2021 – Page 29 – CNC Machining & Turning, Milling, Metal parts

Tool setting point and tool changing point of computer gong

When programming large-scale computer gongs, we should first consider the selection of tool point position,

The tool setting point is the starting point of tool movement relative to the workpiece in NC machining. Since the program is also executed from this point, the tool setting point is also called the program starting point or tool starting point.

When the machining accuracy is not high, some surfaces on the workpiece or fixture can be directly used as the tool face; when the machining accuracy is high, the tool setting point should be selected on the design basis or process basis of the part as far as possible, for example, for the part with hole positioning, it is more appropriate to take the axis of the hole as the tool setting point. The tool setting point must have a certain coordinate relationship with the positioning datum of the workpiece. In this way, the relationship between the machine tool coordinate system and the workpiece coordinate system can be determined. The choice of tool setting point for computer gong processing should be convenient for coordinate value calculation and tool setting.

During tool setting, the tool setting point should coincide with the tool position. The so-called tool position refers to the intersection of the tool axis and the tool bottom surface for flat end milling cutter; the ball end milling cutter refers to the ball center of the ball head part; the turning tool refers to the tool tip; the drill bit refers to the drill tip; the processing for the wire electrode cutting machine tool refers to the focus of the wire electrode axis and the part surface.

Stress and warpage analysis based on two-sided flow technique

According to the solidification effect of gate and the analysis results of packing pressure and temperature distribution

The stress and warpage analysis module calculates the stress changes with time in the wall thickness and plane direction of the product, and the shrinkage of the product along the wall thickness direction at the time of demoulding. Based on the double-sided flow technology, a special double shell element is used to predict the warpage of the product at the time of demoulding.

Function introduction of engraving and milling machine

In terms of appearance and volume:

The volume of machining center is the largest, the volume of large 1690 machine is 4m * 3M, and that of small 850 machine is 2.5m * 2.5m; carving and milling machine is the second, and that of large 750 machine is 2.2m * 2m; carving machine is the smallest.

In terms of mechanical structure:

Machining centers generally use cantilever type, carving and milling machines and carving machines generally use gantry type structure, gantry type is divided into pillar type and fixed beam type, at present, carving and milling machines are mostly fixed beam type.

In terms of index data:

Spindle maximum speed (R / min): 8000 machining center; carving and milling machine is the most common 240000, high-speed machine is the lowest 30000; engraving machine is generally the same as carving and milling machine, engraving machine for high gloss processing can reach 80000, but it is not ordinary motorized spindle, but air floating spindle.

Spindle power: machining center is the largest, from thousands of watts to tens of kilowatts; carving and milling machine is the second, generally within ten kilowatts; carving machine is the smallest.

Cutting capacity: machining center is the largest, especially suitable for heavy cutting, roughing; carving and milling machine is the second, suitable for finishing; carving machine is the smallest. Engraving and milling machine

Speed: because the engraving and milling machine and engraving machine are relatively light, their moving speed and feed speed are faster than the machining center, especially the high-speed machine equipped with linear motor, the maximum moving speed can reach 120m / min

Accuracy: the accuracy of the three is almost the same.

From the processing dimension: the area of the worktable can better reflect this. The smallest worktable area (unit mm, the same below) of domestic machining center (computer gong) is 830 * 500 (850 machines); the largest worktable area of engraving and milling machine is 700 * 620 (750 machines), and the smallest is 450 * 450 (400 machines); engraving machine generally does not exceed 450 * 450, the common is 45 * 270 (250 machines).

In terms of application objects: machining center is used to complete the processing equipment of large amount of milling work pieces, large molds and materials with relatively high hardness, which is also suitable for roughening of ordinary molds; engraving and milling machine is used to complete the finishing of small amount of milling work pieces and small molds, which is suitable for copper and graphite processing; low-end engraving machine is inclined to wood, two-color board, acrylic board and other materials with low hardness Plate processing, high-end suitable for wafer, metal shell polishing.

It is generally believed that machining centers and engraving and milling machines can be used for both products and molds, while engraving machines can only be used for products.

CNC computer gong processing advantages

Computer gong is a kind of artificial intelligence, which is controlled by computer to complete complex processing.

Computer gong processing is also called CNC milling machine processing, CNC milling machine is developed on the basis of general milling machine, the two processing technology is basically the same, the structure is also somewhat similar, CNC milling machine is in the general milling machine integrated digital control system, can be under the control of the program code more accurate milling machine.

