Presumes
Maximum size of parts: L x W x H = 2600 x 400 x 1850 mm
Equipment;
Technological Conveyor automatic speed V=1.2 mtrs/min.
Speed regulation between 0.5-2.5 mtrs/min
- Pretreatment Stand MNA-3-LPG, total size 16,7 mtrs
Enter size L=2,5 mtrs
a. Washing, degreasing and phosphating; L=3,6 mtrs
-number of spray frames – 10
-number of nozzles in frame – 18
-number of nozzles in total – 180
-delivery of the pump – 162 m3/h
-power of the pump – 15 kW
-vessel 4 m3 for active liquid
-inner heat exchanger with LPG burner – 160 kW
-temperature 500C
-mechanical oil separator
– solution filter
-the dosing system, membrane pump with regulator
-washing time – 3 minb. Dripping zone L= 3,1 mtrs
-time of dripping – 2 min 30 secc. First rinsing; L= 1,2 mtrs
-number of spray frames – 4
-number of nozzles in frame – 18
-number of nozzles in total – 64
-delivery of pump – 38 m3/h
-power of the pump – 3 kW
-vessel 1,5 m3 for water
-first rinsing time – 1 minc. Dripping zone L= 3,1 mtrs
-time of dripping – 2 min 30 secd. Fine rinsing; L= 1,28 mtrs
-number of spray frames – 3
-number of nozzles in frame – 18
-number of nozzles in total – 54
-delivery of pump – 33 m3/h
-vessel 1,5 m3 for water
-power of the pump – 3 kW
-one extra spray frame
-number of nozzles in frame – 18
-fine rinsing time – 1 mine. Dripping zone L= 2 mtrs
-time of dripping – 1 min 40 sec
Three openings to connect to exhaust system with three ventilators
Operating space made of stainless steel.
Pipes made of PVC or S/S.
1 unit
- Automatic Dryer after water AST-1-KLPG:
- operating space dimensions L x W x H = 7000 x 3000 x 2800
- air curtains each side to avoid heat losses
- one indirect heat exchanger heated with liquid petrol gas to produce 200 kW of rated power
- three blowers 6000 m3/h of air delivery
- two openings to connect to exhaust system
- temperature sensor and temperature regulator
- overheating sensor
- circulation sensor
- operating space made of zinc plated steel
- thermal insulation 200 mm thick
- drying time 10 min 1 unit
- Automatic Curing Oven APT-2-KLPG for curing powder paints
- operating space dimensions L x W x H = 10200 x 3600 x 2800
- air curtains on one side to avoid heat losses
- two indirect heat exchangers heated with liquid petrol gas to produce 300 kW of rated power, of each
- eight circulation blowers, capacity of each 6 000 m3/h
- two openings to connect to exhaust system
- temperature sensor and temperature regulator
- overheating sensor
- circulation sensor
- operating space made of zinc plated steel
- thermal insulation 200 mm thick
- curing time 25 min
1 unit
- An overhead rail conveying system ATR, for the paint shop including the following:
- straight track with hangers L=400 mm 146 mtrs
- drive station 2 pc
- tension station 1 pc
- chain lubrication station 1 pc
- drawing of the track supporting structure 1 set
Procedure
The powder coating process consists of three steps:
1) Part preparation or the pre-treatment
2) the powder application
3) curing
In part preparation, there is removal of oil, metal oxides, welding scales, soil that is necessary to be done before the powder coating process. There are several chemical and mechanical means of doing this.
In powder application process, the usual method of applying the powder coating to metal objects is spraying the powder by using an electrostatic gun or Corona gun. This gun provides a negative electric charge on the powder. This is then sprayed towards the object which is grounded. This object is then heated. The powder melts in a uniform film and then cooled to form a hard coating. It is a common method to heat the metal initially and spray the powder on the hot substrate. Preheating enables to have a more uniform finish. However, there may be other problems like runs due to excess powder. Another type of gun is called as Tribo gun. This charges the powder by triboelectric function. The powder picks up the positive charge while rubbing along the wall of a Teflon tube in the barrel of the gun. These charged powder particles stick to the grounded substrate. Using a Tribo gun requires a different mixture of powder, than the more common Corona guns. Tribo guns are not concerned with some of the problems linked with Corona guns. Some of these problems are back ionization and the Faraday Cage effect. Specifically adapted electrostatic discs are used for applying powder. A different method of applying powder coating is called Fluidized Bed. In this, the substrate is heated and dipped in an aerated, powder-filled bed. The powder melts and sticks to the hot object. More heating is required to finish the curing of the coating. This method is usually used when the desired thickness of coating becomes more than 300 mm. This is the usual method of coating most dishwasher racks.
In Electrostatic Fluidized Bed Coating there is less powder depth in the bed. An electrostatic charging media is kept in the bed. As the fluidizing air lifts it up, the powder material becomes charged. Charged particles of powder move upward and a cloud of charged powder above the fluid bed. When a grounded part passes through the charged cloud, the particles will be attracted to its surface. The parts are not preheated.
In Curing, when a thermoset powder is exposed to elevated temperature, it melts, flows out and then chemically reacts to form a higher molecular weight polymer in a network-like structure. This cure process called crosslinking needs a certain degree of temperature for a particular length of time in order to reach full cure and establish the full film properties for which the material was designed. The powders cure at 200 degrees celsius in 10 minutes. Convection cure ovens or infrared cure ovens are used to serve the application of energy to the product to be cured.
