Basic knowledge of the hottest high speed cutting

Basic knowledge of high-speed cutting

historical background

the term high-speed cutting (HSM) generally refers to vertical milling at high speed and high surface feed. For example, the concave of aluminum alloy aircraft wing frame is cut with a high metal removal rate. In the past 60 years, high-speed cutting has been widely used in metal and non-metallic materials, including the production of parts with specific surface shape requirements and the cutting of materials with hardness higher than or equal to 50 HRC. For most steel parts quenched to about HRC, the current cutting options include:

it will also infringe machine parts

rough machining and semi finishing cutting of materials under soft (annealing) working conditions

heat treatment to achieve the final hardness = 63 HRC

electrode machining and electrical discharge machining (EDM) of some parts of molds (especially small radius deep pits inaccessible to gold cutting tools)

suitable cemented carbide, cermet Finishing and Superfinishing of cylindrical/flat/concave surfaces with monolithic cemented carbide, mixed ceramics or polycrystalline cubic boron nitride (PCBN) tools

for many parts, the production process involves a combination of these options. In the case of mold manufacturing, it also includes time-consuming finishing. As a result, the production cost is high and the preparation time is long

in mold manufacturing industry, it is typical to produce only one or several same products. During the production process, the products are constantly changing. Due to product changes, measurement and reverse design are required

the main standard is the quality level in terms of mold size and surface roughness. If the quality level after processing is low and cannot meet the requirements, manual finishing is required. Manual finishing can produce satisfactory surface roughness, but it always has a bad impact on the accuracy of size and groove shape

one of the major difficulties in mold manufacturing has been solved, but now it is still necessary to reduce or eliminate manual polishing, so as to improve quality, reduce production costs and shorten preparation time

the main economic and technical factors in the development of high-speed cutting

slow control response

the increasingly fierce competition in the survival market leads to the continuous setting of new standards. The requirements for time and cost efficiency are getting higher and higher. This forces the continuous development of new processes and production technologies. High speed cutting offers hope and solutions

materials new and more difficult to machine materials have emphasized the need to find new cutting solutions. The heart of aerospace industry is made of heat-resistant alloy steel and stainless steel. The automotive industry uses different bimetallic materials, compact graphite iron, and increases the amount of aluminum. Mold manufacturing industry must face the problem of cutting high hardness quenched steel, from rough machining to finish machining. The high demand for quality is the result of unprecedented fierce competition

if used correctly, high-speed cutting can provide some solutions in this field. An example is the replacement of manual finishing, which is particularly important for molds with complex 3D grooves

the requirements of the process for shorter processing time - only a few times of card loading and simplified logistics (logistics) requirements can be solved by high-speed cutting in most cases. A typical requirement in the mold manufacturing industry is to complete the cutting of all completely quenched small parts in one loading. Using high-speed cutting can reduce and eliminate the time-consuming EDM (electrical discharge machining) processing

Design and development one of the main methods in today's competition is to sell novel products. At present, the average life cycle of cars is four years, computers and accessories are one and a half years, and three months. The prerequisite for the rapid change of style and rapid development of products is high-speed cutting technology

multifunctional surfaces of complex product parts have been added, for example, newly designed turbine blades have new and optimized features and functions. Early designs allowed polishing by hand or robot (manipulator). Turbine blades with new and complex shapes must be polished by chips, preferably by high-speed cutting. There are more and more examples of thin-walled workpieces that must be machined by cutting (medical equipment, electronics, national defense products, computer parts)

the great development of product equipment cutting materials, tool handles, machine tools, controls, especially cad/cam features and equipment may meet some requirements, which are proposed by new production methods and technologies and must be met

the original definition of high-speed cutting

in 1931, salomons theory in a German patent said: cutting at a certain high cutting speed (times higher than conventional cutting), the temperature of chip removal on the cutting edge began to decrease

from the above conclusion: it seems that there is an opportunity for conventional tools to improve productivity at high chip speed

what is the definition of high-speed cutting today

the discussion of high-speed cutting is chaotic to some extent. There are many viewpoints, many mysteries, many methods and many methods about the definition of high-speed cutting. Let's take a look at several of these definitions:

in the following discussion, we will discuss the parameters that affect the high-speed cutting process. It is very important to describe high-speed cutting from a practical point of view, which can also provide many practical guidelines for the application of high-speed cutting

actual cutting speed

because the cutting speed depends on the spindle speed and the diameter of the tool, high-speed cutting should be defined as the linear relationship between the actual cutting speed higher than a certain level - the cutting speed and the cutting speed of conventional cutting

the exception is the high-speed cutting characteristics in hardened tool steel when cutting in aluminum and other non-ferrous metals and finishing and superfinishing processes of all materials

