DISPOSITIVO REFRIGERADO INTERNAMENTE PARA FIXAÇÃO DE PEÇAS EM RETIFICADORAS CILÍNDRICAS

Abstract

This invention relates to a device for fixing disc-shaped and similar parts, applied to cylindrical grinding, which allows the circulation of coolant or cooling fluid within the system, capable of reducing the temperature of the workpiece during grinding. The abrasive machining process is characterized by the removal of material through abrasive grains, generating high machining temperatures that damage the workpiece and the cutting tool. The application of cutting fluids, in turn, minimizes the machining temperature, but on the other hand generates high costs regarding disposal and labor liabilities. Thus, this invention allows the application of fluids preferably at low temperatures through a closed system, eliminating waste and reducing costs compared to the application of conventional fluids.Its constituent is based on a system for fastening disc-type parts and similar components, along with a fluid circulation system that allows rotation and perfect sealing during its application. The equipment and its use are claimed.

Description

"INTERNALLY COOLED DEVICE FOR FIXING PARTS IN CYLINDRICAL GRINDING MACHINES"

[001] The present invention relates to a device for fixing disc-shaped and similar parts, applied to cylindrical grinding, which allows the circulation of coolant or cooling fluid within the system, capable of reducing the temperature of the workpiece during grinding. The abrasive machining process is characterized by the removal of material through abrasive grains, generating high machining temperatures, which damage the workpiece and the cutting tool. The application of cutting fluids, in turn, minimizes the machining temperature, but on the other hand generates high costs regarding disposal and labor liabilities. Thus, the present invention allows the application of fluids preferably at low temperatures through a closed system, eliminating waste and reducing costs compared to the application of conventional fluids.Its design is based on a system for securing disc-type parts and similar components, along with a fluid circulation system that allows for rotation and a perfect seal during application. State of the art

[002] Grinding is the most widely used abrasive machining process in industry today. This abrasive method is characterized by the contact of numerous abrasive grains with the surface of the workpiece, simultaneously removing material in the form of chips. In this way, the large number of deformations and shears during chip formation releases a quantity Petition 870200158403, dated 12 / 17 / 2020, page 14 / 41 -2 / 15 substantial heat, which in turn increases the temperature in the contact zone between the workpiece and the tool (grinding wheel). Thus, upon reaching a high temperature, both the workpiece and the grinding wheel suffer damage. The workpiece under excessive temperature may undergo expansion and deformation on its surface, producing dimensional errors, which goes against the role of the grinding process as a finishing and precise adjustment process. In addition, intense heat causes significant microstructural changes in the workpiece material, altering its mechanical properties and reducing its performance, which reduces the safety and quality of the ground material. Furthermore, the mechanical resistance of the abrasive grains themselves and the bonding agent that fixes these grains is also reduced. This decrease in the resistance of the grinding wheel components causes premature wear of the tool and reduces the final quality of the workpiece, directly harming the product and the cost of the process.Therefore, temperature is a major bottleneck for grinding, given that the industry demands high quality parts produced in conjunction with high productivity, which forces production methods to develop and improve cooling methods in machining.

[003] At the beginning of the 20th century, water was used to cool machining processes, which increased productivity and the quality of manufactured parts. However, water causes oxidation in both parts and machines, harming the entire production chain. Thus, tests led to the development of oil-in-water emulsions as a more efficient cooling method, which sufficiently mitigates oxidation and achieves the desired lower cutting temperature. However, the use of oil in cutting fluids, regardless Petition 870200158403, dated 12 / 17 / 2020, page 15 / 41 -3 / 15 of its mineral, semi-synthetic or synthetic composition causes damage to the health of the machine operator and people nearby who come into contact with or inhale the cutting fluid. Furthermore, its components are extremely harmful to the environment, which prompts international bodies to create increasingly stringent legislation on the disposal of cutting fluids, forcing the industry to pay a high cost for the proper disposal of these fluids.

