The new adjustable knob cutting (SWC) heavy-duty turning process is not only to improve the productivity and equipment utilization rate of heavy-duty parts, but also requires reducing energy consumption and performing dry cutting. In combination with the actual situation of modern cutting processing in my country, when designing a new adjustable knob cutting heavy-duty turning tool, the optimization relationship between tool materials, tool coatings, and tool geometry should be comprehensively considered. It should also solve the integration of roughing and finishing processes under different cutting conditions and the degree of realization of new technical requirements for dry cutting and green cutting. Its related technologies and management methods should serve and optimize the high-efficiency requirements of the entire processing process. Therefore, the promotion and application of advanced technologies of the new adjustable knob cutting heavy-duty turning tool system are of great significance to improving the benefits of heavy turning.https://samhotool.com/steel-milling-bit/
Heavy turning refers to turning with a cutting speed Vc ≥ 38m/min, a back cutting amount ap ≥ 10mm, and a feed rate f ≥ 0.5mm/r. Due to the limitation of process conditions in my country, the heavy-duty turning tools in the production site generally have a back cutting depth of ap=25mm, a feed rate of f≥1.0mm/r, and a cutting speed of Vc≥40～60m/min. Compared with ordinary processing, the cutting depth is large, the cutting speed is low, and the feed speed is slow. In addition, the vibration caused by factors such as poor workpiece balance, uneven distribution of machining allowance, and imbalance of some parts of the machine tool during the cutting process. The dynamic imbalance process of processing consumes a lot of maneuvering time and auxiliary time.
Compared with ordinary turning tools, heavy-duty machining has a large cutting amount, and the working conditions and tool reinforcement methods are also very different. The design of the tool has its own significant characteristics. Therefore, the heavy-duty turning processing of the tool tumor cutting cannot be only reflected in one process or one equipment, but should serve the improvement of the efficiency of the entire production line. The overall performance of multiple aspects including tool structure, geometry, tool body material, cutting edge material, tool coating, etc. should serve the entire system. The application engineering problems of the heavy-duty turning processing technology of the tool tumor cutting and the tool system that is easy to operate and manage must be solved in a timely manner.
Systematic Selection of Tool Materials and Edge Geometry Parameters for Heavy Duty Machining
Cutting Mechanism of Tool Nose in Heavy Turning
The depth of heavy cutting can generally reach 30-50mm, and the allowance is uneven. The hardened layer on the surface of the workpiece makes the tool wear in the rough machining stage mainly abrasive wear. The cutting speed is generally 15-20m/min, and the cutting edge is in the area and time period where the built-up edge occurs. Therefore, on the basis of giving full play to the strength of the advanced material of the tool, and improving and optimizing the tool structure and geometry, the built-up edge generation and elimination rules can be effectively used for cutting. It is also possible to start by increasing the thickness of the cutting layer and the amount of feed, and make full use of the “wiper” technology of large feed with the wiper edge (that is, using a short straight line or a short large radius arc to connect the tool tip radius and the auxiliary cutting edge. The technology can reduce the roughness of the machined surface), improve the finish of the machined surface, and achieve the purpose of reducing cutting force, reducing friction, and performing efficient processing of dry and green cutting.
Systematic Changes in Material Properties and Structure for Efficient Heavy Turning Tools with Nodule Cutting
The selection of blade material and model of heavy-duty tool for cutting tumors must meet the high-efficiency requirements of the processing system conditions, otherwise, it will have a negative impact. Therefore, the wear resistance and impact resistance of the tool material must be considered. Ceramic tools with low bending strength and poor impact toughness are not suitable for heavy-duty turning with uneven allowances, and CBN also has the same problem. The friction coefficient of cemented carbide is low, and the tool has strong high-temperature durability. It is suitable for rough processing of high-hardness materials and heavy-duty turning, but specific process measures are required.
When processing steel materials, K-type cemented carbide has large plastic deformation of the workpiece during heavy-duty turning, severe friction, and high cutting temperature. Therefore, it is rarely used in heavy-duty turning. If a heat pipe tool is used, the cutting edge is effectively and continuously cooled, and the adaptability will be enhanced. P-type cemented carbide has high hardness, high wear resistance, high heat resistance, anti-adhesion diffusion ability, and anti-oxidation properties. It is a commonly used tool material for heavy-duty turning and is suitable for processing steel materials. However, when turning at low speed and the cutting process is not stable, the toughness of YT-type alloys is poor, which will cause chipping. Especially when processing some high-strength alloy materials, the durability of YT-type cemented carbide decreases quickly and cannot meet the use requirements.
In order to further improve the processing efficiency, the tool material should be selected from M-type tools or fine-grained and ultra-fine-grained alloy tools (such as 643, etc.). Compared with P-type cemented carbide, the increase in its life before regrinding far exceeds the loss of life after regrinding. Because its other advantage is sharp cutting edge, that is, it can also replace high-speed tools in occasions with harsh processing conditions, and its application range is relatively wide. In addition, the fine-grained alloy has good wear resistance and is more suitable for processing cold-hardened cast iron products. The efficiency can be increased by more than 1 times compared with YW-type tools. Generally, the above processing conditions cannot be fully met, so the heavy cutting tool structure must consider and adapt to the replacement of different types of tool materials due to insufficient or changed processing conditions. That is, to adapt to the needs of replacing the same and different types of blades and adjusting the geometric parameters of the cutting edge, the corresponding changes in the tool structure should be conducive to the specific requirements of operation and management.
