WHIRL SINTER PLANT (currently we do not carry this out!)
Free-programmable coating plant BZ-3
With the help of whirl sintering component parts may be coated with an all-around surface protection in a regularity, which could not be achieved in other coating processes. For the sector of fittings of the casting industry we have developed a plant, which exceeds the quality of current coating options by far.
Thus the quality of the coating in the process of coating the preheated casting parts with a pistol always depends from the pistol operator. As good as the operator leads the pistol, as good is the coating quality regarding layer thickness and surface quality. Rough surfaces and irregular layer thicknesses determine the picture.
In the case of whirl sinter coating with a robot, which can maintain very exact layer thicknesses, there limits, which cannot be solved better technically, or which can only be solved at significantly higher financial expenses. A unit weight of more than 60 kg is hardly be economically solved with a whirl sinter robot. Also, there are coating imperfections in the interior, which result from the fact that the component parts cannot be turned or for construction reasons are only turned incompletely after the coating.
These imperfections of the two coating methods described above can be fully excluded with our whirl sinter plant BZ-3. At the same time in the serial plant a capacity up to 120 kg may achieved. Higher capacities are subject to a surcharge.
Description of the process
The coating plant is designed for the whirl sinter coating of complexly formed metal parts with synthetic powder. This plant may be used for nearly every fluidifiable synthetic coating powder.
After the sand blasting and cleaning by blowing down the parts are positioned on a pallet conveyor or linking belt conveyor.
Upon pressing a button the lifting door at the furnace opens and the positioned parts are moved into the furnace. After a cycle the door closes again. The furnace should be adjusted to a preheating temperature of up to roughly 220°C. After the lapse of the preheating time (roughly 20 - 30 min.) the parts are positioned on the feeder table of the whirl sinter plant. In the case of heavy parts a quick release device is added to the hot parts. Light parts are manually inserted in the quick release device.
Thereafter the automatic program of the coating centre is taken into operation by pressing a push button. The undercarriages and lifting devices take the loaded quick release device and transports it from the feeder table to the handling unit. The handling unit, the arms of which then immerse in the whirl sinter bath, turns the loaded quick release device in the fluid bath in various directions and axles, partly more than 360°.
Once the coating process has finished, the lifting device of the undercarriage is switched on automatically, lifts the loaded quick release device out of the handling unit and takes it to the settling table.
Before reaching the settling table the quick release device is taken manually or automatically to the cooling track, after roughly 10-20 min. of cooling down the coated work pieces may be taken from the quick release device. Depending on the construction of the parts and the powder type used either the repair of the contact points and packaging or the after-heating for the hardening of the coating follows.
With the automatic, program-controlled 360° turning in various ways in the whirl sinter baths, the work pieces are coated with a regular coat thickness. In particular, also on the interior surfaces.
As the temperature of the work pieces, the transporting and handling times, as well as the immersion times of the preheated parts in the fluid bath are controlled automatically, the coating qualities are reproducible in large batches. Therefore the coating conditions specified by the customer for the special application are met reliably with the use of the coating centre.
As the automatic process can be varied with the programmable logic controller, the handling and coating process of the BZ-3 is very flexible. It may therefore be adjusted within huge limits to the special product specifications as well as different local production conditions and requirements.
The plant is designed to heat the furnace automatically so that with the beginning of a shift the operating temperature is already achieved. At the end of the shift the button "follow-up" is pressed at the furnace so that the plant automatically reaches the operating standstill.
Coating capacity of the coating centre
Theoretically the undercarriages and lifting devices may return to the handling unit with a newly loaded quick release device every 2 min.
The real coating capacity, however, is significantly influenced by the construction and the weight of the work pieces to be coated as well as the process organisation of the relevant production company.
Furthermore, the actual coating capacity is determined by the number of preheated parts, which a particular quick release device can take up in one batch. This number can vary, for example between 1 and roughly 15 parts depending on the size of the work pieces. The furnace's preheating capacity must be adjusted to the theoretically possible speed of the coating centre.
