WO2015006846A1

WO2015006846A1 - Toolholder with internal system for heat transfer with phase-change fluid

Info

Publication number: WO2015006846A1
Application number: PCT/BR2014/000239
Authority: WO
Inventors: Arthur Alves FIOCCHI; Luiz Eduardo de ÂNGELO SANCHEZ; Rubens Roberto INGRACI NETO; Vicente Luiz SCALON
Original assignee: Universidade Estadual Paulista "Julio De Mesquita Filjho"
Priority date: 2013-07-17
Filing date: 2014-07-16
Publication date: 2015-01-22
Also published as: BR102013018189A2; BR102013018189B1; WO2015006846A8

Abstract

The patent of invention relates to a toolholder with a structural body containing an internal system of channels through which flows a fluid that changes phase on receiving the thermal energy, generated during machining, which is transmitted through the tool; the aim is to extract the heat generated in the process, thereby extending the life of the cutting tool and promoting the maintenance of the quality of the component produced.

Description

INTERNAL SYSTEM TOOL HOLDERS

FIELD HEAT TRANSFER IN CHANGE OF INVENTION FIELD

The present invention relates to a tool holder with internal phase-shifting fluid heat transfer system comprising a cutting tool holder acting as a heat exchanger to assist in dissipating the thermal energy generated in machining processes.

BACKGROUND OF THE INVENTION

The mechanical industry uses the material removal machining process to shape the parts, that is, to manufacture them to precise measurements. The cutting tool is usually fixed to a holder known as a tool holder which in turn is attached to the machining machine tool. The tool used for this removal or cutting process is generally made of a more mechanically resistant material than the part material. Even so, the tool suffers wear, mainly due to heating during the removal process, causing it to deteriorate and lose the cutting capacity, leading to its destruction; This characterizes the critical situation commonly referred to as "end of life".

To minimize the temperature on the cutting tool in order to extend its life, it is common to apply a coolant, known as cutting fluid, over the cutting region between the contact of the workpiece and the tool. This cutting fluid consists essentially of water, but also chemicals, to minimize part and machine tool oxidation, improve lubricity and cooling capacity, and bactericides, to prevent proliferation of living agents, among other types. of additives.

Machining is also possible in the absence of cutting fluid. With the use of more heat resistant tool materials, however, the cost of these cutting tools is considerably higher.

Alternative known for the extension of the cutting tool life is the cooling of the cutting zone using fluid phase change temperature below room temperature such as liquid nitrogen (N ₂ n acid _{_qu)>} technique called "cryogenic milling" .

In order to remove heat from the cutting tool, it was published in an international article in the International Journal of Machine Tools & Manufacture, in the paper entitled Investigation of the effects of cooling in hard turning operations, by A. Noorul Haq and T. Tamizharasan, In 2006, a water-filled heat pipe was attached to the base of the cutting tool. The fluid coming into contact with the warmer region of the tube vaporizes, removing some of the heat produced in the machining process. After evaporation, by capillary effect, the water migrates to colder regions condensing again. However, unlike liquid nitrogen, the water phase change occurs at much higher temperatures, around 100 ° C.

In any machining process there is intense heat generation from chip formation. This energy comes basically from three sources: plastic deformation of the material in the primary shear plane (Primary Shear Zone - ZCP); chip deformation and friction in the region of the chip-tool interface, where the secondary shear plane (Secondary Shear Zone - ZCS) is located; and the friction between the tool and the part produced by their contacts (Tertiary Shear Zone - ZCT). Each of these zones contributes to the temperature rise in the cutting region in a different way. Most studies focus only on the primary shear zone (ZCP) and the secondary shear zone (ZCS), as the tertiary shear zone is significant in heat generation only in high flank wear. Recent approaches show that the temperature increase in the cutting tool occurs mainly due to ZCS; although it is noteworthy that the ZCP also contributes to this heating and indirectly affects the temperature distribution on the outlet surface. During material removal, the chip flow has a convective effect, carrying with it the energy generated in the ZCP, which when passing through the chip-tool interface exchanges heat by conduction with the outlet surface, heating the tool.

Thus, it is clear that heat generation in the ZCP affects distribution throughout the system. It can be said that the increase in temperature at the tool outlet surface is due to the combined effect of heat generated on the ZCP and ZCS, not each one individually. In addition, the thermal properties of the tool and workpiece (thermal conductivity), the mechanical properties of the material, the tribological conditions, the length of the chip contact and the cutting parameters are also key parameters in the heat dissipation distribution. generated.

As several studies show, the biggest problem with thermal power generation is that heat generation during the process is detrimental to the machining operation. It has been scientifically proven that at higher temperatures tool wear is more pronounced, resulting in a shorter tool life and making it difficult to maintain the specified dimensional tolerances for workpiece and roughness.

