Talking Technical P3
Part 3: Speed up changeovers with a mould transfer system
In the third instalment of our series of articles looking at improving productivity in injection moulding, Craig Forrester of Stäubli Connectors UK, looks at mould transfer and loading.
A key element in the operation of an efficient and flexible injection moulding shop is the ease and speed of changing moulds; mould transfer systems that safely and efficiently bring the mould out of store and into the moulding machine can often provide a significant productivity improvement and are a key element in moving towards ‘Single Minute Exchange of Dies’ (SMED).
Maximising flexibility and productivity on injection moulding machines is essential in a competitive environment. Minimising downtime on mould changeover provides one of the best opportunities to improve production flexibility and profitability. Significant reductions in changeover times have been achieved using transfer and loading systems, in some applications changeover times have been reduced by over 70 percent, even where quick mould change solutions have already been installed.
Selecting which type of mould transfer system is best for any application requires analysis of many parameters, including the frequency of mould changes, mould size and weight and the target changeover time. From this data the optimum system can be determined, a system that provides a reliable and easy to use operation requiring the minimum of maintenance.
Transfer systems can be tailored to all types of applications, they are not just suited to the heaviest larger moulds but do frequently provide an efficient and effective system for handling smaller moulds too.
Significant time savings can be made by bringing the mould up to operating temperature prior to loading into the moulding machine. Transfer systems can include a stop at a preheating station on route from the storage area to the machine, reducing downtime, resulting in improved efficiency and cost saving.
New installations often include a degree of additional automation such as the use of rail carts; a rail mounted loading/unloading table transfers moulds from the storage area direct to the moulding machine. Rail carts can service several or even an entire line of machines. A more versatile option is the fully manoeuvrable cart, permitting free movement of moulds between several machines and the storage areas. Adjustable height and reach mechanisms can be built into the cart to ensure compatibility with different machines and storage systems while locking devices on the cart ensures safe and secure transfer of the moulds.
One type of efficient layout for mould loading is positioning one system between two machines; the two-directional loading table serves both machines and provides maximum flexibility and efficiency for each production cell, incorporating if required a preheating station. Where automatic mould changing is required then positioning a loading/unloading system on each side of a machine is ideal and provides the fastest method of mould changing. On one side, the mould from the previous production run is unloaded, while simultaneously on the opposite side the new mould is loaded.
Mobile mould transfer and loading table systems can provide service to a number of moulding machines or be dedicated to a single machine; operation can be manual or automatic, each designed to match with the existing workshop layout, work practices, tooling and available budget.
Maintenance and repair of moulds also needs to be fast and efficient to avoid production delays. Dedicated maintenance stations are available fitted with turnover mechanisms to provide a convenient and secure platform holding the mould in the correct position for the work required.
Mould transfer and loading systems need to be tailored to each specific application; there is no standard solution that will meet all requirements. In selecting the optimum solution many technical and operational features need to be considered, balanced against the overall objective in terms of reducing the mould changing cycle time and the budget available.