October 2020 – Page 2 – CNC Machining & Turning, Milling, Metal parts

Computer gong oil leakage

(1) Influence of clearance factor

The leakage is directly proportional to the size of the seal gap, and the larger the gap, the greater the leakage.

(2) Influence of internal and external pressure difference

The leakage is directly proportional to the internal and external pressure difference of the seal, and the greater the pressure difference, the greater the leakage.

(3) Influence of medium viscosity

The leakage of computer gong processing is inversely proportional to the viscosity of medium. The smaller the medium viscosity, the easier the leakage occurs.

(4) Effect of seal length

In the gap damping, the leakage is inversely proportional to the seal length. The larger the seal length is, the less likely it is to leak.

(5) Influence of ambient temperature

The leakage rate is directly proportional to the ambient temperature. Generally, with the increase of temperature, the viscosity of liquid medium becomes thinner, and the molecular motion of gaseous medium intensifies, which makes the leakage increase.

(6) Performance influence of sealing materials

Including the compactness, pressure flexibility, wear resistance, aging resistance, corrosion resistance, high temperature resistance and processability of the material, the change of leakage condition can be determined.

(7) The velocity effect of relative motion

In rotating shaft or reciprocating movement of the seal, high-speed computer gongs processing its relative speed has the greatest impact on the leakage. Generally speaking, the higher the rotating speed of the rotating shaft, the faster the medium leakage. Moreover, in reciprocating motion, the leakage of medium is also related to the direction of motion.

(8) Influence of vibration and shock on machine tools

The vibration and impact produced by the machine itself or by external forces have a direct impact on the medium leakage.

In order to completely eradicate the oil leakage phenomenon of machine tools, attention should be paid to all aspects of design, manufacturing, use and maintenance. Dongguan Mechanical parts processing ensures that the work in each stage fully meets the requirements of relevant standards. In the actual work of CNC machining, it is necessary to investigate and study the leakage of existing equipment, find out the parts of oil leakage, analyze the causes of oil leakage, and take effective measures At the same time, information feedback should be done to ensure that the same leakage problem will not happen again.

CNC Machining Shop

CNC Machining Shop. CNC Machining Shop is a China CNC precision machining manufacturer and Chinese CNC machining company with state-of-the-art CNC manufacturing factory based in China. We provide custom 3-5 axis CNC Machining Services, CNC milling services, CNC turning services and manufacture CNC Machined Parts in our China precision CNC machining factory.

On the processing of computer gongs

Computer numerical control: computer numerical control, referred to as CNC, generally known as CNC abroad, rarely use the concept of NC. Numerical control machine tools refers to the machine tools equipped with computer numerical control system, referred to as CNC machine tools. We have seen CNC machines, but we don’t understand them very well. Let’s take a look at CNC precision parts processing machine tools.

It usually controls the position, angle, speed and other mechanical quantities and the switch value related to the mechanical energy flow direction. The generation of numerical control of computer gong machining depends on the emergence of data carrier and binary data operation. In 1908, the perforated sheet metal interchangeable data carrier came out; at the end of the 19th century, the paper-based control system with auxiliary functions was invented; in 1938, Shannon carried out fast data calculation and transmission at MIT, laying the foundation for modern computers, including computer digital control systems. The numerical control technology of high-speed computer gong machining is developed in close combination with machine tool control. In 1952, the first CNC machine tool came out, which became a great pioneering work in the history of world machinery industry.

characteristic

Compared with ordinary machine tools, CNC precision parts machining machine tools have the following characteristics:

High machining precision and stable machining quality;

It can carry out multi coordinate linkage and process parts with complex shapes;

When the machining parts are changed, only the NC program needs to be changed, which can save the production preparation time;

The machine tool itself has high precision and rigidity. It can choose favorable processing amount and high productivity (generally 3 ~ 5 times of ordinary machine tool);

High degree of automation of machine tools can reduce labor intensity;

Mass production, easy control of product quality;

The requirements for the professional quality of operators are low, and the technical requirements for maintenance personnel are high.

In CNC precision parts processing, the staff should have a very familiar understanding of the machine tool. Mold processing is a kind of artificial intelligence, which is completed by computer control machine tool. The most complex part of the computer gong lies in the control system. The computer processing the computer sends various instructions to control the three axis servo motors of the machine to cooperate with each other according to the established route, so as to process various complex processes and ensure high machining accuracy.