High Efficiency Characteristics of Indexable Insert size and Replacement System Performance for Heavy Turning tools with Cutting Tool Nose
The specific requirements for the size of indexable inserts for heavy-duty turning are as follows. The minimum side length of a square insert is 19mm, and the minimum side length of a triangular insert is 19mm. Pentagonal cutters are an economical method for improving productivity, and the minimum side length of the insert is 13mm. The minimum side length of the diamond-shaped insert is 16mm. The tolerance of the main geometric parameters of the insert blank and the flatness deviation should comply with the relevant provisions of YS/T553-2006. In order to improve the convenience, reliability and standardization of the efficient management and use of adjustable tool systems and the quality level of process integration, the accuracy grade of the insert should be A or F.
In order to facilitate the adjustment of the front and rear angles, the back angle relative to the initial front angle of the cutting edge should be selected between 15°, 20°, and 25° (codenamed D, E, and F), so that there is an adjustment amount of about 7 to 15°. If the amplitude of the adjustment change of the main deflection angle is large, the blade shape should be selected between S, C, and M models. Therefore, in order to replace the blade, the cutting part of the tool should leave a dimension for adjusting the blade backing amount on the vector line of the back cutting amount of the cutting edge. Based on the basic requirements of green cutting, the main rake angle of the tool groove should change between 45° and 60°. In this way, the change of the main rake angle of the cutting edge can increase the cutting thickness and reduce the cutting force without increasing the feed rate. It can also store part of the machine tool power to varying degrees to improve productivity.
The change of the geometric parameters of the blade edge should have the following characteristics. Front angle γo=15~30°, back angle αo=5~8°, main rake angle κr=45~75°, blade inclination angle λs=3~6°, transition edge main rake angle κrε=30~15°, secondary rake angle κ’r=15~30°, wiper edge rake angle κr1=0°, wiper edge inclination angle λs1=0~10°. The negative chamfer width of the main cutting edge must be less than the cutting thickness ap (=f·sinκr), bγ1=(3/4～1/2)f, the radius of the tool tip rε=0.3～1.0mm, the length of the polishing edge is 1.5 times the back cutting amount, and the blade inclination angle is +15°, which plays a scraping role. The negative rake angle of the cutting edge is similar to =-30° obtained by chamfering, and the efficiency will be improved.
The initial phase angle parameters of the tool groove κcγ=60°∪45°, αco=(25°∪20°∪15°), λcs=6°, and the secondary deflection angle κco=-30°. The blade angle is γpo=15°∪20°∪25°αpr=20°∪15°, and the blade inclination angle λps=0°. When κr<90°, the main and secondary edge inclination angles are obtained by adjusting the rake angle by about 15°. This, combined with the insert’s replaceable capabilities, enables optimization of the tool edge geometry and cutting parameters.
Turning Tool Coating
In order to make the tool have high reliability, tool coating is indispensable. Since the tool coating has a function similar to that of coolant, it can produce a protective layer to isolate the tool from the cutting heat, so that the heat is rarely transferred to the tool. Thus, the tip of the tool can be kept hard and sharp for a long time. The coating with a smooth surface can also reduce friction to reduce cutting heat and keep the tool material from being affected by chemical reactions.
Heavy cutting tool tumor cutting blades should use multi-coated tool blades with TiAlN coating and Mo2 soft coating. It has the characteristics of high hardness and good wear resistance, as well as the function of replacing coolant with low friction coefficient and easy chip flow. In dry cutting technology, tool coating plays a very important role. The technical problem of low bonding strength between coating and base material has been solved and should be applied to heavy turning as soon as possible.
Reduced Chip Breaking Controllability and Insert Pressure Plate Technology with Adjustable Chip Breaking Width
Generally, due to the defects of structure and function, the optimization of the parameters of the cutting edge rake angle of non-adjustable tools is not ideal. Therefore, when turning steel parts with large cutting depth and large feed rate on heavy lathes, the chips are wide, thick and purple, and the power consumption is large. The C-shaped chips formed are more likely to damage the cutting edge or splash and injure people. The actual working rake angle of the heavy turning tool edge of the built-up edge cutting tool is large (the actual front foot formed by the built-up edge can be around 50°). The power consumption is reduced by about 1/3, and the color of the chips changes from white to yellow.
And due to the role of the transition edge and the negative edge, the radius of the arc at the bottom of the chip breaker groove is increased (the width is generally 10mm). The chips can be curled upward and rolled into spiral-shaped clockwork chips. And they can collide and break on the processing surface, or fall by their own weight, and the controllability is strong. The blade cutting edge will not be broken by impact, and the production efficiency can be greatly improved. However, the problem of adjusting and regrinding the cutting edge angle has not been solved well. The change of working and cooling conditions and the imperfection of the chip blocking mechanism will also reduce the controllability of chip breaking. Therefore, the technical problem of the blade pressure plate with adjustable chip breaking width should be solved in time.
