The choice of tool system is one of the important contents in the configuration of CNC machine tools, because the tool system not only affects the production efficiency of CNC machine tools, but also directly affects the processing quality of parts. According to the performance of the CNC machine tool (or machining center) and the characteristics of the CNC machining process, the tool and the
TOOL HOLDER system can be optimized to achieve twice the result with half the effort.
A commonly used tool holders CNC machine tools compared with the general
classification processing methods, CNC machining aspects of the tool rigidity, precision, durability and balancing performance requirements more stringent. The selection of the tool should pay attention to the structure and process analysis of the workpiece, combined with the processing capability of the CNC machine tool, the workpiece material and the content of the process.
Commonly used tool holders for CNC machining are mainly divided into drilling tool holders, boring tool holders, milling cutter holders, thread cutter holders and straight shank cutter holders (end mill holders and collet chucks). .
Second, the choice of common tool holders for CNC machine tools
1.
Tool Holder structure form The structure of the CNC machine tool holder is divided into two types: integral type and modular type. The integral shank has its working part of the clamping tool integrated with its shank for positioning on the machine. This kind of tool holder has poor adaptability to the change of machine tools and parts. In order to adapt to the change of parts and machine tools, the user must stock the handles of various specifications, so the utilization of the handle is low. The modular tooling system is a more advanced tooling system in which each toolholder can be assembled from a variety of serial modules. Different assembly parts are available for different machined parts and machine tools, and a variety of tool holder series are available to improve the adaptability and utilization of the tool holder.
The choice of the structure of the shank should be both technically advanced and economically reasonable: 1 For some long-term repeated use, it is not necessary to assemble a simple tool with an integral shank, so that the tool is rigid and cheap (such as the outer contour of the machined part) End mill cutter shank,
Spring Collet shank and
DRILL CHUCK shank, etc.) 2 When machining multi-variety and small batch parts with frequent changes in hole diameter and hole depth, modular shank should be used to replace a large number of whole The type of shank handle reduces the processing cost; when 3 pairs of CNC machine tools are used, especially when the machine tool spindle end and the tool changer are different, the modular tool holder should be used. Since the intermediate modules (posts) and working modules (tooling modules) used in each machine tool are universal, the equipment investment can be greatly reduced and the tool utilization rate can be improved.
2. Tool holder specifications CNC tool holders mostly use 7:24 conical tool holders, and the corresponding type of tensioning structure is matched with the machine tool spindle. There are various specifications for the shank, commonly used are No. 40, No. 45 and No. 50. At present, it is widely used in China, such as ISO7388-1983, GB10944-1989, MAS403-1982, ANSI/ASMEB5.50-1985, etc. When selecting, the tool holder specifications should be considered to be compatible with the machine tool spindle and manipulator.
3. The number of specifications of the tool holder The integral TSG tool system includes 20 kinds of tool holders, and the number of specifications is up to hundreds. The user can select the specifications of the tool holder according to the CNC machining process of the typical parts processed. Meet the processing requirements without causing a backlog. Considering that the CNC machine works with a certain number of shanks in the pre-adjustment or tool grinding, the number of shanks is usually 2 to 3 times that of the required shank.
4. The matching of the tool and the tool holder pays attention to the matching of the tool holder and the tool, especially when selecting the tapping tool holder, pay attention to the size of the taper transmission square head. In addition, the single-edge boring tool on the CNC machine tool can avoid scratching the workpiece when retracting, but pay attention to the position of the tool tip relative to the keyway on the shank: some machine tools require the same orientation as the keyway, while some machine tools require It is perpendicular to the keyway orientation.
5. Use high-efficiency and compound tool holders to improve machining efficiency. High-efficiency tools and tool holders should be used whenever possible. For example, the double-edge boring tool holder can be used for the rough boring, which can improve the machining efficiency and reduce the cutting vibration. The strong spring collet can not only clamp the straight shank cutter, but also clamp the perforated cutter through the post. . For typical workpieces with large batch sizes and complex machining, composite tools should be used whenever possible. Although the composite tool and the tool holder are more expensive, the composite tool is used in the machining center, which can combine multiple processes into one process and be completed by one tool, which is beneficial to reduce the processing time and the number of tool changes, and significantly improve the production efficiency. . Specially designed composite shanks can also be considered for some special parts.
6. Strengthening tool system management As the number of CNC machine tools increases, the number of tool holders will increase dramatically. A flexible manufacturing system with 5 to 8 CNC machine tools, the number of tool holders can reach more than 1000. How to make these tools get reasonable and effective use is the key work of tool management. The contents include: the introduction of the tool holder procurement or supplementary plan; the pre-adjustment of the tool data; the scheduling and storage of the tool; the judgment and control of the tool life.
Third, the development of CNC machine tool holder 1. Special function of the tool holder In recent years, there are some special functions of the tool holder on the machining center, mainly the following types.
Speed increasing shank (increasing speed head): automatic tool change can be realized. For example, NIKKEN's NXSE speed-increasing head can reach 20000r/min in 0.8s when the machine spindle speed is 4000r/min.
Multi-axis shank: It can machine multiple holes at the same time, which is equivalent to multi-axis machining head. The multi-axis combined with the speed-increasing tool holder can form a dual-function multi-axis speed increasing tool holder.
Internal cooling shank: This shank is used in conjunction with a twist drill or deep hole drill with a coolant passage in the core. The special oil supply system is used to inject high-pressure cutting fluid into the cutting part for good cooling and lubrication. And remove the chips.
Corner shank: The head of this shank can be rotated at 30o, 45o, 60o, 90o, etc., with five-face machining function. Mounted on a vertical machining center, the vertical machining center has the function of a horizontal machining center for the bottom clearance of deep pockets.
2. New high-speed cutting tool holder With the development of high-precision high-speed cutting technology for CNC machine tools, the tool holder system suitable for high-speed cutting has been well developed and developed. For example, the
Hsk Tool Holder of OTT Company of Germany and the KM tool holder of Kenamental Company of the United States have an axial positioning accuracy of 0.001 mm, and under high-speed rotation, the tool holder is locked more firmly, and the radial runout does not exceed 5 μm. The HSK shank is a typical double-positioned hollow shank with a 1:10 short taper, taper shank and spindle end face. The main features are:
·The combination of tapered surface and end surface over positioning can effectively improve the connection rigidity of the tool system, and the repeat positioning accuracy is high;
·Using hollow structure and shortening the length of the taper, the handle quality is lighter, which can shorten the moving distance of the tool change and speed up the tool change speed, which is beneficial to realize high-speed automatic tool change;
· Adopt 1:10 taper, the taper shank is shorter, the wedge shape effect is good, it has strong torsion resistance, and it can suppress the slight displacement caused by vibration;
·The shank and the main shaft are locked by the expansion claws. The higher the rotation speed, the larger the centrifugal force (expansion force) of the expansion claws, the larger the locking force and the good high-speed performance.
· In order to improve the dynamic balance accuracy of the tool system at high speed, an automatic correction dynamic balance device can be installed on the tool holder.
March 20, 2019
