March 2021 – Page 10 – CNC Machining & Turning, Milling, Metal 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

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.

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.

CNC computer gong processing high precision parts attention

Don’t think that high-precision parts processing is a common processing without attention. If we ignore some details, it may have a great impact on the processing of parts. Then, what are the precautions for high-precision parts processing?

For high-precision parts, the processing is very strict. The processing procedures include feed and output. There are specific requirements for the size and accuracy, such as 1 mm plus or minus micrometers. If the size is too wrong, it will become a scrap. At this time, it is equivalent to reprocessing, which is time-consuming and laborious. Sometimes, the whole processing material will be scrapped, resulting in an increase in cost. At the same time, the parts are definitely unusable.
For the processing of high-precision parts, the main requirements are the size, such as the diameter of the cylinder, there are strict requirements, positive and negative errors within the specified range are qualified parts, otherwise they are unqualified parts; There are also specific and strict requirements for length, width and height, as well as positive and negative errors. For example, if the diameter of an embedded cylinder (take the simplest basic parts as an example) is too large and exceeds the allowable error range, it will cause the situation that it cannot be inserted. If the actual diameter is too small and exceeds the lower limit of the allowable negative error, it will cause the problem that it is too loose and not firm. These are all unqualified products, or the length of the cylinder is too long or too short, which is beyond the allowable range of error. They are all unqualified products, and they have to be scrapped or reprocessed, which will inevitably lead to the increase of cost.
The requirement of high-precision parts processing is actually the most important dimension problem. It must be processed in strict accordance with the additional drawings. The actual size of the processed parts will not be exactly the same as the theoretical size of the drawings, but as long as the processing size is within the allowable error range, they are all qualified parts. Therefore, the requirement of precision parts processing is to process in strict accordance with the theoretical size Line processing.
The second is the advanced precision parts processing equipment and testing equipment. The advanced processing equipment makes the processing of precision parts simpler, higher precision and better effect. The detection device can detect the parts that do not meet the requirements, so that all the products sent to customers can really meet the requirements.

CNC computer gong processing complex parts technology

The continuous fine blanking die for complex parts is the frontier basic technology of fine blanking technology, and it is expected to promote the whole fine blanking technology in China. Taking the synchronizer gear ring, clutch plate, longitudinal compound continuous fine blanking process and continuous fine blanking die for complex parts as the breakthrough point, the key technology of fine blanking die design and manufacturing is studied, so as to realize the rapid improvement of fine blanking die technology in China and shorten the gap with advanced countries as soon as possible.

Study on the life promotion of fine blanking die and its related key technologies

Die life is a comprehensive reflection of die materials and the level of supporting products. Taking the life of fine blanking die as the leader to carry out technical research can not only solve the problem that the life of fine blanking die is too low, but also drive the technical development of die materials, fine blanking process, supporting tooling and other auxiliary products.

Research and development of fine blanking precision forging composite technology

Precision blanking and precision forging are two advanced manufacturing technologies developed in parallel. If the precision blanking parts are too thick and need precision forging, the precision forging must be too thin. They are closely related. The basic idea of developing precision forging and fine blanking compound process is to find the combination point of the two processes (such as gear parts with wheel hub and cam parts with short shaft). The precision forging in China has a long history and has a high level, so it is a good way to improve the overall level of precision blanking technology in China.

Types of CNC metal processing technology

Time effect elimination method

Aging elimination is a traditional method to reduce quenching residual stress. As aluminum alloy materials, especially aviation aluminum alloy materials, are very sensitive to temperature, the increase of aging temperature will obviously reduce the strength index, resulting in excessive precipitation of mgzn2 and other strengthening phases, resulting in over aging phenomenon. Therefore, aging treatment after quenching is usually carried out at a lower temperature (less than 200-250 ℃), which affects the stress relief effect (only 10-35%)

Mechanical stretching the principle of mechanical stretching is to apply a certain amount of permanent tensile plastic deformation to the quenched aluminum alloy plate along the rolling direction, so that the plastic deformation will occur after the superposition of tensile stress and the original quenching residual stress, so that the residual stress can be relaxed and released. The results show that more than 90% of the residual stress can be eliminated by mechanical stretching. However, this method is only suitable for the parts with simple shape, and it has high requirements on the microstructure uniformity of aluminum alloy sheet before drawing, so it is mostly used in aluminum processing plants.
Die cold pressing method