The main component of the body part of the computer gong processing is casting, which is also a major reason affecting the accuracy of the computer gong machine tool. It can even be said that the quality of casting determines the grade of machine tool and the stability of future use. What are the requirements for casting manufacturing, that is, no deformation and enough rigidity. CNC machining does not deformation refers to the actual processing process after leaving the factory, the accuracy of the machine tool remains good, deformation will affect the accuracy. The machining rigidity of mechanical parts is enough for the machine tool to meet the needs of heavy chip processing.

Turn milling compound machining

According to the accuracy requirements, that is, the dimensional accuracy, positioning accuracy and surface roughness of the workpiece, the control accuracy of the CNC lathe is selected. Reliability is the guarantee to improve product quality and production efficiency. The reliability of CNC machine tool means that the machine tool can run stably for a long time without failure when it performs its functions under specified conditions. That is, the average time between failures is long, even if there is a fault, it can be recovered in a short time and put into use again. Select the machine tools with reasonable structure, excellent manufacturing and mass production. Generally, the more users, the higher the reliability of CNC system.

Turning center 2. Machine tool accessories and tool selection

Machine tool accessories, spare parts and their supply capacity, cutting tools are very important for CNC lathes and turning centers that have been put into production. When selecting machine tools, the matching of tools and accessories should be carefully considered.

Pay attention to the identity of control system

Manufacturers generally choose the same manufacturer’s products, at least the same manufacturer’s control system, which brings great convenience to the maintenance work. Teaching units, due to the need for students to be knowledgeable, choose different systems, equipped with a variety of simulation software is a wise choice.

Select according to the performance price ratio

Do not idle and waste functions and accuracy, and do not choose functions irrelevant to your own needs.

Protection of machine tool

If necessary, the machine tool can be equipped with fully enclosed or semi enclosed protective devices and automatic chip removal devices.

When selecting CNC lathe and turning center, the above principles should be considered comprehensively.

Determine the process requirements of typical parts and the batch of processed workpieces. The function of NC lathe is to prepare well in the early stage, and the precondition of reasonable selection of CNC lathe meets the process requirements of typical parts.

The process requirements of typical parts are mainly the structural size, processing range and precision requirements of the parts. According to the accuracy requirements, that is, the dimensional accuracy, positioning accuracy and surface roughness of the workpiece, the control accuracy of the CNC lathe is selected. Reliability is the guarantee to improve product quality and production efficiency. The reliability of CNC machine tool means that the machine tool can run stably for a long time without failure when it performs its functions under specified conditions. That is, the average time between failures is long, even if there is a fault, it can be recovered in a short time and put into use again. Select the machine tools with reasonable structure, excellent manufacturing and mass production. Generally, the more users, the higher the reliability of CNC system.

Turning center 2. Machine tool accessories and tool selection

Pay attention to the identity of control system

Select according to the performance price ratio

Do not idle and waste functions and accuracy, and do not choose functions irrelevant to your own needs.

Protection of machine tool

If necessary, the machine tool can be equipped with fully enclosed or semi enclosed protective devices and automatic chip removal devices.

When selecting CNC lathe and turning center, the above principles should be considered comprehensively.

Firstly, determine the process requirements of parts and the batch of processed workpieces, draw up the functions that the CNC lathe should have, prepare well in the early stage, and reasonably select the preconditions of CNC lathe to meet the process requirements of typical parts. The process requirements of typical parts mainly include the structural dimension, processing range and precision requirements of the parts. According to the accuracy requirements, that is, the dimensional accuracy, positioning accuracy and surface roughness of the workpiece, the control accuracy of the CNC lathe is selected. Reliability is the guarantee to improve product quality and production efficiency. The reliability of CNC machine tool means that the machine tool can run stably for a long time without failure when it performs its functions under specified conditions. That is, the average time between failures is long, even if there is a fault, it can be recovered in a short time and put into use again. Select the machine tools with reasonable structure, excellent manufacturing and mass production. Generally, the more users, the higher the reliability of CNC system. General import system has Japan Sanling, farnac, Germany’s Siemens, domestic Guangshu, Kandi, new generation more commonly used

CNC lathe processing materials are: 304, 316 stainless steel, carbon steel, copper, aluminum, alloy, plastic, POM, etc. However, the products of different materials need to choose different quality cutting tools to ensure the accuracy required by each product. Composite machining is one of the most popular machining technologies in the field of mechanical processing. It is an advanced manufacturing technology. Compound machining is to realize several different processing technologies on one machine tool. Compound machining is the most widely used and the most difficult one is turn milling compound machining. Turning milling compound machining center is equivalent to the compound of a CNC lathe and a machining center.

