The company Buxtrup from Ahlen in Westphalia has been developing and producing washing and drying machines as standard or specialpurpose machinery for 35 years. Thirty years ago, when single glazing was gradually replaced by double glazing in house construction, Buxtrup worked on the machinebased production of double glazing. A glazier had his production facilities in the same town, and what was more obvious than to develop the machines for this customer and at the same time to use this practical experience in the construction sector. The machines are for washing and drying flat glass panes and for pressing together two panes with an aluminium frame between them.
The machine frame and casing are made completely of stainless steel, and the individual movement sequences are controlled pneumatically. The glass transporting level is at an angle of 30°, to achieve easier handling of the glass panes. The flat glass panes run from left to right through a washing zone and then a drying zone, before they reach a backlit control zone where they are checked by the operating personnel for cleanness and absence of streaks. In order to be able to process panes of different sizes, the control zone is fitted with rodless cylinders, at the customer‘s request. Controlled by optical sensors, the roller conveyors are adapted to the size of the panes coming in by the positioning of the rodless cylinders. This adaptation can be implemented by the actuation of two solenoid valves, and has the additional advantage that no complicated safety guards have to be installed. Thanks to the pneumatic drive, the forces are so small that even the unintentional jamming of a finger does not cause any injuries, and the roller conveyor can be moved by hand. The glass panes are washed by revolving brushes and demineralised water, to ensure that there are no mineral residues on the glass.
The filtered air is blown onto the panes through flat nozzles to allow the water to flow off easily. The clean, dry glass panes are trans-ported to the end of the machine runout, and after the visual check are transported to the limit stops of the press. When the first glass pane is transported into the press, it is lifted with the help of vacuum suckers, while the spacer frame with the butyl seals is placed on the second pane. After manual clearance, the pane with the frame is moved exactly under the lifted pane. This is where pneumatics plays a part again: In order to be able to move the pane into the press on a flat level, air nozzles are fitted and the pane hovers on the jets of air from these nozzles. The gap between the panes can be filled with the inert gas argon or other gases for better thermal insulation, before the pressing operation begins. To fill the gap with gas, the press area is sealed off, and if necessary the press area can be further subdivided for smaller panes, in order to keep gas losses as low as possible. The panes are pressed together with a compressed air cylinder with a diameter of 125 mm. A pneumatically controlled ISO 1 valve, which is actuated by a V 15 solenoid valve, supplies air to the compressed air cylinder via a separate pressure controller. The contact pressure can by adjusted easily and accurately with this pressure controller, depending on the size of the panes. Due to its elasticity, compressed air is ideally suited for pressing operations with sensitive or fragile parts, and prevents the destruction of the glass panes, which cannot be ruled out if a mechanical press is used. To control the individual processes, Buxtrup decided in favour of the 10-fold V 15 valve unit. Herr Friggemann, the foreman in the company, explains: "The V 15 was selected because it has small dimensions but a high flow rate, and with the multi-pole interface and as a fully assembled and tested unit, it saves us time during assembly." He adds, with a twinkle in his eye, that the price must be right as well. "In general it can be said that the use of pneumatics is ideal in special purpose machine construction; it is fast, robust, can be actuated directly from the PLC, and no matter how small the company, there‘s still enough air." With these words he said goodbye, after we had thanked him for his support in the preparation of this report. The following operations are controlled pneumatically: Glass mounting Pressing Coupling Butterfly valve Sealing inside and out Air cushion Opening tappets Cross arm up and down .Band saws , Bimetal BandSaw Strip , Bimetal BandSaw Blades , Band Saws For Metal Cutting , Band Saw Machine , Circular saw machine , Special purpose machine
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