The selection of CNC tools and the determination of the cutting amount are important contents in the CNC machining process.
It not only affects the processing efficiency of CNC machine tools, but also directly affects the processing quality.
At present, many CAD/CAM software packages provide automatic programming functions, and these software
Generally, it prompts the relevant issues of process planning in the programming interface, such as tool selection, processing path, etc.
Planning, cutting amount setting, etc., as long as the programmer sets the relevant parameters, it can automatically
Generate NC programs and transfer them to CNC machines for machining. Therefore, the tool selection in NC machining
The selection and determination of cutting parameters are completed in the state of human-computer interaction, which is different from ordinary machine tool processing.
In stark contrast, it also requires programmers to master the principles of tool selection and cutting amount determination.
The basic principle is to fully consider the characteristics of CNC machining when programming, and to be able to correctly select the cutting tool and
Cutting amount.
The selection of NC tools and the determination of cutting parameters are important contents in the NC machining process.
It not only affects the processing efficiency of CNC machine tools, but also directly affects the processing quality.
The development of CAD/CAM technology makes it possible to directly use CAD design data in NC machining.
become possible, especially the connection between the DNC system microcomputer and the CNC machine tool, making the design, process
The entire process of planning and programming is completed on the computer, and generally does not need to output special tools.
art files.
Currently, many CAD/CAM software packages provide automatic
Generally, it prompts the relevant issues of process planning in the programming interface, such as tool selection, processing path, etc.
Planning, cutting amount setting, etc., as long as the programmer sets the relevant parameters, it can automatically
Generate NC programs and transfer them to CNC machines for machining.
Therefore, the selection of tools and the determination of cutting parameters in NC machining are in the state of human-computer interaction
This is in sharp contrast to ordinary machine tool processing, and it also requires programmers to
It is necessary to master the basic principles of tool selection and cutting amount determination, and fully consider the CNC machining process when programming.
According to the characteristics of the tool, it is possible to correctly select the cutting tool and the cutting amount.
Types and characteristics of cutting tools commonly used in CNC machining
CNC machining tools must adapt to the characteristics of high speed, high efficiency and high degree of automation of CNC machine tools.
Generally, it should include general-purpose knives, general-purpose connection handles and a small number of special-purpose handles. Shank to be connected
The tool is installed on the power head of the machine tool, so it has been gradually standardized and serialized. CNC cutting tool
A class has many methods. According to the structure of the tool, it can be divided into: ① integral type; ② inlaid type, using welding
Or machine clip type connection, machine clip type can be divided into two types: non-reversible and indexable; ③ special types, such as
Composite cutters, shock-absorbing cutters, etc. According to the materials used in the manufacture of knives can be divided into: ① high speed
Steel cutting tools; ② hard alloy cutting tools; ③ diamond cutting tools; ④ other material cutting tools, such as cubic boron nitride
Knives, ceramic knives, etc. From the cutting process, it can be divided into: ①Turning tools, divided into outer circle and inner circle
Holes, threads, cutting tools, etc.; ② Drilling tools, including drills, reamers, taps, etc.; ③
Boring tools; ④ Milling tools, etc. In order to adapt to the durability, stability and ease of cutting tools of CNC machine tools
Adjustable, replaceable, etc., in recent years, machine-clip indexable tools have been widely used.
Up to 30% to 40% of the entire CNC tool, and the amount of metal removal accounts for 80% to 90% of the total.
Compared with the tools used on ordinary machine tools, CNC tools have many different requirements.
It must have the following characteristics: ①Good rigidity (especially for rough machining tools), high precision, anti-vibration and thermal deformation
Small; ②Excellent interchangeability, convenient for quick tool change; ③Long life, stable and reliable cutting performance; ④Tool
The size of the tool is easy to adjust to reduce the time of tool change adjustment; ⑤The tool should be able to reliably break chips or roll
6. Serialization and standardization to facilitate programming and tool management.
Selection of CNC machining tools
Tool selection is carried out under the human-computer interaction state of NC programming. according to the machine tool
The processing capacity, the performance of the workpiece material, the processing procedure, the cutting amount and other related factors
Correct selection of knives and handles. The general principle of tool selection is: easy installation and adjustment, good rigidity,
High durability and precision. Under the premise of meeting the processing requirements, try to choose a shorter tool holder to
Improve the rigidity of tool machining.
When selecting a tool, the size of the tool should be adapted to the surface size of the workpiece to be processed.
In production, end mills are often used to process the peripheral contours of plane parts; when milling planes, you should choose
Carbide blade milling cutter; when processing bosses and grooves, choose high-speed steel end mills; process rough surface
Or when roughing holes, you can choose a corn milling cutter with a carbide insert; for some three-dimensional surfaces and
For the machining of variable bevel contours, ball end milling cutters, ring milling cutters, tapered milling cutters and disc milling cutters are often used.
milling cutter.
