raw materials and dust production bays
RECEPTION, STORAGE AND RELEASE INTO THE PRODUCTION PROCESS OF RAW MATERIALS
The first step in the manufacture of thin ceramic slabs is the reception and storage of incoming raw materials. The basic ingredients that go into a finished tile are clays, sands and feldspars. These are routed to separate storage silos in a covered area of the factory. Before being accepted, however, all raw material consignments undergo rigorous quality checks to ensure they comply with the Company’s specified standards.
When the time comes for their use, each raw material making up the required mix is checked for quality and consistency by an automatic computerised weighing and dispensing system that will deliver the exact amount of each ingredient.
MILLING THE RAW MATERIALS
This weighing and dispensing system conveys the required raw materials to the grinding bay. Here they are fed into what’s known as a Continuous Mill. Water and pebbles are added to the mix. The pebbles will help grind up the ingredients as the mill turns. The resultant mixture will be a very fine paste with some 30% moisture content, known in the industry as “slip”.
ATOMIZING THE SLIP
The liquid suspension is forced at high pressure into a drying chamber where it is dispersed as a fine spray. The resultant dry powder is known as atomized dust. This fine-grained dust is now the ideal consistency for the subsequent production steps, allowing the material to move smoothly through the next phases. From the drying chamber, the dust is taken by conveyor belt to storage silos until needed on the tile production line.
pressing and decoration area
LOADING THE ATOMIZED DUST
The atomized dust, now with a moisture level of around 5%, is loaded into a hopper, passed through a sieve to remove any impurities, and then delivered to dispensers at the beginning of the production line. There are 2 dispensers at the head of the line since some products will require additional materials at this stage to give the tile surface a special effect. This will provide a first surface decoration.
The pressing phase is a key moment in the tile-making process. The main element is the hydraulic press and its control unit. The press is made of sheet steel and can exert pressures of up to 15,000 tons. It is the only press in the whole world able to make large 3 by 1 metre ceramic slabs. The press has a matrix on the upper part, and a conveyor belt below. The conveyor belt carrying the dust-mix is pushed upwards during the compaction or pressing phase by a rectangular piston. During pressing most of the air contained between the granules of the dust-mix is expelled. The result is a smaller, highly compacted tile body.
This pressing technique is state-of-the art. Traditional dust-pressing technology uses a ram to compact dust contained in a mould or die. The new pressing method does away with the die and so avoids most of the stresses caused by lateral thrust against the sides of the retaining die.
On leaving the press, the compacted slabs have rough, jagged edges. Special burrs at the trimming station will even off the tile edges.
The conveyor belt carrying the slabs now enters a gas-fired drying chamber. Special jets evenly distribute hot air above and below the ceramic slabs as they pass through the drying chamber on special rollers. On exit, the tiling slabs will have a residual humidity of 0.5%.
The production line employs latest generation decoration equipment. Seven silk-screen Rotocolor printers apply background dyes, a range of graphic designs and protective surface glazes. These are combined with an innovative digital ink-jet printer with 6 print-head bars. Each bar can carry a different colour pigment, meaning that up to 6 colours can be applied. The ink-jet printer operates like a plotter making repeated passes over the slab as required.
This digital decoration technique ensures high-resolution patterns or pictures. There’s no limit to the graphic designs possible. The line also caters for smaller formats.
gas-kiln firing and slab holding bay
The thin ceramic slabs are fired in natural-gas kilns with special gas burners. The slabs are baked for around 35 minutes at extremely high temperatures peaking at 1210 °C.
After firing, the cooling phase requires great care to ensure the finished slabs will be perfectly flat, exactly the right size and with no internal stresses.
The firing and cooling process boasts another important feature. As well as enabling the production of large-size, thin ceramic slabs, it is also a much more environment-friendly production process, consuming less energy and releasing fewer pollutants and less CO2 into the atmosphere.
FIRST SELECTION OF MATERIAL ON EXIT FROM THE KILN
At the kiln exit an automatic sorting machine makes a first selection of the fired slabs. This exit-check is essential for the subsequent processing phases, an indispensable in-process quality check that contributes to overall product excellence.
FIRED SLAB HOLDING BAY
The fired ceramic slabs are automatically removed and stacked on special racks. The loaded racks are then transported by laser-guided vehicles (LGVs) to their allocated place in the warehouse. They will be retrieved for finishing as per customer orders.
finishing and final slab selection
Whatever their size, slabs can be made available as simple 3 mm thick tiles for wall cladding requirements or in the 3.5 mm thick “Plus” version ideal for flooring applications.
The “Plus” version requires a special gluing production line. Here, a fibreglass underlayer is glued to the bottom of the slab. This backing considerably improves the tile’s mechanical strength and affords excellent bending and shock resistance.
The gluing line comprises:
- An electric multi-tier vertical drying chamber ensuring constant temperature throughout the gluing process.
- A glue-spraying station where the conveyor belt receives a protective paper covering supplied by a paper feed roll.
- A mesh applicator that unrolls and applies the fibreglass backing.
- A glue applicator robot programmed to apply glue over the whole slab surface right to the outer edges of the tile
- An electric multi-tier vertical drying chamber to accelerate glue drying.
The tile-cutting line handles all slab types, with or without the fibreglass backing. On exiting the firing kiln, the ceramic slab is 3070×1040 mm in size. It is now snap-cut to the exact format size of 3000×1000 mm or smaller. For simplicity’s sake, the cutting line comprises:
A computerized digital-control grinding machine. This is used exclusively for slabs with fibreglass backing. The slabs are loaded upside down, the underlayer uppermost. The grinder then trims the fibreglass backing to align exactly with what will be the finished-tile edge.
- An automatic slab-turning device. This machine only engages if the line is processing fibreglass-backed slabs.
- A computerized digital-control scoring machine for the topside of the slab. The machine scores the tile along the cutting line that will give the exact finished slab size.
- A snap-cutter. Separator rollers exert pressure along the incision previously cut into the tile surface causing a sharp clean break.
- An edge smoother. Here the slab edges are smoothed to remove the sharp blade-like edges left after snap-cutting.
- A slab loader. The slabs, now cut and smooth-edged, are loaded onto racks and taken by LGVs to the subsequent sorting line.
All cutting operations are performed by automatic digital-control machines. However, tiles undergo a further quality check by automatic sizing machines when they reach the final selection line. A last visual inspection of each tile surface is also made by expert operators before the slabs pass to the packing and dispatch bays.
Packing operations are automated. A mechanical arm loads the packed boxes onto pallets, which are then conveyed by LGVs to the warehouse.
With its latest investment in top-end technology, Panariagroup confirms its commitment to its mission of Excellence, Research and Innovation with the aim of developing new product lines and forward-thinking solutions to meet ever more demanding customer expectations.
Thirty-years’ experience and the know-how of top ceramic specialists allow Panariagroup to keep ahead of the field, a leader in the manufacture of unbeatable tiles. The Company is passionately committed to maintaining its market leadership and asserting Italian style excellence in luxury ceramic tiles throughout the world.