Flexible powder coating with shuttle system

A new powder coating line with shuttle conveyor system enables Interroll Conveyor GmbH to fully utilize its production capacities - also thanks to the consistent interlinking of production and the high degree of automation.

The Interroll Group is a leading global provider of material handling solutions. The company moved into its new site in Obrigheim in the summer of 2021. The new production facility is characterized on the one hand by the interlinking of the entire production and on the other hand by a high degree of automation. As a specialist for material flow, Interroll also relied on a smart and future-oriented system concept in the area of powder coating. The decision was made in favor of a powder coating system from Afotek GmbH, which uses the Afotek Shuttle Conveyor System (ASF) to implement very flexible processes in batch size 1 and thus meets Interroll's requirements for a high degree of flexibility with regard to the variety of parts and materials. Optimal coating processes can only be achieved by perfectly adjusted parameters during pretreatment, drying, coating and baking. ASF makes this possible through individually adjustable processing cycle times in the individual process steps. This not only shortens throughput times, but also significantly reduces process costs.

The extensive product portfolio of the Interroll group of companies includes platform-based products and services relating to conveyor rollers, motors and drives for conveyor systems, conveyors and sorters as well as flow storage systems. When planning the system, the focus was on modularity and flexibility, as Interroll manufactures a wide variety of components in several standard colors and from different materials. The plant operator's requirement to produce a perfect surface quality with the lowest possible reject rate, and at the same time to coat small batches and individual parts as required, meant that only an absolutely flexible plant concept was possible. The powder coating system is connected to the welding shop and the preparatory workstations at the feed point by a lifting and lowering station, so that the components can be fed in and removed ergonomically and with little strain on the workers' backs.

The lifting and lowering stations consist of one or more transport rails which are raised and lowered by means of wire rope hoists. Within the system, 6.2-meter-long product carriers transport the workpieces with a maximum size of up to 6 x 0.8 x 2.5 meters and a maximum workpiece weight of 250 kilograms per shuttle through the system. The material throughput is up to 1.25 tons per hour.

The pretreatment plant is equipped with a single-chamber system in which the three treatment steps of degreasing, multi-metal conversion and rinsing take place in sequence. The use of multi-metal chemistry enables the plant operator to clean a wide range of material types (various aluminum alloys and steel) in the pretreatment stage in a space-saving and energy-efficient manner. Multi-metal degreasing offers advantages in many respects: On the one hand, it hardly forms any residues and, at the same time, leads to very little stress on elastomers. This leads to a significantly longer bath service life as well as a significantly longer durability of wear parts in the plant technology. The bath service life is also optimized by an oil separator, which is used for continuous bath maintenance. This makes the pretreatment process extremely low-maintenance for the plant operator. After pretreatment, the components are transported by ASF to the adhesive water dryer, where they are dried in preparation for subsequent powder coating.

Double coating enables flexible processes

The coating concept of the plant is also characterized by the possibility of automated double coating of the components. This means that after the coating and curing process, the components are moved back into the powder booth by the automated component recognition system for the second coating pass. In this process, the second coating is applied directly after the annealing process, thus achieving a high coating thickness. The powder booth is a plastic booth from Wagner, equipped with eight vertically arranged and movable application guns. Before entering the fully automated powder booth, an automated part recognition system is also installed, so that the coating window is precisely defined and overspray is minimized. An additional floor extraction system ensures that any overspray that occurs can be reused, disposal of the residual powder is kept to a minimum, and the coating process can be operated in a cost-optimized manner. Thanks to the high degree of automation of the powder booth, only a very small amount of personnel is required for the coating process itself. In addition, a manual work station is installed in each case for the pre- and post-processing of complex components. With automatic powder coating, the conveyor speed can be continuously adjusted.

After the coating process, the parts are conveyed independently to the powder baking oven. There they can be stopped individually and conveyed through the oven at different speeds. The times required for the component mix for annealing and baking are adapted to the requirements of the powder used and the corresponding component. The furnace has a total of four furnace positions, which can be moved individually, so that individual baking times are possible for each product carrier. In this way, different components and different types of powder can be fired in the furnace in parallel.

The individual shuttles can be moved in any desired direction - independently of each other, precisely positioned and at different speeds. Cross-travel carriages allow shuttles to be moved at a 90-degree angle to the conveying direction. The shuttle transport system allows a high degree of flexibility. The shuttles are lubrication-free and thus extremely low-maintenance; they can also be continuously adjusted to different speeds. The modular and compact design can be expanded at any time and allows the conveyor system to be adapted to virtually any spatial conditions. For example, pre- or post-processing stations or buffers can be retrofitted without affecting ongoing production. ASF is a very low-maintenance system that requires no grease, oil or other lubricants. Time-consuming and cost-intensive work such as changing chains or tensioning the chain is also eliminated. Lubricant dripping is also avoided, making the system suitable for cleanroom applications.

State-of-the-art control technology

The extremely low-maintenance shuttle conveyor technology also increases the availability of the system compared to conventional systems. The modular design also means that only a limited stock of spare parts is required. Another elementary advantage of the transport system is that it is capable of passing over interruptions within the conveyor rail. This makes it possible, for example, to avoid static openings within the gate wings at the ovens and to minimize heat losses. The plant is equipped with a Siemens Simatic S7-1500 and features the latest control technology. Plant visualization is by means of a digital plant twin on a 22-inch touch display.During the fully automatic process sequence, detailed information on operating states, work steps, orders and goods carriers is displayed on the plant computer.

Reading points enable parts to be tracked within the coating system, so that each process step of the component to be coated can be recorded and queried. Each shuttle can be provided with detailed job data that can be called up permanently. This includes basic data such as order and article numbers, but also, for example, color or powder designations, the number of pieces per shuttle, or the curing parameters. Via the Afotek dashboard, it is also possible to track the current system status from any end device. It visualizes relevant process data clearly and in real time. All other interfaces are also prepared via OPC UA in order to be able to implement holistic process linking at short notice. A subsequent link with an internal ERP system is thus possible without further ado. On request, all process parameters are also stored and can be retrieved at any time. Remote maintenance without downtime.

The qualified team of in-house automation technicians and engineers can also provide appropriate plant support during production as part of remote maintenance. A special feature of the plant is that the Afotek team has already commissioned it 100 percent virtually. This made it possible to identify weak points in advance and optimize the plant flow. The commissioning of the entire plant could thus be completed in just a few weeks.

Afotek Anlagen für Oberflächentechnik GmbH
www.afotek.de