NEW VERTICAL POWDER COATING PLANT WITH FLASH OXIDIZING IN LINE (FOX)

1) PRE-TREATMENT TUNNEL

The pre-treatment tunnel is the part of the plant that treats the profiles' surfaces to prepare them for subsequent coating process. SAT S.p.A., for the pre-treatment tunnels, makes use of the "cascade" technology, which gradually replaced the "spray" system since it grants the following advantages:

1) Less maintenance required (no nozzles to clean periodically)

2) A more strong chemical attack (the chemical solution covers the piece in a similar way to immersion)

3) Reduced consumption of chemicals (due to the regular flow of the liquid along the profiles only few drops are generated and the drag out between two contiguous tanks is lower)

4) About 70% reduction of electrical power installed (pump with lower prevalence and flow, and therefore smaller electric motors)

By the end of 2009 SAT S.p.A. introduced a new "Modular" version of pretreatment tunnel with stainless steel tanks and external structure and PVC walls.
The modularity of the tunnel grants:

1) A standard module to be used for each stage

2) A time reduction as far as regards the installation period

3) A simplification of the maintenance operations

4) The spare parts interchangeability (all the pumps have the same prevalence and flow).

2) FOX

The system has been thought as an innovation to apply to vertical powder coating lines. By means of it the profiles receive a flash oxidizing layer with a thickness between 3 and 8 microns before the following coating phase.
Basically it consists of:

1) Hook transfer unit to divide in continuous the line of profiles arriving from the pre-treatment tunnel in two groups of 22 hooks each one proceeding on a separate conveyor (two conveyors working in parallel);

2) Hook transfer unit from conveyor to profiles support jigs (there are 6 jigs working in total, 3 for each side)

3) Double bridge crane to take the jigs

4) One tank where the oxidizing process takes place, one tank for the following rinse

5) Hook transfer unit from jigs to conveyor

Working Cycle:

1) The hooks, driven by two conveyors in parallel in groups of 22 units, once arrived to the transfer position, corresponding to the oxidizing tank area, are transferred from the conveyors to the jigs (always in groups of 22);

2) The double bridge crane takes the two jigs in the parking position (A) and dip them into the tank where they stay as long as the profiles receive from 3 to 8 oxide microns. The jigs are laid on adequate supports located on the tanks edges. The electric current is brought directly to the profiles through special "piano" contacts able to adapt themselves to any kind of section;

3) Once laid the jigs at the oxidizing tank position, the bridge crane takes the free jigs in the rinses tank parking area (B) (the profiles, in this case, have just been transferred from the jigs to the conveyors) and transfers them to the oxidizing tank parking area (A) (ready to receive the profiles that must be treated in the oxidizing tank);

4) The bridge crane moves towards the rinse tank where it takes the jigs and deposit them into parking position (B) to allow the profiles transfer from the jigs to the conveyor;

5) Finally the bridge crane takes the jigs from the oxidizing tank with the treated profiles and dip them into the rinse tank.

2) FAST CLEANING BOOTH

This booth has been developed in compliance with the need of the most demanding powder coating markets in terms of industrial performances, healthy working environment, ergonomic use, cost effectiveness and quality of the final product. The entire powder coating application system has been re-design with the aim to get a colour change time in less than 5 minutes. The booth foresees the recovery circuit for the over-spray and is provided with electrostatic powder coating deposition equipment.

The booth is suitable also for refitting of existing vertical powder coating plants replacing the old equipment.
1) CLEANING

a) the cleaning process of the booth foresees a series of operations scheduled, according to a logic sequence automatically managed

b) the whole cleaning process of the booth (including the guns) does not require any intervention of the operator

c) Thus the booth cleaning time takes less than 5 minutes.

Solutions studied to reach that result:

1) Four sliding belts (vertical walls and booth bottom floor) automatically cleaned in continuous.

2) As far as regards the powder hoses, inner part and external surface of the guns a cleaning process automatically managed through an optimized sequence of operations has been studied.

2) QUALITY

a) With reference to previous generation of booth models, thanks to an accurate study of the air extraction system and of the profiles path in the booth the powder deposition efficiency has been improved that is an increase of the share of powder that applies directly on the profiles. With the same number of guns it is possible to increase the conveyor speed even with profiles difficult to be painted.

b) Quality of the coating improvement both in terms of uniformity of the layer thickness and in terms of powder penetration: thanks to the cloud of powder which surrounds the profiles all around in the booth before being extracted through the vertical slots.

