How to improve injection moulding process

Challenging applications of hot runner technology together with recent developments targeted to improve injection moulding process

by Stefano Sandri

At K 2019, HRSflow (Hall1, Booth D05) presents examples for perfectly balanced Family Tools with extremely different part volumes, an extended cylinder range, the new SA series of nozzles for small shot weights, as well as HRScool, HRSflow’s innovative solution for hot runner injection moulding in which water cooling of the associated actuators can be completely eliminated.

Expertise on family tools

Family moulds for the cost and time efficient production of different parts in a single shot, have traditionally been associated with problems caused by traditional pin control methods, including poor balancing causing e.g. warpage issues. HRSflow’s hot runner technology provides a broad potential to improve the quality of the parts, to avoid cost for additional process tuning, to broaden the process window and to extend lifetime of the tool. Using servo driven valve gate technology to independently control stroke, timing and force of each individual pin, can overcome existing limitations in terms of close similarity in size, weight, wall section and volume, whilst ensuring all cavities are being filled simultaneously, preventing from overfeeding and flash formation. At K show HRSflow showcases a family mould for the production of high quality upper and lower bumper parts in one shot. Both parts are moulded using PP 14% talc and are characterized by large volume differences, i.e. 3333 cm³ and 2170 cm³ respectively. The use of the FLEXflow technology enables flawless surfaces without any flow mark and an accurate control of deflection on each component. The mould is equipped with a twenty-one-nozzle, electrically-driven valve gate hot runner system including two angled nozzles. A second family mould example is the hot runner system for a one-shot production of three high-quality polypropylene parts for a car interior door module, with volumes of 560 cm³, 338 cm³ and 58 cm³ and wall thickness ranging from 2.3 mm to 3 mm. The mould is equipped with an eight-nozzle, electrically-driven valve gate hot runner system designed for sequential injection moulding, allowing for a cycle time of approximately 55 s. Both hot runners are equipped with the new FLEXflow one manifold servo driven valve gate cylinders with reduced cut out, higher accuracy and enhanced repeatability.

Extended range of cylinders

Another highlight of the company is a new a series of pneumatic cylinders which can be easily installed without removing the hot runner from the mould plate. Designed for excellent thermal insulation, they do not require cooling for a wide range of polymers. Thanks to the modular design concept and a reduced number of parts they stand out through easy maintenance. The cylinders are available with or without end stroke, as damped version, also with end stroke, and with pressure sensor.

High-performance hot runners

HRSflow also presents the SA Series, its smallest series of screwed-in hot runner nozzles for very low shot weights, with a very compact cut-out, dedicated to process small technical components and designed to have optimal thermal conditions for high flexibility in processing engineering polymers, even with high fibre loads or high viscosities. Another highlight is HRScool, the innovative solution for hot runner injection moulding, that allows to completely eliminating water cooling for the most common automotive applications.

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