Imitating Stone

February 28, 2003
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A new whole-body decoration technology can streamline the tile manufacturing process while realistically reproducing the look of natural stone in porcelain tile.

Over the past decade, stone has become an increasingly popular material in both residential and commercial building projects. Many people are attracted to it for aesthetic reasons—its natural colors and textures lend a feeling of warmth and well being to the indoor environment. However, as a natural material, stone is also very expensive and difficult to control. These drawbacks have made ceramic tile an attractive replacement. But while ceramic tile manufacturers have been able to successfully emulate the look and feel of natural stone with a variety of intricate glazing techniques, the beauty of these tile is only “skin deep”—scratch the surface, and the color and variation disappears.

Recently, a new technology* was introduced that allows ceramic tile to more closely imitate natural stone by transferring the decoration throughout the entire tile body. With a combination of variegated ceramic powders and a sophisticated filling system, the new technology can streamline the tile manufacturing process while realistically reproducing the look of travertine, marble, granite and other natural stone materials in porcelain tile.

Figure 1. The desired tile pattern is entered into this computer interface.

Creating “Stone” Tile

The new technology comprises a single, sophisticated filling unit, which can be added to an existing tile press.** A series of electronically controlled actuators, which are governed by a PC with a highly versatile interface, allows the unit to precisely deposit a variety of ceramic powders into a “filler box.” These powders are then transferred to the press die without any alteration of the decorative pattern inside the die cavity.

Figure 2. A schematic of the new technology.
To create the “stone” tile, the press operator first enters the desired pattern into the user-friendly computer interface (see Figure 1). The filler box is equipped with a programmable dual-axis dosing system, which determines what colored powders are released and also sets the release pattern that will generate the desired visual effect (see Figure 2). A “block” of ceramic powders is then built layer by layer with a varied filling pattern, which is achieved through the use of different colored and textured ceramic materials. Some of the powders might be atomized or re-granulated, while others are dry-ground or micronized, and still others might be in the form of flakes or grains. These different powders are all combined in the filler box to achieve the varied look of natural stone.

Figure 3. The finished tile realistically imitates natural stone.
Once the powder block is fully formed, it is sliced to obtain a portion that contains the desired stratification, in much the same way a slab is cut from a block of quarried rock (see Figure 2). The sliced portion is transferred to the die cavity of the tile press using specially designed linear filling systems that prevent any accidental re-mixing of the colored powders. Simultaneously, the dosing system “tops off” the level of powder in the block and prepares it for the next sectioning sequence.

Figure 4. The system can also be used to create products with geometrical effects for large installations.

Ensuring a Beautiful Surface

In conventional ceramic tile pressing systems, a scraper is used to level the powders in the die cavity and ensure that they are fully compressed in the die. This type of system works well when only one type or color of powder is used. However, when the die cavity is filled with a variety of powders that are perfectly distributed throughout the die, the scraper mixes the powders and destroys the surface design. A grinding (on green tile) or polishing (on fired tile) step must be added to the manufacturing process to restore the design.

As an alternative solution, an optional patented suction device can be obtained with the new system that “rebuilds” the design within the die by using a vacuum to remove a thin top layer of powder from the die cavity after the scraper has leveled the powder. The result is a perfectly level surface with a natural finish. The surface can also subsequently be pressed with a non-planar upper punch to obtain a structured, veined design.

The new technology produces porcelain tile with whole-body effects (i.e., throughout the thickness of the tile) that realistically imitate natural stone (see Figure 3), and it also produces excellent results with non-polished tile or structured tile surfaces. Variations of the system can also create products with geometric patterns that are ideal for large installations (see Figure 4). The finished tile do not require glazing; however, in some cases, a polishing step might still be desired after firing to obtain a particular surface effect.

Capturing New Market Share

Ceramic tile is already a popular alternative to natural stone. It is more cost-effective and reproducible, while providing a similar level of durability and aesthetic appeal. With this new filling technology, ceramic tile will be able to even more closely replicate the look of natural stone, providing the potential to capture an even greater portion of the stone industry’s market share. Additionally, by eliminating time-consuming glazing steps, the technology will enable tile manufacturers to further enhance their competitive edge.

References:

*Monolithos 3-D, developed and patented by Sacmi Imola S.C.R.L., Imola (Bologna), Italy

**The technology can be installed on all Sacmi lines with presses that have an inter-column clearance of 1750 mm (approx. 5.75 ft)

For more information

For more information about this new technology, contact Sacmi Imola S.C.R.L., Via Selice Provinciale, 17/A, 40026 Imola (Bologna), Italy; (39) 542-607111; fax (39) 542-642354; e-mail sacmi@sacmi.it; or visit http://www.sacmi.it or http://www.sacmiusa.com. In the U.S., contact Sacmi USA Ltd., 3434 106th Cir., P.O. Box 7858, Des Moines, IA 50322; (515) 276-2052; fax (515) 276-2084; or e-mail mail@sacmiusa.com.

Sidebar: Technical Specifications

Effective maximum die filling width
1575 mm (~5.2 ft)

Effective minimum/maximum die filling length (fired)
300-600 mm (~1-2 ft)

Required inter-column clearance on press
1750 mm (~5.75 ft)

Die aperture
115 mm (~4.5 in.)

Maximum distance from press center line
4700 mm (~15.4 ft)

Maximum uncompacted filling thickness
65 mm (~2.6 in.)

Installed electrical power
22 kW

Available accessories
Fixed brush, suction device

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