In general, heating in the machining process basically leads to four undesirable operating results: deformation of the part; coloration on machined surface; falsification of workpiece measurements, where there is a discrepancy between measurements made during and after the tool action due to the heat generated; and difficulty for the operator to handle the machined part, ie remove it from the machine, transport it etc. These negative characteristics about heating in machining processes make it urgent to keep the tool at low temperatures through the use of technologies to dissipate this heat generated. The processes traditionally used for cooling these operations are those described above.

Document PI0901570-1 features a tool holder provided with a damping means that eliminates the vibratory effects due to cutting forces and machining speeds. However, this invention does not address the issue of heat transfer, or cooling, required for the machining operation.

A rotary tool holder is described in document PI0507046-5, which allows the tool to rotate at its end. However, the patent does not address the influence of refrigeration on the machining operation.

CA2645860 deals with a tool holder with internal cavities allowing the insertion of a cartridge-like device into it as well as the circulation of cutting fluid. This cartridge is used as a container for monitoring sensors such as vibration, stress and temperature measurement as well as damping system for the cutting tool. However, in this device the internal cavities have the function of accommodating the cartridge and, unlike the common devices that use damping system, allow the cutting fluid to pass through the body of the tool holder. This cutting fluid is therefore applied in a manner conventional, that is, it is sprayed through a jet-shaped nozzle over the cutting interface. This invention does not deal with the extraction of heat conducted by the cutting tool by evaporation of the coolant within the tool holder.

The technique described in this document allows the construction of a structural and functional device to support one or more cutting tools and which has internal channels for fluid circulation, promoting heat removal by fluid phase change.

The object of the present invention is, in particular, to reduce the temperature in the cutting region by removing heat through the cutting tool with the aid of a phase-shifting fluid-circulating tool holder. This minimizes the application of cutting fluid to the machining process as hydrocarbon-based ones are deteriorated and should not be disposed of in the environment as it is a chemical harmful to human health. action considered an environmental crime if it is done.

SUMMARY OF THE INVENTION

The invention relates to a tool holder with an internal phase-shifting fluid heat transfer system composed of a structural body, called a tool holder, which has internal channels near or within the cutting tool for refrigerant circulation.

The other features of the invention are:

- The body of the tool holder may be made of ceramic, cast iron, stainless steel, high speed steel, mechanical steel, hard metal, carbon steel, whether or not heat treated, or other metallic, ceramic, polymeric, composite materials, among others;

- an interface between the tool and the holder cavity tools can be introduced to aid heat transfer, made of electrolytic copper, hardened or not, aluminum, silver, gold, graphene, superconducting ceramics or other good heat conducting material;

- When the tool has a clamping hole, it can be filled with a cylindrical pin of conductive material to increase heat removal, and its fixation in the tool holder by interfering adjustment, welding or mechanical compression;

- for commercial cutting tools without a hole there will be no cylindrical pin for clamping and a clip can be used to press the cutting tool against the tool holder and the conductive interface;

- For sealing between the conductive interface and the tool holder, phenolic polymeric resin, epoxy, polyethylene or the like may be used, a welded joint with or without addition material, interfering fit, sealing rings or joints or threaded joints; and

The connection channels between the tool holder internal circuit, the pressurization system and the heat exchanger may be made of polymeric resin, metal ducts or other materials inert to the fluid used. BRIEF DESCRIPTION OF THE FIGURES

The following description and associated figures, all given by way of non-limiting example, will make the invention well understood.

Figure 1 shows the technical drawing in section of the tool holder (1), with the cutting tool (2) coupled by the clamp (5), and the external connections through which the fluid circulates.

Figure 2 shows schematically the cooling system comprising the tool holder (1), the heat exchanger (12), the pump (13) and the connection channels.

Figure 3 represents the thermal flux generated in a thermal operation. machining through the cutting tool and the conductive interface, leading the fluid to the phase change.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figure 1, the tool holder (1) has below the cutting tool (2) a chamber (3) in which the heat generated by the cutting process causes the internally circulating refrigerant to evaporate. Steam leaves the tool holder through the inner channel (4). The cutting tool (2) is fixed by a clamp (5) which has its tightening torque given by a screw (6) attached to the tool holder (1). Below the cutting tool (2), between the cutting tool (2) and the chamber (3), an interface (7) of material with high thermal conductivity such as copper can be included in order to promote heat exchange. between cutting tool (2) and fluid. Fluid enters the chamber (3) through the fitting (8) and leaves the tool holder through the fitting (10). Connections can be threaded, welded, inserted by interfering fit, or even glued to the toolholder frame (1). The fluid flows through the external heat transfer and pressurization systems and enters the tool holder (1) through the connection channel (9), and exits the tool holder (1) through the connection channel (11).

