Grooving is an important process in turning, and the characteristics of chip formation and discharge make it unique in almost every way.
Innovative insert designs and coatings can improve the efficiency and quality of grooving, but there are a number of machining points that must be mastered in order to complete this process successfully.
This article lists 10 processing points for using the grooving tool.
1. Understand the groove type
It is important to understand the three main types of grooves, they are: outer groove, inner hole groove and end face groove.
Outer grooves are the easiest to process because gravity and coolant can help chip removal.
In addition, the machining of outer grooves is visible to the operator, and the machining quality can be checked directly and relatively easily, but some potential obstacles in the design or clamping of the workpiece must also be avoided.
Generally speaking, the cutting effect is best when the tip of the grooving tool is kept slightly below the centerline.
Grooving of internal holes is similar to that of external diameter, except that the application of coolant and chip removal is more challenging. For internal grooving, the best performance can be obtained when the tip position is slightly higher than the centerline.
For end face grooving, the tool must be able to move in the axial direction, and the radius of the flank of the tool must match the radius of the machined surface.
The cutting edge position of the grooving tool is slightly higher than the centerline.
Inner hole grooving
End face grooving
2. Processing machine tools and applications
In the grooving process, the design type and technical conditions of the machine tool are also basic elements to be considered. Some of the main performance requirements for machine tools include:
- With enough power, it can ensure that the tool runs in the correct speed range without stalling or jittering;
- With high enough rigidity, it can complete the required cutting without chattering;
- With a sufficiently high coolant pressure and flow can help chip removals;
- With high enough accuracy.
In addition, in order to produce the correct groove shape and size, it is also important to properly adjust and calibrate the machine tool.
3. Understand the material characteristics of the workpiece
Familiarity with some characteristics of the workpiece material (such as tensile strength, work hardening characteristics, and toughness) is critical to understanding how the workpiece affects the tool. When processing different workpiece materials, different combinations of cutting speed, feed rate and tool characteristics are required. Different workpiece materials may also require specific tool geometry to control chipping, or use specific coatings to extend tool life.
4. Choose the right tool
The correct choice and use of tools will determine the cost-effectiveness of machining.
The grooving tool can machine the workpiece geometry in two ways:
One is to process the entire groove shape by cutting in once;
Secondly, the final size of the groove is roughed out by cutting into multiple steps.
After selecting the tool geometry, a tool coating that improves chip evacuation performance can be considered.
5. Form tools
When machining in large quantities, forming tools should be considered.
The forming tool can cut all or most of the groove shapes by cutting in one time, which can free up the position of the tool and shorten the processing cycle time.
One disadvantage of non-blade forming tools is that if one of the teeth breaks or wears faster than the other teeth, the entire tool must be replaced.
An important factor that needs to be considered is to control the chip generated by the tool and the machine power required for forming cutting.
6. Choose single point multi-function tool
The use of multi-function tools can generate tool paths in the axial and radial directions.
In this way, the tool can not only machine the groove, but also turn the diameter, interpolate the radius, and angle. The tool can also perform multi-directional turning.
Once the blade enters the cutting, it moves axially from one end to the other end of the workpiece, while always maintaining contact with the workpiece.
Using a multi-function tool can spend more time cutting the workpiece, rather than for tool change or empty stroke movement.
Multi-function tools also help to reduce the machining process of the entire workpiece.
7. Use the correct processing sequence
Rational planning of the optimal machining sequence requires consideration of a number of factors, such as the change in workpiece strength before and after the groove is machined, as the workpiece strength decreases after the groove is machined first.
This may prompt the operator to use a lower-than-optimal feed rate and cutting speed in the next process to reduce chatter.
And lowering the cutting parameters can lead to longer machining times, shorter tool life and unstable cutting performance.
Another factor to consider is whether the next process will push the burrs into the already machined grooves.
As a rule of thumb, consider starting with the furthest point from the tool holder after the OD and I.D. turning is completed, followed by machining the grooves and other structural features.
8. The role of feeding rate and cutting speed
Feed rate and cutting speed play a key role in groove machining. Incorrect feed and cutting speed can cause chatter, reduce tool life and extend machining cycle times.
Factors that affect feeding 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.
For a variety of different tools, while it is possible to list many sources of information on “optimal” feeds and cutting speeds, the most up-to-date and practical information usually comes from the tool manufacturer.
9. Selection of blade coating
The coating can significantly improve the life of the carbide blade.
Since the coating provides a lubricant layer between the tool and the chip, it also reduces machining time and improves the surface finish of the workpiece.
Commonly used coatings today include TiAlN, TiN, TiCN, etc. For optimum performance, the coating must be matched to the material being processed.
10. Cutting fluid
Proper application of the cutting fluid means providing sufficient cutting fluid for the cutting point where the grooved insert comes into contact with the workpiece.
The cutting fluid serves the dual purpose of cooling the cutting area and assisting in chip removal.
Raising the cutting fluid pressure at the cutting point is very effective in improving chip evacuation when machining blind bore internal diameter grooves.
For grooving of some difficult materials (e.g. high toughness, high viscosity materials), high-pressure cooling offers significant advantages.
The concentration of water-soluble oil-based coolant is also critical for the trenching of difficult materials.
Although the typical coolant concentration range is 3% to 5%, in order to improve the lubricity of the coolant and provide a protective layer for the blade tip, you can also test the effect of increasing the coolant concentration (up to 30%).
Finally, you can watch a demonstration video of grooving tooling below:
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