The invention relates to a method for the chip-removing production or machining of a workpiece and a correspondingly equipped machine, and in particular the aspect of discharging the chips produced during the machining process.

A liquid, hereinafter also referred to as coolant, such as oil or other partially synthetic coolants or lubricants, or such as a liquid form based on emulsions, is used for lubricating and/or cooling the machining process. In the broadest sense, the machining process then creates a mixture of chips and coolant. In order to separate the chips and coolant, the chips are often removed from the machine using a magnetic-belt chip conveyor. The basic mode of operation of a magnetic-belt chip conveyor is known to the person skilled in the art and is moreover explained again below with reference toFIG. 1. The majority of the coolant entrained by the chips or chip accumulations removed from the mixture in this case flows back into the machine, such that said machine can maintain a coolant/lubricant circuit.

The manufacturers of magnetic-belt chip conveyors in this case optimize the liquid return flow by means of the design and process parameters of the chip conveyor that are available to them.

These parameters include the length of the discharge region in the form of a stationary, oblique surface which protrudes from the coolant tank. The longer this selected discharge region is, the more time remains for releasing the coolant from the chip accumulations, and for the return flow of said coolant to the coolant tank. In particular if the conveyance of the magnetic-belt chip conveyor is interrupted occasionally, a long discharge region is advantageous, since more time remains for releasing the coolant from the chips. However, this advantage must be weighed against an increased material requirement in the manufacture of the chip conveyor, and a larger necessary footprint.

The pitch angle at which the oblique discharge surface of the chip conveyor is positioned relative to the horizontal can also be varied to a certain extent. Of course, the downhill force increases with a steeper pitch angle and thus both the process of releasing the coolant from the chip accumulations and the return-flow speed increase.

The width of the discharge surface or discharge path is also an available design parameter for optimization, in particular for complying with the necessary conveying capacity, since a larger width allows the conveying speed to be reduced when the required cross section of the chip accumulations is the same, and thus allows more return-flow time for the coolant. Considered inversely, this allows the cross section of the chip accumulations to be reduced in the case that the conveying speed is maintained, whereupon the chip accumulations of a smaller cross section can release the coolant contained in said accumulations better than would be the case if the cross section of the accumulations were larger. However, the width of the chip conveyor is usually also limited for design reasons relating to the machine construction, apart from a higher material expenditure.

A further design parameter which can be used is the spacing of the magnets in the chip conveyor. When the conveying speed is the same, a reduced spacing of the circulating magnets leads to a reduction in the cross section of the chip accumulations and therefore, in turn, leads to an improvement in the release of the coolant. When the chip-discharge quantity of the circulating conveyor is the same, however, this requires a larger number of magnets and therefore a higher material expenditure.

By increasing the conveying speed as a process parameter, a smaller cross section of the chip accumulations, and therefore an improved release of the coolant, can likewise be achieved, this also, however, reduces the time available for the return flow, such that a suitable compromise is also to be found here, and the conveying speed cannot be increased arbitrarily.

Depending on the field of use of the magnetic-belt chip conveyor, which use also determines the required conveying rate, the aforementioned parameters are suitably matched to one another in order to discharge the chip accumulations at the end of the discharge region with as little coolant as possible.

A residual quantity of coolant that nevertheless remains and is inevitably discharged together with the chips beyond the discharge region can be separated from the collected chips, if required, using a suitable separation process which is connected downstream, for example by said coolant being allowed to trickle out of a chip container and drained, or optionally further being removed by pressing or centrifuging. This recovered coolant can then also be supplied back to the machining process.

The problem addressed by the invention is that of further improving the method of the type mentioned at the outset.

This problem is solved in terms of the method by a development of the method of the type mentioned at the outset, which development is substantially characterized in that the return flow is deflected out of the discharge path and/or the discharge path has at least one point at which the supporting surface is temporarily withdrawn from the discharged chips.

The invention is in this case based on the knowledge that, in particular in the case of rolled chips, as are often produced during the machining of metallic workpieces, and in particular liquids having a comparatively high viscosity, the proportion of the liquid which is discharged together with the chips can be determined to an extent that dispensing with a possibly complex recovery process no longer seems justified, such that the above-mentioned coordinated selection of the available parameters for the chip conveyor should be as optimized as possible. Furthermore, the invention is based on the knowledge that the optimization of the parameters explained above, which was previously familiar to a person skilled in the art, does not lead to a satisfactory solution.