1、 Testing standard of computer gong before processing

Divide the center and copy the number. After each division, first copy the work coordinate number, and then recheck whether the distance from the center to both sides is consistent after clearing, so as to ensure that the division and copy are correct.
Tool selection, tool loading, tool setting and z-axis coordinate counting. Select the right tool according to the programming list, clean the tool head and nozzle thoroughly before installing the tool, and use the calibration table to check whether the tool has deflection after installing the tool. Check again after reading the number of correct knives to avoid the serious loss to the company caused by the wrong number of correct knives.
transmit program, start processing: use the single section execution before the knife, transfer the speed and feed speed to the slowest, slow down the knife, watch the machine tool showing the Z axis margin, check whether there is any abnormal, if abnormal, press the pause button immediately, find out the reason to solve the anomaly, confirm that everything is adjusted to the right speed to start processing.
In the process of machining, it is necessary to observe whether the machining is abnormal and whether the tool is worn. If the tool is seriously worn, it is necessary to stop grinding to ensure the normal machining.

Difference of NC milling machine

The biggest difference of CNC milling machine is that the machining center has the ability to exchange machining tools automatically. By installing different tools on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changing device in one clamping, so as to realize a variety of processing functions.

Machining centers are classified into horizontal and vertical machining centers according to the spatial position of the spindle. According to the classification of process uses: boring and milling machining center, composite machining center. According to the special functions, there are single table, double table and multi table machining centers. Machining center of single axle, double axle, three axle and changeable headstock.

Technology standard of high speed computer gong

The machining center is an efficient and high-precision CNC machine tool. The workpiece can be processed in multiple processes in one clamping. At the same time, it is equipped with tool library and automatic tool change function. The rich functions of machining center determine the complexity of programming.

The machining center can realize the linkage control of three or more axes, so as to ensure the machining of complex surface. In addition to linear interpolation and circular interpolation, the machining center also has various functions, such as processing fixed cycle, automatic compensation of tool radius, automatic compensation of tool length, graphic display of machining process, man-machine dialogue, automatic fault diagnosis, off-line programming, etc.

Machining center is developed from CNC milling machine. The biggest difference between CNC milling machine and machining center is that the machining center has the ability to exchange machining tools automatically. By installing different tools on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changing device in one clamping, and a variety of machining functions can be realized.

The broad meaning of benchmark is “basis”. The datum in mechanical manufacturing refers to the points, lines and surfaces used to determine the geometric relationship between the geometric elements on the production object. According to different functions and applications, datum can be divided into design datum and process datum, and process datum can be divided into process datum, positioning datum, measurement datum and assembly datum.

The technology of high-speed CNC machining is the premise to ensure the production of high-quality parts.

On lathe, the shape and size of the blank can be changed by the rotary motion of the workpiece and the linear or curvilinear motion of the cutter, and it can be processed to meet the requirements of the drawing.

Ordinary machine tools are more and more difficult to meet the needs of processing precision parts. At the same time, due to the improvement of production level, the price of CNC machine tools is falling from time to time. CNC precision parts processing mainly includes ultra precision turning, mirror grinding and grinding.

The primary premise of CNC precision parts processing is the accuracy of process datum. Datum on mechanical drawings are represented by capital letters a, B, C, D, etc. with a specific reference symbol with circle. When the reference symbol is aligned with the surface and its extension line or the dimension limit of the surface, the surface is taken as the datum. When the datum mark is aligned with the dimension line, it means that the solid center line of the dimension is taken as the datum. It is a more general statement that the process is accurate.

Assembly benchmark refers to the precision used to determine the position of parts in components or products during assembly. Measurement datum refers to the specification for the size and position of the machined surface to be measured during the inspection of parts. Positioning datum refers to the datum used for positioning the workpiece in the machine tool or fixture during machining.