Die cold pressing method is to eliminate the residual stress of aluminum alloy die forgings with complex shape through strictly controlled limited cold shaping in a special finishing die. In fact, the term “die pressing” is not accurate enough, because its main mechanism is to make the local material of aluminum alloy die forgings subject to “tension” or “compression”. When the finishing die is pressed down, the finishing punch is embedded into the draft angle of the end face and edge (rib) of the aluminum alloy die forging, which actually causes the “tensile” effect on the web part of the die forging. Therefore, this method is to adjust rather than eliminate the overall stress level of the parts. It can release the residual stress in some parts of the aluminum alloy die forging and increase the residual stress in other parts.

Properties of various materials processed by CNC

The positioning accuracy and repeated positioning accuracy of CNC lathe are very high, so it is easy to ensure the consistency of the size of a batch of parts. As long as the process design and program are correct and reasonable, combined with careful operation, the parts can obtain higher processing accuracy, and it is also convenient for the quality control of large-scale computer gong processing. CNC lathe is a technology intensive Mechatronics typical large-scale computer gong processing products, maintenance personnel need to understand both mechanical and microelectronic maintenance knowledge, but also equipped with better maintenance equipment.

Using metal mold, filling mold under high pressure and high speed, rapid solidification under pressure is a metal forming method with high efficiency and high precision, but the manufacturing cost of die-casting machine and die-casting mold is high; mass production, small and medium-sized thin-walled castings mainly composed of zinc alloy, aluminum alloy, magnesium alloy and copper alloy, are also used for iron and steel castings.
Use wax mould to make a whole refractory shell mold outside the wax mould. After the wax pattern is melted off by heating, it is poured by gravity. The casting has high precision and good surface quality, but the cost of die making is high and there are many processes. Manual operation, poor working conditions; various production batches, mainly carbon steel, alloy steel alloy and difficult to process high melting point alloy complex parts are suitable, casting quality is generally less than 10kg.
Casting with metal mold under gravity can refine the structure of non-ferrous alloy castings. Gray iron castings are easy to produce white, with high productivity, no dust, high equipment cost, and poor labor conditions in manual operation. Mass production is mainly made of non-ferrous alloy, and can also be used for thick wall, simple or medium complex small and medium-sized castings of cast steel and cast iron.
Using metal mold, graphite mold and sand mold to fill mold and solidify under gas pressure, the casting is compact, the metal yield is high, and the equipment is simple; single piece, small batch or mass production, medium large thin-walled casting mainly made of non-ferrous alloy.
High precision pattern, self hardening refractory slurry, gravity casting, high precision casting, fine surface roughness, but expensive ceramic slurry; single piece, small batch production of medium, small, thick wall medium complex castings, especially suitable for metal mold, template, hot box and various kinds of hot forging die.
Casting with metal sand or sand mold under the action of centrifugal force, and processing with computer gong, the structure of casting is compact, the equipment is simple, the cost is low, and the productivity is high, but the machining capacity is large; large quantities of iron pipe, copper sleeve, roller, metal bearing bush, cylinder sleeve and other rotary body castings are produced in single piece and batch.
use foam polystyrene plastic moulds to replace wood or metal mold parts locally or completely, and burn them when pouring. It can save wood and simplify the working procedure, but the dust and harmful gas are relatively large; for medium and large castings produced in single piece or small batch, 1-2 pieces are suitable, or for the parts of castings with difficult mold removal. Machining is now accessible to many industries, it also has a lot of processing methods, such as, gantry grinding and so on, the machining center can choose the best process line and cutting parameters, effectively reduce the auxiliary time in processing, so as to improve production efficiency. The production efficiency of machining center is high. And because of its automatic tool changing function, it can usually save complex tooling, reduce the installation, adjustment and multiple tool setting of processing parts and other relatively complex and tedious work.

CNC computer gong vmc-650 model

Vmc-650 mechanical characteristics and control system characteristics: mechanical characteristics:

1、 High rigidity, heavy cutting

All of them are made of high-quality resin sand wear-resistant casting, strong and tough rib, super large column, wide and low seat, honeycomb structure. After annealing treatment, the stress is removed and the deformation does not occur for a long time.
The three-axis adopts the rectangular guide rail with strong rigidity, which can bear heavy cutting, precision grinding of worktable and quenching treatment, greatly enhancing the surface hardness.