At present, most of the turn milling compound machining is completed on the turning center, while the general turning center only changes the ordinary turret turret of CNC lathe into the turret turret with power tool, and the spindle adds the c-axis function. Due to the limitation of turret structure and dimension, the power of power head is small, and the speed is not high

CNC engraving and milling machine

The spindle speed of engraving and milling machine is high, which is suitable for processing small cutting tools, and its torque is relatively small. It focuses on the “carving” function, such as wood (wood carving machine for special processing of wood), dual color board, acrylic plate and other plates with low hardness. It is not suitable for CNC processing of large workpieces with strong cutting. At present, most of the products marked with engraving machine banner are mainly for processing handicrafts with low cost, Due to the low precision, it is not suitable for mold development, but there are also exceptions, such as wafer engraving machine. Advantages: it can carry out relatively small processing and high machining accuracy. High speed machining is possible for soft metals; disadvantage: heavy cutting is not possible due to poor rigidity.

Troubleshooting of CNC engraving and milling machine

（1） . usage environment

CNC engraving and milling machine is a high-tech mechatronics equipment, which has certain requirements for the working environment.

The voltage is required to be stable and avoid large fluctuation. It is better to use voltage regulator.
The machine should not work in strong acid and alkali environment for a long time.
Avoid strong electricity, strong magnetism and other equipment that seriously affect the signal transmission of engraving and milling machine. Such as: welding machine, launch tower, etc.
Use three core power supply to ensure good grounding of engraving and milling machine and reduce interference.

（2） . processing problems

Operators

The proficiency and sense of responsibility of operators also have a great impact on the machining accuracy.

Wear and tear of the machine

CNC engraving and milling machine wear is inevitable in the process of use, with the passage of time, machine wear will reduce the accuracy of the machine.

Rationality of processing technology

In addition to CNC engraving and milling machine to ensure the machining accuracy, reasonable processing technology is also very important. CNC machining in order to ensure the accuracy of processing, please pay attention to the rationality of the processing technology.

Tool use

The machining accuracy is affected by the manufacturing process and accuracy of the tool itself. Therefore, please select the suitable tool for machining.

（3） . maintenance and maintenance

CNC engraving and milling machine is mostly used in processing business, which produces a lot of powder foam and dust. During use, attention should be paid to keep the screw rod, polished rod and other parts clean and lubricated, timely clean up the dust and add oil to the transmission parts; the operator should clean and add oil in time, and it is strictly forbidden to plug and plug with electricity.

（4） . software usage problems

There are many engraving and milling software for CNC engraving and milling machine. In order to meet your engraving and milling requirements, please select the correct operation software. At present, most enterprises in CNC cutting machine tool industry rely on reducing the product price to obtain the market. The result is that the product price is low, the added value is low, the profit is low, and the enterprise does not have enough funds for sustainable development. Low price competition, imitation and OEM production are limited to a certain historical stage. With the development of the industry and the upgrading of competition, it is the best choice for enterprises to improve the technical content of products, have independent patents and designs, and pay attention to brand building and marketing.

The decorative development trend of CNC machine tools can be seen. CNC cutting machine tools emphasize more on mechanical properties, simple operation, economic price, stable processing accuracy and so on. Nowadays, with the increasing demand for popularization and batch processing of metal materials, CNC cutting machine tools should not only meet the above functions, but also have the applicability of multiple cutting methods. At present, CNC cutting machine tools can be divided into flame cutting and plasma cutting. In recent years, with the continuous improvement of downstream industry demand, the CNC machine tool accessories put forward greater demand and higher requirements.

