Germany Benzinger 5-axis glass processing center 5@work

Product introduction

The 5 @work is a 5-axis machining center developed for the special requirements of the watch and jewelry industry.

Due to its design and spindle configuration, this 5-axis machining center offers a great deal of freedom and possibilities that are not possible with conventional milling centers. Whether rings, bracelets, jewelry or watch parts, any surface is diamond milled, engraved, twisted, faceted, etc., or in combination with our FourC, the stones are set up fully automatically.

 

Automatic workpiece loading and unloading device,

toolholder magazine for all sizes, turning operations and many other equipment details make the 5 @work a highly productive and flexible machining center for the watch and jewelry industry.

 

Using specially developed parametric CNC programs and a special user interface, these machines can be programmed and operated easily and intuitively. With our additional CAD cam package Benzinger Creative, various designs for milling and stone setting can be designed and manufactured directly in CAD. Using the CAM module, these designs can be directly converted into 5 @work 5-axis milling solutions.

 

Product Specifications Model:

Number of axes 5-axis

Horizontal / Vertical Vertical

Material to be processed For glass

Other Features Milling Cutter

X-axis 250 mm (10 in)

Y-axis 260 mm (10 in)

Z-axis 150 mm (6 in)

Speed 30,000 rpm (188,496 rad.min-1)

Output power 1 kW (1.36 hp)

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East China numerical control: CNC machine tools powerhouse products to break the monopoly of powerful countries

Listed on June 12, East China numerical control (002248), is the development, production and manufacture of CNC machine tools, CNC machine tools, key functional components (CNC systems, encoders, high-speed precision machine tool spindles, tool magazines, etc.) and general machine tools for the main business of high-tech enterprises, in the research and development and production of large-scale rail plate CNC molding grinder with the international leading level.
Products to break the monopoly of powerful countries
East China Numerical Control is currently one of the few domestic enterprises with both advanced design and production capacity of gantry grinding machines and gantry milling machines. With the help of this technical compound advantage, the company won the bidding in the project of Beijing-Shanghai high-speed railroad (Beijing-Tianjin Intercity Demonstration Section) of the Sixth Bureau of China Railway of the Ministry of Railway in February, 2006, and successfully contracted a BZM-650 Bo-format CNC grinder specializing in rail plate, which breaks the long-standing monopoly of Germany, the strongest country of the manufacturing sector, and ensures the smooth progress of the Beijing-Tianjin Intercity Railway Transportation Project. Smooth progress of the Beijing-Tianjin Intercity Rail Transportation Project.
Independent innovation for the East China numerical control to break the monopoly of powerful countries to provide a guarantee. Tang Shixian, chairman and general manager of the company, said that since its inception, East China CNC has always insisted on taking the road of development of independent innovation, high-tech scientific research and development as the enterprise can maintain rapid development of the foundation and the key to the hard, software and constantly increase the investment in the two aspects of the market competitiveness continues to increase. The company will account for more than 5% of the annual sales income of funds invested in technology development, through self-development, cooperative development, the introduction of digestion and other ways to have a number of patents and know-how, respectively, reached the international advanced or domestic leading level.
By 2006, East China Numerical Control has developed into a medium-sized enterprise in the domestic machine tool industry, entering a period of rapid growth. According to the China Machine Tool Industry Association statistics, in 2006 the company’s CNC gantry machine tool products accounted for about 7% of the domestic product market share; surface grinding machine products accounted for about 13% of the domestic product market share in the country ranked in the top five in the same industry; universal rocking-arm milling machine market share of about 19% in the country ranked first in the same industry in a dominant position.
Performance will grow rapidly
Tang Shixian said that the company through the IPO of the new “CNC gantry machine tool technology transformation project”, “CNC cylindrical grinding machine production project” and “CNC roll grinding machine production project”. The project is a high technology content, with independent intellectual property rights of the project, the fund-raising project after production, the company’s scale and strength will be on a new level, the company’s performance in the next few years will achieve rapid growth.
According to the project plan, after the completion of the project investment, East China CNC CNC gantry machine tools, CNC cylindrical grinding machine and CNC roll grinding machine production will be added 200 units / year, 120 units / year and 27 units / year. After the three projects reach production, the company’s sales revenue and total profits will have a greater growth. According to Haitong Securities forecast, the company’s 2008-2010 operating income is expected to increase from 398 million yuan in 2007 to 1.211 billion yuan in 2010, the three-year compound growth rate of net profit is expected to exceed 50%.
According to the plan, by 2010, East China CNC will enter the ranks of large machine tool manufacturers. Tang Shixian said that the domestic machine tool industry is a low degree of concentration of the industry, the company’s future will be specialized development as the leading direction, the formation of technology, brand and scale advantages in certain industry segments; and, the company will use the capital market platform to accelerate industry integration, not excluding the acquisition of mature production capacity at the right time.
Tang Shixian said that the future of the world’s machine tool manufacturing industry will gradually transfer to Asian countries, China’s machine tool industry will appear “to replace imports – exports – localization of functional components,” the evolution of the process! China’s machine tool industry will face great opportunities for development. East China CNC will seize the opportunity to achieve sustained and stable benign development.

