Industrial liquid paint guns: dispensing and spraying

In industrial liquid coating, coating quality depends on the balance between the feeding system, mixing, paint atomization, and overspray management.

Achieving a uniform, adherent, and durable film requires controlling viscosity, pressure, film thickness (DFT), transfer efficiency, and booth operating conditions. The choice of dispensing guns-Air Spray, HVLP, Airless, or electrostatic systems-directly affects aesthetic performance, process repeatability, and consumption optimization.

In highly specialized industrial settings, paint application is not a simple spraying operation, but an integrated system in which technology, process parameters and plant design must operate in a coordinated manner to ensure controlled quality and compliance with production requirements.

In automotive, aerospace, cosmetics and pharmaceuticals, advanced manufacturing, high-level aesthetic finishes, performance requirements (chemical resistance, anti-corrosion, durability, regulatory compliance), strict control of the result and operational flexibility are required.

In highly repetitive industrial liquid coating processes, such as in the automotive and aerospace sectors, control of liquid coating application is crucial to ensure film uniformity, waste reduction and compliance with technical specifications. Even minor variations in spray parameters can generate surface defects and coating nonconformity.

Indeed, liquid application allows:

• Multilayer applications (primer, basecoat, clearcoat).
• High gloss finishes and controlled textures.
• Control and modulation of dry film thickness (DFT).
• Management of large surfaces and complex geometries.
• High level of aesthetic and color customization.

In industrial coating, dry film thickness (DFT) is generally controlled within defined micron ranges depending on the anticorrosive, aesthetic or regulatory specifications required by the project. Maintaining these parameters consistently is critical to ensure performance and durability over time.

In liquid industrial plants, the final quality of coating depends on the synergy between three fundamental systems:

Power system

It ensures constant flow and pressure to the applicators (dispensing guns). The choice of pumping technology–piston, diaphragm or gear pumps, pneumatically or electrically driven–depends on: product viscosity, required flow rate, number of applicators, feeding distance and frequency of color changes.

Mixing and dosing system

In 2K two-component (base + hardener) or 3K multicomponent (base + hardener + thinner or additive) systems, the mixing and proportioning system ensures the correct ratio between the different components of the product, guaranteeing the stability and repeatability of the process. An incorrect mixing ratio can affect thedrying of the paint, thus the adhesion and durability of the coating.

Dispensing guns and application systems

It concerns the mode of fluid atomization, i.e., paint delivery by dispensing guns, automatic or manual, which have specific advantages depending on the model. Some types integrate electrostatic assistance to improve transfer efficiency and reduce overspray.

Atomization quality is affected by parameters such as fluid pressure, paint viscosity, nozzle diameter, and spray system configuration. Improper adjustment of these variables can compromise spray stability and uniform distribution of the applied film.

The atomization of the fluid is therefore crucial for:

• Producing uniform films;
• Ensure that the paint adheres to the substrate;
• Achieve the best aesthetic performance;
• Reduce overspray in the cabin;
• optimize consumption.

In the industrial environment, suboptimal atomization can generate surface defects such as orange peel, dry spray or excess overspray, resulting in increased consumption and reduced transfer efficiency. For this reason, control of the atomization process is a critical element in the design and operation of liquid coating plants.

The selection of spray technology is not solely a functional choice, but represents a design decision that affects process stability, paint transfer efficiency, and operating cost per square meter treated.

Spraying technologies are distinguished by the method of fluid atomization and the possible integration of electrostatic assistance, aimed at improving transfer efficiency and spray distribution through electrostatic attraction of particles. Proper classification must therefore start from the physical principle by which the paint is fragmented.

The spraying technology and the level of automation inherent in the process are inseparable from the booth design.

Manual implants

In manual booths with horizontal or vertical flow, the dispensing guns are controlled by the operator in charge of painting the parts. While manual gun management provides the flexibility to adapt to variable productions in terms of batch numbers and part characteristics, it also penalizes process control because it introduces a factor of variability in film application, related to the possibility of operator error.

Automatic plants

In automatic booths, dispensing guns are mounted on horizontal or vertical arms or reciprocators, whose movement is governed by software for centralized management of the industrial plant. This ensures repeatable processes, controlled in every detail, which are essential in serial productions where the need for film standardization is highest. In the case of rotary plants for the Cosmetics&Pharma segment, the application is managed by rotary bells or rotary bells.

In industrial liquid coating, the quality of the end result does not depend solely on the technologies used, but is determined by the control of key process parameters:

• Fluid viscosity.
• Fluid pressure.
• Air pressure and flow rate in HVLP systems.
• Application distance and angle (spray pattern).
• Forward speed and exposure time.
• Cabin environmental conditions.
• Flash off (time for controlled evaporation of solvents between paint passes).

To ensure the stability of critical parameters over time, thus the quality and repeatability of the result, it is essential to implement structured procedures and systematic controls in the painting process. Recommended best practices include:

This allows the most common defects of liquid applications to be averted:

• Casting.
• Orange peel.
• Craters.
• Dry spray.
• Inclusions.
• Poor adherence.

From defining critical parameters to choosing the level of industrial automation to managing overspray and transfer efficiency, each variable contributes to the repeatability, sustainability and final quality of the coating.

The quality of the applied film is thus the result of the perfect balance between physical parameters, plant configuration and design expertise. It is precisely in the ability to govern this complexity that the expertise of the supplier of industrial coating booths and equipment is measured.