Cutting and cutting groove art

It is well known that the cutting and grooving process has the same basic objective as ordinary turning operations, that is, the workpiece is machined to the desired shape, meets the accuracy requirements, and maximizes productivity. However, in addition, cutting and grooving applications have their own characteristics in terms of tool strength and stiffness and chip control. Toolmakers can only meet the special needs of cutting and grooving processes with innovative tool design and advanced coolant delivery strategies.



Tool Design Tips As with normal turning operations, the cutting and grooving process uses a stationary tool to cut the rotating workpiece. The first thing to consider is to configure the tooling system so that the required workpiece shape is produced. Therefore, the design of the cutting and grooving tool system differs depending on the size and depth of the workpiece. For example, for deep grooving and cutting operations on large workpieces, and for shallow grooving and cutting operations on small workpieces, the tool manufacturer will provide cutting and direct and clip-on configurations in the holder. Slot blade.

An example of this is the Seco brand new series of star-mounted design inserts, which have four cutting edges and are therefore called the X4 series. This blade has a cutting width of between 0.5 mm and 3 mm (0.02"-0.12") designed to minimize material consumption during cutting and to accurately cut and simulate small and medium-sized complex parts. Shape processing. Depending on the width of the cutting edge, the maximum depth of cut of the tool is between 2.6mm and 6.5mm (0.10" and 0.26"), and the maximum diameter of the severable bar is between 5.2 and 13 mm (0.20" and 0.52") between. The stand-up design of the blade directs the cutting forces to the shank, maximizing stiffness, stability and productivity.



After determining the basic shape of the insert, the choice of the rake angle of the cutting edge has become a key factor in the effectiveness of the cutting and grooving. The zero-degree front rake tool can achieve vertical alignment with the workpiece and transfer the cutting force directly to the shank, increasing accuracy, tool life and surface roughness. However, after the cut is completed, the zero-degree tool will leave tiny protrusions or tips at the center of the severed bar. If you do not want to leave a protrusion, use a knife with a small rake angle to cut off the protrusion as it passes through the center of the workpiece. In addition, in some workpiece materials, the front corner tool is not prone to burrs.



After setting up the basic tool configuration, the material properties of the workpiece usually determine the most suitable blade model for machining the workpiece. Difficult-to-machine workpiece materials or interrupted cuts should generally use blade types that have higher strength and impact resistance, while highly abrasive workpieces require blade models designed for wear resistance.



Tool Application Recommendations There are specific setup recommendations for cutting and grooving tools. When installing the tool, care should be taken to make the blade and workpiece axis truly perpendicular. This minimizes the axial force on the tool and prevents friction on the sides of the blade. For the tool position, the center height of the cutting edge should be as close to the center of the workpiece as possible, and the deviation should be within +/-0.1 mm/0.004". This is also to prevent excessive pressure on the tool, so as to avoid shortening the tool life.



Cutting parameters for cutting and grooving tools differ from ordinary turning. If the spindle speed is constant, the cutting speed will decrease to zero when the cutting tool reaches the center of the bar stock. Slowing down can put heavy pressure on the tool and can cause the workpiece material to adhere to the cutting edge. Therefore, the feed rate (up to 75%) should be reduced when the tool approaches the center of the part. In addition, the cutting speed can be adjusted to minimize vibration. The blades used in the cutting and grooving process are usually narrow blades, which tends to cause chipping instability. Therefore, as far as possible, the blade is fixed in the shortest tool bar, and it is clamped in the thickest tool bar without disturbing the workpiece. These measures also help to control the vibration. Ensuring the rigidity of the machine itself (which is necessary in any machining operation) also helps to reduce unwanted vibrations.



Chip control problems The cutting and grooving process is characterized by a very narrow cutting area, which presents challenges for chip control during processing. Especially in the cutting process, the cutting tool is surrounded on both sides by the workpiece material, limiting the chip discharge path. Finally, depending on the material of the workpiece, the thin chips generated during the cutting and grooving process do not tend to break. Uncontrolled ribbon chips can cause chip jams, damage the workpiece, and endanger the operator's safety. Not only that, chip control issues can also hinder the implementation of unattended or "fully automated" processing.