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Taiwan Master Xinde CNC Universal Cylindrical Grinder Series

Taiwan Master Xinde CNC Universal Cylindrical Grinder PMG-60CNC/100CNC

 

(Product Characteristics

The SUG CNC series is designed for the combined OD/ID grinding of long shaft workpieces and is suitable for small to large quantities and even small quantities of various types of production. The GU CNC series grinding machines are capable of performing OD grinding, OD taper grinding, endface/shoulder grinding, and ID grinding in a single clamping setup, which can shorten the process time, reduce the production cost, and ensure the grinding accuracy. This series of grinding machines are suitable for OD/ID compound grinding operations in the manufacturing industries such as automobile and motorcycle parts, tooling machine parts, hydraulic/pneumatic/electronic motor parts, and so on. Equipped with high rigidity, low vibration and high cutting capacity dynamic spindle to ensure grinding accuracy. Reinforced ribbed box design of this machine is cast in Meehanna cast iron to ensure high rigidity and stability of the machine. Handmade high-precision spatula, Turcite-B abrasion-resistant patches and dynamic lubrication system ensure the quality and service life of the machine.

1、Grinding Wheel Head: Equipped with rotary axis B (any angle), including straight-feed grinding wheel, inclined-feed grinding wheel and internal grinding wheel.

2.Bore grinding spindle: Bore grinding motor adopts built-in spindle design, which can save space and balance the weight of bore grinding and external grinding wheels.

3、Ring Type Inductive Scale : X/B axis adopts Austria AMOSIN absolute inductive scale to ensure the positioning accuracy and repeatability of the grinding wheel head. The inductive scale is unlike the optical scale which is easily affected by dust.

4、X-axis moving method adopts linear slide mechanism, positioning method adopts absolute inductive ruler.

5、(Ⅳ)series main wheel table C-axis function, precise control of speed, with the ability to grind shaped workpieces, such as cams, crankshafts.

6、The center height of workpiece spindle is only 192mm, which makes workpiece replacement or grinding wheel replacement operation easier.

7、(Ⅲ)series X/Z/B three-axis computer numerical control, (Ⅳ) series X/Z/B/C four-axis computer numerical control, control the left and right feed point as well as grinding conditions such as grinding wheel feed rate.

8、(Ⅲ)series controller adopts FANUC Oi-TD with three-axis FANUC servo motor.

9、(Ⅳ)series controller adopts FANUC 31i, with four-axis FANUC servo motor.

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Italy SISMA jewelry laser processing machinery introduction

SISMA Italia is a worldwide reference in the design and production of ultra-high precision mechanical and laser systems.

Founded in 1961, SISMA has been able to build more than 130 models of machines for the automatic production of gold chains, thanks to its accumulated experience. Today, at the forefront of laser system development, SISMA has been able to extend its expertise to create production solutions for marking, welding, cutting, engraving and additive manufacturing. SISMA has made a career out of innovation, combining a modern and independent production organization with a large number of highly specialized human resources, thus guaranteeing the highest product quality and a timely response to market changes and requirements.

I. Series of laser marking and engraving machines for gold jewelry

Integratable resources, compact desktop systems, stand-alone systems with support bases and workstations.

SARTY, desktop laser marking and engraving system.

Versatile:

SARTY is a compact desktop laser marking and engraving system with rugged construction. It can be quickly adapted to handle different objects by simply changing the template.

Highly productive:

Load/unload options during processing, and the consequent elimination of downtime, make the SARTY ideal for marking multiple parts in a single batch.

Functionality:

SARTY is compatible with Coaxial Vision Systems (CVS) for automated part recognition and comes with powerful, flexible software that connects to company databases.

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High Precision CNC Gear Grinding Machine

Gear grinding machine is a kind of gear processing equipment widely used in machinery manufacturing industry, its main function is to grind gears made of various metal materials to improve its precision, surface quality and service life. This article will introduce the structure of the gear grinding machine, working principle, classification and application areas and other aspects of knowledge.

First, the structure and working principle of gear grinding machine
Gear grinding machine is usually composed of the following parts: host, table, grinding head, cooling system, control system and so on. Among them, the host is the main body of the gear grinding machine, responsible for supporting and fixing other parts; the worktable is used for placing and fixing the gears to be processed; the grinding head is an important part of the grinding machine, which is equipped with abrasive and coolant, used for grinding gears; the cooling system is responsible for providing coolant to reduce the temperature of the grinding process; the control system is used to control the operation of the entire gear grinding machine.

The working principle of the gear grinding machine is mainly based on the grinding principle. In the working process of the gear grinding machine, the abrasive inside the grinding head rubs against the surface of the gear to be processed, grinding down the metal on the surface of the gear, so that it gradually approaches the ideal shape. At the same time, the flushing effect of the coolant can take away the heat generated by grinding, reduce the temperature of the gear and prevent thermal damage.

Classification of Gear Grinding Machine
According to different classification standards, gear grinding machine can be divided into various types. According to the different principles of grinding, gear grinding machine can be divided into spread into the method of gear grinding machine and molding method of gear grinding machine. Spreading method grinding machine using a pair of gear meshing movement for grinding, its processing accuracy is higher, suitable for high-precision gear processing; Forming method grinding machine is based on the shape of the gear to be processed to make the corresponding grinding wheel for grinding, its processing efficiency is higher, but the accuracy is relatively low.

In addition, according to the number of grinding axes and the number of grinding wheels, gear grinding machine can be divided into single-axis, double-axis and multi-axis types. Single-axis gear grinding machine has only one grinding wheel axis, which is mainly used for roughing; double-axis gear grinding machine has two grinding wheel axes, which can be used for roughing and finishing; multi-axis gear grinding machine has more than one grinding wheel axis, which can be used for efficient multi-face grinding.
Imported gear grinding machine procurement consulting telephone: 13501282025

Third, the application field of gear grinding machine
Because the gear grinding machine has high precision and high efficiency, its application areas are very wide. In the field of automobile manufacturing, all kinds of gear parts need to be ground to improve precision and wear resistance; in the field of wind power, large-size gears need to be processed to ensure the stable operation of the wind turbine; in the field of shipbuilding, large gear parts need to be ground to improve its load-bearing capacity and stability.