It is understood that the next few years will be the high-speed development and shock period of CNC machine tool industry. The direct consequence of this high-speed shock is that the polarization trend in the current decoration CNC machine tool brand camp is more obvious and expanded. CNC machining is expected to be able to survive in the market in the next few years, the number of CNC machine tool enterprises will drop sharply. However, the high-speed vibration of CNC machine tool industry will also bring great opportunities to make the market operation more rational and standardized.

Offset of tool point in computer gong machining

The materials for computer gong machining are usually free cutting steel and copper. The free cutting steel has higher sulfur content and phosphorus content. Sulfur and manganese exist in the steel in the form of manganese sulfide. Manganese sulfide plays a lubricating role in the steel, making the steel easier to cut, thus improving the production progress of lathe bed. So what should be paid attention to when CNC lathe processing?

When aligning the workpiece, it is only allowed to move the chuck by hand or turn on the lowest speed for alignment, and do not turn on the high speed for alignment.
When changing the rotation direction of the spindle, the spindle should be stopped first and then. It is not allowed to change the rotation direction suddenly.
When loading and unloading the chuck, only rotate the V-belt manually to drive the spindle to rotate. It is absolutely forbidden to directly start the machine tool and force it to loosen or tighten. At the same time, a board should be placed on the bed to prevent accidents.
The tool installation should not extend too long, the gasket should be flat and straight, and the width should be consistent with the width of the tool bottom surface.

In order to set the knife conveniently, the imaginary point P is often used to set the knife. If there is no tool tip radius compensation, undercut will occur when turning cone or arc. When the accuracy of the part is high and there is a cone or arc, the solution is to calculate the trajectory size of the tool tip arc center, and then compile and calculate the local compensation.

Is the tool position compensation caused by the radius r of tool tip arc when turning dimensional surface. When the tool position compensation is carried out in Z and X directions at the same time, the actual contact point a between the cutting edge and the workpiece moves to the set point P of the tool tip during programming. The compensation amount of R can be calculated by the following formula: when programming the conical surface of the workpiece, the base point coordinates are the coordinates of the base point of the workpiece contour (Z and x) plus the compensation amount of the radius of the tool tip arc R (DZ and DX), thus solving the problem that there is no compensation for the radius of the tool tip arc Questions. Because there is an arc at the tool tip, the workpiece contour is formed by the tool motion envelope, so the motion path of the tool location does not coincide with the contour of the workpiece. In the full function CNC system, the tool compensation instruction can be used to program conveniently according to the contour size of the workpiece. In the economical CNC system, the path of the cutter location can be calculated according to the contour size of the workpiece and the cutter. According to this programming, it can also be solved by the method of local compensation.

In order to improve the work efficiency and reduce the errors of various operations, the safe operation that should be paid attention to in the process of C is summarized as follows:

Try to install the clamping material first and then the cutting tool to prevent the hand from touching the tool when installing the clamping material. If the tool has been installed, the worktable should first be moved to the outside to ensure that the clamping material will not interfere with the tool, so as to avoid injury or breakage of the tool.
After stopping, it is necessary to observe whether the spindle stops rotating when disassembling the tool.
Don’t hold or pinch the edge of the knife when unloading it to avoid scratching.
In the process of machining mechanical parts, operators are not allowed to observe the cutting position closely to prevent chips from falling into eyes.
The wrench should be placed in the tool storage area after use, not on the y-axis shield or beam.
Before CNC machining, check the position of the oil nozzle before opening the oil pump switch to avoid spraying to other positions when flushing oil.
When suspending observation during machining clearance, the worktable must be moved away from the cutting position.
Inspection. After processing, before disassembling the workpiece, it is necessary to conduct preliminary inspection on the size or appearance of the workpiece. The workpiece can only be disassembled after passing the inspection, so as to avoid positioning problems of secondary processing and scrapping of the workpiece after disassembly. For some key dimension data of the disassembled workpiece, further inspection is needed to meet the requirements.

