Shining a light on freeform machining

The headlamp lens mould machined with various different types of Horn end mill
The headlamp lens mould machined with various different types of Horn end mill

To highlight the numerous solutions it offers for milling freeform surfaces, German tooling manufacturer Horn, whose UK subsidiary is in Ringwood, Hampshire, points to a recent application involving the machining of a plastic injection mould for mass producing the lens of a headlamp.

The large number of surfaces, shoulders and radii required the use of many different tools. High-feed milling cutters with indexable inserts from Horn's DAH 8 system were used for roughing the mould. For finishing, different variants of solid carbide end mills from the Horn DS tool system were employed.

The titanium implant produced using different Horn DS titanium milling cutters
The titanium implant produced using different Horn DS titanium milling cutters

In addition to various diameters of ball nose end mills, circle segment end mills were used. The advantage of the latter – in contrast to ball or torus milling cutters – is that fewer passes were required to achieve a given freeform surface quality, lowering the machining cycle time.

In the medical sector, a complex titanium implant was produced on a 5-axis machining centre using Horn DS titanium milling cutters. The shape of the implant comprises numerous freeform surfaces, has about 20 different radii and contains many fillets arranged at different angles. A milling cutter of 10mm diameter and with a corner radius of 0.2mm and another of 6mm diameter with a 0.5mm corner radius completed the roughing. For finishing, a 1mm diameter end mill was used.  

For the other operations on the implant, DS cutters of 10, 6, 4, 2 and 0.6mm diameter were used, as well as a 2mm diameter ball nose end mill and a DCG solid carbide, coated thread milling cutter with three cutting edges.

In a single pass, the tool mills a M3.5 x 0.5 through-hole thread, which is 8mm deep and inclined at 35°. Milling two tapered recesses proved to be highly challenging. Their 43° taper is about 2mm and must end in a geometrically perfect apex, requirements that were met using a Horn micro milling cutter for the roughing and finishing passes.

Horn Cutting Tools
www.phorn.co.uk

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