purchasing infrared/convection equipment

Purchasing Infrared/Convection Equipment Faith-based technology decision can often be wrong. By Buddy Miller, Managing Partner, Architectural Powder Choice, LLC, Claxton, Ga.

D o you always test equipment before purchasing it? My company's recent experience with a previously owned infrared convection oven

shows the importance of such tests. This oven did not work for our part configuration--a lesson cost- ing us $73,000 for the oven and the unhappiness of our supplier, a powder manufacturer. Not only is it important to test a purchase before buying, but it is crucial to test it on one's own products. (Ed. note: This is particularly true of spray booths, something that many fabricators know little about. Instead, they purchase the booth and expect it to work. Vendors often leave out addi t ional purchas ing options because they are in a bidding war and know that, in many cases, the low bidder gets the contract.)

In our case, a recent evaluation of an infrared convection oven, purchased by the previous management and never used in production, revealed deficiencies tha t were both counter to the claims of the manufacturer and to our qual i ty and production needs as a The oven control panel allo~

powder coating applicator. The oven manufacturer 's

claims regarding the mate- rials to be heated and cured contradict scientific data on powder manufacturing. For instance, our client's material product data sheet states a need for 10 minutes at 400°F to expect a cure for the product. In con- trast, the oven manufacturer claimed its oven can accomplish the given task in two minutes. Over the past five months, many conversations (some very con- tentious) occurred between the manufacturer and my company, the applicator, as faith in this $73,000 oven waned. Under the guise of "protecting the privacy of customers," no other oven customers or examples of similar applications were forthcoming.

For the record, I must state that, from the start, I doubted the technology of our infrared convection oven. Oven testing, using a Data Paq T M (an instru- ment tha t is used to perform a temperature profile

allows the adjustment of critical heat and power settings.These must be calibrated to the line speed and product mass on each project to ensure a consistent heat pattern.

of an oven), was conducted last spring by a powder manufacturer on our production line. Even at the lowest line speeds, the results were discouraging. The testing was intended to determine if the powder manufacturer 's powder could be cured in the oven. The manufacturer wanted the oven to successfully pass these tests. When poor results were shared with the oven manufacturer , oven manufac tur ing staff reacted by shooting the messenger, suggesting that "lack of experience, poor understanding of the technology, and meager industry contacts" account- ed for the powder manufacturer 's skepticism.

Before beginning our newly re-engineered oper- ation, I was determined to objectively evaluate the infrared convection oven: I set out to gather the sup- port of my major powder supplier and the oven manufacturer. I wanted to ensure we had a valid par tnership tha t would result in the best possible outcome. We needed all part ies to agree on the capabilities of the oven so that warranties and quality control test ing stan- dards could be measurably met.

I contacted the manufacturer of the infrared convection oven and my major powder supplier and arranged to run tests. It was important to include the powder manufacturer in our tests. As previously stated, the oven manufacturer claimed that the oven performs a full cure in two minutes. Such a claim contradicts information on powder heat requirements. Two very qualified representatives from the powder company came to the test--a technician and a sales engineer, both educated and experienced. They brought good reputations and objectivity to the evaluation.

To protect the reputation of the oven company and to ensure tha t the oven would be set to optimum performance levels, I asked the oven company to send a representative to the testing. The company president told us he understood the technology com-

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pletely. Before and during all tests, the infrared convection oven was set to his instructions. A standard white TGIC polyester powder was used, a powder not provided by the powder manufacturer on site.

The powder application system we built is designed for a line speed of eight feet per minute. I intended to s tar t line speeds at approximately five feet per minute. For the purposes of testing, we started at five feet, then four, and finally went to line speeds of three feet. Temperatures were adjusted upwards, and the coating was evaluated by both the MEK 50-double rub cure test and the crosshatch adhesion test.

Results were consistent at all temperatures and line speeds: all cure tests failed early in the MEK rub process. The crosshatch adhesion tests were sur- prisingly good, regardless of poor cures.