Surface roughness of computer gongs

Because the spindle speed and range of CNC machine tools are far higher than ordinary machine tools, and the output power of the spindle is large, compared with the traditional processing methods, higher requirements are put forward for the CNC machining tools, including high precision, high strength, good rigidity, high durability, and the size stability, convenient installation and adjustment, and the characteristics of the spindle drive system of CNC machine tools. This requires that the structure of the tool is reasonable, the geometric parameters are standardized and serialized. NC tool is one of the preconditions to improve the machining efficiency. Its selection depends on the geometry of the parts to be processed, the material state, the fixture and the rigidity of the selected tool. The following aspects should be considered:

(1) The cutting tool is selected according to the cutting performance of the part material. If turning or milling high strength steel, titanium alloy, stainless steel parts, it is recommended to select indexable carbide tool with good wear resistance.

(2) Select the tool according to the hardware parts processing stage. That is to say, in the rough machining stage, the cutting tool with better rigidity and lower precision should be selected; in the semi finishing and finishing stage, the machining accuracy and product quality of the parts should be guaranteed; the tools with high durability and high precision should be selected; the precision of the tools used in the rough machining stage is the lowest, while that in the finishing stage is the highest. If the same tool is selected for rough machining and finish machining, it is recommended to select the tool eliminated from finish machining during rough machining, because most of the tool wear out of finishing machining is slight wear on the edge, and coating wear and polishing. Continuous use will affect the quality of finish machining, but the impact on rough machining is small.

(3) According to the characteristics of NC lathe processing area, the tool and geometric parameters are selected. The tool with large diameter and small ratio of length to diameter should be selected if the structure of the part is allowed; the end edge of the cross center milling cutter for cutting thin-walled and ultra-thin-wall parts should have enough centripetal angle to reduce the cutting force of the cutter and cutting parts. When processing aluminum, copper and other soft material parts, the end mill with larger front angle should be selected, and the number of teeth should not exceed 4.

When selecting the tool, the size of the tool should be compatible with the surface size of the workpiece to be processed. In production, end milling cutter is often used for peripheral contour processing of plane parts; when milling plane, carbide blade milling cutter should be selected; when machining boss and groove, high-speed steel end milling cutter should be selected; when hardware processing blank surface or rough machining hole, corn milling cutter with cemented carbide blade can be selected; Ball end milling cutter, ring milling cutter, conical milling cutter and disc milling cutter are often used in the machining of solid surface and variable bevel profile.

In the process of free-form surface machining, because the cutting speed of the ball end cutter is zero, in order to ensure the NC machining accuracy, the cutting row spacing is generally very small, so ball end milling cutter is suitable for surface finishing. The end milling cutter is far better than the ball end milling cutter in both surface processing quality and processing efficiency. Therefore, under the premise of ensuring that the parts can not be cut, the end milling cutter should be selected as far as possible when rough machining and semi finishing surface machining. In addition, the durability and accuracy of cutting tools are closely related to the price of cutting tools. It must be noted that in most cases, although the selection of good tools increases the cost of cutting tools, the improvement of processing quality and efficiency brought about by this can greatly reduce the whole processing cost.

In the machining center, all the tools are pre installed in the tool library, and the corresponding tool change action is carried out through the tool selection and tool change instructions of the NC program. It is necessary to select the corresponding standard tool holder suitable for the machine tool system specification, so that the tool for NC machining can be quickly and accurately installed on the machine tool spindle or returned to the tool magazine. The programmer should be able to understand the structure size, adjustment method and adjustment range of the tool holder used by the machine tool, so as to ensure that the radial and axial dimensions of the tool can be determined and the arrangement order of the tool can be arranged reasonably.

The surface geometric characteristics of NC machining include surface roughness, surface waviness and surface texture. Surface roughness is the basic unit of geometric characteristics of machined surface. When machining workpiece surface with metal cutting tools, surface roughness is mainly affected by geometric factors, physical factors and NC machining process factors.

(1) Geometric factors

From the geometric point of view, the shape and geometric angle of the tool, especially the radius of the tool tip arc, the main deflection angle, the secondary deflection angle and the feed rate in cutting parameters have a great influence on the surface roughness.

(2) Physical factors

Considering the physical essence of the cutting process, the metal material plastic deformation is caused by the corner of the cutting edge and the extrusion and friction behind the tool, which seriously worsens the surface roughness. When the plastic material is processed by numerical control lathe to form strip chip, it is easy to form chip accretion with high hardness on the rake face. It can replace the rake face and cutting edge for cutting, so that the geometric angle of the cutter and the back feed can be changed. The contour of the chip accretion is very irregular, so that the depth and width of the workpiece surface are constantly changing. In CNC machining, some chips are embedded in the workpiece surface, which increases the surface roughness. The vibration during cutting increases the surface roughness parameters.