In addition, in the field of mining machinery, aerospace, medical equipment and other fields, a variety of metal and non-metallic materials made of gear parts also need to be ground to improve their performance and service life. Therefore, with the development of the machinery manufacturing industry and the continuous progress of technology, the application prospects of gear grinding machine will be more broad.

In short, this paper provides a detailed introduction to the structure, working principle, classification and application areas of the gear grinding machine. It is of great significance to understand and master this knowledge to improve the productivity and product quality of the machinery manufacturing industry. In the future, with the continuous progress of technology and the expansion of application areas, gear grinding machine will be used and developed in more fields. Understand and study the history of Chinese and foreign translation from the macro and micro perspective, understand the differences and commonalities between Chinese and foreign translation theories and their mutual influences, and at the same time, conduct personalized research on the influential translators and translation theorists in the history of Chinese and foreign translation, search for the basic laws of the development of Chinese and foreign translation theories, so as to lay down the basic translation theoretical foundation for engaging in professional translation.

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Difficulties in 5-axis machining

The method and machine tool of five-axis machining, as early as the 60s of the 20th century, the foreign aviation industry has begun to adopt it in order to process some large pieces with continuous smooth and complex free-form surfaces, but it has not been widely used in more industries, and it has only developed rapidly in the past 10 years. The main reason is that there are many difficulties in five-axis machining, such as:

1. Programming is complex and difficult.

Because five-axis machining is different from three-axis, in addition to three linear movements, there are two rotational movements involved, and the spatial trajectory of the resulting motion is very complex and abstract, which is generally difficult to imagine and understand. For example, in order to process the required spatial free-form surface, it is often necessary to go through multiple coordinate transformations and complex spatial geometric operations, and at the same time, it is necessary to consider the coordination of the movement of each axis, avoid interference, collision, and interpolation motion should be timely and appropriate, etc., so as to ensure the required machining accuracy and surface quality, and the programming difficulty is even greater.

Second, the requirements for CNC and servo control systems are high.

Since five-axis machining requires five axes to coordinate movement at the same time, it is required that the CNC system must first have at least the function of five-axis linkage control; In addition, because there is the addition of rotary motion in the synthetic motion, this not only increases the workload of interpolation operation, but also because the small error of the rotary motion may be amplified and greatly affects the accuracy of machining, so the numerical control system is required to have a higher operation speed (i.e., the processing time of a shorter single program segment) and accuracy. All of this means that the CNC system must add a processor to the RISC chip for processing (i.e., a CPU structure with multiple high digits). In addition, as mentioned earlier, the mechanical configuration of the five-axis machining machine tool has a tool rotation mode, a workpiece rotation mode and a hybrid of the two, and the numerical control system must also be able to meet the requirements of different configurations. Finally, in order to achieve high-speed and high-precision five-axis machining, the CNC system should also have a look ahead function and a large buffer storage capacity, so that the motion data can be calculated and processed in advance before the program is executed, and multi-stage buffer storage can be carried out, so as to ensure that the error of the tool is still small when running at high speed. All these requirements will undoubtedly increase the complexity of the CNC system structure and the difficulty of development.

The mechanical structure design and manufacture of three-axis and five-axis machine tools are also more complex and difficult than those of three-axis machine tools.

Because the machine tool needs to add two axis of rotation coordinates, it is necessary to use a table that can tilt and rotate or a spindle head component that can rotate and oscillate. For the two additional components, it is required not only to have a compact structure, but also to have a large enough torque and the sensitivity and precision of the movement, which is obviously much more difficult than the design and manufacture of ordinary three-axis machining machine tools.

The development trend of five-axis machine tools

The first is the linear motor drive technology. After more than ten years of development, linear motor technology has been very mature. The problem of susceptibility to interference and large heat production has been solved, and the positioning technology of linear motor not only stops quickly in high-speed movement, but also some machine tool manufacturers use damping technology to solve it.

The advantages of linear motors are linear drive, no transmission chain, no wear, and no backlash, so they can achieve the best positioning accuracy. Linear motors have high dynamics and can accelerate more than 2 g. The linear motor drive also has the characteristics of high reliability and maintenance-free.

The second is the use of dual-drive technology. For the wider workbench or gantry type, if the intermediate drive is adopted, the driving force can not be guaranteed to be in the center, which is easy to cause tilting, so that the dynamic performance is poor. With dual drivers, dual encoders, and one driver module, the dynamic performance is perfect. One drive command, two drives work at the same time, the grating ruler to detect whether the two points are balanced, if not, through different commands to achieve balance. Of course, the development of five-axis linkage machine tool technology is far more than this, and many technologies will be reflected in DMG’s machine tool products.

The influence of temperature on the machining accuracy of the machine tool

Thermal deformation is one of the reasons that affect the machining accuracy, the machine tool is affected by the change of the ambient temperature of the workshop, the heating of the motor and the friction of mechanical movement, the heat of cutting and the cooling medium, resulting in the uneven temperature rise of each part of the machine tool, resulting in the change of the shape accuracy and machining accuracy of the machine tool. For example, if a 70mm×1650mm screw is machined on a CNC milling machine with ordinary precision, the cumulative error of the milled workpiece from 7:30 a.m. to 9:00 a.m. can vary by up to 85m compared with the workpiece processed from 2:00 p.m. to 3:30 p.m. At constant temperature, the error can be reduced to 40m.

