, increase material utilization, and reduce painting costs. In automotive body painting, over the past five years, Germany has developed rotary dip-conveyor technology and robotic cup electrostatic spraying machines to replace the 9-cup electrostatic automatic spraying machine technology. Rotary dip-conveyor technology comes in two types: the RoDip-3 conveyor and the Vario-Shuttle. This rotary dip-conveyor technology completely solves the problems existing in pre-painting treatment and electrophoretic body conveying processes with a completely new concept. The advantages of this technology are significant, far surpassing those of push-rod and swing-rod chain conveyors for car bodies. It offers benefits such as smaller processing tank capacity, lower operating costs, superior electrophoretic coating quality, significantly reduced grinding workload, increased material utilization, reduced cleaning water consumption, and environmental friendliness. Both the RoDip-3 conveyor and the multi-functional shuttle are technologically advanced rotary immersion conveyor systems. The multi-functional shuttle allows for individual adjustment of the car body's operating mode during processing, offering excellent flexibility. Adjustments can be made according to the car body structure and process requirements, regardless of whether the car body is facing upwards or downwards, or different entry/exit angles. However, it lags behind the RoDip-3 conveyor in terms of processing tank volume, operating costs, electromechanical maintenance workload, and the impact of the hanger on the electrophoretic field. Taking the electrophoretic coating process as an example, the RoDip-3 conveying method can reduce the initial tank fill by 36m³, shorten the tank replenishment cycle by 20%, reduce the tank circulation volume by 20%–25%, shorten the electrode spacing, appropriately lower the electrophoresis voltage, reduce energy consumption, and reduce the maintenance workload of the conveyor, thus reducing relative costs by about 20%. In addition, RoDip-3 also has a single-chain, single-arm rotary type (RoDip-3+), suitable for conveying car bodies in pretreatment and cathodic electrophoresis lines with a capacity of less than 20 units/hour. From a coating process perspective, the rotary immersion conveyor technology eliminates the problems encountered in the pretreatment and electrophoresis processes of car bodies, making it a relatively ideal advanced and practical technology in terms of technology, economy, and environmental protection. Currently, two car body pretreatment and cathodic electrophoresis lines with an annual production capacity of over 120,000 vehicles equipped with RoDip-3 technology in China have been put into operation. Over a decade ago, automated electrostatic spraying equipment for body coating lines with an annual production capacity of 200,000 to 300,000 vehicles per year (intermediate coating) and 120,000 to 150,000 vehicles per year (topcoat coating) primarily consisted of nine high-speed rotary cup electrostatic spraying stations (ESTA, composed of reciprocating side and top sprayers). With advancements in robotics and electronic control technologies, the level of automation has continuously improved. Small, lightweight, high-speed cup-type electrostatic spray guns have been successfully developed. Currently, ESAs composed of 3 to 4 robots have replaced the nine-cup ESAs, mainly due to the following advantages of robotic sprayers: 1. High coating efficiency: 3 robots can handle the spraying tasks of a nine-cup ESA; 2. Suitable for multi-variety mixed-flow production and medium- to small-volume body coating lines; 3. Low investment and low operating costs: A three-cup ESA composed of three robots, while requiring 2.7 times more electricity, consumes only about 35% of the compressed air and cleaning solvents, and requires only about 35% of the maintenance workload of a nine-cup reciprocating ESA. Robotic spray painting machines offer high degrees of freedom and reproducibility in their coating trajectories. Their coating efficiency is influenced not only by the spray spacing but also by the sprayer's moving speed, which is related to the recoating interval and spray width. We can optimize these factors through film thickness simulation experiments to set the most suitable coating trajectory and conditions for coating efficiency. For the robot configuration of automated electrostatic spraying stations (ESTA), it is generally considered that, while ensuring production capacity and coating quality, the fewer robots (spray cups) per station, the better, in order to reduce investment, operating costs, and maintenance workload. The number of robots required depends on the area to be painted at the station, the dry film thickness, the production cycle (painting time), the characteristics of the spray cup (such as the paint output, spray width, rotation speed, and shaping air jet volume), static voltage, and painting efficiency. It can be calculated using the following formula: 1. Paint consumption (i.e., paint amount sprayed per vehicle body or station) Q=S×δ/(T×NV) Where: Q—Paint consumption (ml/unit); S—Painting area of ​​the station (or vehicle body) (m2); δ—Dry film thickness (mm); T—Painting efficiency (T, E), generally 80%～85%, up to 94%; NV—Paint solids content at the application viscosity. For example, if the electrostatic spraying area on the exterior of the car body is 10m2, the thickness of the intermediate coat or base coat (including clear coat) is 35-40mm, and the solid content at the application viscosity is 45%, then Q = 10 × 35 / (0.85 × 0.45) = 915ml/unit. 2. Number of robots (spray cups): When the production cycle of the car body is 1.7min/unit, 3 robots are selected per station. The calculation method is as follows: n400 = Q / (m × t × K) = 915 / (400 × 1.5 × 0.6) = 2.54 units; n350 = Q / (m × t × K) = 915 / (350 × 1.5 × 0.6) = 2.90 units. In the formula: n—number of robots (units); Q—paint volume of the car body at this station (ml/unit); m—paint output of the unit (spray cup) (ml/min) (related to the characteristics of the spray cup, with values ​​of 400ml/min and 350ml/min); t—spraying time (min), which is the production cycle time of the car body minus the time for color change and cleaning or the downtime between two car bodies (generally minus 0.2min for color change); K—correction coefficient, affected by factors such as the speed of the spray gun and the spray width. The more spray cups configured, the smaller the K value, generally taken as 0.6. During the electrostatic spraying process, excessively fast spray gun movement speed will affect the electrostatic spraying effect, and should generally be controlled within 0.6m/s. To achieve a better metallic shimmer effect, electrostatic spraying of metallic base coat (BC) is generally divided into two thin coats (dry film thickness 15-20mm): the first coat (BC-1) uses cup-type electrostatic spraying, and the second coat (BC-2) uses robotic arm air spraying. To improve material utilization, BC-2 also adopts rotary cup electrostatic spraying. A special cup electrostatic spray gun for BC-2 has been successfully developed, which is characterized by fast spray gun movement speed, high shaping air pressure, large air volume, and multiple re-spraying times (up to 7 times).