Machining is the heart of the modern manufacturing industry and offers a versatile production method with exceptional possibilities. Grooving is one of the extremely useful and useful machining techniques when cutting grooves.
In this article, we will take a closer look at grooving and discuss what it is, what cutters are needed for it and what types of operations exist.
What is slot milling?
Grooving, also known as slot milling, is a machining process in which a groove is milled into the workpiece using a rotating cutting tool. The groove can be any shape and size, the possibilities are endless. However, the slot cutter and machine must be able to form the shape of the slot on the solid part.
Types of slot milling techniques and their cutters
There are numerous slot milling techniques for different geometries, machine tools and applications. Each type has specific cutters and requirements.
End milling
End milling is done with a standard end mill or milling cutter. It is a versatile grooving tool that can produce closed grooving, non-linear grooving profiles and even variable depth grooving.
The process is similar to face milling, in which both the side and face of the tool are cut. The difference is that slot milling creates a closed groove at both ends, while face milling aims to smooth the surface of the part.
Because end mills come in a variety of sizes and materials, grooving with end mills is the preferred method for machinists. They can withstand high cutting forces and cut deeply. Furthermore, special end mill designs can also suppress vibrations and improve surface finish.
Side milling
Side milling is another technique for creating channels. In this method, a side milling tool performs the cutting, with the cutting occurring primarily through the edge of the tool.
It is a stable cutting method that can withstand cutting forces and vibrations. With a sufficiently rigid spindle and balance, a horizontal milling machine can produce high-precision channels.
T-Slots
T-slot cutting is a special method for cutting T-shaped slots. T-slots are commonly used in industrial machines, especially machine bases.
A special T-slot cutter is used. In general, a T-slot milling operation is preceded by a normal slot milling operation. This first process creates space for the shank of the T-slot cutter. However, this is only necessary for closed slots. For open channels, the T-slot milling cutter can carry out the milling process directly.
Woodruff Spring Slots
Another important application of slot milling is the machining of keyways for keyway connections. Designers use keyed connections to connect load-bearing components for efficient load transfer. For example, gears can be attached to the shaft with a key connection.
The female part of this connection, the keyway, is made with a keyway cutter. A Woodruff keyway cutter can be used to create the keyway or key seat in which the key sits to lock the assembly.
Group milling
Components such as milling machine work tables have several parallel slots that are useful for attaching accessories and the workpiece to the machine base. For parts with parallel grooves, it is convenient to use a group milling machine.
In this type of grooving, several grooving cutters are mounted on the same spindle, each cutting grooves in the material at the same time. The process is therefore very productive and saves time. However, due to the high cutting forces, the spindle and machine tool must be sufficiently rigid.
Tips and practices for slot milling
Grooving requires care and skill to achieve ideal results in terms of surface quality, material removal rate and accuracy. Here you will find useful tips and tricks for optimizing slot milling performance.
Deceleration instead of radial input
The cutter input must be smooth and not overload the tool. It is recommended to use a deceleration motion to avoid fully engaging the tool at once, which can cause excessive vibration and also be disastrous for the tool.
In general, a ramp angle of at least 45° is sufficient to avoid impacts to the tool and machine. Additionally, for harder materials or deep channels, machinists can use a ramp angle of up to 180° (axial entry).
Chip removal is essential
Slots are closed structures that usually have only one open end. This means there is less space for chips to escape from the cutting zone. If they become stuck in the cutting zone, they can affect surface quality, tool life and part tolerances.
Therefore, proper control of chip removal during grooving is essential. It is generally recommended to cut the groove in at least two passes. This way, there is enough space for chip removal in the second and subsequent passes, which can be programmed to have high material removal rates.
Another solution is special tools, such as chipbreaker cutters. They produce very fine chips that easily come out of the cutting zone. Additionally, coolant/lubricant flushes and compressed air are also popular methods for removing chips from grooves.
Keep the spindle loaded
Another tip is to ensure that there is no point in the cutting cycle when the spindle is completely unloaded. To ensure this, at least one cutting tooth must always be engaged with the workpiece. This can be adjusted by plunging the tool radially into the workpiece.
The reason for this advice is that interrupted cutting is not good for the surface finish of the grooves. Furthermore, it is counterproductive as less material is removed per unit of time without providing any additional benefit. Additionally, the repeated impulse load it places on the system can cause vibration and reduce the life of the machine.
Up milling
The debate about reverse and synchronous milling in machining also applies to slot milling. When possible, machine operators should choose down milling because it offers better stability and chip evacuation properties. However, the setup must also be robust enough to withstand the load pattern of down milling.
Prefer larger cutting diameters
When machining deep grooving, the stability of the grooving tool is often an issue. Long tool swings when cutting deep grooves can bend the tool and, in extreme cases, even break it.
In this case, a large diameter tool is preferable due to its greater strength. Additionally, tools made from stiffer materials are another way to solve such problems.
However, this is often not an easy task as most slots are narrow but deep. Choosing large tools is not an option. In these situations, train drivers simply need to do the best they can with the resources and limitations available.
Optimize feed
Cutting feed planning is another central aspect of efficient slot milling. High feed rates can cause thermal problems, while low feed rates can reduce productivity. Therefore, to avoid these problems, a balanced federation is always preferable.
This is a broad topic with much more detail that justifies an in-depth study of cutting feed and other machining parameters before finalizing your cutting program.
Toolpath techniques for slot milling
Modern machine tool experts improve machining performance through efficient tool path planning. Through extensive research and experimentation, the industry has developed numerous tool path solutions for grooving operations that improve overall process quality, part quality, and machine tool condition.
Conventional
Conventional milling is the simplest path for grooving and consists of straight cuts along the axis of the groove. It is productive and easy to program. Furthermore, it is compatible with most cutting tools.
Disadvantages include high vibration with deep grooves and difficult-to-cut materials. As the tool is always in the cut, it is exposed to high radial forces, which makes it unstable when making deep cuts. Furthermore, it also causes rapid heat generation.
Trochoidal
Trochoidal milling is a special path technique in which the tool follows a trochoidal path. It is extremely beneficial in slot milling because it is more stable, gives the cutting edges enough time to cool, and leaves enough space for efficient chip evacuation.
Furthermore, it is suitable for difficult-to-cut materials due to the lower average radial cutting forces. However, it requires more complex programming and tool selection.
Surrender
When plunging, the entire groove is processed exclusively by axial cuts, like drilling, but with a milling cutter. This is not the most productive method, but it is the most stable because the absence of radial forces minimizes tool deflections, vibration and heat problems. Therefore, this method is preferable for setups where the tool is prone to any of these issues. This includes long tool overhangs and deep grooves.
Furthermore, immersion does not leave a good surface finish, especially on the groove walls. Therefore, a final cut using other traversing methods is necessary at the end.
Concluding
Grooving is indeed a useful machining process with diverse applications in industry. Expands the scope of manufacturing and allows the production of complex geometries.
Common questions
What machines are used for slot milling?
Grooving can be performed using standard milling machines, both horizontally and vertically. In certain cases, machinists may also use other machines, such as drilling machines or punching machines.
What materials can be processed with slot milling?
The groove is compatible with all machinable materials. Metals (steel, titanium, copper, iron), plastics and wood.
What types of cutters are used for slot milling?
There are a variety of cutters suitable for slot milling. Depending on the geometry of the groove, an end mill, a shell end mill, a corner mill, a T-slot mill, a multi-milling chuck, a wood slot mill, etc. can be selected as a cutting tool.