For another example, a precision double-end grinding machine for double-end grinding of 0.6~3.5mm thick thin steel sheet workpieces, processing 200mm×25mm×1.08mm steel sheet workpieces can achieve mm dimensional accuracy, and the bending degree is less than 5m in the full length. However, after continuous automatic grinding for 1 hour, the size change range increased to 12m, and the coolant temperature increased from 17°C at start-up to 45°C. Due to the influence of grinding heat, the spindle journal elongates and the front bearing clearance of the spindle increases. Accordingly, the addition of a 5.5 kW chiller to the machine’s coolant tank was a perfect result.

Practice has proved that the deformation of the machine tool after heating is an important reason affecting the machining accuracy. However, the machine tool is in an environment where the temperature changes everywhere at any time; The machine tool itself will inevitably consume energy when working, and a considerable part of these energy will be converted into heat in various ways, causing physical changes in the components of the machine tool, which are very different because of the different structural forms, the differences in materials and other reasons. Machine tool designers should grasp the formation mechanism of heat and the law of temperature distribution, and take corresponding measures to minimize the impact of thermal deformation on machining accuracy.

Temperature rise and temperature distribution of the machine tool

  1. Natural climate influences

China has a vast territory, most of which is in the subtropics, and the temperature varies greatly throughout the year, and the temperature difference varies differently in one day. As a result, people intervene in different ways and degrees of temperature in the room (e.g. on the shop floor), and the temperature atmosphere around the machine can vary greatly. For example, the seasonal temperature change range in the Yangtze River Delta region is about 45 °C, and the diurnal temperature change is about 5~12 °C. The machining workshop generally has no heating in winter and no air conditioning in summer, but as long as the workshop is well ventilated, the temperature gradient in the machining workshop does not change much. In the Northeast, the seasonal temperature difference can reach 60 °C, and the diurnal variation is about 8~15 °C. The heating period is from late October to early April of the following year, and the design of the machine shop is heated, and the air circulation is insufficient. The temperature difference between the inside and outside of the workshop can reach 50°C. Therefore, the temperature gradient in the workshop in winter is very complex, the outdoor temperature is 1.5 °C when the measurement is timed, the time is 8:15-8:35 in the morning, and the temperature change in the workshop is about 3.5 °C. The machining accuracy of precision machine tools will be greatly affected by the ambient temperature in such a workshop.

  1. The influence of the surrounding environment

The surrounding environment of the machine tool refers to the thermal environment formed by various layouts within the close range of the machine tool. They include the following 4 aspects.

(1) Workshop microclimate: such as the distribution of temperature in the workshop (vertical direction, horizontal direction). When day and night alternate or when the climate and ventilation change, the temperature of the workshop changes slowly.

(2) Workshop heat source: such as sun exposure, heating equipment and high-power lighting radiation, etc., they can directly affect the temperature rise of the whole or part of the machine tool for a long time when they are close to the machine tool. The heat generated by adjacent equipment during operation can affect the temperature rise of the machine in the form of radiation or air movement.

(3) Heat dissipation: the foundation has a good heat dissipation effect, especially the foundation of the precision machine tool should not be close to the underground heating pipeline, once it is ruptured and leaked, it may become a heat source that is difficult to find the cause; An open workshop will be a good “radiator”, which is conducive to the temperature equalization of the workshop.

(4) Constant temperature: It is very effective for the workshop to maintain the accuracy and machining accuracy of precision machine tools by adopting constant temperature facilities, but the energy consumption is large.

  1. Thermal influencing factors inside the machine tool

1) Structural heat source of machine tool. Electric motor heating, such as spindle motors, feed servo motors, cooling and lubrication pump motors, electric control boxes, etc., can generate heat. These conditions are permissible for the motor itself, but have a significant adverse effect on components such as spindles and ball screws, and measures should be taken to isolate them. When the input electric energy drives the motor to run, except for a small part (about 20%), it is converted into the heat energy of the motor, and most of it will be converted into kinetic energy by the moving mechanism, such as spindle rotation, worktable movement, etc.; However, it is inevitable that a considerable part of it is still converted into friction heat during movement, such as the heat generation of bearings, guide rails, ball screws and gearboxes.

2) Cutting heat of the process. In the cutting process, part of the kinetic energy of the tool or workpiece is consumed by the cutting work, and a considerable part is converted into the deformation energy of cutting and the friction heat between the chip and the tool, forming the heating of the tool, the spindle and the workpiece, and the heat of a large number of chips is transmitted to the workbench fixture and other components of the machine tool. They will have a direct impact on the relative position of the tool and the workpiece.

3) Cooling. Cooling is a countermeasure to the temperature increase of the machine tool, such as the cooling of the electric motor, the cooling of the spindle components, and the cooling of the basic structural parts. High-end machine tools often equip the electric control box with a chiller and force cooling.

  1. The influence of the structural form of the machine tool on the temperature rise

In the field of thermal deformation of machine tools, the structural form of machine tools is discussed, usually referring to the structural form, mass distribution, material properties and heat source distribution. The structural shape affects the temperature distribution of the machine tool, the direction of heat conduction, the direction of thermal deformation and matching, etc.