(3) Technological factors

From the perspective of technology, the influence on the surface roughness of metal parts is mainly related to cutting tools, workpiece materials and CNC processing conditions.

Accuracy of slender rod like tools

Accuracy analysis of machining slender rod-shaped tools by CNC machine tools: the improvement of the accuracy of rod-shaped tools has always been a difficulty in tool manufacturing. The main reason is that the effective part of the tool is too long and the cutting edge of the tool is too far from the clamping part during manufacturing. Because the cutting edge is too far away from the clamping part, and the chuck has certain clamping accuracy (generally 0.002 ~ 0.005mm), the radial circular runout at the cutting edge of the cutter may have reached 0.005mm ~ 0.01mm (or even greater) before grinding. Due to the large grinding force and the large elastic deformation of the tool, there will be many problems in the machining process, such as the asymmetry of the tool groove, the size of the tool’s outer circle, the parameters of the cutting edge and the shape error are not up to the requirements, and even the tool is broken in serious cases. The following is a simple analysis of the accuracy of the tool when machining slender rod-shaped tools with CNC machine tools.

1、 The influence of machine tools on tool accuracy. The influence of machine tool accuracy on tool accuracy the accuracy of machine tool is the key to determine the accuracy of any tool, and the slender rod-shaped tool is no exception. The support block equipped with this machine tool is mainly used for CNC machining slender rod-shaped tools. Its position can be adjusted in the horizontal and longitudinal direction, and can be positioned according to the actual situation. If the position of the support block in the transverse direction (i.e. the axial direction of the tool) is not reasonable, the qualified slender rod-shaped tool cannot be machined. If the support block is too low, the support force to the tool is not enough, which will cause the tool groove to form an inverted cone in the axial direction; if the support block is too high, the support block will force the tool against the tool, which will lead to the tool groove forming a cone along the axis. Therefore, the accurate positioning of the support block is also very important to the accuracy of the tool.

2、 The influence of CNC grinding wheel on tool accuracy. All parameters of the cutter are determined by the relative motion between the grinding wheel and the cutter. Therefore, the diameter of the grinding wheel, the angle of the grinding wheel directly participating in the cutting, the flange length of the grinding wheel shaft, the wear of the grinding wheel and the grain size of the grinding wheel all affect the accuracy of the cutter. The accuracy of grinding wheel angle measurement or input may cause: the width of cutting edge belt does not conform to the requirements; the angle of stepped cutter’s step surface does not meet the requirements; the position or angle of tool back angle has error; the groove angle of chip removal groove has error.

3、 The cooling effect of the coolant on the grinding area will directly affect the accuracy of the cutting tool when machining hardware parts. The selection of coolant with good performance and proper cooling pressure is conducive to the coolant entering the grinding zone, which can take away the cutting heat and chips in time, and effectively reduce the surface roughness of the tool.

CNC punch press is a kind of equipment which can automatically blanking sheet metal according to the NC machining program. The ideal processing program should not only ensure that the hardware parts can be processed to meet the design requirements of qualified parts, but also can make the CNC punch get reasonable application and give full play to its performance.

With the development of stamping equipment, more and more numerical control blanking technology is used. Through the research and analysis of the process characteristics of numerical control processing, this paper puts forward some matters that should be paid attention to in the program design of numerical control punching, and illustrates the correct method to complete each work with corresponding examples. The author of the article has rich practical experience, because some articles have strong practicability.

When designing numerical control program, whether it is manual programming or automatic programming, it is necessary to analyze the processing technology of hardware parts before programming, and then work out the processing scheme, formulate the correct and reasonable processing process, and select the appropriate mold and processing speed. In the design of numerical control program, hardware processing plant should pay more attention to some process methods of program design. If some process details are ignored, sometimes even if the processing program is correct, due to the unreasonable process method of the program, it is impossible to process qualified parts. What’s more, it will cause alarm and damage to the machine tool.

