Gear shaping machine
Gear shaping machines are continuously working gear cutting machines in which the gear kinematics is simulated during the shaping of the workpiece and tool in the form of a gear with parallel axes. In gear shaping, the tool and the work wheel rotate according to their number of teeth. At the same time, the cutting wheel performs the stroke movement in the axial direction that is necessary to remove the chips. During the return stroke (idle stroke), the cutting wheel is lifted from the work wheel in order to avoid a collision with the toothed workpiece as it continues to roll. The gear-shaped tool has relief-ground, involute-shaped flanks.
The working process carried out on gear shaping machines is called gear shaping .
operation area
Gear shaping machines are used to produce straight or angled internal and external gears .
The main areas of application are the production of:
- Internal gears for smaller quantities
- Internal gears in blind holes , i.e. non-through holes
- External gears when there is no run-out, that is, when hobbing is not possible
Examples of workpieces that are often geared by gear shaping :
- Internal ring gears for planetary gears
- Coupling hubs
- Drive shafts
Structure and kinematics
Gear shaping machines consist of a round table on which the workpiece to be geared is clamped. The shaping tool is located above the workpiece and executes a stroke movement parallel to the workpiece axis of rotation. The workpiece and the shaping tool rotate continuously around their axes so that both roll into each other like a planet gear in a ring gear. The shaping tool is basically a pinion with cutting edges on the lower face. In addition, as a third movement, the shaping tool moves radially into the workpiece until the set final depth is reached. After reaching the final depth, the workpiece has to make one complete revolution so that the toothing is rolled out over the entire circumference.
The tool only removes chips during the downward movement . Shortly before the upward movement, the tool is lifted slightly from the workpiece. It is necessary to lift the tool off the workpiece in order to protect the cutting edges during the upward movement and to avoid a collision with the workpiece as it continues to roll.
By changing the infeed depth of the shaping tool, the tooth thickness of the workpiece teeth can be selected as desired. Since the tooth thickness cannot be measured directly, the tooth thickness is determined indirectly by measuring the distance between two rollers that are placed opposite in the gaps between the teeth.
With older, conventional gear shaping machines, all three movements are continuous. The speed ratio of cutting wheel and workpiece (and thus the number of teeth generated on the workpiece) is set using change gears. The radial infeed is controlled by a cam , depending on the manufacturer . The cutting wheel travels through the curve to the roughing depth and the workpiece makes one complete revolution without any further infeed. This is followed by infeed to the finishing dimension and one last full revolution of the workpiece without infeed. This ensures that the tooth thickness is the correct dimension over the entire circumference.
Modern CNC gear shaping machines have independent drives for all movements. Therefore, different gear strategies are possible with such machines, for example:
- Diving without rolling with subsequent rolling circulation
- Diving with rolling with subsequent rolling circulation
- Degressive diving with subsequent roller circulation
In order to produce helical gears on gear shaping machines, the cutting tool must also perform a rotary movement around its own axis when moving up and down. The cutting tool must also be helical and have the same helix angle as the workpiece to be cut. In conventional machines, the required rotational movement is generated mechanically by a screw guide in the machine. When changing from straight to helical teeth, a complex conversion of the machine is necessary. In the case of CNC-controlled machines, the required rotational movement can be generated by the control and an additional drive.