[004] In view of the foregoing, research carried out in the main patent databases demonstrates the innovative nature of the present invention. Patent CN102470506B deals with a device for quick clamping of parts subjected to cylindrical grinding, consisting of a fixed part and another controlled by a servo motor. This invention differs from the present proposal by not containing a fluid circulation system inside. Another patent dealing with a workpiece holder for grinding is presented in JP2009214276A, which proposes a system that allows for the reduction of the workpiece change time on the machine tool, providing less production time. Another patent presenting a workpiece holder system is seen in US20030232584A1, conceived as an automatic actuation system, also aiming at reducing machining time.Regarding lubrication-cooling systems, US patent 3594953 presents a system for applying cutting fluids for thread grinding, consisting of several nozzles positioned in distinct regions. Internal cooling is seen in patent WO2015006846. In this patent, the authors propose a fluid circulation system with a phase change in the gate. Petition 870200158403, dated 12 / 17 / 2020, page 16 / 41 -4 / 15 tools applied to turning, thus allowing fluid circulation in a closed system without fluid loss.

[005] As seen, only patent WO2015006846 presents an internal fluid circulation system. However, the system is applied to the cooling of the tool holder, and not the workpiece, as proposed in the present invention, and is also applied to the turning process, as opposed to the cylindrical grinding process presented here. Patents CN102470506B, JP2009214276A, US20030232584A1 and US3594953 present techniques focused only on workpiece clamping systems and external lubrication, contrary to the innovative idea of ​​internal cooling presented here. In this way, cutting fluid or some environmentally friendly fluid can be applied circulating through the device, requiring less maintenance and less risk to people's health, which reduces operating costs and increases its efficiency compared to external cooling on the workpiece.Furthermore, it is possible to apply nanofluids and cryogenic fluids that have high cooling power capable of significantly increasing heat conduction through the workpiece, drastically reducing the temperature in the cutting zone. Thus, with the use of this proposed device, the chances of thermal damage and shape deviations in the ground workpiece are mitigated. In this sense, it is possible to reduce the amount of coolant poured onto the cutting zone during machining.

[006] Therefore, the internally cooled device for fixing parts in cylindrical grinding machines is unique and innovative, incorporating in its use a strong trend towards increasing grinding efficiency along with preserving the environment, in addition Petition 870200158403, dated 12 / 17 / 2020, page 17 / 41 -5 / 15 of the cost reduction in refrigeration processes. Therefore, the proposed device can contribute to both industry and society. ADVANTAGES OF THE INVENTION

[007] The proposed invention proves to be a provider of important improvements in its area of ​​application, namely:

[008] Reduction of temperature by the device in the workpiece-grinding wheel contact region and, mainly, of the entire workpiece. This is possible through the greater thermal conduction caused by the temperature difference between the surface of the heated workpiece and the cooled workpiece support.

[009] Increased productivity, given the possibility of increasing input parameters, such as material removal rate, due to the lower cutting temperature provided by the device, which reduces manufacturing time.

[010] Reduction of thermal damage to the workpiece, since the greater heat removal during grinding reduces microstructural changes in the material. Thus, burning and variations in hardness and mechanical strength are mitigated.

[011] Reduction of surface distortions, as the part will undergo less thermal expansion during grinding, which increases the precision and uniformity of chip removal. In this way, the amount of rework and parts outside geometric tolerances is reduced, which generates savings in time and money for the industry. Petition 870200158403, dated 12 / 17 / 2020, page 18 / 41 -6 / 15

[012] Reduction of grinding wheel wear, given that the mechanical resistance of the bond and abrasive grains is directly proportional to the temperature to which they are subjected. The described device reduces the temperature of the workpiece-grinding wheel contact and, consequently, the abrasive grain and the bond will withstand greater stresses, reducing their wear.

[013] Reduction in the amount of cutting fluids needed for cooling the grinding process, due to the lower cutting temperature provided by the device. In this way, the cost required for purchasing, storing, maintaining and disposing of the fluids will be drastically reduced. In addition, the impact on the environment and the health of people in contact with the process will be significantly reduced by the lower use of cutting fluids.

[014] Increased applicability of alternative cutting fluid and environmentally friendly methods, such as minimum quantity lubrication (MQL), whose use is restricted depending on the cutting temperature. Thus, the industrial and social gains are notable, in addition to enabling the improvement of these promising alternative techniques.

[015] To enable dry grinding in some cases, since the heat removal from the workpiece by the device may be sufficient to avoid significant microstructural changes in the workpiece. In addition, it would be advantageous to adjust the material removal rate, reducing it in order to decrease the heat generated during cutting to the point of not requiring cutting fluids, which would bring about a great reduction in costs and complexity of the process due to the non-use of fluids in grinding. Petition 870200158403, dated 12 / 17 / 2020, page 19 / 41 -7 / 15

[016] Prolonged use of the refrigerant fluid, as it will circulate in a closed system without contamination, also sparing the employee from excessive exposure to it.