1) The structural form of the machine tool. In terms of overall structure, the machine tool has vertical, horizontal, gantry and cantilever type, etc., and the thermal response and stability are quite different. For example, the temperature rise of the headstock of the lathe with variable gear speed can be as high as 35°C, so that the spindle end is raised, and the thermal equilibrium time is about 2h. In the case of the inclined bed-type precision turning and milling machining center, the machine tool has a stable base. The rigidity of the whole machine is significantly improved, the spindle is driven by a servo motor, and the gear transmission part is removed, and its temperature rise is generally less than 15 °C.

2) The influence of heat source distribution. On machine tools, the heat source is often thought of as an electric motor. Such as spindle motors, feed motors and hydraulic systems, etc., are actually incomplete. The heat generation of the motor is only the energy consumed by the current on the armature impedance when bearing the load, and a considerable part of the energy is consumed by the friction work of the bearing, screw nut and guide rail. Therefore, the motor can be called the primary heat source, and the bearing, nut, guide rail and chips can be called the secondary heat source. Thermal distortion is the result of the combined influence of all these heat sources. The temperature rise and deformation of a column mobile vertical machining center in the Y-direction feed movement. The table does not move during the Y-direction feed, so it has little effect on the thermal deformation in the X-direction. On the column, the farther the point from the guide screw of the Y-axis, the smaller its temperature rise. The effect of heat source distribution on thermal deformation is further illustrated when the machine is moved in the Z-axis. The Z-axis feed is farther away from the X-direction, so the influence of thermal deformation is smaller, and the closer the column is to the Z-axis motor nut, the greater the temperature rise and deformation.

3) The influence of mass distribution. There are three aspects of the influence of mass distribution on the thermal deformation of machine tools. First, it refers to the mass size and concentration, which usually refers to changing the heat capacity and the speed of heat transfer, and changing the time to reach thermal equilibrium; Second, by changing the layout form of the mass, such as the arrangement of various ribs, the thermal stiffness of the structure is improved, and the influence of thermal deformation is reduced or the relative deformation is kept small under the same temperature rise; Third, it refers to changing the form of mass arrangement, such as arranging heat dissipation ribs outside the structure, to reduce the temperature rise of machine tool components.

4) Influence of material properties: Different materials have different thermal performance parameters (specific heat, thermal conductivity and linear expansion coefficient), and under the influence of the same heat, their temperature rise and deformation are different.

Testing of the thermal performance of machine tools

  1. The purpose of the thermal performance test of the machine tool

The key to controlling the thermal deformation of the machine tool is to fully understand the changes in the ambient temperature of the machine tool, the heat source and temperature changes of the machine itself, and the response (deformation displacement) of the key points through the thermal characteristics test. Test data or curves describe the thermal characteristics of a machine tool in order to take countermeasures, control thermal deformation, and improve the machining accuracy and efficiency of the machine tool. Specifically, the following objectives should be achieved:

1) Test the surrounding environment of the machine tool. Measure the temperature environment in the workshop, its spatial temperature gradient, changes in the temperature distribution during the alternation of day and night, and even the influence of seasonal changes on the temperature distribution around the machine tool.

2) Test the thermal characteristics of the machine tool itself. Under the condition of eliminating environmental interference as much as possible, let the machine tool be in various operating states to measure the temperature change and displacement change of the important points of the machine tool itself, record the temperature change and the displacement of key points in a long enough period of time, and also use the infrared thermal phase to record the heat distribution in each time period.

3) Test the temperature rise thermal deformation in the machining process to judge the influence of the thermal deformation of the machine tool on the accuracy of the machining process.

4) The above test can accumulate a large amount of data and curves, which will provide a reliable criterion for the design of machine tools and the control of thermal deformation by users, and point out the direction of effective measures.

  1. The principle of thermal deformation test of machine tools

Thermal deflection testing begins with the measurement of temperature at several relevant points, including the following:

1) Heat source: including feed motor, spindle motor, ball screw transmission pair, guide rail, spindle bearing.

2) Auxiliary devices: including hydraulic system, refrigerator, cooling and lubrication displacement detection system.

3) Mechanical structure: including bed, base, slide plate, column, milling head box and spindle. An indium steel probe is held between the spindle and the rotary table, and five contact sensors are configured in the X, Y, and Z directions to measure the comprehensive deformation in various states to simulate the relative displacement between the tool and the workpiece.

  1. Test data processing and analysis

The thermal deformation test of the machine tool should be carried out in a long continuous time, continuous data recording, and after analysis and processing, the thermal deformation characteristics reflected are highly reliable. If error culling is carried out through multiple trials, the regularity shown is credible.

A total of 5 measuring points are set up in the thermal deformation test of the spindle system, among which points 1 and 2 are at the end of the spindle and close to the spindle bearing, and points 4 and 5 are respectively at the milling head housing near the Z guide rail. The test time lasted for 14 hours, of which the spindle speed in the first 10 hours was alternately changed in the range of 0~9000r/min, and from the 10th hour, the spindle continued to rotate at a high speed of 9000r/min. The following conclusions can be drawn:

1) The thermal equilibrium time of the spindle is about 1h, and the temperature rise after equilibrium changes in the range of 1.5°C;

2) The temperature rise mainly comes from the spindle bearing and the spindle motor, and the thermal performance of the bearing is good in the normal speed range;

3) The effect of thermal deformation in the X direction is very small;

4) The Z-direction expansion and contraction deformation is large, about 10m, which is caused by the thermal elongation of the spindle and the increase of the bearing clearance;

5) When the speed continues at 9000r/min, the temperature rise rises sharply, rises sharply about 7°C within 2.5h, and there is a tendency to continue to rise, and the deformation in the Y and Z directions reaches 29m and 37m, indicating that the spindle can not run stably when the speed is 9000r/min, but it can run in a short time (20min).