In view of the change of working conditions of heavy-duty machining and turning, the working part of the front chip rolling of the pressure plate with adjustable chip breaking width is welded with a 3-5mm thick carbide sheet. The lower part of the front end presses the carbide blade, while the rear end is closely matched with the spherical inner arc surface of the baffle. The displacement is adjusted by the limited reciprocating linear motion of the lower part of the pressure plate to adapt to the needs of replacing different types of blades with inscribed circle radius changing within a certain range and adjusting the clamping after blade regrinding.
The upper pressure plate can make limited reciprocating motion on the contact surface of the lower pressure plate, and can be effectively tightened by the pressure plate bolts, with high strength. The adjustment amount of the upper pressure plate is plus or minus 1-2mm, which can make the chips roll out in a spiral shape. The adjustment amount of chip breaking width should be determined according to the size of the chip profile. The chips should not violently impact the front end of the pressure plate, otherwise the cutting part of the turning tool will be broken. Blunt or broken blades should also be replaced in time, and the chips and slag should be cleaned from the pressure plate. The impact of the cutting head on the chip stopper during the processing is not very large, and the multifunctional pressure plate structure with adjustable chip breaking width of this heavy-duty turning tool has a better effect.
This type of indexable blade should form a variable interface composite beam with the shim and the groove. The length of the edge extending from the shim and the front end of the groove should not exceed 2mm, so as to facilitate the grinding of the blade and adjust the main deflection angle. The blade has two types of single bevel and rectangular section. When there is an assembly error between the shim and the blade joint surface, it should be corrected in time to ensure the assembly accuracy. The clamping bolt is located above the pressure plate and is a floating pressure device that is not easily damaged by chips. It is more suitable for heavy-duty cutting, requiring good coordination of all components and high contact performance, otherwise it will produce large vibrations, which is not conducive to improving production efficiency and processing quality.
Turning Tool Structure and Tool System
The heavy-duty machining system for cutting of blade tumors requires that the tool structure can adapt to the relevant adjustment, replacement and change requirements in the machining system within the smallest range. Therefore, not only the parameters of the components of the cutting part and the supporting part must be effectively changed within a similar range, but also the matching accuracy must meet the dynamic and static stiffness requirements of the tool structure. Therefore, the parameters of different types of tool grooves must have corresponding initial phase angles.
The cutting part of the tool head can not only make limited round trips in the plane straight line and limited longitudinal motion of the arc, but also make the matching accuracy and connection strength of the corresponding blade positioning pin and blade adjustable pressure plate, arc spherical adjustable pressure plate and tool rod components. It has good balance performance, excellent rigidity, no abnormal vibration, and an overload shedding device when subjected to large cutting forces. Therefore, the square supporting sleeve and the tool rod should adopt a hot-installed structure through calculation. The material can be forged and turned with 45# steel or 4OCrMo, and the heat treatment hardness is 45~48HRC. The elastic deformation should meet the dynamic and static stiffness requirements of the tool’s structural performance, so that it can be used as a supplement to the machine tool function and meet the high efficiency needs of the processing system.
Practice has proved that the heavy-duty adjustable turning tool simple tool system has strong adaptability. It has initially realized intensive and green cutting, effectively improving the economy of process measures. It can be applied from general lathes to the most modern CNC lathes. The tool change time is only 1/20 to 1/10 of that of general lathe tools, and the repeated positioning accuracy is high, and the processing size stability is very good. It is an extension of modular heavy-duty turning tool technology and has great development prospects. The main processing purpose of the rough processing stage is to remove the excess. The cutting depth should be increased, and the efficiency can be increased by more than 5 times. Due to the large cutting depth during heavy cutting, the cutting force is large. Correspondingly, a lower cutting speed is selected, generally 10 to 15m/min, and the feed rate is 1 to 2mm/r.
Selection of Cutting Parameters
On large machine tools (cutting power Pm above 40kW), when processing large medium carbon steel, cast steel, and forged steel workpieces, it is recommended to use cutting parameters:
V=70m/min,f=1.2～1.5mm/r,ap=33mm,
On machine tools with cutting power Pm=25kW, when processing medium-sized workpieces:
V=5Om/min,f=3.15mm/r,ap=11mm;
Transforming large integrated turning tools into S.W.C adjustable tools can increase the comprehensive processing efficiency to more than 80%.
The S.W.C. tool tumor cutting processing efficiency brought by the tool system formed by adjustment is relatively high. Aiming at the specific characteristics of the machining system and the geometric parameters of the cutting edge changing in a similar range, the initial phase angle of the system tool angle is reasonably selected to optimize the adjustment performance of the components and mechanisms. Including a tool holding system with similar functions to the CAPTO tool system. And integrating the characteristics of heat pipe tools, it can not only effectively perform green dry cutting, but also form a system function that is easy to operate and manage. Therefore, the technical content is relatively high. Compared with ordinary high-feed turning tools, its superiority can be clearly seen, which is worthy of further research, discussion and promotion.
