A steel clutch shaft (42CrMo4) is machined with High Dynamic Turning. Since the tool’s angle-of-approach can be adjusted during machining, all contours can be finished in one setup, including undercuts. Photo Credit: Ceratizit
The Team Cutting Tools of Luxembourg-based Ceratizit Group has developed an alternate approach to turning that it calls “High Dynamic Turning” (HDT), which, combined with the dynamic FreeTurn tooling system, uses a turn-mill center’s B axis or milling spindle to perform the turning process. In contrast to conventional turning, where the contour is created with an indexable insert at a fixed angle-of-approach to the workpiece, this solution allows for 360 degrees of freedom as the tool approach and point of contact in the machine can be varied during machining.
In 2019, Ceratizit first showed the turning technology at an open house in Reutte, Austria, on an Emco Hyperturn 665 MCplus. According to Dr. Uwe Schleinkofer, head of R&D cutting tools for Ceratizit Austria, HDT allows all traditional turning operations such as roughing, finishing, contour turning, face turning and longitudinal turning with just one tool.
How HDT Works
Instead of the classic, static position of the insert in the holder, HDT uses the milling spindle to the tool’s angle-of-approach to the workpiece. The use of the spindle drive, in conjunction with the slim, axial tool design of Ceratizit’s FreeTurn tools creates a degree of freedom of 360° without the risk of collision, thus providing a high degree of flexibility. Due to the rotation around its own tool axis, the cutting edge in action can be changed without interrupting the machining process.
Additionally, the angle-of-approach is freely variable at any time and can even be changed during the cutting process. According to Mr. Schleinkofer, this design is completely new and allows the machining of undercuts, for example, by changing the angle-of-approach, in one setup. This not only enables flexible machining of almost every workpiece contour, but also optimum chip formation, higher feed rates and an increased tool life, Mr. Schleinkofer explains.
The Tool and Toolholder
As the name suggests, in High Dynamic Turning, static turning tools are replaced by dynamic ones. One such dynamic tooling solution is FreeTurn by Ceratizit. The defining characteristic of FreeTurn tooling is its simple structure. The toolholder, together with its slim shank and axial concept that optimizes the direction of the cutting forces into the spindle, form a stable unit (see graphic). The slim design allows machining in narrow workpiece contours right up to the chuck. Cooling channels ensure coolant supply to the machining area.
At the top of the tool shank there is a multi-sided insert, which is simply screwed in place. The FreeTurn insert can consist of several cutting edges with different properties. This allows for different approach angles, corner radii or chip breakers as well as roughing and finishing operations in one tool. Different coatings and cutting materials are conceivable. To start with, there will be a selected range of tools suitable for many applications. The tools are not carved in stone, Mr. Schleinkofer says. “If a customer demands five cutting edges he gets five cutting edges.”
The tool can therefore be adapted to the machining requirements offering the advantage of replacing several tools. This, in turn, leads to significant savings in tool change times, tool magazine loadouts, and tools themselves. Components with highly complex contours can be machined using only one FreeTurn tool.
To prove this point, Ceratizit demonstrated the HDT process live during the company’s open house event in Reutte.
The Process—a Practical Example
Two different parts were machined on an Emco Hyperturn 665 MCplus: A bike hub made from aluminum (AlCuMgPb) and a steel clutch shaft (42CrMo4). A HSK-T63 tool adapter with a FreeTurn insert, which can be configured according to customer demands (for example, with roughing and finishing cutting edges on one insert).
In the case of the aluminum rotor hub, one tool is used for roughing (1500 min-1, ap = 2 mm, f = 0.4 mm/rpm) and finishing (2000 min-1, ap < 1 mm, f = 0.25 mm/rpm). Since the angle-of-approach can be adjusted during machining, all contours can be machined in one setup (even undercuts, which cannot be realized with a standard 90° approach angle), and empty travels are eliminated because the tool cuts in both directions, top to bottom and vice versa. According to Mr. Schleinkofer, compared to conventional turning, four tools can be saved and the process time reduced from 2:10 to 1:35 minutes.
To machine the clutch shaft made from 42CrMo4 steel, the same tool adapter and tool were used. Roughing is performed with a cutting speed of 200 m/min (ap = 3-5 mm, f = 0.3-0.45 mm/rpm), and so is finishing, but with a lower depth of cut (ap = 1-2 mm) and feed rate (f = 0.25 mm/rpm). These parameters can usually lead to high cutting forces, which in conventional turning result in vibrations. Since the maximum main cutting force in HDT is directed axially towards the tool (in the direction of the spindle — see graphic below), vibrations are eliminated and the tool holding force is not exceeded, ensuring a stable process.
In summary, High Dynamic Turning provides the following advantages:
- Dynamic machining of almost any tool contour
- 90% less empty travel
- 40% higher feed rates
- Adjustable feeds in the process
- Higher surface quality due to ideal adjustment of the tool and angle
- Top/bottom machining
- Different approach angles
- Flexible angle-of-approach during machining
- Chip control with different tool cutting edge angles— for example 95°, 75°, 45°
- Preparation for shoulder machining by changing the angle
To demonstrate that HDT, by no means, requires only the latest machines and controls, the live demonstration was performed on a ten-year-old Emco Hyperturn 665 MCplus. However, the machine has to meet certain requirements.
- Linear Axes: X-axis, Y-axis, Z-axis
- Rotational Axes: B-axis, C-axis
- The milling spindle serves as a toolholder and requires an HSK-T and PSC tool interface/connection as well as cutting edge compensation in the Y-level
- Control systems for the spindle axis
- Coupling of the spindle axes (synchronous Y-axis movement)
Software and Programming
Ceratizit is working on programming and software developments with various partners (Siemens NX, Esprit, Open Mind, and many more) and early-stage programming is currently possible with Siemens Sinumerik 840D, Mazatrol and Fanuc controls. While HDT is now programmed manually in-house, programing and machine cycles are in development.
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