product development | Conformal cooling Right:
Schematic showing the
complex high performance
parallel cooling circuits in this additive-built mould insert
Below: Conformal cooled inserts are used in the complex ribbed areas at the front of Rowenta’s steam irons
different individual models. And the model cycles are shorter than you’d expect – a new range is added every four years,” says Maier. “Fewer irons are bought at the beginning of the year. Then we manufacture about 6,000 irons a day. But later in the year, that number jumps to between 9,000 and 10,000.” As Rowenta carries out its moulding in-house, it is able to use multi-component technology that is highly customised. The aim, according to Maier, is to automate anything that can be on each production cell. Conformal cooling is used in the most critical parts of the tools – sections with complex ribs or where space is restricted - to ensure the tight dimensional control required for trouble-free automated module assembly. The company uses conformal cooling tool inserts produced using the LaserCusing technology developed by Hofmann Innovation, integrating these into conventionally-built and tempered moulds. Hofmann’s LaserCusing system (which is marketed by its Concept Laser subsidiary) uses an additive building process that creates a mould insert layer-by- layer from metal powder melted together by a laser. It is claimed to create a 100% fully dense metal compo- nent and is said to be able to process a range of stainless and tool steels. The additive building technique allows cooling channels to be placed close to the mould surface and to follow the surface contour – conformal. Typically, cooling channels of around 5mm diameter are used and are placed between 2-3mm of the surface. Hofmann
claims that, when applied selec- tively in a mould tool, the use of LaserCused inserts is cost neutral. For engineering and functional
reasons, irons are well suited to the application of conformal cooling due to the pronounced ribbing in the front area. “The key benefit is the lack of distortion. It accounts for the positive assembly characteristics, that is, the excellent dimensional accuracy of all the different mandrels and metal tubes that have to fit perfectly,” says Maier. In a three-component part,
there are clearly identifiable cycle time improvements, too. Hofmann Innovation claims typical cycle time reductions of
between 10 to 30%. Maier says start-up is also much faster, with the required dimensional
accuracy achieved very quickly. With close to a decade of conformal cooing experi-
ence, Rowenta has developed a good understanding of how to get the best out of the conformal technology. Maintaining a high volume of coolant flow is essential and corrosion inhibitors are used to prevent build-up of sediment and particulate contamination. Coolant channels also have to be appropriately sized and positioned - parallel cooling is used at particularly challenging points to ensure maximum cooling of the cavity surface. This is all determined during the product development process and carried out in conjunction with the project managers and engineers at Hofmann Tool Manufacturing. Irons are subject to safety checks by national or
international testing organizations, such as the VDE, GS or UL inspections. The majority of checks are carried out at Rowenta to shorten the release time. This requires a certain degree of flexibility from all involved. Toolmakers, such as Hofmann, are brought on board in the very early stages of a project and remain involved throughout the development process. “In a standard range, this means about 12 months of
project time, from design studies through model making to the finished series-production tools. For an innovative product with new electronic functions, a project of this kind could last up to 16 months,” says Maier.
For more information: ❙
www.hofmann-innovation.com ❙
www.concept-laser.de
22 INJECTION WORLD | October 2013
www.injectionworld.com
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