machine tool

Abstract

A machine tool for machining a metallic workpiece (2), in particular made of an aluminum material, by means of a cutting tool (7), wherein the machine tool comprises a minimum quantity lubrication system (23) that supplies a tool contour (15) of the cutting tool (7) active in the machining process with coolant / lubricant (mMMS), and a tool changing unit (31) by means of which a tool change (ΔtW) takes place, during which the cutting tool (7) is released from its machining position and positioned in a tool magazine (33), characterized in that the machine tool comprises a cleaning unit (37) with a means (43) for applying cleaning agent (mLauge) to the active tool contour (15) and with a means (49) for applying neutralizing agent (mÖl), by means of which a two-stage cleaning process (R) can be carried out after the cutting tool (7) has been released from its machining position,namely a cleaning process step (Δt, R ), in which material residues can be removed from the tool contour (15) active in the cutting process (Δtspan), and a downstream neutralization process step (ΔtN) in which a neutralizing agent (mOil) can be applied to the active tool contour (15) for the chemical neutralization of cleaning agent residues, that a cleaning agent used in the cleaning process (R) is a lye (mLauge), and that the neutralizing agent is an organic oil (mOil) which reacts with the lye residues in the neutralization process step (ΔtN) to form soap.

Description

The invention relates to a machine tool for a machining tool for machining a metallic workpiece, in particular made of aluminum material, according to the preamble of claim 1.Such a cutting tool is used in vehicle construction, for example in the production of cylinder head bores, for drilling from a solid material. Alternatively, the cutting tool can also be used, for example, as a reamer for drilling an already prefabricated bore. A common metal-processing machining process is usually carried out in wet machining, in which the machining tool is integrated into a closed cooling / lubricant circuit and is flooded with the cooling / lubricant, so that the heat produced in the machining process is dissipated from the machining tool.In contrast, the present invention relates to a machining with minimal quantity lubrication (MMS), in which the coolant / lubricant is supplied to the cutting tool as an aerosol with a very low oil content, which is significantly lower than in the case of wet machining. In a machine tool of the generic type, the cutting tool is clamped into a tool holder which is detachably fastened to a drive spindle of the machine tool. The minimum amount lubrication system of the machine tool supplies coolant / lubricant to the cutting tool during the cutting process. In addition, the machine tool has a tool change unit, by means of which a tool change takes place, in which the cutting tool is released from its machining position and is positioned in a tool magazine and, if appropriate, an exchange tool holder together with the exchange tool is clamped onto the drive spindle.The use of minimal quantity lubrication leads, especially in the case of a longer duration of use of the cutting tool in the cutting process, to the problem that, owing to the significantly reduced quantity of coolant / lubricant, no thermodynamic equilibrium is established on the tool contour which is active in the cutting process, but rather the cutting tool becomes ever hotter. This situation leads, especially in the machining of aluminum workpieces, to the risk that the aluminum material adheres firmly by adhesion to the active tool contour of the machining tool. This results in premature tool breakage of the cutting tool. Such baking is particularly obtained at very high process temperatures, as can occur in a machining process carried out with minimal amount lubrication.DE 10 2014 016 368 A1 discloses a cleaning unit for cleaning the tool contour of the cutting tool that is active in the machining process. It is known from DE 10 2014 104 581 A1 that a cutting tool can be cleaned additionally, for example, with sodium hydroxide solution, when the construction cutting begins. From EP 3 130 653 A1 a lubricant composition is known which is usable for a minimum amount lubrication in a metal working machining process. DE 196 37 086 A1 discloses a cleaning system which removes machining residues from workpieces. DE 10 2014 101 123 A1 discloses a system for cleaning a workpiece made of metal after a machining process.The object of the invention is to provide a machine tool which enables reliable machining of a metallic workpiece with reduced tool outlay compared to the prior art.The object is achieved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims.The invention is based on the finding that as the duration of use of the cutting tool increases, more and more aluminum material sets on the active tool contour and this leads to the disadvantages mentioned above. Against this background, the machine tool according to the characterizing part of claim 1 has a cleaning unit, by means of which a cleaning process takes place after the chip-forming tool has been released from its chip-forming position. In the cleaning process, material residues, i.e. aluminum baked onto the active tool contour in particular, are detached from the cutting tool. In this way, it is ensured that, when the cutting tool is used again in a cutting process, the active tool contour is at least largely, in particular completely free of material residues.In a technical implementation, the cleaning unit can preferably be assigned specifically to the tool changing unit and / or the tool magazine. In this way, the cleaning process can be effected shielded from the around of the chip process, so that direct contact between an operator and a used cleaning agent, for example sodium hydroxide solution or another suitable alkali, is prevented.The invention is based on the fact that in the prior art, avoiding such adhesion of material usually by permanently cooling the cutting tool during the cutting process is associated with great process-related complexity. In departure from this, such common cooling measures are dispensed with during the machining process and, according to the invention, a completely new solution approach is followed in which a process-complicated cooling during the machining process is dispensed with and, after the machining process, any adhesion of material to the cutting tool which has taken place is dissolved in a subsequent cleaning process.The cleaning process has a cleaning process step in which at least the tool contour of the cutting tool that is active in the cutting process is wetted with a cleaning agent. The cleaning process step is preferably carried out immediately after the machining process, for example during a storage period in the tool magazine. In this way, the cleaning process step can be carried out at an even higher process temperature of the clamped-out cutting tool, whereby the