Infrared Questions & Answers
Last year we published a book about infrared that was very well received. The following is an extract from one of the popular section of "The Infrared Handbook", Questions & Answers.
Common Questions and Answers About Infrared
The following questions and answers are based on conversations B-Tec has had with end users in the automotive refinishing market over the past several years. Included are points to consider when purchasing infra-red paint curing equipment.
Q. What is the difference between short wave and medium wave?
A. Short wave is faster curing than medium wave as it takes the paint to a higher temperature and has no warm up time. When purchasing infra-red short wave equipment, make sure the unit has a flash-off or half-power timer. The reason for initially running the unit at half power is to ease the solvents from the paint before the intense heat is applied. If this is not done, the paint could be skinned, trapping solvent that will produce solvent pop (a pinhole effect) to the finish.
Medium wave units do not require a flash-off timer as their emitters can take several minutes to reach full power. The same can be said for catalytic infrared, which is also medium wave.
Q. What size area can be covered with a mobile infra-red system?
A. Generally speaking, not much more than the infrared head size itself, unless of course its a moving arch. Short wave infra-red does not warm air directly, so it tends to be only heating the localized area, but there will be a certain amount of spill-over and heat-transfer from the heated part via conduction. Establish what the curing area of a unit is before purchasing to ensure that it will give you the desired coverage. Area coverage increases as you increase the distance from the panel, but this also reduces the temperature and increases the curing time.
Q. How fast will infra-red cure paint?
A. The fastest time on urethane is about 6 minutes with an average time of about 12 minutes. It would be foolish to attempt a quicker cure for the sake of a couple of minutes. Check that the manufacturer can provide good data on curing and, if possible, on the paint you are using.
B-TEC Systems produces its own curing data that shows you exactly what the curing time will be on the various products and by brand, the only company that does this.
Q. How much does it cost to run?
A. Using a 3kW unit, like our B-Tec IR-B03, for example, costs less than 10c per repair. (Based on a 15 minute cure cycle)
Q. Do you need to remove plastic and rubber parts?
A. Most of the heavier plastic parts can be heated with no adverse effect, but it is recommended that they be allowed to cool before handling as they could deform when hot. Any thin plastic moldings should be removed if adjacent to a cure area, or can be masked using foil tape over the sensitive part. This will reflect away approximately 50% of the infrared energy.
Q. Will infra-red cure waterborne paints?
A. Yes. In Europe and in many States in the USA, where the use of waterborne paint is already common, infrared systems are used effectively on waterborne primer. Waterborne basecoat is best dried using only air movement. If infrared is used on basecoat it is advisable to only run on half power. If the infrared unit has temperature control set it at 70°c / 158°f. The exception to that advice is when drying waterborne basecoat on spray-out cards with our ST-01 paint sample dryer which uses both infrared and air movement. Dry time is around 90 seconds.
Q. Why does black paint cure quicker than white?
A. Infrared is a wave form that can be reflected. Silver and white colors will reflect away a certain amount of infrared energy, although the difference in curing time between white and black is only about two minutes.
Q. Which products can I cure using infra-red?
A. All two-pack / urethane paint systems including, primer surfacers, high-build primers and clears / topcoats. It can also be used on lacquers and some air drying products. Remember when you are using infrared energy to accelerate productivity, you are doing 2 things, curing and drying. The heat generated is speeding up the molecular cross linking of the paint (curing), whilst the heat is also accelerating the evaporation of solvents and in some cases water (drying). Infrared can also be used for body fillers, waterborne paints, sealants and bonding products. Ask for more specific paint curing data when purchasing infrared equipment
Q. Can IR be used safely when curing paint on aluminum?
A. Yes, this has been done for many years and curing times are similar to mild steel. Aluminum is a very good conductor; therefore it heats quickly and also cools quickly when IR is switched off. In some cases aluminum panels will distort slightly as heat increases, but returns to its original shape quite quickly. If erring on the side of caution and you have temperature control system, set at 180F and add 4 minutes to full bake cycle.
If you have questions about anything that’s not been covered, please let us know we will be delighted to give you the answers. [email protected]
Peter Phillipson
Technical Sales & Marketing Manager (IR)
B-TEC Systems USA
www.bteccleaners.com