As described in figure 2, the refrigerant, after its total or partial evaporation, due to the transfer of heat generated in the machining process, leaves the tool holder (1) through the connection (10) and goes through the connection channel (1). to the heat exchanger (12) within which it is condensed. The fluid in the liquid phase flows to the pump (13), which forces its circulation into the tool holder (1) through the connection channel (9). The refrigeration system operates in a steady state, with continuous flow of fluid through the interior of the tool holder, heat exchanger and pressurization system. Figure 3 shows the working principle of the tool holder internal cooling system (1). The thermal energy generated during the cutting process of the part (14) forming the chip (15) is transferred through the cutting tool (2) and the conductive interface (7) to the coolant inside the chamber (3), absorbing this thermal energy vaporizes partially or totally. The heated fluid leaves the tool holder, circulating through the inner channel (4), to the connection channel (11), from where it goes to the heat exchange and pressurization system shown in figure (2).

The tool holder or the tool itself may be manufactured to utilize heat exchange enhancing technologies such as ultrasonic agitation, micro-channel flow, fin surfaces and porous media in coil-shaped geometries and any other techniques to the same end. Also, during its manufacture characteristics can be inserted that allow changes in the system pressure - such as variations in the diameter of the channel (4) - so that the refrigerant changes phase in different temperatures, favoring the heat exchange. Differentiated geometries are used to make the evaporation chamber in order to direct and regulate the flow of the fluid jet that enters the tool holder. At the outlet of said chamber of the tool holder, other differentiated geometries ensure the steam output towards the heat transfer system.

The circulation of fluid within the tool holder or the tool itself may be forced or natural convection based and therefore utilize the effects of density variation with evaporation and / or heating for fluid movement in the system.

The thermal contact resistance between the tool and the tool holder can be reduced by applying thermal paste, increased flatness, decreased roughness or any surface treatment for this purpose.

An example of application is the machining of automotive and aeronautical parts of difficult-to-alloy alloy steels. This is due to the large thermal energy generation, high shear stresses, low thermal conductivity of these materials and high tool wear rate, as well as the intrinsic need to maintain design criteria such as dimensions and surface finish. Using a surface-coated or uncoated cutting tool, connected to the tool holder with internal phase-shifting fluid heat transfer system; The present technology aims to extend the life of the cutting tool by reducing non-productive time by sustaining the desired quality of longer produced parts.

Claims

1. MATERIAL COOLING DEVICE characterized by the heat transfer of the cutting tool by the forced circulation, or natural convection inside or of the tool itself, of a phase changing fluid as a function of the temperature reached in the operation. Machining

2. MATERIAL COOLING DEVICE characterized by the use of water, carbon dioxide, ammonia, refrigerants or other fluids which, under different pressures, preferably evaporate in the temperature range from -50 ° C to 200 ° C. preferably between 0 ° C and 50 ° C.

3. COOLED MACHINE MACHINE DEVICE characterized in that it comprises at least one tool holder, a means for heat exchange and an element for forced circulation of fluid or natural convection.

Cooled material machining device according to one of Claims 1 to 3, characterized in that it uses a heat exchanger element or the environment itself to condense the vaporized phases again, allowing the refrigerated device to operate in a closed loop.

Cooled material machining device according to one of Claims 1 to 4, characterized in that a fluid circulation system, external or internal to the tool holder, based on forced circulation using pumps, compressors or other devices. to this end.

6. MATERIAL MACHINING TOOLS OR TOOLS characterized by a structural body provided with internal channels and an internal heat transfer system using heat exchange intensification technologies such as ultrasound, micro-channel flows, fin surfaces and porous media, coil-shaped geometries and any other techniques to the same end, whether applied separately or applied together.

7. TOOL HOLDER OR TOOLS FOR

MACHINING MATERIALS according to claims 1 to 6, characterized in that the thermal contact resistance between the tool and the tool holder can be reduced by the application of thermal paste, increased flatness, decreased roughness. or any surface treatment for this purpose, whether applied separately or applied together.

8. MACHINE TOOL HOLDER OR TOOL HOLDER according to any of claims 1 to 7, characterized in that it conducts the phases from the evaporation chamber directly into the atmosphere or on the part being machined.

MATERIAL TOOL HOLDER OR TOOL HOLDER according to any of claims 1 to 8, characterized in that it is made of one or more materials of high thermal conductivity, as well as the other elements of the system, preferably ceramic, iron. cast, stainless steel, high speed steel, mechanical steel, carbide, cermets, carbon steel, whether or not heat treated, copper, aluminum, silver, gold, graphene, superconducting ceramics, composites, polymers or other materials.

10. TOOL HOLDER OR TOOLS FOR

MACHINING MATERIALS according to claims 1 to 9, characterized in that said tool holder can work with one or more tools.

11. TOOL HOLDER OR TOOLS FOR MACHINING MATERIALS according to any one of claims 1 to 10, characterized by channels constructed within the tool holder or within the tool itself characterized by geometries regulating the flow, pressure, direction and flow direction of the fluid.

12. TOOL HOLDER OR TOOLS FOR

MACHINING MATERIALS according to Claims 1 to 11, characterized by material removal applications using defined or undefined geometry tools in different areas not limited exclusively to the automotive, aeronautics, mining, ceramics, chemistry, drilling, energy, marine, logging, metal-mechanical, dental, medical, conductive materials processing, semiconductor, optical and electronics products.