reactivity of the cleaning agent is increased.The cleaning process is carried out in two stages, namely with the cleaning process step already mentioned above and a subsequent neutralization process step. In the neutralization process step, detergent residues on the cleaned cutting tool contour are neutralized, for example, by means of an organic oil.In the cleaning process step, the cleaning agent (preferably sodium hydroxide solution) is preferably temporarily wetted onto the cutting tool contour. This takes place at a time interval after the machining process. The neutralization process step can preferably take place at a time interval after the cleaning process step. With regard to a temporally compact embodiment of the cleaning process, both the cleaning process step and the neutralization process step can take place, for example, during a storage period in which the cutting tool is positioned in the tool magazine.In one technical realization, the wetting of the tool contour with the cleaning agent and / or with the neutralizing agent can be effected by spraying and / or by immersion in a liquid bath. In this case, the means for wetting the tool contour can be integrated in the tool magazine and / or in the tool changing unit.In the neutralization process step, the organic oil reacts with the caustic residues to soap.The minimum amount lubrication during the machining process can be carried out in a manner known per se with the aid of a metering device in which the coolant / lubricant is preferably metered as an aerosol into the machining tool. The coolant / lubricant is metered in, in this case-in a manner delimiting from a closed coolant circuit during wet processing-without being incorporated in a closed operating medium circuit. This means that the coolant / lubricant metered in is not recirculated again after the metered addition.The invention and its advantageous embodiments and developments and its advantages are explained in more detail below with reference to drawings.The following are shown: FIG. 1 shows a schematic illustration of a machine tool during a machining process; FIGS. 2 to 4 are views corresponding to FIG. 1, illustrating a tool change and a cleaning process; and FIG. 5 is a time chart showing the use of the cleaning agent, the neutralizing agent and the cooling / lubricant during a time sequence of a machining process and the cleaning process.FIG. 1 shows, in a roughly simplified manner, a machine tool which has a machine spindle 3 to which a tool holder 1 is detachably fastened. A cutting tool 7 is clamped in a chuck, not shown, of the tool holder 1, which is shown in FIG. 1 in a machining position in which a machining of a workpiece 2 can take place. The cutting tool 7 has, for example, groove-shaped chip spaces 9, which extend along a tool longitudinal axis as far as a tool tip. In FIG. 1, only one of the chip spaces 9 can be seen. In addition, the cutting tool 7 has, at its tool tip according to FIG. 1, cutting edges 19 which each project slightly beyond an end face of the cutting tool 7 with a front-side cutting edge and project slightly beyond the cutting tool periphery with their radially outwardly directed cutting edges.Cooling / lubrication lines 21 (FIG. 1 ) are integrated in the machining tool 7, which are fluidically coupled to a minimum quantity lubrication system 23. The minimum quantity lubrication system 23 has a pressure accumulator 25, in which, by way of example, a coolant / lubricant and / or air under pressure is stored. The pressure accumulator 25 is coupled via a supply line 27 to the cooling / lubrication lines 21 of the machining tool 7. Depending on the position of a control valve 29 connected in the supply line 27, the flow path to the cutting tool 7 is open or closed.The machine tool is also assigned a tool change unit 31, by means of which a tool change takes place. During such a tool change, the tool holder 1 clamped onto the machine spindle 3 together with the cutting tool 7 is released from the machine spindle 1 and transported into a tool magazine 33. In addition, an exchange tool holder 1 positioned in the tool magazine 33 together with the exchange tool 35 can be transported to the machine spindle 3 and mounted thereon.As can be further seen from FIGS. 1 and 2, a cleaning unit 37 is assigned to the tool magazine 33, by means of which cleaning unit, after removal of one of the replacement tools 35 or the current cutting tool 7 and their positioning in the tool magazine 33, a cleaning process R (FIG. 5 ) can be carried out, in which material residues which stick to the active tool contour, i.e. in particular the tool tip, after the cutting process by material adhesion can be removed from the cutting tool 7. The cleaning unit 37 has a solution reservoir 39, which is connected via a solution feed line 41 to solution applicators 43 arranged in the machine tool 33. In addition, the cleaning unit 37 has an oil reservoir 45 which is connected via an oil feed line 47 to oil applicators 49, which are likewise arranged within the tool magazine 33, that is to say shielded from the chip process environment.In each of the two feed lines 41, 47, a solution dosing unit 51 and an oil dosing unit 53 are arranged.FIG. 1 shows the machine tool in a machining process Δtspan(FIG. 5 ) in which the machining tool 7 is driven under pressure and rotation into a workpiece 2 (for example made of aluminum material) in order to produce a bore 55 in the workpiece 2. In this case, the tool contour 15 which is active in the machining process Δtspan is supplied with a coolant / lubricant aerosol mMMS via the minimum quantity lubrication 23. The machining process Δtspanmay have a plurality of such individual bores. After completion of the machining process Δtspan, a tool change ΔtW is carried out with the aid of the tool change unit 31, in which the machining tool 7 is released from its machining position (FIG. 1 ) and is stored in the tool magazine 33 over a storage period Δtstore (FIG. 5 ). At the same time, an exchange tool 35 is removed from the tool magazine 33 and clamped on the machine spindle 3 in order to carry out a further machining process Δtspan.As is shown in the diagram of FIG. 5, immediately after the beginning of the storage time period Δtmount, a cleaning process step tR takes place, in which the tool contour 15 of the cutting tool 7 that is active in the cutting process Δtspan is briefly acted upon by the sodium hydroxide solution (mLauge solution in FIG. 3 ). At a time interval from the cleaning process step tR and at the end of the storage time period Δt lager, a neutralization process step tN follows. In the neutralization process step tN, residual sodium hydroxide solution on the cleaned tool contour 15 is chemically neutralized by applying oil (moil in FIG. 4 ), specifically to form a soap.After the storage period Δtmounthas elapsed, the now cleaned and neutralized cutting tool 7 can be used again, which is now completely free of material residues on the active tool contour 15.

