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Combined transport and

Combined transport and handling system Production-related process sequences and spatial constraints were the main focus of the requirements set out by the Arnold Group regarding the design of a conveying system for glass tubes. The tubes coming directly from production at a temperature of approx. 100°C were to be accepted by the conveying technology, transported, and transferred to the corresponding further processing stations. Although this design sounds pretty straightforward, the engineers at AMI Förder- und Lagertechnik had to develop a technically sophisticated indexing conveyor system that was specifically tailored to the operator’s requirements. The requirement The requirement for a customer from the glass tube production sector was to implement a fully-automated conveying system that was able to execute the handling and transport functions for the tubes – with a diameter of 25 mm and lengths ranging between 90 and 150 mm – coming directly from production at a temperature of approx. 100°C and ultimately combining all of this into an efficient material flow. Within a eight-second cycle, four correctly sorted, i.e. 90 mm long, glass tubes should be transported, picked up by a suction gripper, transferred to a workpiece carrier system with 24 units, and supplied to the machine plant for further processing by the conveying technology. As the Arnold Group had already collaborated with AMI Förderund Lagertechnik on other projects and because it appreciated the company’s ability to meet individual requirements, as well as its specialist knowledge and reliability, the request for a quote and ultimately the contract to develop, construct, produce, and finally implement the indexing conveyor system was awarded to the company from Luckenbach, Germany. LOGISTICS T he Arnold Group supplies a broad range of burners, tools, and standard machines for demanding specialist glass companies in the thermal and mechanical glass processing sector. However, the company’s portfolio also includes complex process solutions, for example, for solar thermal glass tube production processes, the highly accurate resizing of fused quartz glass tubes, the highly automated production of laboratory and light glass, and other special applications for thermal glass processing. The customer directory includes companies from the photovoltaics, glass and fused quartz glass processing, fiber optics, and automotive manufacturing sectors. The framework conditions Certain framework conditions had to be observed in addition to the technical requirements and the request to integrate the conveyor system within the downstream processes following actual production. “Due to the existing on-site infrastructure comprising machines, systems, safety equipment, and a control cabinet, as well as the limited floor space required us to be quite creative when it came to the structural design and implementation,” explains Rolf Quint, design engineer at AMI. Ultimately, the indexing conveyor system had to meet process-related requirements and also had to be integrated within the systems used for subsequent processing. According to Quint, the workpiece carrier (incl. protruding components) 20 WORLD OF INDUSTRIES 2018

used to hold the glass tubes was not allowed to exceed a certain width, for example. The solution and design details Once the persons responsible at the Arnold Group had defined the framework conditions and requirements, the AMI project team was given the go-ahead to develop a suitable conveying system. The construction was based around a belt conveyor with a special toothed belt that guaranteed the accurate acceptance of the glass tubes on to the individual workpiece carriers and exact transfer to the relevant further processing station. With a distance of approx. six meters between the drive axle and steering rod, a split of 24 was selected to bridge the gap between the acceptance and transfer points on the two processing systems. This also enabled the required eight-second cycle to be implemented. Due to the existing machines and systems, a workpiece carrier system with a width of 260 mm was designed, whereby each unit can hold four glass tubes and can be manually adjusted to tubes with a length of 90 to 150 mm, as requested by the customer. If an adjustment is required, this can simply be implemented by the operator via a knurled head screw located on the side of the workpiece carrier. A high-temperature resistant polyamide plastic that even retains its shape at continuous working temperatures of up to 155°C was selected for the device attached to the individual workpiece carriers for accepting the glass tubes. A relevant guide rail is indispensable for ensuring that both the lateral and height positioning of the glass tubes on the workpiece carriers is correct when they are accepted from production and transferred for further processing. Although the toothed belt is equipped with its own lateral guide rail on the conveyor system, the lateral and height positioning of the workpiece carriers must be able to be positioned accurately for accepting and transferring glass tubes. To ensure this, the AMI design engineers developed an internal guide rail system via which the workpiece carriers can be aligned laterally and in height using two adjustable guide elements on both sides of the indexing conveyor. This design solution ensures that the length settings on the workpiece carriers are not affected by interference contours caused by supports, for example, and that a safety barrier of less than the available width of 260 mm could be implemented. A bevel gear with a flange-mounted servo motor and absolute value transmitter supported by an inductive proximity switch at the acceptance position have been implemented to ensure that the cycle of the toothed belt and workpiece carriers is accurate. A light barrier and reflector at the relevant acceptance and transfer stations are also used to check whether the holding fixture on the relevant workpiece carrier is empty before being loaded and following removal. Special handling features 01 Quint: “By developing the indexing conveyor system, we have once again demonstrated that with our specialist knowledge we can implement specific operator requirements.” 02 The knurled head screw on the workpiece carrier is used to adjust it to the length of the tube being accepted 03 The onboard suction gripper unit ensures that the glass tubes are accepted and transferred AMI developed and produced a handling system made up of an aluminum base frame construction to be used for the transfer function to the relevant further processing system. A solid aluminum base plate is provided to secure the linear pneumatic drive, including the guide rail, mechanical stop, and vibration damper. The guide block of the linear drive is designed to support the vertically guided cylinder, on which the four spring-loaded suction grippers – one per glass tube – are attached. All of the pneumatic valves are positioned in close proximity to the relevant drive. This ensures that any delays caused by excessive hose lengths are avoided. The onboard vacuum ejectors for the handling system are positioned in direct proximity to the suction grippers for similar reasons. The advantages are clear to see: Short hose lengths, improved response characteristics, and fewer hoses in the energy chain (only two air supply lines, instead of one air supply and four vacuum lines). The pneumatic hoses, valve cables, and drive signal transmitters are routed via an onboard energy chain – its large turning radius guarantees the long service life of the hoses and cables. Within the energy chain itself, the hoses and cables are routed separately using partitioning strips. Transfer of the glass tubes by the suction grippers to the holding fixture on the workpiece carriers is monitored by a combined light barrier/reflector. This ensures that tubes are only transferred when the holding fixture is free. Conclusion With all of the constructional details and overall design, the design engineers at AMI have developed an indexing conveyor system for glass tubes that can be integrated into an existing production plant including its sub-processes and machines, and that meets the objective of achieving an efficient material flow. Thanks to its low maintenance design, the conveyor system will also demonstrate its efficiency when it comes to maintenance and servicing – the bearings are lubricated for life, for example. Additionally, all of the main elements are made of low-friction plastics and only need to be checked at regular intervals for possible damage. This also applies to the workpiece carriers, where checks are limited to looking for possible deformations caused by excessive temperatures that may have occurred. The operator is more than satisfied with the indexing conveyor system and this project has once again illustrated that collaborating with the responsible persons at the Arnold Group was a key factor to its success, explains Manfred Langen Jr., an employee in the Sales Department at AMI Förder- und Lagertechnik GmbH. Photos: AMI WORLD OF INDUSTRIES 2018 21