25/01/06 Injection molded plastics pallet production

Synventive customizes complex hot runner system for low pressure injection molded plastics display, retail sector, to full-size, extremely tough, transport pallets from AVK Plastics.

Synventive Molding Solutions, one of the world’s largest designers, manufacturers and suppliers of hot runner systems and related components to the injection-molding industry, developed customized hot runner systems for AVK Plastics to enable the production of large size plastics pallets on low-pressure injection molding equipment. Synventive will present this technology together with its range of hot runners systems with shot sizes down to 0.1 grams as well as a new range of hot runner systems for multi-cavity moulds at Plast 2006, in Milano, Italy in hall 9, booth A36 from February 14-18.

Confronted with a major technical challenge in the injection molding of a 100x120cm plastic pallet, Dutch molder AVK Plastics enlisted the aid of Synventive Molding Solutions.

In undertaking the production for pallet supplier Q-PALL GmbH, AVK Plastics had chosen low pressure foamed injection molding as best suited for the economic production of this complex three-dimensional application. Because of the large shot weight of 28kg of foamed PP EPDM regrind, AVK Plastics consulted machine manufacturer Foma Engineering, that had proven experience in injection molding, to investigate the possibility of utilizing an older machine with a large clamping force and back-plate capable of managing this shot size.

Low pressure injection molding (400 Bar) and clamping force of 800 tons enables AVK to utilize a relatively small injection molding machine for this kind of application. Click on photo for High resolution image.

Foma calculated that a clamping force of 1300 tons was needed in combination with an injection pressure of 800 – 900 Bar into a 40°C mold. The machine sought was now within a reasonable size, however shot weight still remained an issue. To prepare and inject sufficient melt within an acceptable cycle time Foma conceived a double barrel design. The upper barrel was to prepare the necessary melt from which it would then be pushed into the lower barrel for injection into the mold.

In order to fit and function with this machine the pallet required intelligent and compact mold design. Since neither AVK Plastics nor Foma Engineering had wide experience with hot runner systems, additional expertise was needed. As one of only a limited number of suppliers able to meet the re-quirements for a hot runner system of this size and high level of customization, Synventive_Molding_Solutions was invited to join the project team.

Hot runner system with exceptional large flow bores minimizes pressure loss, essential for low pressure injection molding.

Because of the large volume of foamed material to be injected, a hot runner system with large flow bores was needed. These large flow bores would also minimize pressure loss, which is essential for low-pressure molding. Valve gates and needles were needed to shut off the nozzles, to prevent the expanding material from flowing back into the nozzles during the packing phase, and to control melt flow during the injection phase. A filling analysis indicated that nine nozzles would result in the optimum flow pattern.

Synventive advised on the specific layout of the system including the special connection with the machine and the type of insert that would ensure optimal processing. In the design the nine nozzles were divided over multiple zones to be operated by the machine instead of a separate controller.

At molding start up, the results were significantly better than had been calculated. The clamping force required was just 800 tons, with a maximum injection pressure of only 400 Bar into a 22°C heated mold. This combination delivered a total injection cycle of approximately 18 seconds.

AVK Plastics is now producing 70,000 – 80,000 pallets a year for Q-Pall and is progressively switching to the use of hot runner systems for the production of other of its pallets that are currently conventional molded.

AVK Plastics BV, part of the internationally operating AVK Group, is specialised in the production of high quality synthetic products by means of both low and high-pressure injection moulding. From 'Display Pallets' for the retail sector, to full-size, extremely tough, transport pallets.

A member company of Advent International, Synventive Molding Solutions is one of the world’s lar-gest designers, manufacturers and suppliers of hot runner systems and related components to the injection-molding industry. With principal headquarter operations in the USA and The Netherlands, Synventive has manufacturing facilities in China, The Netherlands, Germany and the USA. Supported by a global network providing sales and service to customers in more than 50 countries.

Find information about Advent International.