CNC machine tool maintenance guide

The performance of guide rail directly affects the machining accuracy, bearing capacity and performance of the machine tool. The common guide ways of machine tools include sliding guide, rolling guide and hydrostatic guide.

1、 Characteristics of sliding guide, rolling guide and hydrostatic guide

1 slide guide

Sliding guide has the advantages of simple structure, convenient manufacturing, good stiffness and strong seismic resistance. It is widely used in general machine tools, and is often made of cast iron or steel inlaid guide rail. In order to improve the wear resistance and accuracy of the guide rail, the surface of the guide rail is generally quenched and then ground.

2 Rolling Guide

The rolling guide rail is a rolling element installed between the working faces of the guide rail. The rolling element can be ball, roller and needle. The contact between the rolling guide rail and the guide rail is point contact or line contact. Therefore, the friction coefficient of the guide rail is small. The static and dynamic friction coefficients are basically the same, the starting resistance is small, the low-speed motion stability is good, the positioning accuracy is high, the micro displacement is accurate, the wear is small, the accuracy retention is good, and the service life is long. Its disadvantages are poor seismic resistance and high protection requirements. Rolling guide, especially linear rolling guide, has been widely used in recent years. With the development of CNC machine tools to high speed, linear guide rail is more and more widely used.

3 hydraulic guide rail

The hydraulic guide rail used on the machine tool is mainly hydrostatic guide. Hydrostatic guideway is usually filled with pressure oil between two relative moving guide surfaces to make the moving parts float. The oil pressure can be adjusted automatically with the change of the external load to ensure that the friction between the guide surfaces is always in the pure liquid state. Therefore, the friction coefficient of the hydrostatic guide is the minimum and the power consumption is small. This kind of guide rail is not easy to wear, and has good precision retention and long service life. Its oil film thickness is almost not affected by the speed. The oil film has large load-carrying capacity, high rigidity, good shock absorption, stable operation and no creeping phenomenon. The structure of hydrostatic guideway is complex, and the hydraulic device with good filtering effect is needed, so the manufacturing cost is high.

It is very important to select NC tools correctly. The general requirements of NC tools are convenient adjustment, good rigidity, high precision and good durability. On this basis, the cutting performance of workpiece materials, the machining capacity of machine tools, the types of NC machining processes, cutting parameters and many factors related to the working range of machine tools and CNC devices are comprehensively considered.

When compiling the sequence.

The factors affecting the selection of NC tools

When selecting the type and specification of cutting tools, the following factors are mainly considered:

Production property here refers to the batch size of parts, mainly considering the influence of processing interest on tool selection. For example, it may be cost-effective to use special tools in mass production, while it is more suitable to select standard tools for single piece or small batch production.

2 machine type

The NC machine tool used to complete the process affects the selected tool type (drilling, turning or milling). Under the condition that the rigidity of workpiece system and tool system is good, high productivity tools such as high speed cutting tool and large feed rate turning tool are allowed.

3 NC machining scheme

Different types of cutting tools can be used in different NC machining schemes. For example, drilling and reaming drills can be used for hole processing, as well as drills and boring cutters.

4 dimension and shape of workpiece

The size and shape of workpiece also affect the selection of tool type and specification, for example, special tool is used to process special surface.

Surface roughness

For example, rough milling cutter can be used in rough milling, and fine tooth milling cutter is better used in finish milling.

Machining accuracy machining accuracy affects the type and structural shape of finishing tools. For example, the final machining of holes can be processed by drilling, reaming, reaming or boring tools according to the accuracy of holes.

7 workpiece material

Workpiece data will determine the selection of tool data and cutting local geometric parameters. Tool data is related to the machining accuracy and hardness of workpiece.

Performance requirements of NC tools

Due to the characteristics of high machining accuracy, high efficiency, centralized processing procedures and less clamping times of parts, higher requirements are put forward for the CNC tools used. In terms of tool performance, CNC tools should be higher than those used in ordinary machine tools.

When selecting NC tools, first of all, we should give priority to the selection of standard tools. When necessary, we can choose various high-efficiency composite tools and special special tools. When selecting the standard NC tools, we should combine the actual situation and select various advanced tools as far as possible, such as indexable tools, integral cemented carbide tools, ceramic tools, etc.

