One application focus of the Hermle MPA technology is in the field of tool and mould making. Here, additive manufacturing allows for countinuous and uniform cooling of surfaces which can hardly be achieved with conventional production techniques, if it is not impossible. Experience with customer parts has shown a large potential to reduce injection moulding cycle times with additively created parts with conformal cooling. In comparison with tools with tools without effective cooling, time savings of more than 45% could be achieved. With very low porosity in the sprayed material, even surfaces with glossy finish can be offered for some materials, e.g. 1.2344 hot work tools steel.
The picture series shows the main steps in the production of the above shown injection mould. Starting with a blank with predefine cooling channel, the channel volume is filled with a water-soluble material using MPA material application. In a milling step, surplus filling material is removed and the surface contour for the covering steel layer gets defined. Afterwards layers of steel are sprayed on the surface to close the channel. Now the filling material can be removed from the cooling channel and the whole part undergoes a heat treatment, before it gets its finishing.
These three tool inserts each contain a cooling channel following the surface contours.For their production, we used massive blanks in which the cooling channels were milled in. In comparison to layer-by-layer buildup of the whole parts, using blanks is way more time- and cost-efficient.
The additive manufacturing part is reduced to two steps: Filing the channels with a water-soluble material and subsequent application of the respective covering layer of steel (blue marks in the picture).
For the material layer application we use the five axes simultaneous dynamics of the machine to achieve a homogeneous growth on the curved surfaces of the parts. For the two parts shown on the right, layer buildup was carried out radially while the respective blank was rotating on the machine's C-axis.
With MPA technology, different materials can be combined in one part. One application of interest is to embed copper elements as heat conductors in steel components. For the parts shown here, copper was integrated at locations where cooling via a channel is not possible because of geometric limitations. Often these copper elements transport the thermal energy from hot spots to the cooling channel located further inside the part.
Similar to the production sequence for cooling channels, predefined geometries are filled with copper using the MPA process to achieve a thermal coupling between copper and steel substrate. After milling the surface, layers of steel are applied to cover the copper.
Applications with a contrary purpose to confocal cooling are components with integrated heating elements. In the manufacturing process, notches are milled in the blank where the isolated heating filaments are forced in. The part is then covered with a layer of steel using MPA material application. The direct connection of the heating element to the sprayed material provides an outstanding thermal coupling, outperforming normal pressing contacts by far. For local temperature control, additional thermal elements can be integrated as well.