[017] Allows the application of liquid and gaseous fluids with internal circulation, assisted by refrigeration systems that can supply fluids at extremely low temperatures.

[018] Allows hybrid application with MQL systems, enabling the machining of superalloys and difficult-to-machine steels.

[019] The advantages mentioned above guarantee the invention great potential, assisting in machining processes with undefined geometry. Brief description of the Figures

[020] In order to identify the main components presented in this invention, Figures 1 to 6 are briefly described.

[021] Figure 1 shows the system mounted on a cylindrical grinding machine tool. The highlighted components are the cylindrical grinding machine (1), the workpiece (2), the grinding wheel (3), the internal cooling system (4), the fluid inlet tube (5) and the fluid outlet tube (6).

[022] Figure 2 shows the internally cooled device for fixing workpieces in cylindrical grinding machines, showing the workpiece (2), the fluid inlet connection (7), the fluid outlet connection (8), the primary shaft (9), the locking nut (10), the primary spacer (11), the secondary spacer (12) and the rotating cylinder (13). Petition 870200158403, dated 12 / 17 / 2020, page 20 / 41 -8 / 15

[023] Figure 3 represents an exploded isometric view of the main system of the assembly, showing the workpiece (2), the fluid inlet connection (7), the fluid outlet connection (8), the primary shaft (9), the locking nut (10), the primary spacer (11), the secondary spacer (12) and the rotating cylinder (13), the thrust bearings (14), the external seals (15), the internal seals (16) and the secondary shaft (17).

[024] A cutaway view is shown in Figure 4, in order to facilitate visualization of the assembly of the set, with the items indicated in section: the workpiece (2), the fluid inlet connection (7), the fluid outlet connection (8), the primary shaft (9), the lock nut (10), the primary spacer (11), the secondary spacer (12) and the rotation cylinder (13), the thrust bearings (14), the external seals (15), the internal seals (16) and the secondary shaft (17).

[025] Details of how the fluid circulates internally in the system are shown in Figure 5, with the secondary shaft (17), the fluid inlet channel (18) and the fluid return channel (19).

[026] The region of greatest heat exchange is shown in Figure 6, where the primary shaft (9), the primary spacer fitting surface (20), the external nut fastening thread (21), and the internal thread for fastening the secondary shaft (22) are represented.

[027] Figure 7 represents the chemical mapping of the surface performed under conditions without the use of the equipment advocated in this patent. Petition 870200158403, dated 12 / 17 / 2020, page 21 / 41 -9 / 15

[028] Figure 8 represents the chemical mapping of the surface performed under the conditions using the equipment described in this patent.

[029] Figure 9 represents the average roughness values ​​obtained experimentally in this case study.

[030] Figure 10 represents the average values ​​of tangential force obtained experimentally in this case study.

[031] These components are fundamental to the functioning of the system, especially with regard to sealing the internal lubrication system during grinding. Detailed description of the invention

[032] The inventive feature of the presented product consists of a system capable of providing a flow of cooled fluid through an assembly called a workpiece holder applied to the cylindrical grinding process. However, the technical difficulty lies in a cooling system enclosed in a rotating shaft.

[033] The system is mounted on a cylindrical grinding machine tool (1). During grinding, the rotating workpiece (2) comes into contact with the grinding wheel (3). The workpiece is mounted on the internal cooling system (4), which replaces the conventional workpiece holder. The flow of coolant, being liquid, gaseous or a mixture thereof, is carried out through the fluid inlet tube (5) and after heat exchange is expelled through the fluid outlet tube (6). Petition 870200158403, dated 12 / 17 / 2020, page 22 / 41 -10 / 15

[034] The workpiece (2) is fixed onto the threaded fitting of the primary shaft (9) and the secondary shaft (17), in which the primary spacer (11) is placed on its fitting region (20) and the secondary spacer (12) against the workpiece and subsequently fixed by the fixing nut (10) in the external threaded region (21) of the primary shaft.

[035] The assembly of the components previously presented replaces the conventional tool holder applied to disc-type parts subjected to grinding, and can be easily modified to hold parts of other geometries, but which have the possibility of internal fixing, such as bearing races.

