Infra-red curing for powder coating of aluminium sections

A. A number of infrared techniques are available. It is important to understand that infrared is a directional radiant heat source. It is also color sensitive - darker colors tend to absorb more energy than whiter shades. Infrared is a great technique for fairly two dimensional parts of a similar or identical color. In general it is more expensive to operate than a more conventional circulating gas oven.

A. IR heating is often used as preheating system in powder coating plants here in the Netherlands. For aluminum extrusions as well as for steel structures. For Al, IR is used as preheating before entering the oven in order to avoid dust and colour contamination.

A. Depending on what type of IR you are using will dictate what the results will be. Electric IR is more of a line of sight type of IR. Gas IR with a small amount of convection air will cure a three dimensional part throughout. These gas IR ovens will also use 1/3 the energy of a electric IR oven.

A. We have recently switched to IR heat in our paint system. We use high solid conventional paints, not powders, so some things will be different, but many others will hold true. We are using gas catalytic IR emitters and have had very good luck with them. We are now accomplishing in 6 mins. the same cure that took 45 mins before. We do run a wide selection of metal types and weights. Steel, aluminum and a few others. 450 pound steel castings all the way down to aluminum shimms that way less than one pound. We accomplish this by throttling back the gas flow to the emitters. We run from 10% capacity up to 100% capacity. You will get a more even cure with a slight convection air flow, but still be careful of deep recesses and boxes. Our paint cures through internal chemical reaction.

A. To answer the question for Mr. Himanshu Shah, gas IR will be a better option for your heating requirements, but unfortunately natural gas is not in abundance in India. When you select electric IR lamps, make sure you have the right product as maintaining and replacing them is a big hassle.

Would you please post the answer to Mohmoud Aysh of Saaudi Arabia's question on how to build an infrared oven?

Thanks,

Hi, Rob,

If anyone responds to Mohmoud, the response will be here; but no one has so far, and I doubt that anyone is going to do free drawings of ovens. But I can strongly recommend "Powder Coating" by Roger Talbert -- a 141-page softcover published by Chemical Coaters Association International, Cincinnati (ccaiweb.com). It has a 10-page chapter about curing ovens, with sketches, as well as info about dry-off ovens, and it clearly explains the features that should be included in each type of oven and why. Also, there are a number of consultants who could be retained to assist you with the design of an oven. Good luck.

Hi Raji. I think that one is partially answered on this already, with a comment about line of sight, and greater efficiency claimed for gas powered units, etc.

Good luck.

Regards,