Claims

Machine tool for machining a metallic workpiece (2), in particular made of an aluminium material, by means of a machining tool (7), wherein the machine tool has a minimum quantity lubrication system (23), which supplies a tool contour (15) of the machining tool (7) that is active in the machining process with coolant / lubricant (mMMS), and a tool change unit (31), by means of which a tool change (ΔtW) takes place, in which the machining tool (7) is released from its machining position and is positioned in a tool magazine (33), characterized in that the machine tool has a cleaning unit (37) with a means (43) for applying cleaning agent (mLauge) to the active tool contour (15) and with a means (49) for applying neutralizing agent (mOil), by means of which, after the chip tool (7) has been released from its chip processing position, a two-stage cleaning process (R) can be carried out, namely a cleaning process step (Δt R), in which material residues can be removed from the tool contour (15) which is active in the chip process (Δtspan), and a subsequent neutralization process step (ΔtN), in which a neutralizing agent (mOil) can be applied to the active tool contour (15) for the chemical neutralization of detergent residues, in that a cleaning agent used in the cleaning process (R) is a caustic solution (mLauge), and in that the neutralizing agent is an organic oil (mOil), which reacts with the caustic residues in the neutralization process step (ΔtN) with soap formation.Machine tool according to claim 1, characterised in that the cleaning unit (37) is assigned to the tool changing unit (31) and / or to the tool magazine (33), and in that in particular the cleaning process (R) is effected shielded from the machining process environment, so that direct contact between an operator and the cleaning agent (mLauge) is prevented.Machine tool according to one of Claims 1 or 2, characterized in that, in the cleaning process step (ΔtR), the tool contour (15) of the cutting tool (7) which is active in the cutting process (Δtspan) is wetted with the cleaning agent (mLauge), and in that, in particular, the cleaning process step (ΔtR) takes place at the beginning of a storage time period (Δtstore) in which the cutting tool (7) is positioned in the tool magazine (33).Machine tool according to one of the preceding claims, characterized in that the wetting of the tool contour (15) with cleaning agent (mLauge) and / or with neutralization agent (mOil) is effected by spraying and / or by immersion in a liquid bath, and in that in particular the means (43, 49) for wetting the active tool contour (15) is integrated in the tool magazine (33) and / or in the tool change unit (31).Machine tool according to one of the preceding claims, characterized in that the cleaning process step (ΔtR) takes place at a time interval after the machining process (Δtspan).Machine tool according to one of the preceding claims, characterized in that the neutralization process step (ΔtN) takes place at a time interval after the cleaning process step (ΔtR), and / or in that both the neutralization process step (ΔtN) and the cleaning process step (ΔtR) take place during the storage period (Δt lager) of the cutting tool (7).Machine tool according to one of the preceding claims, characterized in that the cutting tool (7) cleaned in the cleaning process (R) is at least largely, in particular completely free of material residues, when used again in a cutting process (Δtspan), and / or in that the neutralization process step (ΔtN) takes place before the renewed use in the cutting process (Δtspan).

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