No acceptable coatings were found in a broad spec- t rum of parameters. Both powder manufacture representatives adamant ly concluded tha t the infrared convection oven did not supply enough time at a fixed temperature. A marked change of color between the side panels and the top section showed that the temperature was uneven. The sides closer to the IR/convection panels were darker by several shades on the

higher temperatures, while the flow characteristics were very poor overall. Later tests on the QC hotplate showed a free-flowing, smooth coating.

The oven manufacturer wished us to consider several of its points: • The powder manufacturer of the tested material

does not use the MEK 50-double rub test for evaluation;

• Reducing the line speed below three feet per minute "might" allow the oven to perform to purpose.

• and "the oven is performing 'exactly' as it was designed." My rebuttal follows:

• The MEK 50-double rub test is a widely accepted test method for TGIC polyesters;

• reducing the line speed greatly reduces production and profits. No profits exist at a three-foot line speed;

• and if this oven is performing "exactly" as designed, why was it designed so poorly for this plant and this specific application? In our final conversation, the president of the oven

manufacturing company indicated that he was very satisfied with the performance of the $73,000 oven.

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Since no extrusion could pass the cure testing, my conclusion differs substantially. More significantly for my company and its reputation, I cannot expect the powder supplier present at the testing to embrace my facility, to offer my customers warranties, and to cer- tify my application with this technology. In my busi- ness, that of architectural or decorative powder applications, warrant ies are controlled by the powder manufacturers. The applicator must adhere to the strictest s tandards of application to meet the demands of the powder technology and manufacturer. In this case, the oven manufactur ing company failed our powder suppliers.

When asked how much the machine was worth, the president stated he "didn't know." When I fur- ther asked him how much he would give me for the oven, he replied, "not a plugged nickel." My feelings exactly.

It is my impression that infrared convection technology would work on flat products, such as panels, but has many problems with shaped products that require a certain even heat, especially outside the line of sight. Because of the many requirements for archi tectural extrusions, one needs to evaluate

every change of mass and shape. Line of sight seemed to be a problem in our testing, where the inside of each coated piece achieved almost no cure.

When it comes to architectural or decorative powder applications, heat can be one's most powerful ally or enemy. When working properly, heat must be in abundance to ensure all molecules touch and to opti- mize the specific powder technology performance. The consequences of too little heat are diminished performance in weathering and even film integrity. Too much heat, however, and you have degradation in powder color and physical characteristics.

In our case, the requirements present definite challenges for infrared convection technology tha t this oven seems incapable of overcoming. Certainly, the oven manufacturer 's president could not demon- s trate one example of a cured powder during his visit. This in light of the fact tha t he presented this oven as capable of providing a "stand-alone" heat source for architectural powder coatings to myself, the previous owner, and to our powder supplier. He made no objection to the extrusion size, extrusion share, or powder application during the trial.

I believe infrared convection ovens can be built to

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The IR/convect ion heat panels must be adjusted for each project to max imize the heat efficiency onto and into the products.

service powder application systems, but in my world of architectural-grade powders on aluminum extrusions, I cannot, to the best of my knowledge, use the full potential of this technology. In fact, I am stuck with a poor excuse for a toaster oven. I cannot allow edges to get glowing hot and cannot heat sides more than tops and bottoms. My customers need unifor- mity in color and cure. To use this technology to gel the coatings also runs the risk of uneven gelling and, thus, tex tur ing the powder and ruining the gloss. Polyesters, TGIC polyesters, and PVDF tech- nologies might react individually and differently.

For now, our facility will use an 80-foot-long convection oven, previously built as a backup. This should serve our current process heating needs.

As for future needs, we will only buy products, whether new or secondhand, after first conducting a thorough investigation.

(Ed. note: the vendor mentioned in this article was not contacted for an opinion.)

For more information, contact the author at buddy, [email protected], glf

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purchasing infrared/convection equipment

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