CD Automation manufactures top-quality thyristor power units for the efficiency enhancement of industrial processes that require precise power and temperature control monitoring. These units are used in a variety of sectors, including the many applications using infrared lamps.
We have previously dealt with the professionalism with which CD Automation accompanies its customers engaged in stretch blow moulding processes. An operation in which infrared lamps play a major role.
The same occurs in a process that is fundamental for the execution of quality paintwork, which we will deal with extensively today: paint drying.
Drying: a thermal process
Basically, heat is required to apply various coatings such as paint and colour. The function of infrared lamps is in fact to ensure the drying of wet water-based coatings and to accelerate the melting process of powder coatings. To optimise the result, it is essential to adapt the infrared emitter to the characteristics of the product to be heated, in terms of wavelength, shape and power. Correct adjustment of the radiation enables rapid absorption of the paint, avoiding overheating and ensuring protection of the material and the environment.
The steps in paint drying
Paint drying is a process normally consisting of two phases: a first, purely physical phase during which the evaporation of solvents (water, hydrocarbons, alcohols, ketones) occurs, and a second, chemical phase in which the polymerisation of the resins (binders) contained in the paint is achieved.
Not all paint products require the chemical phase: thermoplastic (or non-crosslinkable) products finish drying with the evaporation of solvents. In contrast, thermosetting (or cross-linkable) products also have a polymerisation phase.
The steps in paint drying
The drying of paint products generally takes place in an oven, in which the temperature depends both on the type of product, the material of the painted surface and the type of technology adopted.
Drying can be carried out using different equipment:
- gas-fired bare-flame heating panels;
- gas heating panels by catalytic combustion without flame;
- electrically heated tubes, lamps and radiant plates;
- microwave irradiation.
The many advantages of infrared drying
Infrared lamps are able to produce targeted, direct heat on surfaces, ensuring even and rapid drying, for an impeccable result in terms of both aesthetics and protection. In addition, the advanced operation of these heating systems means that moisture is eliminated and operation is based on electricity, which does not require the use of chemicals or fuels, which are harmful to health and costly to the pockets of contractors. This advantage means that infrared lamps can also be used in the presence of flammable substances, such as paint, ensuring the safety of workers.
A radiation in resonance with the material
For the benefits listed above to occur, however, it is necessary that the electromagnetic radiation emitted by infrared lamps is absorbed by the molecules of the paint product. In other words, it is necessary that the energy carried by the radiation is able to induce a vibration in the molecules, known as molecular agitation, with a consequent rise in the temperature of the material.
Since the proper vibrational frequency of a molecule depends on its structure, for IR rays to be easily absorbed, the wavelength of the radiation must be synchronised, i.e. resonate, with that of the material of which the paint product is composed.
Automotive requirements
Industrial painting is a process that is widely used, particularly in the automotive sector, an area that is constantly striving for speed and increased production. The targets set by the sector require a drastic reduction in paint drying times. And it is precisely in the enterprising search for a solution for the automotive industry that the prestigious know-how of CD Automation comes into play.
A tunnel for drying railway carriages
The company, based in Legnano, took part in the design of a tunnel for drying and annealing paints, using infrared lamps, on railway carriages. This paint drying technique was for the first time successfully applied to such large areas, accommodating the customer’s request to increase productivity by converting the existing oven and thus avoiding the construction of a new plant.
Paint drying with infrared lamps: plant design
To reduce paint drying times and increase productivity, two parallel walls consisting of 59 zones each were installed, with two short-wave infrared lamps per zone, for a total of 236 lamps of 3750W and a total system power of 0.9 MW.
The conversion of the hot-air oven to one with IR technology has produced an amazing result: a production time reduced by 12.5 times compared to the performance of the previous convection oven. The total time spent in the oven by the carriage undergoing the industrial painting treatment has in fact dropped from 100 to 8 hours, corresponding to just one working day.
CD Automation’s contribution to paint drying
CD Automation’s team of experts has structured a precise infrared lamp management and control system for the correct management of the power used in paint drying.
The system set up by CD Automation consisted of three REVO PN 24 multi-channel power units and as many REVO PN 12 multi-channel power units and made it possible to:
- optimising consumption;
- monitoring electrical variables;
- early diagnosis of heating element breaks and short circuits on thyristors;
- fieldbus communication.
REVO PN’s valuable contribution to paint drying
CD Automation’s REVO PN unit makes it possible to significantly reduce power peaks, keeping them below contractually agreed levels and avoiding penalties and unexpected expenses.
REVO PN is a modular product, capable of handling up to 24 heating elements. By synchronising the switching on of all channels, problematic voltage peaks are avoided and the power factor is kept close to 1.
Last but not least, REVO PN’s “Dynamic burst firing” mode reduces flickering in short-wave infrared lamp applications.
Want to find out how to make your paint drying processes more efficient and competitive? Contact us and book a free consulting session with one of our experts. You will receive strategic proposals tailored to your needs.