Machining analysis of CNC high precision parts

Analysis of high precision machining industry

The concept, significance and characteristics of high precision parts manufacturing high precision parts manufacturing takes high precision mechanical parts as processing objects. Based on the systematic and integrated theory and technology, according to the structure and requirements of the workpiece, the organic combination and optimization of feeding, processing, detection and handling are realized, and the production of parts is completed under the precise processing conditions.
Application field of high precision parts and components high precision parts and components are used in all walks of life testing equipment – scientific instruments. In China, they are mainly used in the instrument and instrument industry of scientific instruments.
High precision machining has the advantages of high precision, low energy consumption, flexible production and high efficiency. Reducing the size of the whole manufacturing system and precision parts can not only save energy, but also save manufacturing space and resources, which is in line with the production mode of energy saving and environmental protection. It is one of the development directions of green manufacturing.
Compared with ordinary machinery manufacturing, precision machinery manufacturing has high technology content (design and production), excellent processing equipment, high added value, and small batch sales.
Analysis of foreign development situation high precision machinery manufacturing technology is known as one of the key technologies in the 20th century. It is the key development direction in the 21st century and has been highly valued by all countries in the world. Japan, the European Union, South Korea, the United States and other developed countries have invested a lot of human, material and financial resources to develop their own high-precision mechanical parts research and development and technology.
China’s high-precision machinery manufacturing technology was gradually developed in the late 1980s and early 1990s. It is a rapidly developing industry in China today. High precision machinery manufacturing products are widely used in national defense, medical, aerospace, electronics and other military and civil fields.

The purpose of high-precision mechanical parts processing is to realize the concept of “small machine tool processing small parts”, which is different from the manufacturing method and technology of ordinary mechanical parts. It will become the most effective processing method for high precision parts of non silicon materials (such as metal, ceramics, etc.). It can fundamentally solve the problems existing in the processing methods of precision instrument parts.

CNC computer gong processing tool introduction

From the cutting process can be divided into:

Turning tools, including cylindrical, internal hole, thread, cutting tools, etc.; drilling tools, including drill, reamer, tap, etc.; boring tools; milling tools, etc.

In order to comply with the requirements of CNC machine tools for tool durability, stability, easy adjustment, replaceability, etc., in recent years, the machine clip indexable tool has been widely used, reaching 30% – 40% of all CNC tools in quantity, and the metal removal amount accounts for 80% – 90% of the total.

Tool selection

Tool selection is carried out under the condition of human-computer interaction in NC programming. According to the choice of milling cutter, the choice of milling cutter diameter and the number of milling cutter teeth. Selection of milling cutter diameter: generally, small diameter milling cutter is selected as far as possible. Because of the large diameter of milling cutter and the increase of cutting torque, it is easy to form cutting vibration, and the cutting length of milling cutter increases, which reduces the milling efficiency. Of course, not necessarily, when the rigidity of the milling cutter is poor, the larger diameter milling cutter should be selected according to the processing environment to increase the rigidity of the milling cutter.

In the machining process of economical CNC machine tools, because the grinding, measurement and exchange of cutting tools are mostly carried out manually, which takes a long time, it is necessary to reasonably allocate the order of cutting tools.

Rough and finish machining tools should be used

The name of NC milling and machining is diverse. The machining instruments are divided into two categories: fine and coarse. Different work contents and machining products have different examples of necessary tools in the detailed milling process. If only one kind of cutting tool is used for processing, then the processed products are more equal, it is difficult to distinguish accurately, and the processed products are also difficult to meet the use requirements, which is not in line with the actual use. In order to improve the quality level of products, meet the utilization scale and ensure the effectiveness of products, it is only necessary to adopt different cutting tools, combine the real environment of processing and production, and accurately classify the cutting tools.

Compared with ball end tool, flat end tool has a great advantage in surface processing quality and cutting efficiency, so it is necessary to ensure the processing, whether in rough machining or finish machining, flat end tool is preferred. When milling three-dimensional workpieces, it is best to choose the flat end cutter, and combine the material of the cutter and the characteristics of the processed products to make a more accurate choice. In contrast, in order to avoid overcutting phenomenon, it is best to use ball head cutter when milling curved surface products, and pay attention to the accuracy of machining and the interval of cutting, so as not to reduce the work efficiency.

Using the active tool changing effect of machining center to improve production efficiency

With the rapid development of science and technology, the previous NC milling objects and related tools can not meet the new requirements of real processing, and the work efficiency can not meet the new requirements of social development.

