Two technologies are used for sanitaryware production: plaster moulds and high-pressure casting benches with resin moulds.
Mechanized casting benches with plaster moulds is a traditional machinery for sanitaryware production. New mechanized benches and in-house plaster moulds are currently used by Keramin and manufactured with automatic unit with weighing dosing and vacuuming, providing capacity of the moulds up to 100 cycles.
Automated high-pressure casting benches with resin moulds (Italian machinery of Sacmi Imola S.C.) are the latest achievement in sanitaryware production to guarantee notably short production time increasing the quality of the articles. At the same time the resin moulds have much longer durability: one mould provides production of 25 thousand articles and more.
Automated dryer (Progetti production)
Automated glazing units with glazing robot (Sacmi Imola S.C. production). The said machinery provides homogeneous application of glaze to the whole surface and guarantees high whiteness of the articles.
Firing kiln for articles (Sacmi Imola S.C. production).
Intermittent kiln (Sacmi Imola S.C. production) for repairing sanitaryware articles.
Notwithstanding the two ways of sanitaryware production currently in use, the general technological production scheme can be described as follows:
1. Preparation of slip suspension
Slip suspension is a specific body made of raw materials, which according to their functions are subdivided into:
• plastic (clay, kaolin) – the basis of support structure to be formed within the process of casting, drying and firing;
• non-plastics (quartz sand, pegmatite, discards of articles) – stabilization of shape (prevent deformations).
According to the machinery which is used for semi-finished products, various proportions of raw materials are being used. In particular, for high-pressure casting articles the less plastic German clay is used together with the Ukrainian one. We generally use imported raw materials and Ukrainian, Russian, German and Italian components in our production.
2. Manufacturing of semi-finished products
New mechanized casting benches with plaster moulds made it possible to increase the volume of daily production capacity owing to automated technological process and additional drying of plaster moulds. The process of manufacturing of semi-finished products is described herein. Slip suspension is filled into plaster moulds where cast formation is held for 1.5-2 hours. Then the excessive slip is discharged and the article is dried for 30-50 minutes with warm air. The whole technological cycle lasts 3.5-4 hours. As soon as the articles are demoulded, they are treated and dried.
With the use of high-pressure casting benches semi-finished products are manufactured much more rapidly owing to decreasing of time for cast formation. The cast formation is described herein: increasing air pressure to be supplied to the mould up to 13 bar, the water contained in slip leaves through the pores of the resin mould, creating the layer of ceramic body (support). As a result, in 20 - 30 minutes we have a semi-finished product per each mould with equal thickness throughout its entire volume with no deformation.
3. Treatment of semi-finished products. Drying.
Demoulded semi-finished products have an excessive moisture content, meanwhile that of the articles before glazing shall not be more than 1%. That is why after special treatment the demoulded semi-finished products need drying. The drying is held either during transportation on shelves (with temperature about 30° Ñ), or in conveying drier of Progetti production (with temperature up to 100° Ñ). Considering that semi-finished products manufactured with various technologies differ in moisture value (18-20% after plaster moulds and 15-17% after resin ones) the duration of their drying is different. For semi-finished products of plaster moulds it is 1-1.5 days, and starting from 17-18 hours for those of resin moulds.
4. Glazing.
After drying the semi-finished products are subject to glazing, the operation which significantly influences the appearance and quality of finished article. Glazing of semi-finished products manufactured both with casting resin moulds and plaster ones is currently held with 5 glazing units equipped with glazing robot GA 900 EV. Such machinery as well as imported high-quality raw materials for glaze preparation guarantees homogeneous application of glaze to the whole surface and high whiteness of the articles.
After glazing the Keramin decal is applied on wash-basins and cisterns of all collections to make the sanitaryware much more recognizable among competitors.
5. Firing
The final phase of the technological production cycle is firing of semi-finished products in tunnel kiln of Sacmi Imola S.C. production (Italy) for 19-22 hours. Initially the temperature inside the kiln is gradually increased up to 1200° Ñ, and then is likewise decreased. Such temperatures are necessary for high-quality products both regarding the support and glazed surface. This modern firing kiln made it possible to decrease notably the risk of such defects like pin holes, contamination, glaze boiling. Another repairing kiln is used for single firing and re-firing for elimination of defects.
6.Sorting
Sorting is the final phase of quality control system for production technology, used for all principal phases: inspection of articles after casting, drying, glaze application.
It is necessary to emphasize that all articles strictly correspond to quality standards according to GOST 30493-96 and GOST 15167-93, as well as to internally approved technological instruction No.37 relevant to definition of performance criteria for sanitaryware articles. The said instruction toughens the requirements of GOST15167-93 and is fundamental for sorting of the articles. The sorting phase divides articles for PREMIUM and STANDARD class according to the following requirements:
The PREMIUM class articles can have the following appearance defects on their visible and working surfaces:
• Checks: not allowable on wash-basins, max. 10 mm long on cisterns, max. 15 mm long on other articles.
• Dots: max. 2 dots on wash-basins, max. 6 dots on other articles.
• Pin holes: dispersed ones allowable.
• Vitrified spots: max. 0,25 ñm2 of total area allowable.
The total number of allowable defects per article of the PREMIUM class shall not exceed two.
The PREMIUM class articles shall not have such defects as bare spots, contamination, splits, glaze boiling, stains, rippling on their visible and working surfaces. Said defects are allowable on mounting and invisible surfaces only, providing that they do not obstruct mounting or operation. Allowable checks, melting, contamination, splits shall be closed up with white cement or other material at that providing an adequate firmness of closure.
The STANDARD class articles can have the following appearance defects on their visible and working surfaces:
• Bare spots: max. allowable area 1 ñm2.
• Checks: max. 10 mm long on wash-basins, max. 10 mm long on cisterns, max. 15 mm long on other articles.
• Contamination: max. allowable area 0,5 ñm2.
• Splits: allowable on edges adjacent to wall and floor, max. depth 2 mm.
• Dots: max. 5 dots on wash-basins, max. 10 dots on other articles.
• Pin holes: dispersed ones allowable.
• Rippling: allowable.
• Stains: allowable barely visible.
• Vitrified spots: max. 1,0 ñm2 of total area allowable.
The total number of allowable defects per article of the STANDARD class shall not exceed three.
The STANDARD class articles shall not have such defects as glaze boiling on their visible and working surfaces.
