JEC COMPOSITES MAGAZINE - Issue #58 - June - July 2010 - 63

mould

cavity

inductor

Fig. 2: 3iTech® loop representation

or what could be called a “thermal meniscus”, can be optimized through two types of action: the thermal conductivity of the steel, and the length of the “meniscus”. A number of variants and combinations of 3iTech® are proposed as a function of the target process (RTM, thermocompression, plastic injection, vacuum bag, tube manufacturing), of the materials to be processed as defined by a given temperature, heating time and dwell time, and of the part shape complexity involved. The 3iTech® configuration (Fig. 3) required will differ, for example, if you are heating a mould at 400°C (2-10 minutes) or at 120°C (5-15 seconds). Likewise, the results will differ as a function of cavity shape (round or square) and the shape of the inductors used with them (round, square or rectangular). The inductor can also be custom-bent – usually in copper, either with solid cross section or hollow for easier cooling, or flexible to allow layup of highly 3D networks.

Indumold, dedicated exclusively to plastic injection moulding, involves a network of small induction heating coils placed very close to the moulding surface (non-cooled inductors with a diameter of 3-6 mm, placed 3 to 5 mm from the moulding surface). These two solutions are complementary, and provide RocTool with a full range of solutions that can be applied directly to all composite and plastics-processing sectors (Fig.4).

Fig. 4: Part manufactured by Gigaset (Germany) using internal induction heating to skip welding lines and painting

The strong point of this type of process is that it enables “smarter” tooling heating systems by bringing other mechanisms besides inertial effects into play: e.g. dissociating the heating of the mobile and fixed parts of the mould, or locally heating a limited area of the tooling up to a required temperature.

Construction parameters for 3iTech® moulds
The production of a 3iTech® mould is unique in that a number of cavities are formed to receive the induction heating coils. If this network of cavities is two-dimensional, it can be created using machining or drilling methods. For a highly 3D network, the only method that works is 3D machining to create a mould insert. As long as it is compatible with the induction method, any standard mould material can be used, from aluminium to nickelbased alloys like Invar® to all types of steel, including stainless. In order to achieve optimum operation at the required operating temperatures, the choice of mould material is made as a function of the final process. However, it is preferable to use a material that best meets the following criteria: - high thermal conductivity, - good mechanical resistance to hot-working conditions, - good electromagnetic performance (magnetic material), - reduced cost, - availability worldwide. Different cooling set-ups are proposed as a function of the targeted converting process. Usually, a second cooling circuit is installed behind the inductor network, and when materials with a high melting point such as PPS or PEEK are being processed, the cooling circuit is bled prior to heating in order to minimize losses and keep a cold water circuit from coming into contact with a mould heated to 400°C (Fig. 5). Conversely, since the heating time and/or the temperatures in the

Fig. 3: Cross section of 3iTech principle

®

RocTool and KIMW, inventor of the Indumold® technology, appeared predestined to reach an agreement. RocTool had developed a solution dedicated more directly to processing materials with a high melting point, including composites (tubular inductors with a diameter of 6-15 mm, cooled and placed 10-15 mm from the moulding surface), while KIMW’s

No58 June-July 2010 / jec composites magazine

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JEC COMPOSITES MAGAZINE - Issue #58 - June - July 2010

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #58 - June - July 2010
