Rotary drum coating technology for small plastics parts

  • Homogeneous and energy saving coating of mass-produced small plastic components
  • Newly developed coating machine offers higher capacity
  • Focus on air filtration

An increasing number of manufacturers are choosing rotary drum technology for the coating of mass-produced small plastic and rubber components. To address this trend, Walther Trowal, the manufacturer of the Rotamat coating system, has introduced its redesigned Rotamat R80. Compared to its predecessor, the new version offers higher operational flexibility and higher capacity.

Switching from drum coating at room temperature to hot air drum coating technology

For several months now, Walther Trowal has noticed a distinct trend towards the use of rotary drum coaters for the coating and painting of small mass-produced components. Many small-part manufacturers are switching from the drum coating at room temperature to the hot air drum coating technology. Other manufacturers are no longer subcontracting their coating work to external service companies but do it in-house. And some have replaced their single-piece paint systems with rotary hot air drum coaters.

The Rotamat R80 is ideally suited for coating of rubber and plastic parts (source: Walther Trowal)
The Rotamat R80 is ideally suited for coating of rubber and plastic parts (source: Walther Trowal)

Parts no longer have to be individually placed on special racks

With the drum coating method the small parts no longer have to be individually placed on special racks but can be loaded into the Rotamat drum in relatively large batch sizes. This technology is ideally suited for treating small parts made from different plastic materials like elastomers, ABS, PC or PS. Water based as well as solvent based paints can be processed.

The technical features

The new Rotamat R80 has a drum diameter of 800 mm and can handle about 50 kg of parts with a batch volume of 50 liters. This batch size meets the requirements of many manufacturers who must coat complex shaped parts or are processing relatively heavy parts like metal components. The R80 is also available with a drum that offers a diameter of 700 mm and a usable part volume of 30 liters.

Further features:

  • The airflow and the paint application system were optimized to a point where only a very small amount of overspray is created.
  • The inside of the coating drum is equipped with an explosion protected LED light allowing precise observation of the coating process, be it the paint layer buildup or color changes.
  • The new heating control system helps reduce cycle times and energy consumption. A PID controller adjusts the inlet air temperature in relation to the work piece temperature. At the same time it takes into consideration the actual air volume. The new controller reacts extremely quickly. This quick reaction and the better insulation of the drum allowed reducing the electrical energy requirements to 9 kW.

Focus on air filtration

The new exhaust air filter unit increases the possibility for using different paints. This is an important feature for manufacturers who have to coat a large variety of parts with different types of paint. The R80 offers four independently usable stages for filtering the exhaust air so that the particle sizes caught by the filter system can vary within a relatively large range up to filter class F6.

The new filter unit also contributes to a higher part throughput: the user can now use more solvent, thus, speed up the coating process and still meet the standards for the maximum solvent concentration at the work place. Another feature of the new filtration system is the secondary air system that allows the connection to a thermal post combustion installation. The secondary air system limits the air volume pulled by the thermal post combustion installation so that the coating process is not affected.

The company has sold about 300 units since the introduction of the Rotamat coating system.

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