Assuming that on average the coating batch weighs roughly 20 kg, it is possible to coat roughly 4.8 t in one shift in a 2 minute cycle.
Size of the plant
The plant requires roughly a width of 10 m (without cooling track) and a length of 24 m. In addition to this there is the cooling track used, which can be at an angle of 90°, or which may be directly adjacent to the plant. 4.50 m hall height is sufficient as height.
Whirl sinter bath
As initial filling roughly 800 kg coating powder must be filled into the bath. Now compressed air (from the compressed air net or from a side channel compressor) is blown from the bottom through the fluid base into the synthetic powder. This results in the whirl sinter powder fluidifying. If the whirl sinter bath is not required the synthetic powder may be protected with a lid against pollution. The whirling up cannot be seen as a static process, which is adjusted once. Due to changes of the powder levels in the bath the manual readjustment of fluid air is inevitable. This also means that the operator must have relatively free, unimpeded access to the whirl sinter bath during the processing.
The cooling track
All parts set down on the unloading table are either manually or automatically transported to the cooling track. On the cooling track the parts must cool down at room temperature as long as necessary for them to be taken out of the quick release device without damaging the coating.
The powder suction necessary at the whirl sinter plant
At the whirl sinter plant there are 3 acquisition points for suction. The entire handling device with the whirl sinter bath is in a cabin with door openings. The undercarriage is in its movements freely accessible either by opening the doors with the air pressure cylinder or by manually opening via the undercarriage. At the whirl sinter bath there is a side suction for the powder, which gathers the majority of the escaping whirl sinter powder. The second suction point is directly above the undercarriage. All directly rising powders are gathered here. The third suction point is at the outlet of the undercarriage towards the unloading table. It must be noted that generally powder only escapes minimally from the whirl sinter bath. At most in the case of too much whirling up of the powder or during the coating process the increased escape of powder might be possible. The sucked off air is led to filters with an automatic cleaning system.
The ways of the undercarriages and lifting devices are limited in time. The undercarriages and lifting devices may only move if the handling device is set to its normal position. At the unloading table there is an electrical barrier so that no second quick release device may be set down onto another not unloaded quick release device.
Services provided by others
For the assembly and operation of the coating centre
- Oil-free, dry air, max. 7 bar
- Electricity 380 V three-phase current, roughly 50 kW lead performance
- Chimney connection
- Flat, dry hall floor, covered
- Possibility of blowing the sucked off exhaust airs back into the hall
- Assistants and fork lift truck for assembly
Summary of the advantages of the BZ-3 coating process
- Regular interior and exterior coating in a few seconds
- High, consistent coating quality of the surface, interior and exterior, due to the possible turning of more than 360° in various directions and axles
- Reproducible coating quality and layer thickness due to automatic, programmable logic controller and thus avoiding manual works
- Due to the high level of automation any negative impact on the part of the operating personnel is avoided
- Multiple or manifold armament of the handling device is possible depending on the size of the work pieces to be coated.
Example for a coating costs calculation
- Personnel required for the operation of the BZ-3:
- Examples for the work pieces to be coated:
Slide valve with nominal size or DN 100 (=interior diameter 100 mm)
Consisting of a housing, a cover and an attachment each
Surface to be treated (interior and exterior = roughly 0.5 m³ / entire slide valve). Coating capacity of the BZ-3 for the above slide valve.
- Annual working time for 1 shift per 8 hour day is assumed:
Roughly 1,750 hours/year
- Usable operation time of the plant with an efficiency of 70 %:
Roughly 1,250 hours/year
- Number of complete, coated slide valves per year:
At 1 shift/day, 220 shifts/year roughly 75,000 units/year
These production figures are based on an assumed working cycle of 2 min/coating cycle as well as the capacity of the quick release device of 4 valve housings, 8 covers and 8 attachments each per cycle.
The actual coating capacity depends on the size and form of the work pieces, that is on the number of parts, which the quick release device may carry in each coating process.
Furthermore, the actual coating capacity significantly depends on the organisation of the operating process and the logistics for material supply and material flow.