Control of thermal deformation of machine tools

From the above analysis and discussion, the temperature rise and thermal deformation of the machine tool have a variety of influencing factors on the machining accuracy, when taking control measures, the main contradiction should be grasped, and one or two measures should be taken to achieve twice the result with half the effort. In the design, we should start from four directions: reduce heat generation, reduce temperature rise, balance structure, and reasonable cooling.  

  1. Reduce fever

Controlling the heat source is a fundamental measure. In the design, measures should be taken to effectively reduce the heat generation of the heat source.

1) Reasonably select the rated power of the motor. The output power P of the motor is equal to the product of voltage V and current I, in general, the voltage V is constant, therefore, the increase of load, means that the output power of the motor increases, that is, the corresponding current I also increases, then the heat dissipated in the armature impedance increases. If the motor we designed and selected works close to or greatly exceeds the rated power for a long time, the temperature rise of the motor will increase significantly. To this end, a comparative test was carried out on the milling head of BK50 CNC needle groove milling machine (motor speed: 960r/min; Ambient temperature: 12°C).

The following concepts are obtained from the above test: from the heat source performance consideration, whether the spindle motor or the feed motor, when selecting the rated power, it is best to choose about 25% greater than the calculated power, in the actual operation, the output power of the motor matches the load, and the impact of increasing the rated power of the motor on energy consumption is very small. However, it can effectively reduce the temperature rise of the motor.

2) Appropriate measures should be taken to reduce the heat generation of the secondary heat source and reduce the temperature rise. For example, when designing the spindle structure, the coaxiality of the front and rear bearings should be improved, and high-precision bearings should be used. Where possible, change the sliding guide to a linear rolling guide, or use a linear motor. These new technologies can effectively reduce friction, reduce heat generation, and reduce temperature rise. Metal processing WeChat, the content is good, it is worth paying attention to!

3) In terms of process, high-speed cutting is adopted. Based on the mechanism of high-speed cutting. When the linear velocity of metal cutting is higher than a certain range, the metal to be cut has no time to produce plastic deformation, no deformation heat is generated on the chip, and most of the cutting energy is converted into chip kinetic energy and is taken away.

  1. Structural balance to reduce thermal deformation

In machine tools, where the heat source is always present, further attention needs to be paid to how the direction and speed of heat transfer can help reduce heat distortion. Or the structure has good symmetry, so that the heat transfer is along the symmetrical direction, so that the temperature distribution is uniform, and the deformation cancels each other out, becoming a thermal affinity structure.

1) Prestress and thermal deformation. In the higher-speed feed system, the ball screw is often fixed axially at both ends to form a pre-tensile stress. This structure has an obvious effect on reducing the thermal deformation error in addition to improving the dynamic and static stability of high-speed feed.

The axial fixed structure with a total length of 600 mm pre-stretched for 35 m is relatively close to the temperature rise under different feed rates. The cumulative error of the fixed pre-tensioned structure at both ends is significantly smaller than that of the structure with a single end fixed and the free elongation of the other end. In the axially fixed pre-tension structure at both ends, the temperature rise caused by heat generation mainly changes the stress state inside the screw from tensile stress to zero stress or compressive stress. Therefore, it has little effect on the displacement accuracy.

2) Change the structure and change the direction of thermal deformation. The Z-axis spindle slide of the CNC needle groove milling machine with different ball screw axial fixed structures requires a milling groove depth error of 5m in the machining. The axial floating structure at the lower end of the lead screw is adopted, and the groove depth is gradually deepened from 0 to 0.045mm within 2 hours of processing. On the contrary, the structure of floating at the upper end of the lead screw can ensure that the groove depth changes.

3) The symmetry of the geometry of the machine tool structure can make the thermal deformation trend consistent, so that the drift of the tool tip point can be reduced as much as possible. For example, the YMC430 micromachining center launched by Yasda Precision Tools in Japan is a sub-micron high-speed machining machine, and the design of the machine tool is fully considered for thermal performance.

First of all, a completely symmetrical layout is adopted in the structure of the machine tool, and the column and beam are integrated structures, which are H-shaped, which is equivalent to a double column structure and has good symmetry. The approximately circular spindle slides are also symmetrical both longitudinally and transversely.

The feed drive of the three moving axes adopts linear motors, which makes it easier to achieve symmetry in the structure, and the two rotary axes are directly driven to minimize the friction loss of mechanical transmission.

  1. Reasonable cooling measures

1) The influence of coolant in machining on machining accuracy is direct. A comparative test was carried out on the GRV450C-type double-end grinding machine. The test shows that the heat exchange treatment of the coolant with the help of the refrigerator is very effective in improving the machining accuracy.

With the traditional coolant supply method, after 30 minutes, the size of the workpiece is out of tolerance. After using the refrigerator, it can be processed normally to more than 70min. The main reason for the deviation of the workpiece size at 80 minutes is that the grinding wheel needs to be trimmed (to remove metal chips on the grinding wheel face), and the original machining accuracy can be restored immediately after trimming. The effect is very noticeable. Similarly, very good results can be expected for forced cooling of the spindle.