It has become a general trend to adopt the object of active tool change. In the past, most of the CNC milling work was manual operation, which was inefficient and easy to squander a large number of manpower, material resources and financial resources, which was not conducive to the promotion of the quality of the work. Adopting active tool changing technology and scientifically improving the utilization of cutting tools can improve the effectiveness of tool utilization, select cutting tools quickly and adopt active means for cutting. It not only saves time, but also improves the processing quality and effect of milling, and meets the new characteristics of rational utilization of modern science and technology. Of course, the use of active tool changing technology is not only a simple name, it must complete the inorganic combination of itself and the object, and the time and distance of active tool changing should also be precise, in order to improve the production efficiency.

What are the differences of CNC milling machine

CNC machining center is composed of mechanical equipment and CNC system, which is suitable for processing complex parts. CNC machining center is one of the most widely used CNC machine tools with the highest output in the world. Its comprehensive processing ability is strong, the workpiece can complete more processing content after clamping at one time, and the processing accuracy is high. For the batch workpiece with medium processing difficulty, its efficiency is 5-10 times higher than that of ordinary equipment, especially it can complete the processing that many ordinary equipment can’t complete, and it is more suitable for single piece processing with complex shape and high precision requirements or small and medium batch multi variety production. It concentrates the functions of milling, boring, drilling, tapping and cutting threads on one equipment, so that it has a variety of technological means. Machining centers are classified into horizontal and vertical machining centers according to the spatial position of the spindle. According to the classification of process uses: boring and milling machining center, composite machining center. According to the special functions, there are single table, double table and multi table machining centers. Machining center of single axle, double axle, three axle and changeable headstock.

CNC computer gong programming matters needing attention

The speed of white steel knife should not be too fast.
Copper workers use less white steel knives and more flying knives or alloy knives.
When the workpiece is too high, it should be roughened by layers with knives of different lengths.
After roughening with a big knife, use a small knife to remove the remaining material to ensure that the remaining material is consistent.
The plane should be processed with flat bottomed cutter and less ball cutter to reduce the processing time.
When cleaning the corner, check the size of R on the corner first, and then determine the size of the ball knife.
The four corners of the calibration plane should be level.
Where the slope is an integer, the slope cutter shall be used for processing, such as pipe position.
Before each process, think about the remaining allowance after the previous process,

In order to avoid the blank tool or too much processing and knife.

Try to use simple cutting path, such as shape, trenching, single side, less walking around and so on.
When walking wcut, those who can walk finish should not walk rough.
When the shape of the knife is smooth, rough first and then fine. When the workpiece is too high, smooth the edge first and then the bottom.
Set reasonable tolerance to balance machining accuracy and computer calculation time. The tolerance is set to 1 / 5 of the allowance for roughening and 0.01 for smooth cutting.
Do more process to reduce the time of empty tool.

Do more thinking and reduce the chance of mistakes.

Do more auxiliary lines and auxiliary surfaces to improve the processing condition.

Establish a sense of responsibility and carefully check each parameter to avoid rework.
Be diligent in learning, good at thinking and make continuous progress.

17 milling non planar, more ball cutter, less end cutter, do not be afraid of the knife;

18 small knife clear angle, big knife refined;

Don’t be afraid of patching, proper patching can improve the processing speed and beautify the processing effect

20 high hardness of blank material: reverse milling is better, low hardness of blank material: forward milling is better

Good accuracy, good rigidity and finishing: it is more suitable for forward milling, otherwise it is more suitable for reverse milling

It is strongly recommended to use forward milling for finishing the inner corner of parts.

Rough machining: reverse milling is better, finish machining: forward milling is better

Tool material toughness is good, low hardness: more suitable for rough machining (large cutting amount processing)

Poor toughness and high hardness of tool material: suitable for finish machining (small cutting amount machining)

CNC computer gong machining accuracy function debugging

Before the debugging of CNC computer gong processing machine tool, the debugging methods of precision and function of computer gong processing machine tool are as follows:

Using precision level instrument and other testing tools, the main bed level of the computer gong processing machine tool is precisely adjusted by adjusting the pad iron, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool changing device, adjust the position of tool magazine, manipulator, stroke parameters, etc., and then check the action with instructions to ensure accuracy;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic exchange;
After adjusting the machine tool,

Carefully check whether the parameter setting values in the numerical control system and the programmable controller conform to the data specified in the random index, and then test the main operation functions, safety measures, and the execution of common instructions.

Check the auxiliary functions and accessories of the machine. CNC computer gong NC machining is the basis of modern manufacturing technology, this invention for the manufacturing industry, has epoch-making significance and far-reaching influence.