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QUALITY GLASS ETCHING WITH HIGH PRODUCTIVITY
Czech glass decoration
Guyson International's latest automated glass etching machine has been installed in the Czech Republic, a region having a long association with glass, for the Czech manufacturing subsidiary of a large German glass, plastics and printed packaging company who are using it to decorate bottles used in the cosmetic industry.
The 'glass sandblasting' process
The process of glass decoration by blast finishing consists of the propulsion of abrasive particles using compressed air passing at high velocity through nozzles onto the glass substrate to produce controlled erosion.
The surface topography and appearance achieved is the function of many variables. These can include the type of blast media, its size and shape and also the velocity at which it is fired at the component.
Media types can include various grades of aluminium oxide, glass beads, and natural substances such as corncob or nutshells, plastics and metallic abrasives. An angular shape to the media has a more effective cutting action, with the sharp angular faces providing penetrative power and rapid abrasion over spherical media. Virgin alumina, the media most commonly used for glass etching, is generally used in a range of sizes between 45 and 300 micron, depending on the desired effect to be achieved. The velocity of blast is predominantly a function of air pressure, generally set between two and seven bar, but the media flow, the angle of blast gun attack and the standoff distance of the gun from the bottle are all major determinants affecting the type of finish and the process time.
The Guyson Multiblast® system
The Guyson Multiblast® RXS 900 automated blast cleaning system has almost become the benchmark machine for automated glass decoration, equipped with between six and twelve work stations that precisely index the product through the blast process and deliver a clean etched finished product.
The RXS Multiblast® system has been engineered to ensure a high level of process and machine control; the RXS provides an accurate, consistent and uniform finish to every component. By eliminating the inevitable variations in hand processing, component quality, cost control and productivity can be dramatically increased.
The blast chamber
The rubber-lined chamber is most often equipped with eight Guyson model 900 blast guns fitted to fully adjustable arms and directed at the component to ensure maximum coverage effect whilst minimising wear elsewhere in the chamber. Blasting is carried out on two spindles, which rotate in opposing directions to achieve complete coverage from two separate banks of guns, without any shadow or masked areas on any component envelope. After blasting the bottle is air-washed in a separate chamber to clean off residual media and dust, prior to the component exiting the machine.
Moving parts inside the blast chamber must operate at a high utilisation level, often 16 hours per day, five days per week in an abrasive environment, and for this reason the rotating spindles are completely sealed. The blast guns are accurately set to ensure that the abrasive action is confined to the treatment of the bottles. Boron carbide nozzles are fitted to the guns for long life resulting in minimum maintenance downtime.
Cyclone reclamator
This recent system also included a Model CY900/24 cyclone reclamator; this freestanding unit fits between the blast cabinet and the dust collector forming part of the extraction system. Material is extracted from the bottom of the cabinet using the airflow generated by the cyclone and dust collector fans. This material includes good re-usable media, broken down media as well as material removed from the component that has been blasted. Through cyclonic action the re-usable media is separated to the outside of the cyclone, being heavier than the rest, and is delivered back down to the media storage bin, whilst the lighter particles are entrapped in the centre air stream and pulled up through to the dust collector. Including a cyclone separator in the machine specification not only ensures that only good reusable media is retained within the system but can also reduce consumable costs by up to 50% compared with a basic machine configuration.
Dust collector
The dust collector specified for this application was a Model GC16-K5 reverse jet pulse cleaning unit, which provides for continuous cleaning of the filter elements during the operation of the machine. The dust laden air from the cyclone is drawn down through the dust collector by the fan where initial pre-separation takes place as the heavier particles are deflected downwards to the hopper and dust collector bin. The finer dust is carried up to the filter elements where it is retained on the outer surfaces. The cleaned air then passes through the spun bonded polyester filter elements (of wide pleat design for maximum utilisation of filter area and easy cleaning) into the fan chamber where it is exhausted. Since each filter element is cleaned in sequence using a reverse jet of compressed air, this type of dust collector is particularly suitable for continuous blasting applications as the filter elements are effectively cleaned while the machine is operating.
Hot aqueous washing
Residual dust particles remaining on the glass after blasting are removed in an air blow off chamber inside the RXS machine, but many customers in this industry prefer to wash the bottle too after the blasting processes before, for example, printing the name of the perfume and the message in gold lettering.
Sand blaster cell
Guyson also manufactures a range of conveyorised “in-line” aqueous washing machines and have supplied bottle decorators with custom built wash, rinse and dry modules on machines designed to complement the sand blasting operation. In effect, a complete compact sand blaster decoration cell has been created entirely based on Guyson produced equipment and it is a reasonable estimate that about 35% of world production of sandblasted glass perfume bottles are now treated on a Guyson RXS900.
FREE COMPONENT TRIALS
Whether your interest is in blast, wash or ultrasonic cleaning equipment, we offer FREE component trials, with no obligation to buy. To contact Guyson International, call on +44 (0)1756 799911, fax +44 (0)1756 790213, or email info@guyson.co.uk.
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