Grenzebach: cutting process optimization in float glass lines

2011-07-01 | Cutting technology

With roots going back to the 1920s as a repair shop for agricultural machines, Grenzebach as we know it was founded in the 1960s and began manufacturing components for transport and conveyor systems. Since then, it has become a global group, with 1,500 employees and seven production facilities.

Grenzebach is a longstanding supplier and development partner to glass manufacturers for process equipment, automation technology, specialized cutting and handling systems, as well as entire manufacturing lines and cold-end equipment.
Grenzebach also engineers process technology and manufacturing equipment for the photovoltaic and solar thermal industries.
Being a modern global organization with a highly motivated team, the company’s success is based on the expertise and commitment of every employee. Solid engineering and intelligent control systems guarantee safe non-stop operation. Working in partnership with clients, Grenzebach delivers equipment precisely designed for individual production needs. Grenzebach designs and builds equipment for the part of the float line running from the lehr to the warehouse, which is separated into several sections -all precisely connected to one another:
• takeover of the glass ribbon from the lehr;
• cutting the glass ribbon into sheets of optimum size as per order requirements;
• snapping and size control;
• rejection of faulty glass sheets;
• sorting according to size and quality;
• stacking onto glass racks;
• removal and re-insertion of the glass to offline handling.

OPTIMIZATION AND CUTTING
For flat glass makers job-specific optimization and cutting play a key role in managing the cold end of a glass processing line. In fact, this high art of optimization directly affects the achievable peak glass yield. An innovative technical achievement (patent pending) strikes a new path to a significant yield increase in the float glass production business.
The assessment and qualification of nonconformities in the glass ribbon inevitably force glassmakers to score strips of faulty glass for elimination as cullet. So far, the shortest possible ‘cullet sheet’s measured some 600 millimetres as determinedby the roller spacing of the downstream conveyors directing this cullet sheet to the next available drop and elimination section. This minimumsheet length, seen over the full ribbon width, frequently embodied an avoidable glass loss especially when the particular glass defect situation would allow a shorter cullet sheet.

SNAPPING STATION
The Grenzebach innovation now allows to reduce this 600 millimetres sheet to a mere cullet strip of up to 170 millimetres and, subject to the detected defects, to minimize glass loss by up to 70 per cent. Traditionally, the snapping station snaps the scored sheets with the main snapping roller. The snapping station raises this pneumatically actuated or motor-driven roller pinpointed onthe score passing the roller crest. In interaction with the press roll assembly over the conveyor the glass snaps in a controlled way due to flexure, sectioning the endless ribbon into individual sheets.
Depending on the job requirements, these sheets then directly go to the stackers as jumbo sheets or are further cut up to smaller sized sheets. Faulty glass is traditionally snapped and conveyed to the next available cullet elimination point in the very same way. However, the conventional float line roller spacing requires a minimum 600 millimetres sheet for this. The new snapping station provides a moveable roller section that can open and close within a very short time to create a discharge opening. This elimination sequence is initiated by the Grenzebach PPC optimization system and is then materialized by the conveyor line control system.
The new snapping station can now snap and directly eliminate a scheduled short cullet sheet through the roller segment opening. After cullet strip elimination, the conveyor rollers return to their original position and resume their function as standard conveyor rollers for subsequent production. The newly developed snapping station design also reflects numerous customer demands. The top pressure roll assembly is now, for example, driven by servomotors and allows manifold roller position settings (leading or trailing offset or accurate positioning over the glass ribbon). An innovation is the likewise integrated upper snap roll. If necessary, this extra snap roll can snap the cullet strip with a linear down-movement in a specific and adjustable angle of attack. This new feature is to further improve the snapping results in particular situations such as for thicker glass.
An on-site operating terminal provides a variety of parameters for fine tuning the machine performance. The Grenzebach PCPanel visualization software allows for the display and editing of all machine parameters from any operating terminal. The newly developed snapping station is already employed on running projects and will soon prove its yield increasing capacities.

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