2、 High precision

The three-axis drive adopts Taiwan C3 precision ball screw and P3 bearing, which ensures the positioning accuracy and repeated positioning accuracy.
The three-axis adopts Mitsubishi servo motor and spindle motor, direct drive, which provides strong power and ensures the feeding accuracy under the strong bearing capacity.
P3 grade spindle of international famous brand is adopted to ensure the advantages of high reliability, long service life, low noise, small vibration and high precision of the spindle.

Control system characteristics:

1、 Good stability, fast speed and high precision

It adopts the world’s advanced Mitsubishi CNC system, and the M60s series adopts servo drive, which ensures the high stability, high speed and smooth surface of the control system.

2、 It has the advantages of high precision, has the function of manufacturing mold, and is the best choice for mold production.

All M60s series controllers are equipped with RISC 64 bit CPU.
It can correspond to Ethernet and IC card interface.
Coordinate display value conversion can be freely switched (program value display or manual insertion display switching)
Standard internal waveform display function, working position coordinate and center point measurement function.
Buffer correction function expansion: can correspond to IC card / computer link B / DNC / record MDI mode.
The editing mode in the editing screen can be automatically switched to full page editing or full name editing.
Graphic display function improvement: can contain props path data to fully display the working coordinates and the actual position of props compensation.
Simple dialogue program software (developed by APLC, magicpro)_ Navimill dialog program).
It can develop PLC software corresponding to Windows95 / 98 / 2000nt40 / me / XP.

CNC computer gong processing instructions

When only x-axis or y-axis is mirrored, the cutting sequence (forward milling and reverse milling), cutting direction and arc interpolation direction will be opposite to the actual program. When the x-axis and y-axis are mirrored at the same time, the sequence of tool feeding, the direction of tool compensation and the direction of arc interpolation remain unchanged.

Note: after using the mirror command, you must cancel it with M23 to avoid affecting the following program. In G90 mode, the mirror or cancel command can only be used after returning to the origin of workpiece coordinate system. Otherwise, the CNC system can not calculate the movement track behind, and the phenomenon of random tool walking will appear. At this time, we must implement manual origin reset operation to solve the problem. The spindle steering does not change with the mirror command.

[pause instruction]

G04X(U)_ /P_ It refers to the tool pause time (feed stop, spindle not stop). The value after address P or X is the pause time. The value after X should have a decimal point, otherwise it is calculated as one thousandth of the value in seconds (s), and the value after P cannot have a decimal point (that is, an integer), but in milliseconds (MS). However, in some hole system processing instructions (such as g82, G88 and g89), in order to ensure the roughness of the hole bottom, when the tool is processed to the hole bottom, there is a pause time. At this time, it can only be expressed by the address P. if it is expressed by the address x, the control system thinks that x is the x-axis coordinate value for execution.

[differences and relations among M00, M01, M02 and M03]

M00 is the program unconditional pause instruction. When the program is executed, the feed stops and the spindle stops. To restart the program, you must first return to jog state, press CW (spindle forward) to start the spindle, and then return to auto state, press start key to start the program.

M01 is program selective pause instruction. Before the program is executed, the opstop key on the control panel must be opened. The effect after execution is the same as that of M00. To restart the program, it is the same as above. M00 and M01 are often used for inspection of workpiece size or chip removal during machining. M02 is the main program end instruction. Execute this command, feed stop, spindle stop, coolant off. But the program cursor stops at the end of the program. M30 is the main program end instruction. The function is the same as M02, the difference is that the cursor returns to the program head position, regardless of whether there are other program segments after M30.

[address D and H have the same meaning]

Tool compensation parameters D and H have the same function and can be interchanged at will. They all represent the address name of compensation register in CNC system, but the specific compensation value is determined by the address of compensation number after them. However, in the machining center, in order to prevent errors, it is generally stipulated that h is the tool length compensation address, the compensation number is from 1 to 20, D is the tool radius compensation address, and the compensation number starts from 21 (the magazine of 20 tools).