Fast and dynamic: Trochoidal milling in mould making

These milling strategies are among the most modern and effective cutting methods. The basic principle of trochoidal milling is based on maximum tool utilisation: The process uses a small cutting width (ae) and the maximum cutting depth (ap). By using the tool’s entire cutting edge length, it is able to unleash its full power. This is particularly important in the area of mould and die, where enormous quantities of high-strength steel have to be machined. In trochoidal milling, the tool wrap is low, which improves the thermal effect on the tool cutting edge and ensures low mechanical stress. In addition, this procedure leads to longer tool lives as the wear is evenly distributed over the entire cutting edge.

However, not every milling cutter is suitable for this style of dynamic milling. This calls for high-quality solid carbide tools that can withstand machining at extremely high cutting speeds and significantly accelerated feed rates. We present three such tools for different applications in mould and die.

The RF 100 Speed P is specially adapted for machining steel, high-strength steel and cast materials and ensures maximum metal removal rates and outstanding process reliability for roughing and finishing up to 48 HRC. The solid carbide milling cutter is perfectly suited for trochoidal milling. The entire cutting edge length of the roughing end mill is used with a small cutting width (5-15% ae).

RF 100 Speed P in the online shop

In this way, extreme metal removal rates and significantly higher feed rates can be achieved and the cutting forces that occur are much, much lower. In real life, this tool, used in the dynamic GTC process, can cut the machining time by more than half compared to a conventional round plate milling cutter head.

However, many moulds and tools are also machined in a hardened state. Dynamic milling strategies such as GTC are also very effective during hard milling, as the contact time between the cutting edges and the tool is significantly shorter than in conventional milling applications. This in turn has a very positive effect on tool life. However, due to the hard material, only two to a maximum of five percent of the lateral infeed can be used here.

G-Mold 65 U in the online shop

The G-Mold 65 U from Gühring is particularly suitable for the GTC milling of hardened moulds and mould inserts. Its precise geometry ensures high contour accuracy during dynamic milling. This means that complex moulds and contours can be machined with the highest level of precision. At the same time, the end mill has an FEM-optimised radius angle transition, which ensures high radial stiffness and low deflection. This ensures stable milling results and minimises vibrations. In materials such as heat-treated steel with up to 65 HRC, the G-Mold 65 U manages to halve the runtime during pre-finishing when used in a GTC milling process.

During hard machining in mould and die processes, stock on the component often has to be removed quickly and evenly. Under optimal conditions (HSC), dynamic milling can be used here. While most competitors only offer two-fluted milling cutters for this purpose, the G-Mold 55 B is available as a four-fluted variant. By spreading the process over twice the number of cutting edges, the machining time can be almost halved.

G-Mold 55 B in the online shop

A dynamic milling strategy also offers significant productivity advantages for 3D machining with spherical or toric milling cutters. Here, milling is also carried out with very tiny infeeds, taking into account the effective tool diameter. The total feed rate is increased at the same time. For cutting depths ap < 0.2xD, the effective diameter Deff actually engaged must be used to calculate the rotational speed. To increase the tool life, we recommend machining with the spindle tilted.