Thermal Error Analysis and compensation of CNC Dry Gear Cutting Machine Tool (Hobbing/Grinding/Milling) Considering the Thermal Deformation of the Workpiece文献综述

文献综述

Abstract: The need for high-precision machine tools is rising as the machine manufacturing sector develops. High-precision machine tools give not just improved accuracy, but also a higher removal rate than traditional machine tools. High-precision gears are critical for high equipment performance, service life, and durability, such as military machinery and CNC machine tools. For any dry gear hobbing machines, accurate quantification of real-time thermal error is the basis for effective compensation of this kind of manufacturing error in large-volume gear production. Temperature of hobbed workpiece is relatively high, which will lead to the increase of dimension errors, which demonstrates that workpiece thermal deformation has a great Influence on tooth thickness errors in dry hobbing. Computer numerical control (CNC) hobbing machines is on the purpose of obtaining the law of thermal deformation of gear hobbing machines to improve machining precision. According to the structure characteristics of hobbing machines, it is a critical work for the dry hobbing system to reduce and control the thermal impact. Even new hobbing machine tool structure with high thermal stability such as double stand columns was designed to substitute the traditional structure; some new structures, such as air extraction and filtration device, air-cooling component, and magnetic chip conveyor, would affect the thermal energy accumulation of dry hobbing machine tool. The workpiece thermal deformation error compensation model is obtained based on the prediction model of hobbed workpiece temperature. The biggest factor causing the dimensional error of the workpiece. In dry hobbing, the thermal deformation of the workpiece will increase the dimensional error of the workpiece this is caused by thermal deformation. The thermal deformation of workpiece lead to the variation of workpiece parameters.Keywords: Thermal errors. CNC machine tools, Dry hobbing. Workpiece thermal deformation.Introduction: Gear cutting is now the most common method of manufacture for mass-producing gears, particularly automotive gears. Assuming that the average number of cutting processed gears is 15, each vehicle Claudin C, Rech J et al. [1], with 86 million vehicles manufactured in 2014. Per year, 1290 million vehicle gears were manufactured through advanced gear cutting method. Advanced gear cutting is a large-scale industrial manufacturing process. On the other hand, wet gear cutting is a 3commonly used technique. This method, which uses a lot of metal cutting fluid, results in polluting the environment and putting workers health at danger. Dry cutting has been accessible in recent years, and it is expected to swiftly replace wet cutting in the future because to its high efficiency and environmental friendliness. The most significant contributors of machine tool errors, according to Bryan J et al. [2], are thermal errors, which constitute about 4070% of overall machine tool flaws. With the advancement of industry, the demand for processing precision has increased. Recent research on machine tool thermal errors has focused on precision machining (Guo Q et al., Han J et al., Li Y et al., Zhao W et al.,) [35], but few of them examine workpiece thermal deformation when it comes to cutting machine tools (Wang S et al., Yang Y et al., Li X et al., Zhou J et al., Kang L et al.)[6] Because cutting is a semi-finishing process, and because wet cutting uses a metal cutting fluid with high cooling and lubricating properties, the temperature change of the workpiece is too small to impair workpiece precision. More friction and adhesion in dry hobbing, between hob and workpiece will be subjected to higher temperatures. And without metalworking fluid, cutting heat Chip, hob and workpiece are relatively high (Cao H et al., Zhu L et al., Li X et al., Chen P et al., Chen Y et al.,) [7], Which one lead to thermal energy accumulation and temperature rise machine parts. In order to reduce and control thermal shock of dry gear hobbing of new gear hobbing machine tool a structure with high thermal stability, such as double support column, is designed to replace the traditional structure. However, in dry hobbing, the worse the cooling conditions are Weinert K et al., [8] make the temperature of machine parts sensitive to temperature relevant parameters and ambient temperature. in addition some new structures, such as air extraction and filtration devices, Air cooled parts and magnetic chip conveyor will affect the thermal energy accumulation of dry hobbing machine the tool has no thermal control model, which is used to calculate and optimize the thermal energy accumulation value related parameters, it is difficult to make the temperature dry hobbing machine parts are constant, which will cause poor machining accuracy [910], decrease of hob life, The increased temperature of workpiece usually enlarge workpiece size error and tooth profile error, especially for gears with small aspect ratio. In the actual production of dry gear