Many of the tools used for cutting and grooving use specially designed cutting edge geometries to bend and break the chips. If the surface roughness and other conditions permit, the tool feed (also called "stay") can be suspended during cutting to help break the chips. Another chip control method is to use coolant to flush away chips that might clog the cutting area. However, conventional cast coolant does not generally produce enough pressure in the cutting and grooving applications to reach the cutting zone. In addition, the position of the nozzle for pouring the coolant is also difficult to determine, and it is not possible to allow the coolant to flow to the site where it is most needed. Finally, the relatively weak pouring coolant flow may be converted into steam in the cutting zone, which actually forms a barrier, so that the heat generated during the cutting process cannot be dissipated.



An alternative to pouring the coolant is to spray the coolant at high pressure as close to the cutting edge as possible. Today's machine coolant pumps typically provide 20 bar (290 psi) to 70 bar (1015 psi) pressure. For example, Seco's coolant delivery system has a wide range of applicability, operating pressures ranging from as low as 5 bar (72 psi) (may affect productivity), up to 70 bar (1015 psi), and even to 275 High pressure of bar (4351 psi).



For best results, the high pressure coolant must be sent at a fixed point as close as possible to the cutting zone. Tool manufacturers have developed a number of high pressure coolant delivery systems. A popular practice is to deliver coolant through blades. However, the most effective coolant flow creates a “wedge” between the rake face of the insert and the chip, which lifts and breaks the chip. Obviously, when the coolant is conveyed by the blade, it is difficult to guide the flow to the optimal position and no wedge can be produced. This is not enough to bring the coolant into the vicinity of the cutting zone. To form the wedge, the flow must be as close as possible to the cutting edge.

Therefore, Seco developed a set of coolant delivery system called Jetstream Tooling®, which can guide the high-pressure coolant through a deflector located in the shank. The orifices of the deflector create a violent, high-speed coolant flow that penetrates and lubricates the high friction area between the workpiece and the cutting edge of the tool. Recently, in an innovation aimed at controlling chips under difficult conditions, the company applied a technology called Jetstream Tooling® Duo to X4 cutting and grooving arbors. This method can deliver coolant from both outlets. The new Duo technology uses an additional coolant nozzle to flush the gap surface, in addition to the upper nozzle that sprays the optimum point on the rake face. The cutting edge receives high pressure coolant from two opposite directions (above and below) to maximize control of the chip flow and cool the cutting zone.



Specialized cutting points Chip control is particularly critical when machining difficult-to-machine workpiece materials such as titanium alloys and stainless steel. These materials have high strength and high heat and abrasion resistance and are commonly used in the production of high-value parts in the aerospace, power generation and pharmaceutical industries. But it is these characteristics that make these materials an excellent choice for critical applications while also reducing the material's processability. To achieve chip breaking, the chips should absorb the heat generated during the cutting and be softened, but the titanium alloy is a material with poor thermal conductivity and will produce tough chips that are difficult to break.



Sharp tools with a large positive rake angle can efficiently cut titanium alloys and other materials. However, in order to control chips and maximize productivity, high pressure coolant delivery tools are often required. The coolant flow is delivered through a fixed point and a wedge effect is created between the rake face of the insert and the chips, which can be broken into smaller, more manageable pieces.



The cutting and grooving process is an important part of the turning operation and it also brings many unique challenges. Due to the narrow cutting area of ​​these processes, the basic tool shape, geometry, insert material, setting details and cutting parameters must be carefully considered. Chip control is a matter of concern in any machining operation, but in narrow spaces, chip control becomes even more critical if the chips produced by the cutting operation are thin and difficult to break. Tool manufacturers have developed chip control slots that can help solve this problem. In addition, cutting strategies such as pausing feeds can also help. A great way to control chips is to send high pressure coolant at a fixed point. Uncontrollable chips require the operator to monitor all the time. Therefore, the main advantage of continuous chip control is that fully automated/unattended machining operations can be achieved. Like other machining processes, coolant can provide the same advantages in cutting and grooving processes, including longer tool life and/or increased cutting parameters. In short, with today's cutting, grooving tools, technology and innovation, users can maximize productivity in this professional but important process.