The process of crosslinking a polymer paint film occurs under the influence of heat in several stages: melting, gelation and curing. For these processes of forming a polymer coating of powder paint, a polymerisation oven is used.
The principle of operation is to heat the air in the inner volume of the chamber and recirculate it through the heating elements.
To maintain the same temperature throughout the chamber (+/- 5 C), the correct air recirculation rate must be set.
The paint polymerization cycle consists of the following steps:
— products with applied paint are loaded automatically or manually into the oven. The stove is closed with doors or, in an automatic version, with an air curtain that does not allow warm air to pass through;
— on the control panel, the specialist sets the baking program;
— heating the internal volume of the oven to the temperature of powder paint baking. Usually paint manufacturers give a technical passport for the powder or indicate the time and temperature of baking on the box;
— maintaining the set temperature with a delta of +/- 5 C for 10-20 minutes. The temperature inside the oven is displayed on the controller panel;
— turning off the heating and turning on the exhaust fan for 5 minutes. Ventilation of the powder paint drying oven is necessary for suction of hot air and harmful gases formed during the polymerization process;
— signal of the end of the cycle. The product can be pulled out of the oven.
POLYMERIZATION FURNACE DEVICE
The polymerization oven is a modular prefabricated structure with good thermal insulation.
The frame part is made of sheet metal 1.2-1.5 mm thick, the inner lining is made of galvanized steel, the outer elements are powder coated.
The inner cavity of the walls is filled with heat-insulating material. The design of the chamber ensures that the achieved temperature inside the chamber is maintained for a long time, preventing heating of the outer walls. The opening for loading products is closed with heat-insulated doors equipped with a locking mechanism.
Material metal 1.2-1.5 mm
Heating type heating elements / quartz lamps
Construction type sandwich panel
Electricity consumption 36 kW
Adjustment temperature 0-300 °C
The oven has a heating element that can be easily and quickly accessed for replacement or maintenance.
Also, the polymerization oven has a ventilation system that circulates air.
Its design is made so that heat loss is minimal.
STANDARD CHARACTERISTICS OF POLYMERIZATION FURNACES
— operating temperature range: 0-300 °C;
— maximum set temperature: 300 °C;
— working ambient temperature: from 0 to 35 °C;
— relative humidity: up to 65%;
— mode of automatic ventilation of the furnace space at the end of the cycle: yes;
— computer control: yes.
TYPES OF POLYMERIZATION OVEN
Polymerization oven schemes may differ depending on the needs of a particular production. They can be made to order. The main factors affecting the operation of polymerization ovens are the type of fuel, the estimated power and the number of parts to be painted.
There are several types of polymerization ovens:
— dead-end and checkpoints;
— on a thermoblock and on quartz lamps.
DEAD-END AND PASS-THROUGH OVENS
Dead-end polymerization ovens are needed for products in small-scale production. Or in a large production, if there are parts that are painted separately. In the dead-end there is one opening through which the painted product is loaded and unloaded.
Due to the presence of doors on one side for unloading / loading parts, such ovens retain heat better, therefore, they are more economical in terms of energy consumption.
When large parts are to be painted or the volume of work increases, it is better to put continuous polymerization ovens in production. They imply a transportation system. Such ovens are equipped with several openings for loading and unloading products along the conveyor.
Dead end polymerization oven
Continuous polymerization oven
POLYMERIZATION OVEN ON A THERMOBLOCK
shadows (ribbed) of 2.0 kW, mounted in a separate thermoblock with convection. Heat is distributed from the thermoblock throughout the entire volume of the furnace using ventilation ducts.
QUARTZ LAMP POLYMERIZATION OVEN
electrician (quartz lamps)
POLYMERIZATION OVEN CONTROL
The polymerization oven is controlled via the control panel.
Control panel device
The control panel is made of metal. The front panel contains elements for control, signaling and monitoring.
There are wiring devices inside the console.
On the upper plane of the control panel there are warning lamps, control of the technological cycle and a sound indicator that notifies of the end of the polymerization process.
Changing the oven temperature
Enter (hold for 3 sec.) → use the up and down keys (↑ ↓) to select the “Settings” menu → enter → “Temp. back. »→ use the up and down keys (↑ ↓) to select the required value (example 180 / 200C) → enter (hold for 3 seconds) → exit.
Changing the delta temperature of the furnace
Enter (hold for 3 sec.) → use the up and down keys (↑ ↓) to select the “Settings” menu → enter → “Temp. Delta” → using the up and down keys (↑ ↓) select the required value (example 2C) → enter (hold for 3 seconds) → exit.
Enter (hold for 3 sec.) → use the up, down keys (↑ ↓) to select the “Settings” menu → enter → “Heating time” → use the up, down keys (↑ ↓) to select the required value (example 10/15 min.) → enter (hold for 3 sec.) → exit.
Heating element cooling time (blowing / exhausting)
Enter (hold for 3 sec.) → use the up, down keys (↑ ↓) to select the “Settings” menu → enter → “Purge time” → use the up, down keys (↑ ↓) to select the required value (example 3 min.) → enter (hold 3 sec.) → exit.
The control panel controls the technological process and displays:
— temperature regulator setting mode;
— temperature controller programming mode;
— real temperature in the chamber;
— the set temperature of the technological process;
— set time of temperature control;
— the mode being executed at the moment (“PROGRAMMING”, “HEATING”, “SHUTTER”);
— indication of the end of the polymerization process
The power cabinet is also made of metal. It is thanks to the power cabinet that the polymerization oven is switched on.
The power control cabinet is responsible for:
• voltage supply to control elements;
• control of electric heaters.
• control of electric motors.
• protection of electrical circuits.
PARAMETERS FOR SELECTING A POLYMERIZATION OVEN
When choosing a furnace, you need to take into account all its variable parameters, among which the most important are the following:
— furnace equipment: type, shape of the furnace, dimensions, heating system, operating temperature, heat transfer, ventilation, safety at work;
— transport chain conveyor: type, feed rate, working load, shape of suspensions, and the system of fastening the painted parts on them, productivity;
— the parts to be painted: are the determining factor affecting the adhesion of the polymer film, the consistency of the color and gloss of the coating surface;
— powder paint: type, coating thickness, color, gloss, polymerization parameters, special conditions.