Specify the type of groove
It is important to identify the three main types of grooves: outer circular grooves, internal hole grooves, and face grooves.
Cylindrical grooves are easiest to machine because gravity and coolant can help with chip evacuation. In addition, the machining of external grooves is visible to the operator and the machining quality can be checked directly and relatively easily. However, some potential obstacles in the design or clamping of the workpiece must also be avoided.
In general, cutting results are best when the tip of the grooving tool is held slightly below the centerline. Internal grooving is similar to external bore grooving, except that coolant application and chip evacuation are more challenging.
For internal grooving, the best performance is achieved when the tip is positioned slightly above the centerline. To machine the face groove, the tool must be able to move in the axial direction, and the flank radius of the tool must match the radius to be machined. The best results are achieved when the tip of the face grooving tool is positioned slightly above the centerline.
Machine design and technical condition
In grooving, the design type and technical conditions of the machine tool are also basic factors that need to be considered.
Some of the main performance requirements for a machine tool include enough power to keep the tool running in the correct speed range without stalling or jittering, high enough rigidity to complete the required cutting without chatter, high enough coolant pressure and flow to help with chip evacuation, and high enough accuracy.
In addition, in order to machine the correct groove shape and size, it is important to properly calibrate the machine.
Understand the material properties of the workpiece
Familiarity with some of the properties of the workpiece material, such as tensile strength, work-hardening characteristics, and toughness, is essential to understand how the workpiece affects the tool.
Different combinations of cutting speeds, feeds and tool characteristics are required for different workpiece materials.
Different workpiece materials may also require specific tool geometries to control chips or utilize specific coatings to extend tool life.
Forming tools are selected
In high-volume machining, forming tools should be considered. Forming tools produce all or most of the groove shape in a single plunge, freeing up tool position and reducing machining cycle times.
One disadvantage of non-blade forming tools is that if one of the teeth breaks or wears out faster than the others, the entire tool must be replaced. An important factor to consider is the power of the machine required to control the chips generated by the tool and the forming cut.
The role of feed and cutting speed
Feed and cutting speed play a key role in groove machining. Incorrect feed rates and cutting speeds can cause chatter, reduce tool life and increase machining cycle times.
Factors influencing feed and cutting speed include workpiece material, tool geometry, coolant type and concentration, insert coating, and machine performance.
In order to correct problems caused by unreasonable feeds and cutting speeds, secondary machining is often required. While there are many sources of information that can be listed to "optimize" feed and cutting speed for a variety of different tools, the most up-to-date and useful information often comes from the tool manufacturer.
Select the tool coating
The coating can significantly increase the life of carbide inserts. Since the coating provides a lubricating layer between the tool and the chip, it also reduces machining time and improves the surface finish of the workpiece. At present, commonly used coatings include TiAlN, TiN, TiCN, etc. For optimal performance, the coating must be matched to the material being processed.
Correct processing sequence is adopted
Proper planning of the optimal machining sequence requires consideration of a variety of factors, such as the change in the strength of the workpiece before and after the groove is machined, because the strength of the workpiece decreases after the groove is machined first. This may motivate the operator to use a lower than optimal feed and cutting speed in the next operation to reduce chatter, while lower cutting data may result in longer machining times, shorter tool life, and inconsistent cutting performance.
Another factor to consider is whether the burr will be pushed into the machined groove in the next operation.
As a rule of thumb, consider machining from the farthest point from the tool chuck and then machining the grooves and other structural features after the outer and inner diameter turns have been completed.