2) Increase the natural cooling area. For example, adding a natural air cooling area to the spindle box structure can also have a good heat dissipation effect in the workshop with good air circulation.

3) Automatic chip removal in time. Timely or real-time evacuation of high-temperature chips out of the workpiece, table and tool section will be very beneficial in reducing the temperature rise and thermal distortion of critical parts. 

Vision & Vision

Controlling the thermal deformation of machine tools is an important topic in the field of modern precision machining, and the factors affecting the thermal deformation of machine tools are very complex. In addition, the simultaneous development of high speed, high efficiency and precision in modern cutting makes the thermal deformation problem of machine tools more prominent. It has attracted wide attention from the machine tool manufacturing community. Scholars in the machine tool industry at home and abroad have done a lot of research on this and have made considerable progress in theory. The problem of thermal deformation of machine tools has become one of the basic theories in machine tool research.

From the perspective of machine tool design and application, this paper analyzes the influencing factors, measurement and analysis methods of machine tool thermal performance, and proposes improvement design measures. Therefore, we believe that the optimal design of the thermal performance of the machine tool should start from the following aspects:

1) In the design stage of modern high-end machine tools, attention should be paid to the environmental conditions of the future application of the designed machine tools.

2) Controlling and configuring the heat source is key. Controlling the heat source mainly refers to the matching of the control energy consumption and the power source, adopting a new structure, reducing the secondary friction heat source, and improving the utilization rate of energy.  

3) Change the traditional thinking, and promote the cooling, heat dissipation, lubrication, chip removal and other devices from the status of “auxiliary” components of the machine tool to the status of “important” components, which cannot be underestimated.

4) Pay attention to the symmetry of the structure and the design of the direction of thermal deformation, so that the influence of thermal deformation on the accuracy is minimized, especially the research and application of the mathematical model of thermal deformation of structural parts, so as to provide qualitative and quantitative instructions for the design of thermal deformation control. 

Advantages of 5-axis linkage machines

The so-called five-axis machining here refers to the fact that there are at least five coordinate axes (three linear coordinates and two rotary coordinates) on a machine tool, and the simultaneous coordinated movement can be processed under the control of the computer numerical control (CNC) system. Compared with the general three-axis linkage CNC machining, such five-axis linkage CNC machining has the following advantages:

1. It can process continuous and smooth free-form surfaces that cannot be processed by general three-axis CNC machine tools or are difficult to be processed in one clamping. For example, the blades of aero engines and steam turbines, the screw thrusters used in ships, and many shells and molds with special curved surfaces and complex cavities and hole positions, such as ordinary three-axis CNC machine tools, because the attitude angle of the tool relative to the workpiece cannot be changed in the processing process, when machining some complex freeform surfaces, there may be interference or underprocessing (that is, it cannot be processed). When processing with a five-axis linkage machine tool, the attitude angle of the tool/workpiece can be adjusted at any time during the machining process, the interference of the tool workpiece can be avoided and all the processing can be completed in one clamping;

2.it can improve the machining accuracy, quality and efficiency of spatial freeform surfaces. For example, when the three-axis machine tool processes a complex curved surface, the ball nose milling cutter is mostly adopted, and the ball nose milling cutter is formed by point contact, and the cutting efficiency is low, and the attitude angle of the cutter/workpiece can not be adjusted in the machining process, and it is generally difficult to ensure that the best cutting point on the ball nose milling cutter (i.e., the highest point of the ball head line speed) is used to cut, and it is possible that the cutting point falls on the rotation center line that the ball nose cutter line speed is equal to zero, as shown at the tool position a shown in Figure 1. In this case, not only is the cutting efficiency extremely low, the quality of the machined surface deteriorates severely, but also manual repair is often required, so accuracy may be lost. If the five-axis machine tool is used, because the attitude angle of the tool/workpiece can be adjusted at any time, not only can this situation be avoided, but also the best cutting point of the tool can be fully used to cut at all times, or the spiral end mill of line contact forming can be used to replace the ball nose milling cutter of point contact forming, and even milling can be carried out by further optimizing the attitude angle of the tool/workpiece, so as to obtain higher cutting speed, cutting line width, that is, to obtain higher cutting efficiency and better machining surface quality, Figure 3 shows an example comparing the effects of milling the same freeform surface at a constant pose angle with an optimized pose angle. It is not difficult to see that the surface roughness of the blade milled by the constant attitude angle (Sturz method) is one level lower than that of the blade milled by the optimized attitude angle (P milling method – Starrag’s patent), and the time taken by the former is 30%~130% more than that of the latter;
Average Ra value for surface quality grades
N8 1.6-3.2μm
N7 0.8-1.6μm
N6 0.4-0.8μm
N5 0.2-0.4μm

3. In line with the development direction of machine tools that can complete all or most of the processing of the workpiece in one clamping. Because with the development of science and technology and the improvement of people’s material living standards, people’s requirements for product performance and quality are also higher, and the forms are more diversified and personalized. In order to further improve the performance and quality of products, fully meet the user’s requirements, such as energy saving, material saving, lightweight, beautiful, comfortable, etc., modern products, not only aviation, aerospace products and vehicles (such as cars, ships, ships, etc.), but also include precision instruments, meters, medical, sports equipment, as well as household, office appliances and children’s toys and other product parts, are more and more made of the overall material milling, and it also contains many kinds of complex surfaces and oblique holes, inclined planes, etc. These parts, such as those machined with conventional machine tools or three-axis CNC machines, must be completed with multiple machine tools and multiple positioning installations. In this way, not only the equipment investment is large, the production area is occupied, the production and processing cycle is long, and the accuracy and quality are difficult to guarantee. In order to solve these problems, it is necessary to develop machine tools that can concentrate on the process for high-precision, high-efficiency and composite processing, in order to achieve all or most of the processing of the workpiece in one clamping. This has become a major trend in the development of machine tools today, and five-axis machine tools equipped with high-speed machining capabilities are fully in line with this development and may be the best solution. Because it not only has the main functions required by modern production and processing equipment, but also the ergonomics of a five-axis machine tool is about equivalent to two three-axis machining machines, and even more machine tools can be dispensed with.

