Aluminium pre-treatment plant automates and doubles output

Based in the Melbourne suburb of Dingley Village, Rylock designs and manufactures high performance energy efficient windows and doors for energy efficient homes.

The company recently installed a new plant for the pre-treatment of aluminium sections prior to powder coating.

According to Rylock's design engineer, Peter Kennedy, automation of the plant has resulted in the doubling of production output.

The new plant consists of eight large vertical steel towers positioned in a large square pattern, all connected with an overhead structure.

Suspended from the overhead structure are two large lifting frames, onto which stainless steel baskets containing aluminium extrusions are loaded.

These baskets are then moved automatically through a seven stage pre-treatment process.

Basic parameters are able to be changed to account for variations in drying time and chemical strength, so the focus is not only on greater throughput but also on greater control of the variables within the process.

Kennedy explains that seven tanks are involved in the pre-treatment process.

"Tank 1 contains hydrofluoric acid that etches away oxide from the surface of the aluminium sections, while tanks 2 and 3 provide water rinses of increasing purity, and in tank 4 chromate reacts with surface aluminium to form a lattice-like substrate that keys well with powder coating.

"Tanks 5, 6 and 7 provide water rinses of increasing purity," he said. "The pre-treated aluminium sections are then moved to low temperature drying ovens, and then loaded onto the powder coating lines.

Maximum throughput

"Previously, 50 percent of one worker's time was spent with a pendent lifting and lowering baskets through the tanks. Maximum throughput was seven baskets in a day," explains Kennedy.

"The old pre-treatment system was reaching the end of its service life in a factory that was also being outgrown and was operated at its capacity every day.

"Maximum throughput of the new automated system is one basket every 15 minutes. Although not operating anywhere near this capacity yet, the new system allows great flexibility in operation management.

"Pre-treatment previously created a bottleneck that required careful management so as not to effect downstream productivity.

"Pre-treatment now requires minimal input from the operator in the areas of loading and unloading.

"The new automated system frees up the operator to allow him to perform production duties elsewhere in the factory."

Safety benefits

Kennedy says additional benefits include safety because there is now no need for any personnel to be in close proximity during periods of risk, such as possible chemical splash.

"The system is contained within safety barriers with various sensors that ensure the system will not operate while there is potential for people to be within that footprint.

"Another benefit is the improved consistency of pre-treated metal. With this system, time in the reaction tanks (hydrofluoric etch and chromium) is precisely repeated along with exactly repeated draining times and conditions.

"The previous system relied upon the timeliness of operator responses to the timer siren, and how cleanly baskets were lifted and lowered on a centre mounted overhead crane setup.

Much of the control was left to operator prerogative, attentiveness and skill while also carrying out additional tasks.

"Now, parameters can be changed for dipping time in reactants, in relation to reactant concentrations, via visual cues (colour of treated aluminium), monitoring feedback, and seasonal conditions affecting drying times."

Automation technology

The control program for the new pre-treatment plant commands four separate 0.75 kW frequency inverters, which in turn control four NORD helical geared motors positioned at the top of each vertical tower of the plant.

Tony Sculpher, regional sales manager for NORD Drivesystems AU, advises that the NORD geared motors were each supplied complete with an electromagnetic brake and an incremental encoder for individual positioning feedback to the frequency inverters.

These geared motors were selected to complete a high duty cycle."The hollow shaft design and external foot mount gear case provided simplicity to the installation, especially when mounted at the top of each vertical tower," he said.

"These NORD geared motors were selected to complete a high duty cycle and for long life expectancy to help future proof Rylock's new pre-treatment plant.

"Rylock's engineers focussed on making control of the new pre-treatment plant process as simple as possible. For example, a one touch keypad is located on the outside of the control cabinet for ease of operation."

Electrical contractor Proactive, based in the Melbourne suburb of Braeside, was responsible for all electrical installations for the project.

The company's automation electrician, Ramiro Moran, says this included editing the programming on the Allen-Bradley PLC and connection of the motors and sensors.

"Some careful calculations needed to be carried out, including calculation of the hoist weight in order to ensure the right drive for the plant," he said.

The lifting frames, along with two full baskets can weigh as much as 1,600 kg, so counterweights are utilised to offset some of the mass.

Concept, design and mechanical construction of the new pre-treatment plant were undertaken in-house at Rylock.