When free-form surface (mold) machining, the cutting speed of the end of the ball nose tool is
Zero, therefore, in order to ensure the machining accuracy, the cutting row spacing generally adopts the top dense spacing, so the ball head is commonly used
for surface finishing. The flat head tool is superior to the ball in terms of surface processing quality and cutting efficiency.
Head knife, therefore, as long as it is guaranteed not to cut, whether it is rough machining or fine machining of curved surface
For processing, flat-head knives should be preferred. In addition, the durability and precision of the tool are related to the price of the tool
system is huge, it must be noted that, in most cases, the choice of a good tool increases
The tool cost is reduced, but the resulting improvement in processing quality and processing efficiency can make the entire
The processing cost is greatly reduced.
On the machining center, various tools are respectively installed on the tool magazine, and can be selected at any time according to the program
Knife and tool change action. Therefore, standard toolholders must be used in order to make drilling, boring, expanding, milling, etc.
The standard tools used in the sequence can be quickly and accurately loaded into the machine tool spindle or tool magazine. Programmers should
Understand the structural size, adjustment method and adjustment range of the tool holder used on the machine tool, so that when programming
Determine the radial and axial dimensions of the tool. At present, my country's machining center adopts TSG tool system
There are two types of handles: straight handle (3 specifications) and tapered handle (4 specifications), including 16 kinds of handles for different purposes.
During the processing of economical CNC machine tools, due to the sharpening, measurement and replacement of tools
Most of them are done manually and take up a long auxiliary time. Therefore, the arrangement of tools must be reasonably arranged.
column order. Generally, the following principles should be followed: ① Minimize the number of tools;
After that, all the processing steps it can carry out should be completed; ③ The tools for rough and fine machining should be used separately
Even if it is the same size and specification tool; ④ milling first and then drilling; ⑤ surface finishing first, and then
Carry out two-dimensional contour finishing; ⑥When possible, the automatic machining of CNC machine tools should be used as much as possible.
Automatic tool change function to improve production efficiency, etc.
Determination of cutting amount during processing
The principle of reasonable selection of cutting amount is: during rough machining, generally in order to improve productivity
The main, but should also consider the economy and processing costs; semi-finishing and finishing, should be guaranteed plus
Under the premise of the quality of the workmanship, the cutting efficiency, economy and processing cost are taken into consideration. Specific values should be based on
Machine tool manual, cutting quantity manual, combined with experience. Specifically, the following factors should be considered
white:
① Depth of cut t. When the rigidity of the machine tool, workpiece and tool allows, t is equal to
This is an effective measure to improve productivity. In order to ensure the processing accuracy of parts
and surface roughness, generally a certain margin should be left for finishing. Finishing spare parts of CNC machine tools
The amount can be slightly smaller than ordinary machine tools.
② Cutting width L. In general L is directly proportional to tool diameter d and inversely proportional to depth of cut
Compare. In the processing of economical CNC machine tools, the value range of L is generally: L=(0.6～
0.9) d.
③ Cutting speed v. Increasing v is also a measure to increase productivity, but v is not related to tool
Durability is closely related. With the increase of v, the tool durability decreases sharply, so the
The choice mainly depends on the tool durability. In addition, the cutting speed has a great relationship with the processing material.
For example, when milling alloy steel 30CrNi2MoVA with an end mill, v can be around 8m/min
Right; when milling aluminum alloy with the same end mill, v can be selected above 200m/min.
④Spindle speed n(r/min). The rotational speed is generally selected according to the cutting speed v. Calculator
The formula is: v=∏nd/1000. The control panel of the CNC machine tool is generally equipped with a spindle speed adjustment (magnification) switch, which can adjust the spindle speed by an integer multiple during the machining process.
⑤ Feed speed vF. vF should be based on the machining accuracy and surface roughness requirements of the parts
And tool and workpiece material to choose. An increase in vF can also improve production efficiency. Processing surface
When the roughness requirement is low, vF can be selected larger. During processing, vF can also be manually adjusted through the trim switch on the machine control panel, but the maximum feed speed is limited by the rigidity of the equipment and the performance of the feed system.
With the wide application of CNC machine tools in actual production, the formation of quantitative production lines, digital
Control programming has become one of the key issues in NC machining. In the process of NC programming
In the process, it is necessary to select the tool and determine the cutting amount in real time under the state of human-computer interaction. Therefore, programmers
The operator must be familiar with the selection method of the tool and the determination principle of the cutting amount, so as to ensure the processing of the parts
Work quality and processing efficiency, give full play to the advantages of CNC machine tools, improve the economic benefits and
production level.