Problem solving on tap
Problem solving on tap
Keywords: Assembly, Packaging
To the non-specialist, the production of a new or updated version of an existing product involving the assembly of a number of discrete formed and moulded plastics and elastomeric components may not sound a technically demanding task. While this might possibly be true for low volume non-precision items, continuous high-speed production involving the assembly of high-precision, close-tolerance, engineered products with ultra-low reject rates, presents a completely different picture. The design and building of highly automated assembly systems, which combine both high through-put and low reject rates to provide a cost-effective solution, can involve some of the most advanced technologies and applied methodologies in virtually every engineering discipline, from software systems to mechanical design.
Specialising in supplying custom-designed process automation solutions based on systems integration for a wide range of industrial applications, but with particular experience of downstream systems and processes within the injection moulding industry, ATM Automation recently completed a major project for David S. Smith Worldwide Dispensers. An acknowledged leading international specialist manufacturer of plastic liquid dispensers and related products, including plastic press-taps, the company has until recently designed a large proportion of its own specialised production machinery. However, it is now looking increasingly to outsource this function to external specialist suppliers,enabling it to focus on its core components production business.
In a world-first for the company, DSS Worldwide Dispensers awarded Leicester-based ATM Automation a £400,000 contract to design and build a new, fully automated assembly system for one of its latest products, a new design based on a larger variant of one of its existing plastic press taps (see Plate 7).
Installed in mid-January 2001 and due to enter full commercial service, the new automated integrated assembly line from ATM Automation is capable of exceeding comfortably the specified continuous production rate of 3,000 finished units per hour. Taking an integrated systems approach to the design, the new line incorporates a variety of standard, modular, proven technology elements,integrated with custom designed units and systems manufactured in-house by ATM to create an autonomous, stand alone, unmanned assembly system. While the dedicated line has been designed to meet the specific assembly requirements for a single new press tap, the use of modular mechanical sub-systems means that it can also be modified, if necessary, by installing new or additional operating stations to provide flexibility for future applications.
Plate 7 ATM Automation's assembly system for DSS Worldwide Dispensers
The innovative automated rotary assembly system is based on a combination of mechanically coupled, cam-operated, active machine-stations and an indexing table. The integrated mechanical and microprocessor-based design eliminates the need for the complex interlocked controls demanded by pneumatic systems to ensure total synchronisation, the entire machine operating through mechanically coupled and synchronised links, with centralised plc controls, ensuring long-term repeatability.
In operation, the principal injection-moulded component parts comprising the body, valve and press-button which are assembled to form the press tap, are fed externally by linear conveyors or vibratory bowl-feed systems, incorporating guides and baffles to ensure correct orientation. Despite the large physical size of the tap-body, this together with the other components is delivered to assembly jigs on the rotary indexing transfer table at a rate in excess of 70 parts per minute. The table indexes sequentially between each of the machine-stations which incorporate photo-sensor controlled pneumatic grippers,again synchronised through positive mechanical linkages.
Valve and body units assembled on the first rotary machine are transferred in groups of four to a fully-automated test-station using a "walking beam"indexing system. The machine subjects each of the four units to a positive leak-test before loading them on to a further feed system on a second rotary machine. Parts which fail the leak test are rejected from the machine at this point in the process. As part of the final assembly, individual press taps undergo a unique sterilisation process, irradiated by a powerful ultra-violet(UV) light-source, which forms one of the sequential operating stations on the machine. Enclosed in a specially-designed translucent housing incorporating UV filters, a clamshell shutter mechanism opens to project a collimated beam of UV light on to each press tap for a precisely-timed period. Tested, sterilised,fully-assembled units are passed to a discharge conveyor system. This conveyor is used to position cartons beneath a discharge chute, enabling an accurately-collated number of finished taps to be automatically packaged,avoiding the possibility of manual contamination.
The entire automated assembly line is housed in a fabricated walk-in enclosure, with clear polycarbonate glazing panels. All component feedhoppers and vibratory bowls are installed adjacent to the machine, but outside the main enclosure. The containers are provided with close-fitting, hinged transparent protective dust-covers, allowing component levels to be easily checked and replenished. The design concept for the new machine, created by the design team at ATM Automation, using the latest CAD technology and working in close partnership with David S. Smith Worldwide Dispensers, has proved so successful that a second machine has already been ordered by the customer.
For further information contact Clare Moody, at ClareCommunications. E-mail: clare@clarecomms.co.uk Tel: +44(0)161 707 0992.