[036] The main component of the present invention is the heat exchange carried out internally by a system for fixing rotating parts. The rotating cylinder (13) allows the primary (9) and secondary (17) shafts to rotate while remaining fixed. The rotation is allowed because the rotating cylinder (13) has 2 thrust bearings (14) which, when the nut (10) is tightened, fit onto the machined seats inside the cylinder (13). The inserted fluid, at the appropriate temperature, flow rate and pressure, is sealed by means of external seals (15) and internal seals (16).

[037] The fluid that enters through the inlet connection (7) flows through the inlet channel (18) and flows to the internal threaded region (22), where it circulates and returns through the return channel (19) and is removed by the system through the fluid outlet connection (8). The machined thread in the heat exchange region (22) promotes a larger surface area for heat exchange, maximizing the thermal parameters.

[038] That being said, the authors evaluated the effectiveness of the present invention through a case study, carried out in a controlled environment. A Petition 870200158403, dated 12 / 17 / 2020, page 23 / 41 -11 / 15 following, the methodologies and results obtained are exemplified. Controlled tests in cylindrical grinding

[039] The functionality and feasibility of the present invention were tested in controlled grinding tests. A Sulmecânica brand cylindrical grinding machine equipped with a Fagor CNC was used. The ground component had a circular geometry, with an outer diameter of 57 mm, an inner diameter of 30 mm, and a thickness of 5 mm, manufactured from AISI 4340 steel, hardened and tempered, with an average hardness of 55 HRC. The lubrication-cooling method adopted was the MQL type, at a flow rate of 120 ml / h, using a biodegradable cutting fluid, model Accu-Lube LB 1000, manufactured by ITW Chemicals. The low thermal dissipation presented in the MQL methods was influential in the choice, considering that the present invention proposes a workpiece cooling system independent of the cooling provided by the cutting fluid. The technical tests were carried out using cubic boron nitride grinding wheels, model SNB151Q12VR2, supplied by Nikkon Abrasivos.The cutting parameters used were: cutting speed of 32 m / s and feed rates of 0.5 and 0.75 mm / min. For each test, a new grinding wheel was used, considering that the grinding wheel was broken into small parts for later analysis. Analysis of the grinding wheel cutting surface

[040] Applying fluids in low volumes, as verified in MQL, can negatively affect the final quality of the workpiece. Clogging of the cutting surface due to the presence of Petition 870200158403, dated 12 / 17 / 2020, page 24 / 41 -12 / 15 Machining debris results in less effective material removal, since the micro-cutting edges of the grains are covered, preventing the removal of more material and the effective action of the cutting fluid. To characterize the effectiveness of this invention, scanning electron microscopy (SEM) images of the grinding wheel cutting surface were performed, along with chemical mapping performed by energy dispersive spectroscopy (EDS). For this purpose, a Carl Zeiss EVO LS15 instrument was used. Analysis of the roughness of the test specimens.

[041] Roughness is one of the most evaluated factors in determining the final quality of ground components. Increasing the grinding temperature reduces the hardness of the ground component, which increases the clogging rate on the grinding wheel and impairs material removal by the abrasive grains. In terms of roughness, this parameter can be evaluated in Ra, Rz, Rq, among others. For the present situation, the final quality of the test specimen was quantified in terms of the arithmetic mean roughness (Ra). The arithmetic mean roughness was measured in three equidistant surface regions at 120°, using a Taylor Hobson Surtronic3+ roughness meter, using a cutoff of 0.25 mm and a sample length of 1.25 mm. Analysis of the tangential grinding force

[042] The machining conditions were quantified in terms of tangential force. The power consumed during grinding was determined by means of an acquisition system mounted on the cylindrical grinding machine. Hall sensors were attached to the electrical wiring. Petition 870200158403, dated 12 / 17 / 2020, page 25 / 41 -13 / 15e, an encoder fixed to the rotation axis of the electric motor, sent voltage, current, and rotation signals during machining. The acquisition system was connected to a module (Curvopower) and a board (PCI-6035EDAQ-16 bits), sending the data to LabView 7.1 software at an acquisition rate of 2 kS / s. With the data regarding the peripheral speed of the grinding wheel and the power consumed, the tangential force was calculated using MatLAB 9.0 software. Results of the grinding wheel cutting surface analysis

