Dynamic and Trochoidal Milling (2)

Utilizing Milling cutters with agile machines the right way.

Information provided by
Product manager of round tools in EMEA

Building on the last article describing the Chip Thinning Effect being fundamental to all High Velocity Machining strategies we would like to discuss here the most famous Machining Method which is called Trochoidal Milling.

Trochoidal Milling as subset of Dynamic Milling
One of the very first applications of Dynamic Milling was in slotting where the tool diameter is much smaller than the slot width but much deeper than 1xD. Here the tool performs a type of repeating, close to circular movements. This style of application is called Trochoidal Milling from the Greek word “toros” meaning wheel.

The most basic method in programming is the Static Trochoidal milling method which consist of repeating circles combined with a linear motion at a constant feed rate. A more advanced method is with D-shaped tool movements that try to optimize on the engagement angle (phi) leading to constant chip thickness. By lifting the end mill between being in the cut and moving in a rapid motion to the start of the next pass, the idle time is reduced to a minimum.

There are numerous other special Trochoidal tool paths that imitate pendulum movements or shifts between conventional and climb milling to further optimize idle time.

The end mill for trochoidal milling should be at least 15% - preferably 35% - smaller in diameter than the width of the slot. The step-over between each D-Lane is often mixed up with radial engagement (Ae). If the end mill performs a straight movement within the D-Lane the step-over (W) would be equal to the radial engagement (Ae) but that’s seldom the case is this is not inefficient. If this were the case, the end mill would need to be far smaller than the preferred tool diameter to width of slot ratio.

Cutting data at Trochoidal Milling
The applicable step-over values depend very much on the machine’s capability to accelerate and decelerate, say the agility and respective accuracy of the machine. This means that the machine’s control telling the drives to produce a 10mm wide slot also results in an actual 10mm wide slot in the workpiece. The more agile the machine the smaller the step-over and respectively the Ae value can be, e.g., 2% of the end mill diameter. This is where the highest MRR possible can achieved. If the machine is less agile or the moving masses are too large due to the size or design of the machine, a 10% step-over is more likely to be optimal. A good starting value is 5% with following optimization.

Of course, we have a diverse selection of advanced cutting tools to meet your specific needs and the appropriate cutting data tables to cover almost all materials and machine dynamics.

Suitable tools for Trochoidal Milling
V7Plus Chip Splitter having a 4xD Length of Cut is the dedicated tool for machining deep cavities in Steel and Stainless-Steel materials. The Chip Splitters provide a pre-finished surface quality and help the chip management avoid recutting chips and improve power consumption. In addition, the regular 4 and 6 flute V7Plus offers a significant portfolio of sizes for shallower applications.

TitaNox-Power is a perfect solution for challenging materials such as Titanium, Nickel base alloys, and stainless steel. Depending on the application, the 4-flute version provides a bit more safety regarding the available chip room in the flutes. In comparison, the 5 Flute version should be considered as the default solution providing more productivity and tool life at a given diameter to be used. In specific markets, the new TitaNox-Power HPC is already available as an alternative.

As the name indicates, the Alu-Power HPC is the preferred solution for non-ferrous applications. The highest rpm capabilities and its “ski-jump” flute geometry allow for improved chip formation and evacuation. In addition, a Chip Breaker version is available in specific markets for further increased productivity.

These are only significant examples. Other product lines are suitable besides V7Plus, TitaNox-Power, and Alu-Power HPC, depending on the material and its hardness.

We are ready to meet your needs; please reach out to us.