3) RUNNING COSTS

a) The high efficiency of the deposition allows also a relevant reduction of the powder consumption in case of very small lots that are painted in powder-waste modality and in general, with all lots, during the waste-powder phase that occurs at the beginning of a new lot after a colour change (before switching to the powder-recovery modality). Thanks to the four sliding belts automatically cleaned, the powder, during the powder-recovery modality, is recovered in continuous so comparing with the situation of the previous generation booth model (where the powder lays on the walls until the colour change operations are carried out and finally is wasted), the fast cleaning booth will allow to have an additional share of saved powder.

4) SAFE ENVIRONMENT

a) Per garantire un ambiente di lavoro più sano e pulito è stato studiato un sistema di aspirazione particolarmente efficace. Lo stesso rimane operativo sia durante la fase di spruzzatura sia durante l'attività di pulizia per cambio colore. Questa circostanza limita lo spazio di movimento delle particelle di polvere contenendole all'interno delle tre pareti verticali della cabina. In questo modo l'aria intorno all'operatore resta sempre pulita. Inoltre, lo stesso operatore, non intervenendo più nelle operazioni di pulizia della cabina e delle pistole, non è più esposto, come accade nelle cabine a due teli, ad un ambiente polveroso. Thanks to the automatic cleaning of booth walls, guns powder hoses, the operator of the booth remains outside to control the process, to clean the powder centre and to feed the booth with required powder. The area of the booth can be surrounded by protective fences and the personnel will not be forced to have contact with the booth and the guns anymore.

b) The whole system has been studied in compliance with ATEX directive.

5) PLANT PRODUCTIVITY LEVEL

a) Thanks to the reduced colour change time, the flexibility of the line will increase.

3) OVENS

The drying oven evaporates the water film left on the profiles' surfaces after the chemical treatment in the tunnel. The operation must be carried out before applying powder.
The polymerization oven is where the powder polymerization takes place at a temperature generally between 170 and 200° C.

Drying Oven As far as regards the drying oven, SAT S.p.A. can propose two versions:

1) The "U" shape path drying oven: drying chamber with "U" shape path and environment heating carried out by means of a cylindrical heat exchanger fed by a burner.

2) The "Energy saving" drying oven: drying chamber with straight path and environment heating carried out by means of hot water battery . The advantages of this configuration are:

a) Reduction in thermal energy consumption (no burner installed but hot water battery heated by the water of the burner closed circuit. The energy required by the drying oven is partially provided by the curing oven fumes heating recovery).

Polymerization Oven

As far as regards the polymerization oven, SAT S.p.A. can propose two versions:

1) A polymerization oven consisting of pre-oven, curing chamber, heating group made up by a cylindrical heat exchanger fed by a burner.

2) A polymerization oven with "Revolving Doors"/ "Constantly Closed" (Patent).

It consists of a curing chamber and a heating group made up by a cylindrical heat exchanger fed by a burner. The difference with the other version is represented by the three "Revolving Doors" insertion in correspondence of the oven front side. The "Revolving Doors" allow the entrance/exit of the profiles from the oven keeping the same entrance/exit constantly closed creating therefore a barrier between the internal side of the component and the external environment. This innovation introduces important advantages if compared with the other version:

a) No need of an IR oven to jellify statically the powder on the profile surface before the curing oven entrance (thanks to the lack of relevant swinging of the profiles along their path throughout the curing oven and thanks to the absence of a strong air flow against the profiles covered with fresh powder);

b) No need to foresee an operator to clamp a chain at the bottom of the profiles in order to limit the mobility of the profiles and avoid that the swinging of the profiles in the curing oven could allow the profiles to touch each other with consequent release of fresh powder (risk of color cross contamination) or damage/jam of the profiles (one worker less per shift);

c) Drastic reduction of the energy consumption of the whole system: no energy consumption for the IR oven (thermal energy for the gas catalytic combustion and electric energy for the pre-heating of the IR oven catalytic panels); reduction of the thermal consumption of the curing oven, thanks to the permanently closed doors of the oven and to the elimination of the flow-rate of exhausted air from an extraction point placed inside the curing oven;

d) Final product quality improvement: due to the physical separation between the building environment and the curing oven, the exchange of air between the oven and its surrounding environment results to be drastically reduced therefore the quantity of pollutant airborne dust particles that can enter into the curing oven and deposit on the profiles surface will be reduced as well.