Individual requirements? Individual coating process!
The process sequences used by the wheel coating plants depend on the desired surface quality. A three-layer paint system is used for standard wheels. For machine-polished wheels, up to six coats can be applied – including, based on experience, a layer of anti-corrosion paint or anti-corrosion powder, clear powder and/or clear paint (also as an ABD coating). In the wheel coating plants from Rippert, the different procedural steps are separated by conveyor equipment. The wheels are automatically transferred to the next process step by articulated robots.
Coating plant processes in detail - Chromium-free pretreatment
- The pretreatment of the wheels is agreed with the respective chemical supplier before being carried out.
- Following the pretreatment, the wheels pass through the rotating blow-off zone to remove adhesive water. Rippert has developed and patented this innovative process: in this zone, the water is removed quickly and precisely from the wheels with the help of rotating nozzles.
- The wheels then continue into the adhesive water dryer. This completely dries the wheels at up to 220°C – even in the micropores. This significantly reduces the risk of surface disturbance in the subsequent processes.
- The cascade and cycle flow management systems reduce the amount of fresh and waste water required for the rinsing process. The water is purified in a chemical-physical waste water treatment plant.
- Priming takes place in an air-conditioned, insulated, glazed space. This, in turn, contains up to three cabins for powder coating. The wheels are given a coating with clear powder or primer powder (in light grey, black or another colour) with corona spray guns.
- The powder is gelled and cured in a powder curing oven.
- The wheels are then cooled to a precisely defined temperature in the cooling zone.
Basecoat (primarily in silver colours)
- The wheels are heated in an infra-red preheating oven.
- The base coat is applied using high rotation atomisers and electrostatic spray guns. The wet paint cabins have a cross-flow venturi washout. The paint sludge is handled in a separate circulation. Using a solvent-based base coat enables a (wet-on-wet) treatment with an intermediate flash-off process.
- The paint is flashed off and dried. Exhaust air streams containing solvents are treated either with a thermal or a regenerative oxidiser.
There are three processes used for the application of clearcoat (wet paint, polyester powder or acrylic powder):
- The wet-on-wet application of clearcoat is carried out directly after the base coat.
- The clearcoat is first applied with polyester powder and then with clear wet paint.
- The clearcoat is applied with an acrylic powder.
On the one hand, conveyor technology is the combining element of the individual processes, while on the other, it refers to the material-handling elements within the process steps. The material-handling equipment is adjusted to specific requirements based on the same standard. The wheels are cleaned in an upright position in the pretreatment stage. The hangers used in the pretreatment stage run through the cleaning and pickling process along a classic circular conveyor track. In the dryers (up to 250°C), open footstep and support bearings are used with heat-resistant grease. To ensure a consistent coating, the wheels are transported horizontally for coating. In the application areas, protection against the penetration of overspray and powder is a key target. Guide rails, synchronising devices, rotating units – the portfolio of the robust material-handling equipment is complemented by additions from rotating units to robust sensor holders.
Flexibility is also desirable here. Of course, Rippert will make a robot recommendation, but every customer will prefer the robots their company is familiar with. We are flexible here – from ABB to Kuka to Fanuc. Where necessary, or in marginal cases, the operational capability of the desired robots will be tested to prevent any nasty surprises.
The gripper units are manufactured by Rippert and are electrically driven. The benefits of servo drive technology over pneumatic are convincing.
Every wheel is recorded in a database before it is loaded up for coating. The basis of a good coating is the "gentle" handling and treatment of the wheel. The individual geometric wheel data (grip geometry, grip heights, masking types...) is a requirement for this.
The type of pretreatment used is automatically adjusted according to the following process. Individual preheating temperatures and cooling lines can also be changed here. A "recipe" is passed on before every application step. This contains the optimal setting for the spray guns, the amount of paint and the coating movements.
This information is then available anywhere in the plant where it is needed. Furthermore, all quality assurance regulations can be fulfilled and documented in this way.
Our employees are at your disposal, should you have any questions or wishes! Speak to us directly or fill in the quotation request form below. We look forward to receiving your message!