4. the advantages of mold processing.
In traditional mold processing, vertical machining centers are generally used to complete the milling of workpieces. With the continuous development of mold manufacturing technology, some weaknesses of the vertical machining center itself are becoming more and more obvious. Modern mold processing generally uses ball nose milling cutter to process, ball nose milling cutter brings benefits in mold processing is very obvious, but if you use vertical machining center, the linear speed of its bottom surface is zero, so that the finish of the bottom surface is very poor, if you use four-axis and five-axis linkage machine tool processing technology to process mold, you can overcome the above shortcomings.
The clamping of workpieces is made easy due to the use of a five-axis simultaneous machine (fig. 1). There is no need for special fixtures during processing, which reduces the cost of fixtures, avoids multiple clamping, and improves the machining accuracy of molds. The use of 5-axis technology to machine the mold can reduce the number of fixtures used. In addition, the five-axis simultaneous machine tool can eliminate many special tools in machining, so the tool cost is reduced. Five-axis linkage machine tools can increase the effective cutting edge length of the tool, reduce the cutting force (Fig. 2), improve the service life of the tool, and reduce the cost. The use of five-axis linkage machine tool processing mold can quickly complete mold processing, fast delivery, better ensure the processing quality of the mold, make the mold processing easier, and make the mold modification easy.

Rationalization of milling cutter selection

1. Reasonable choice of milling tool applications with different tooth counts

Sparse-tooth milling cutters are unequal-pitch milling cutters. Because of the wide chip-bearing groove, they are suitable for milling long-chip metals such as stainless steel and aluminum alloy; and because the milling cutter has a small number of teeth milling metal at the same time, the cutting force generated is small, which is suitable for low-power spindle machine tools or workpieces with weak workpiece clamping.

Dense-tooth milling cutters are milling cutters with moderate number of teeth and have a wide range of versatility. They are usually recommended as the first choice.When the milling cutting force is required to be small, the method of reducing the number of blades is usually adopted, but the adjacent positions must be removed evenly.

Special dense tooth milling cutters are used in machine tools with sufficient spindle power. When the workpiece is clamped enough, the high-efficiency metal removal rate of large cutting depth and large tool walking can be obtained.It is also suitable for milling metals such as gray cast iron that require low chip capacity.

2. Reasonable choice of tool diameter

The choice of milling cutter diameter is usually based on the width of the workpiece and the effective power of the machine tool. By convention, the diameter of the milling cutter is selected according to the size of the workpiece, especially the milling width of the workpiece, but for a given face milling cutter, its optimal milling width is 70-80% of the nominal diameter of the milling cutter.So that the milling width is approximately equal to 2/3 of the diameter of the milling cutter, it can ensure that the blade cuts into the workpiece immediately from the beginning, with almost no friction. The milling width is less than 1/2 of the diameter of the milling cutter, and the blade begins to “rub” the workpiece. During rough milling, if the radial cutting width is less than 2/3 of the diameter of the milling cutter, the amount of tool travel will be increased, and the tool life will be improved.

3. Reasonable choice of the main declination angle of the tool

The main declination angle is the angle formed by the tool body and the front edge of the blade. The main declination angle will affect the chip thickness, cutting force and tool life. If the main declination angle is reduced at a given feed rate, the cutting thickness will be reduced. This is due to the fact that the cutting edge contacts the workpiece in a wider range. Reducing the main declination angle allows the blade to gradually cut into or exit the surface of the workpiece, which helps to reduce the radial pressure, protect the cutting edge of the blade, and reduce the chance of damage to the cutting edge, but its negative impact is that it will lead to an increase in axial pressure, which increases the possibility of vibration when machining thin-section workpieces and causes deviations on the machining surface.

Fourth, the reasonable choice of milling blades

It is best to use pressed blades for roughing, which can reduce processing costs.The dimensional accuracy and sharpness of the pressed blade are worse than that of the ground blade, but the edge strength of the pressed blade is better, it is resistant to impact during roughing and can withstand a larger depth of cut and feed.Sometimes the pressed blade has a chip rolling groove on the front tool surface, which can reduce the cutting force, but also reduce the friction with the workpiece and chips, and reduce the power requirement.However, the surface of the pressed blade is not as tight as that of the ground blade, the dimensional accuracy is poor, and the height of each tip on the milling cutter body differs a lot.Because the pressing blade is cheap, it is widely used in production.

For precision milling, it is best to choose a grinding blade.This kind of blade has good dimensional accuracy, so the positioning accuracy of the blade in milling is high, and good machining accuracy and surface roughness can be obtained.In addition, the development trend of grinding and milling blades used in finishing is to grind out the chip rolling groove to form a large positive front angle cutting edge, allowing the blade to cut on a small feed and a small depth of cut.For cemented carbide blades without sharp front corners, when small-feed and small-cut deep processing is used, the tip of the blade will rub against the workpiece and the tool life is short.

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