hobbing, the ambient temperature is unstable the state of the machine tool will lead to the poor temperature consistency of the hobbing workpiece, which will make the tooth surface the thickness of some hobbing workpieces cannot meet the design requirements. There are usually three ways to reduce thermal errors: Thermal error avoidance, thermal error control 4and thermal error compensation (Wu CW et al., Tang CH et al., Chang CF et al., Shiao YS et al., 2012)[11].Compared with thermal error avoidance and thermal error control, thermal error compensation this technology is relatively cost-effective (Li Y et al., Zhao W et al., 2012) [12]. External equipment for mass production gear, considering the thermal deformation of the workpiece. The compensation model is divided into two parts: workpiece compensation thermal deformation error compensation model and device tool thermal error compensation model. The relationship between the two the temperature and thermal deformation error of hobbing workpiece are analyzed.Research status Home and Abroad: The metalworking industry is one of the leading industries in the world because it plays a vital role in the economy as a whole, supporting the economy as a whole through its products machinery, industrial and technical equipment, machine tools, knives, parts and materials and promoting the development of other industries and economic sectors. It has the highest value in the gross industrial product (35-45% in developed countries) covers more than 30% of the worlds industrial workforce. Nowadays, there are increasing demands on environmentally friendly manufacturing around the world, as well as requirements for improved metals/materials. This creates new challenges for machining operations and places higher demands on high-performance tools. Both are known as environmentally friendly (Bhokse et al., 2015), [14]. It refers to a sustainable production that does not represent a threat to future generations and does not come at the expense of future generations. Cleaner production does not necessarily mean increased financial investment. The goal is to reduce environmental pollution in the manufacturing process, including those generated by cooling/lubrication using coolants and emulsions (Krolczyk et al., 2016) [15]. Greg Landgrafetel. in his article (Landgraf, 2004) describes some of the advantages of dry cutting as follows: no water and atmospheric pollution; the solid waste generated is easier to recycle in the form of fragments, can be sold at a higher price without additional metalworking fluid cleaning costs; and there is no danger to operator health; Considering that the cost of using the coolant is estimated at 16% of the total cost of machining, dry cutting is economical (Sharma et al., 2016) [16]. This cost is estimated at 16-20%), which is about 3-4 times the cost of the tool; for high-speed machining, less cutting force is required to use dry cutting; in intermittent cutting (such as milling), dry machining is suitable because it can increase the life of the tool. On the other hand, Neil Canter (2009)[17] in his article describes some of the advantages of dry cutting, similar to the above advantages, but also some of the limitations of this 5kind of machining, as follows: some companies show that the cost of maintaining and handling metal working fluids is much lower than 16% of the companys total manufacturing costs; without the use of coolant, surface finish and tool life are severely affected, Because a lot of heat and friction is generated during cutting, this fact can significantly increase manufacturing costs and reduce productivity; not all machining operations are suitable for dry cutting; and some metal alloys that are cut are easier to dry machine than others. (Graham et al., 2003 ;) [18] Highlights the advantages of dry cutting under highspeed machining conditions and demonstrates the overcoming of dry cutting limitations as research in the field evolves. As a result, the increasing demand for hard machining and high-speed machining in general, especially under dry cutting conditions, has led many researchers to devote themselves to the development of manufacturing processes to obtain good surface finishes and part accuracy, low energy consumption and maintain long tool life reducing the impact of industrial activity on environment and health. Chongqing Machine Tool (Group) Co., Ltd., Chongqing 400055, China. [7]Gear hobbing is the leading manufacturing technology for mass production of gears, especially for automobile gears. However, the widely used wet gear hobbing process, which consumes lots of metalworking fluids, leads to environmental pollution and healthy risk of workers. In recent years, dry hobbing becomes available. And it would replace wet hobbing in the coming future quickly, due to its high efficiency and environmental friendliness. Dry hobbing, the thermal deformation of workpiece lead to the variation of workpiece parameters. The following parameters are mainly affected by workpiece thermal deformation: tooth profile, tip diameter, root diameter, face width, etc. The thermal deformation of tooth profile will deteriorate the machining precision