The following problems should also be considered when selecting cutting tools for CNC machine tools

The type, specification and accuracy grade of NC tools shall meet the processing requirements, and the tool data shall be compatible with the workpiece data.
Good cutting performance. In order to adapt to the large back feed and high feed rate when the tool is used in rough machining or workpiece processing of difficult to machine materials, the tool should be able to accept high-speed cutting and powerful cutting. At the same time, the same batch of cutting tools must be stable in terms of cutting performance and tool life, so as to realize tool change according to tool life or manage tool life by CNC system.
High precision. In order to meet the requirements of high precision and automatic tool change in NC machining, the tool must have high accuracy. For example, the radial dimension accuracy of some integral end mills is as high as 0.005mm
High reliability. To ensure that the NC machining will not occur unexpected damage and potential defects affecting the processing

Influence of cutting tools on accuracy

However, these standards impose various restrictions on milling cutters and inserts, which stipulate the shape and thickness of the blades, the inscribed circle of the cutting blades, the dimensions of the blade holder and wedge clamping parts, and the size of the cutter body. Due to the limited design range of blade material, edge and chip breaking groove, the standard tool suppliers and production are limited by the machining function.

However, today, the concept of milling cutter tends to be flexible. Computer gong machining provides tool developers with the freedom to adopt new tool and blade design. These designs can be optimized. With the new tool concept, CNC machining can better solve the problems of machining safety, accuracy, surface quality, metal removal rate, tool overhang, high-speed cutting, and the ability of different cutting paths Question.

Today’s milling tools are constantly optimized to meet the needs of modern production, machine tools and data, and are widely accepted by all industries. The new cutting tool can remove metal several times faster, with smaller cutting force and better orientation. Its typical runout is only a fraction of that of the old standard tool. Therefore, the machining tolerance can always be controlled in a smaller range, and the cutting edge loss is also smaller and more ideal. The axial and radial runout is very small, which means that the cutting edge accuracy is improved, so the surface quality of the workpiece is better, the tolerance is smaller, the tool life is longer, and the cutting load is more evenly distributed, so as to improve the cutting speed and reduce the noise, vibration and loss.

The use of tools also helps to increase spindle speed, high speed feed and hard part milling, and extends the opportunities for dry cutting. The design of these tools is more concise, and the amount of work required for adjustment and maintenance is very small. The cutter body is rigid and accurate in size. It is made of pre hardened steel to ensure that the blade is accurately and firmly installed on the milling cutter body, and the appropriate tooth pitch can be selected according to different application.

The new milling tools use the blade material and groove type developed for specific data or process. The functions and achievements of the new milling cutters equipped with these blades are far better than those of ISO or ans standard tools and inserts. Compared with most standard blades, modern new blades and tools can provide larger positive rake angle and more complex groove shape, thus reducing cutting force and forming synergistic effect of faster and more stable metal removal.

Strengthen the concept of die precision

Die is a precision forming tool used for batch forming and stamping. Mold precision includes the accuracy of parts obtained in processing and the quality awareness of ensuring product accuracy during production. However, the mold precision generally refers to the accuracy of working parts of mold.

① The concept of precision in mold processing refers to the degree of conformity between the actual geometric parameters and the designed geometric parameters after the mold parts are processed and assembled.

② The concept of precision in die and mould production refers to the various thinking modes and quality consciousness formed gradually by the employees in the production practice to guide their production behavior. It is a kind of quality consciousness that the enterprise staff and workers always implement the quality consciousness of grasping the product precision in their behaviors.

The precision of mould includes four aspects: dimension precision, shape precision, position precision and surface precision. Due to the working time of the mold, the upper die and the lower die are two parts, so the position accuracy between the upper and lower dies is the most important among the four kinds of precision.

When the machining precision is very high, the mold is often surplus but force is insufficient. The precision of the die is about 1.0 ~ 0.01 mm, which is much higher than that of the former one. However, such as the engine components, but the accuracy is required to be less than one thousandth of a millimeter, or even smaller. Therefore, it is impossible to completely replace cutting with die.

Mold now its own smoothness, roughness has been a great leap forward. However, the mold itself is also made by machine tools. If the accuracy of the machine tool used to manufacture the mold itself can not pass the standard, the precision of the products produced must not be high.