[043] Figure 7 shows the chemical mapping obtained for the condition without the application of the cooled workpiece holder, while Figure 8 shows the mapping performed on the cutting surface of the grinding wheel that was applied together with the present invention. It can be seen that the presence of iron, represented by the red element, is more intense with the use of the conventional workpiece holder. The reduction in adhesion seen in Figure 8 is due to the reduction in temperature generated by the cooled tool holder. Heat generation at the contact interface still remains; however, an internal heat exchanger in the workpiece allowed the heat flow to be altered. The reduction in heat accumulation in the workpiece allowed the material to maintain its hardness, preventing material adhesion to the grinding wheel's cutting surface. Results of the roughness analysis of the test specimens.

[044] Figure 9 represents the average roughness values ​​obtained. For both feed rates, the application of the cooled workpiece holder promoted lower average roughness values. The deficiency in heat dissipation observed during the application of MQL makes clogging easier. Petition 870200158403, dated 12 / 17 / 2020, page 26 / 41 -14 / 15 grinding wheel cutting regions, resulting in an increased contact area between the chip and the tool. Due to this, higher roughness values ​​were observed. Therefore, the application of the present invention can improve grinding conditions and reduce roughness by up to 23% in this case study. Result of the tangential force analysis during grinding.

[045] Tangential force is directly related to the electrical power consumed during machining. In the case of grinding, better material removal conditions promote reductions in stress, reducing vibrations, temperature, and production costs. Figure 10 presents the average results of the tangential force obtained experimentally during grinding in this case study. As pointed out in the results on roughness, the greater thermal dissipation promoted by the present invention was beneficial, contributing to a reduction in tangential force of up to 24%. The reduction in tangential force allows us to infer better machining conditions with the present invention, since the material removal volumes were maintained. Conclusion of the tests

[046] The case study proved the effectiveness of the present invention. The advantage provided by the temperature reduction through a workpiece holder reached reduced values ​​compared to the conventional technique. The proven reduction in roughness and tangential force are reflections of the reduction in adhesion indicated by the chemical mapping in EDS.

[047] As presented, the system has the necessary technical aspects to promote the circulation of refrigerant fluid in a Petition 870200158403, dated 12 / 17 / 2020, page 27 / 41 -15 / 15 system for securing rotating parts. It is noted that any modifications aimed at improving the functionality presented by this invention are already supported.

Claims

CLAIMS 1 - INTERNALLY COOLED DEVICE FOR FIXING PARTS IN CYLINDRICAL GRINDERS, comprising a support system for disc-shaped parts (2) or internal clamping geometries, characterized by being constituted by a static rotating cylinder (13), in which thrust bearings (14) are arranged that support the kinematic coupling and rotation of a primary shaft (9) and a secondary shaft (17) that are concentric; said primary shaft (9) comprises, in its core, an internal threaded region (22) configured as a thermal interface chamber, in which the machined thread geometry provides an increase in surface area for heat transfer by conduction; the device further comprises external (15) and internal (16) seals arranged between the rotating components (9, 17) and the static cylinder (13) to ensure the dynamic tightness of a closed circuit of coolant fluid. 2 - DEVICE, according to claim 1, characterized in that the fluid circuit is defined by an inlet connection (7) that communicates with an inlet channel (18) arranged longitudinally inside the secondary shaft (17), conducting the fluid to the thermal interface region (22) and returning through a return channel (19) to an outlet connection (8) arranged in the rotating cylinder (13). 3 - DEVICE, according to claim 1, characterized in that the workpiece (2) is fixed by axial compression between a primary spacer (11), seated on a fitting region (20) of the primary shaft (9), and a secondary spacer (12) in direct contact with the face of the workpiece (2), the assembly being tensioned by a fixing nut (10) Petition 870260063760, dated 06 / 29 / 2026, page 15 / 16 2 / 2 coupled to an external thread (21) of said primary shaft (9). 4 - DEVICE, according to claim 1, characterized in that the thermal interface region (22) consists of an intersection cavity between the primary shaft (9) and the secondary shaft (17), where the machined thread acts as an element for maximizing heat exchange between the circulating fluid and the conductive structure of the primary shaft (9). 5 - DEVICE, according to claim 1, characterized in that the closed circuit is configured for the circulation of refrigerants in liquid, gaseous or two-phase mixtures, operating independently of the external lubrication and cooling system of the rectifier (1).

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