Pollution-Free Aluminum Extrusion Cuts Costs, Improves Quality

The Client
A leading multinational aluminum extruder.

The Challenge
The client was experiencing extreme problems with their existing anodizing facility. They needed to add finishing capability that would: 1) result in a tougher, more durable finish for architectural applications, 2) meet strict state and federal environmental regulations, 3) reduce operating costs, and 4) offer their customers a wider variety of finish colors and textures from which to choose.

The Solution
To meet these challenges, the client, accompanied by key technical members that today manage Modean Industries, traveled throughout the United Kingdom, Germany, Austria, Italy, and Switzerland to visit several aluminum extruder installations in order to evaluate the merits of both liquid and powder coatings.

The client’s engineering team established the standards required for the coating to meet the Architectural Aluminum Manufacturers Association for commercial specifications. Working with two powder manufacturers, several tests were performed on a variety of product samples in the United States. Powder coating exceeded all of the standards established by the AAMA using a single coat as compared to the two coats necessary with liquid coating. The outcome: the client selected powder coating as their coating of choice.

The 30-ft.long aluminum extrusions were bundled to be pretreated in a 9-stage immersion station with dry-off. After dry off, the parts were manually loaded horizontally on a load bar mounded on a power-and-free conveyor. The power section of the conveyor carried the racked extrusions through the automatic powder booths where they were electrostatically coated with deflector-less automatic guns moving at 18 FPM. There was a second automatic booth for quick color change, followed by a manual booth used for manual re-enforcement if needed. The rack was then transported through a cure oven cured at 400 deg. F.

As a load bar carrying coated extrusions exited the environmentally controlled coating room it headed for the 400F curing oven, a limit switch activates its cure cycle, and a photo sensor counts the conveyor “dogs” on top of each successive load bar as it passed by.

Once fully inside the oven the direction of travel automatically shifted 90 degrees, and the load bars were carried laterally rather than lengthwise through the oven. As each load bar approached the oven exit it stopped until released by a signal from the system’s microprocessor. The programmable controller compared monorail conveyor speed to the number of load bars that entered the oven based on the count of the optical sensor. When these two variables indicated that the lead load bar and its rack of coated extrusions had been in the oven for the designated time, it was released to rejoin the monorail that carried it out of the oven. The bake oven had capacity for a total of 11 racks at one time.

This microprocessor control system made the cure cycle independent of the monorail conveyor line speed, and a similar system was used to avoid over loading the free conveyor unload station. Another control feature was that, should the conveyor stop for any reason, the oven would automatically turn down to a 200F holding temperature to avoid over baking any extrusions in the oven at the time.

The monorail conveyor carried the racks back to the free section of the conveyor where they were unloaded manually.

Benefit to Client
The system provided the utmost in flexibility and was able to handle extrusions up to 30 feet long. Color change was relatively simple and swift, enabling the company to provide any color the customer desired. Housekeeping was easy with virtually no over-spray, and no messy paint sludge to deal with as in liquid coating operations.

Conclusion
The new powder coating system cut energy costs, improved product finish with a vast array of colors and gloss, operated pollution free and over-spray recovery was up to 98%, making the system extremely economical.

2018-12-21T13:11:55+00:00
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