According to the invention, on the other hand, the discharge path and the coolant return flow are influenced independently of favorably set parameter constellations, by means of which influence the quantity of coolant discharged by the chips can be further reduced in a satisfactory manner. As a result of the deflection of the return flow from the discharge path, a reabsorption of the coolant which is already flowing back from advancing chip accumulations can be completely, predominantly, or at least partially avoided, as a result of which the subsequent chip accumulations can reach the end of the discharge path in a drier state. By the supporting surface being temporarily withdrawn from the discharged chips, the chip accumulations are subjected to a jumping movement, as a result of which, or upon the landing of said chips, the release of the liquid from the chip accumulations is increased.

The discharge path can in this case extend over a certain width, which can correspond to the width of a conventional magnetic-tape chip conveyor; the discharge path is therefore planar rather than linear.

The magnetic force acts on the chip accumulations by means of first regions which have a strong magnetic field and move along the discharge path in the discharge direction, which first regions are separated by second regions which have a lower magnetic field. This is achieved, for example, by arranging elongate (transverse to the direction of discharge) magnets spaced apart from one another on a circulating belt, as in a conventional magnetic-belt chip conveyor.

A return-flow region for the return-flowing liquid (coolant) is preferably arranged under the discharge path in the direction of gravity.

In a particularly preferred embodiment, at least two deflection points are provided along a discharge path, and the ratio β of the spacing between two consecutive deflection points in the discharge direction to the spacing between two consecutive first regions in the discharge direction is preferably less than 1/(1+γα), where the dimensionless parameter (factor) γ is at least ⅕, preferably at least ⅓, in particular at least ½, and where a is the ratio of the speed of movement of the first regions to the return-flow speed of the liquid. In this design, a satisfactorily low quantity of discharge is determined. In this case γ is greater than ⅗, in particular is greater than ⅘, and in particular reaches or even exceeds 1. In specific designs, in particular for highly viscous coolants (kinematic viscosity of more than 50 mm2/s (measured at 40° C.)), β is less than ⅛, in particular less than 1/10. For medium-viscosity coolants (kinematic viscosity in the range of 5-50 mm2/s), reasonable results are already obtained where β is less than ¼, in particular where β is less than ⅙. In the case of low-viscosity coolants (kinematic viscosity if less than 5 mm2/s), a β which is less than 0.8 may also lead to reasonable results.

In a preferred embodiment, the method is carried out using coolants which have a kinematic viscosity of preferably greater than 2 mm2/s, more preferably greater than 3 mm2/s, in particular greater than or equal to 5 mm2/s. In particular in the case of special applications in the toothing machining process, however, it is preferred for the kinematic viscosity of the coolant to be no greater than 50 mm2/s, preferably no greater than 44 mm2/s, in particular no greater than 36 mm2/s.

With regard to an average gradient of the discharge path (which substantially determines the magnitude of the acting downhill force), values of 35° or greater are preferable, values of 40° or greater are more preferable, in particular of 50° or greater. By contrast, it is expedient if the average gradient of the discharge path is no steeper than 85°, more preferably no steeper than 75°, in particular no steeper than 65°.

With regard to the conveying speeds (speed at which the magnets/regions of a strong magnetic field move), speeds of greater than 0.2 m/min, more preferably greater than 0.35 m/min, in particular greater than or equal to 0.5 m/min, can be used in a suitable manner. However, it is preferred for the conveying speed to be no greater than 3 m/min, more preferably no greater than 2 m/min, in particular no greater than 1 m/min.

Appropriate minimum lengths of 30 cm or more, preferably 60 cm or more, in particular 1 m or more, are considered for the length of the discharge paths. It is also preferred for the length to be no greater than 3 m, more preferably no greater than 2.5 m, in particular no longer than 2 m. With regard to the width of the discharge path, values of at least 10 cm, preferably at least 20 cm, in particular at least 25 cm, are preferred. In this case it is further preferred for the width to be no greater than 80 cm, more preferably no greater than 65 cm, in particular no greater than 50 cm. In the case of coolants which have a very low-viscosity, the conditions for β are not as stringent, in this case β can also be less than 4, 3 or 2.