of next process, shaving or grinding, if the tooth thickness cannot meet the design requirements. So, the purpose of compensating workpiece thermal deformation errors is to make sure that tooth thickness value of hobbed workpiece is larger than the minimum design requirements. According to the character of hobbing, temperature of points on the same cylinder of hobbed workpiece are approximately equal.The development status of dry gear hobbing process:In recent years, environmental safety requirements have been set around the world, and many companies. As part of this effort, coolant-free metal cutting methods have been developed and implemented in factories not only to improve the working environment but also to protect the environment. However, for turning and milling machines, few complete dry cutting machines operate completely without 6coolant, while others switch from wet machining to MQL (Minimum Lubrication). Against this background, the shift to completely dry cutting machines is progressing in the field of gear cutting, especially hobbing. For hobbing applications, dry cutting methods using carbide Hobbs have been proposed, but they have not been widely accepted because the problem of tool chipping has not been solved. Later, due to improvements in surface treatment technology, high-speed steel coated hobbing machines and dry-cut hobbing machines were introduced, and the dry hobbing machines for gears developed rapidly. Dry cutting is the development direction of machining. Just two decades ago, cutting fluid was very cheap, accounting for less than 3% of the cost of most machining processes. To overcome shaving as the traditional soft-finishing method, new tool concepts are presented that aim to increase the process performance regarding tool life and workpiece quality. In dry cutting, enhanced heating of workpieces, tools and machines leads to thermoelastic deformation, which in turn leads to dimensional deviations as well as the geometric deviations of the machined parts. The workpiece is heated for a complete process sequentially to analyze, reduce, and compensate for thermoelastic deformation. Aiming at this problem, the multi-scale simulation method is verified temperature and the resulting longitudinal deformation of the workpiece. Thermal stability prediction in future work, deformations of radial dimensions will require additional verification through improved experiments and model features.Recent trends in gear production: As mentioned above, gear tooth finishing is based on Deformation due to heat treatment is expected usually before the heat treatment process. This However, recent stringent requirements for higher accuracy, Tips for processes such as gear grinding and honing Happens more often after finishing gear heat treatment. Due to sophisticated processing technology For example, shaving teeth has not taken root yet overseas, dry gear hobbing environmentally friendly and costeffective. Arrive to this end, Mitsubishi Heavy Industries developed the worlds first dry gear cutting system. More specifically, developing knives protected by Super Dry Coating and gear hobbing machines suitable for dry cutting are realized dry hobbing. Use dry cutting. During hob cutting, the hob tip reaches high temperatures cause it to wear out quickly. Hob Improved tools protected by Super Dry coating heat strength. Since this makes cutting Speed increased from traditional 100 to 120m-min-1 up to 200 m-min-1 simultaneous suppression tool nose wear doubles tool life and productivity greatly improved. It refers to a sustainable production that does not represent a threat to future generations and does not come at the expense of future generations. Cleaner production does not necessarily mean 8increased financial investment. The goal is to reduce environmental pollution in the manufacturing process, including those generated by cooling/lubrication using coolants and emulsions. The heat flux into the workpiece the change of internal heat energy inside a control volume was evaluated below the cutting edge. Workpiece deformation by the simulation the chip formation by a thermomechanical finite element analysis. Thermomechanical energy conversion of the cutting process and to calculate the heat flux that is entering the workpiece. Process heat input, heat exchange with the environment and calculated heat and temperature thermoelastic deformation of the workpiece. Gear hobbing is one of the most productive processes for dry gears. The quality of the gear depends tool quality, workpiece accuracy, The quality of machined gears results of the accuracy of the tool, workpiece as well as kinematic errors of the hobbing machine.References:1. Claudin C, Rech J (2009) Development of a new rapid characterization method of hobs wear resistance in gear manufactur ingapplication to the evaluation of various cutting edge preparations in high speed dry gear hobbing. J Mater Process Technol 209(11):51525160. doi:10.1016/j.jmatprotec.2009. 02.0142. Bryan J (1990) International status of thermal error research. CIRP Ann Manuf Technol 39(2):645656. doi:10.1016/S0007 8506(07) 63001-73. 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