vf=fz n z

shallow depth cutting

very necessary and typical high-speed cutting applications are cutting where the cutting depths AE (radial cutting depth) and AP (axial cutting depth) and the average chip thickness HM are much smaller than conventional cutting. Therefore, the metal removal rate q is much smaller than the conventional one. The exception is the finishing and superfinishing processes of cutting and all materials in aluminum and other non-ferrous metals. Q= AP AE VF [cm/min] 1000

high speed cutting characteristics in hardened tool steel

in the mold manufacturing industry, the largest economic workpiece size is about 400 400 150 (length, width and height). The maximum size is related to the relatively low material removal rate in high-speed cutting. Of course, it is also related to the dynamic characteristics and size of the machine tool. As mentioned above, most of the molds are quite small in full cutting (single clamping). The typical processes are rough machining, semi finishing, finishing and in many cases super finishing. The milling of round corners and arcs always leaves a certain margin for the tools in the subsequent process. In many cases, a tool is used

usually the diameter range is mm. In 80 to 90% of cases, the cutting material is solid carbide end mills or ball end mills. End mills with large rounded corners are often used. The cutting edge of the overall cemented carbide tool is strengthened, and the rake angle is zero or negative (mainly used for materials with hardness above 54 HRC). A typical and important design feature is that the core is thickened for maximum bending strength

it is advantageous to use ball end mills with short cutting edges and contact length. Another important design feature is the cutting capacity, which is necessary when cutting along the steep wall. Smaller cutting tools with indexable inserts can also be used. Especially for rough machining and semi finishing. These cutters should have great handle stability and bending stiffness. The taper handle improves the rigidity, and the handle made of heavy metal also improves the rigidity

the groove shape of the mold should be shallow and not too complex. Some groove shapes are also suitable for high-speed cutting with high productivity

the better the combination of contour cutting tool path and forward milling, the better the cutting effect

the principle that should be followed in a finishing or semi finishing process is to adopt shallow depth cutting. The cutting depth shall not exceed 0.2/0.2 mm (ae/ap). This is to avoid excessive bending of the tool handle/cutting tool, so as to maintain the small tolerance and groove accuracy of the die. The evenly distributed allowance of each tool is also a condition to ensure constant and high productivity. When ae/ap is constant, the cutting speed and feed rate should always be kept at a high level. In this way, the mechanical changes and the load on the cutting edge will be smaller, and the tool life will be improved

cutting parameters

typical cutting parameters of tic, n or TiAlN coated integral cemented carbide end mills on hardened steel (HRC):

rough machining

actual cutting speed vc:100 m/min, AP (axial cutting speed):% of tool diameter, AE (radial cutting depth): tool FL pendulum impact testing machine is mainly used for metal Charpy impact test diameter%, FZ (equipment feed rate per tooth should be closed according to the specified steps):0 1mm/tooth

semi finishing

actual cutting speed vc:m/min, AP (axial cutting speed): percent of tool diameter, AE (radial cutting depth): percent of tool diameter, FZ (feed rate per tooth):0.05-, 15 mm/tooth

finishing and superfinishing

actual cutting speed vc:m/min, AP (axial cutting speed):0 2 mm, AE (radial cutting depth):0 2 mm, FZ (feed per tooth):0 2 mm/tooth

of course, these values are related to the outer rod, overhang, application stability, tool diameter, material hardness, etc. These values are only typical values and specific application values. In the discussion of high-speed cutting, sometimes we can see that the cutting speed mentioned is extremely high and unrealistic

it is recommended to use dry milling with compressed air or high-pressure oil mist

practical definition of high-speed cutting

HSM is not a high-speed cutting speed in a simple sense. It should be considered as a process with specific methods and production equipment

high speed cutting does not require high-speed spindle cutting. Many high-speed cutting applications are carried out with medium speed spindles and large-size tools

if the hardened steel is finished at high cutting speed and high feed, the cutting parameters can be 4 to 6 times that of the conventional

in these cases, the cutting speed VC may be calculated by the nominal diameter of the tool rather than the effective diameter of the cutting. For example:

90 angle end mills, with a diameter of 6 mm. The spindle speed when the actual cutting speed is 250 m/min = 13262 r/min

ball end mill, the nominal diameter is 6 mm, and the effective cutting diameter is 2.15 mm when the axial cutting depth AP is 0.2 mm. The spindle speed when the actual cutting speed is 250 m/min = 36942 r/min

HSM means high productivity cutting in the rough machining of small-size parts to finish machining, finish machining and ultra finish machining of any size parts

as the shape of parts becomes more and more complex, high-speed cutting becomes more and more important

now, high-speed cutting is mainly applied to machine tools with a taper of 40