In a further preferred embodiment, the condition β<1/(1+γα) is applied at the start of the discharge path, but the condition can also be present along the entire discharge path between two consecutive deflection points. The discharge path begins with the exit from the liquid accumulation. In terms of the device, a design embodiment would preferably be implemented starting from the intended minimum level in the tank or even below said level. A regular arrangement of the diversion points along the conveying direction, as well as transversely to the conveying direction, is possible and easier to manufacture, but not necessary. The number, shape and arrangement of the diversion points can vary in the discharge direction and also transversely thereto (in the width direction).

In one possible design, a deflection point is assigned to a support withdrawal point, in particular each deflection point is assigned to a circulation withdrawal point. The quantity of coolant released due to the jump can thus be deflected promptly and quickly.

The invention can also be used on a plurality of chip conveyors connected in series.

In a particularly preferred embodiment, the return-flowing liquid (coolant) flows into a return-flow chamber, and the discharge path is separated from one or more openings by a barrier. As a result, a larger chip concentration is largely prevented from reaching the return-flow chamber and possibly clogging the chamber or clogging the openings. In one possible embodiment, one or more portions are provided in which liquid flowing back from a deflection point flows back, spatially separated from and parallel to a liquid flowing back from a deflection point which is subsequent in the discharge direction, the discharge path at said parallel-flow portions in particular having a ramp portion upstream of a support withdrawal point.

In this case the ramp portion can form the barrier explained above, the coolant flowing back from the diversion point which is subsequent in the discharge direction can already flow back in the return-flow chamber. The coolant that flows back earlier may only reach the return-flow chamber somewhat downstream.

The average additional gradient of the ramp portions compared to the basic gradient of the conveyor may be at least 5°, preferably at least 12°, in particular at least 20°. Depending on how high the basic gradient of the conveyor already is, it is preferred for the average additional gradient of the ramp portions to be no greater than 50°, more preferably no greater than 45°, in particular no greater than 40°. For the jump height at the jump points (measured orthogonally to the conveying surface defined by the conveyor (surface28in the drawings)), it is preferred for said height to be at least 1 mm, more preferably at least 2 mm, in particular at least 3 mm. The jumps should also be no higher than 15 mm, more preferably no higher than 12 mm, in particular no higher than 9 mm. A very suitable range is between 4 and 8 mm in jump height.

In terms of the device, a machine is provided, in particular a toothing machine for the chip-removing production or machining of a workpiece, in particular of a toothing on a workpiece, by means of a machining tool, in particular a toothing tool, comprising a supply device for a liquid used for lubricating and/or cooling the machining process, a collecting region, in which the liquid which is mixed with the chips produced during the machining process collects, and a chip discharge device for discharging the chips along a discharge path counter to the downhill force by means of a magnetic force, which device allows a return flow of the liquid carried away by the discharged chips, which flow is caused by the downhill force, the toothing machine being substantially characterized in that the chip discharge device has at least one deflection point at which the liquid return flow is deflected out of the discharge path, and/or has at least one support withdrawal point at which the supporting surface is temporarily withdrawn from the discharged chips.

The advantages of the machine according to the invention can be found in the advantages of the method explained above, likewise the advantages of the further developments of the machine in the form of the dependent machine claims. Insofar as chips are also generated during, for example, metal machining processes, such as drilling or turning workpieces, that are additionally carried out as part of toothing machining processes, the above-mentioned discharge principle can likewise be used, as well as for generally different types of machining processes in which metallic chips accumulate in a mixture with a coolant.

In terms of design, the chip discharge device preferably has a first, stationary, oblique surface as a chip discharge surface, on which the chips which are to be discharged move upward, and a second, stationary, oblique surface on which the return-flowing liquid runs downward. The first can preferably be detached, in particular removed, from the second.

Furthermore, a chip discharge device having the essential aspects as explained above is also protected, which device is suitable for a machining machine, in particular a toothing machine, as well as an attachment for forming a chip discharge device, which attachment likewise has the relevant features and, by being placed on magnetic-belt chip conveyors, which in particular are already conventional, forms a chip discharge device having the features explained above. In terms of the method, the separation steps of the method are also protected independently of the chip source.

The dimension of the spacing between the regions (magnets) and the chip discharge surface is selected such that the magnetic force is still sufficient to move the chip accumulation along the discharge path without said accumulation getting caught and/or sliding back. It is also selected in such that the return-flow chamber which is formed as a result can accommodate the return flow in terms of volume.

