Guide bushing, machine tool with guide bushing and method for operating such a machine tool

Abstract

Guide bushing (10) for guiding a material rod, with a collet chuck (30) axially displaceable in a collet chuck receptacle (20) and an actuator (40) designed for axial movement of the collet chuck (30), characterized by at least one sensor (50) directly or indirectly detecting the axial position and / or the radial extension of the collet chuck (30) in the collet chuck receptacle (20).

Description

[0001] The invention relates to a guide bush for guiding a material bar, comprising a collet mounted axially displaceably in a collet chuck holder and an actuator configured for axial movement of the collet chuck. Furthermore, the invention relates to a machine tool having such a guide bush and a method for operating such a machine tool.

[0002] Machine tools with clamping devices are generally known, for example from US 4 068 545 A, US 2007 / 0 151 429 A1, DE 60 2004 012 063 T2, DE 101 38 942 A1 and JP 2002 - 337 001A.

[0003] Guide bushes are used in Swiss-type automatic lathes for guiding and / or clamping stationary or rotating bar stock. Setting up the guide bush involves correctly adjusting the collet chuck inserted into the guide bush, depending on the bar stock being machined.

[0004] For example, to correctly adjust a pull system guide bush, the collet is screwed into the guide bush just deep enough so that it rests evenly on the workpiece without being loose or exerting clamping forces.

[0005] However, the correct adjustment of the guide bush can sometimes be difficult, especially when chips or other contaminants lead to premature jamming.

[0006] If the aforementioned collet is not screwed in far enough in such a case, the force required to clamp the material bar cannot be sufficiently applied due to the short travel of the actuator moving the collet, causing the material bar to slip. This operating error by the machine operator is usually only noticed some time after machining has started and significantly disrupts the throughput.

[0007] The object of the invention is therefore to create a guide bushing that facilitates the setting up of a collet.

[0008] This object is achieved according to the invention by the guide bushing having the features of claim 1, by the machine tool having the features of claim 8, and by the method having the features of claim 9. The subclaims represent advantageous embodiments of the invention.

[0009] The basic idea of ​​the invention is to directly or indirectly detect the axial position and / or the radial extension of the collet in the collet holder of the guide bush. If, for example, the radial extension of the collet is detected, deviations from a previously known (calculated) value of the optimal screw-in depth of the collet, which may arise from contamination, for example, can be detected if the diameter of the material bar is known. Determining the position of the actuator connected to the guide bush relative to the guide bush also allows conclusions to be drawn about the screw-in depth, the degree of contamination or wear of the guide bush clamping a material bar, or the available travel range of the actuator in relation to a material bar of known diameter.In particular, the measurement of the radial extension and / or axial position of the collet or actuator provides the opportunity to correlate the collected values ​​and to optimize the position with regard to the pressure acting on the material bar and / or the clamping force with the available travel path of the actuator.

[0010] According to the invention, a guide bush for guiding a material bar is provided, with a collet mounted axially displaceably in a collet holder and an actuator configured for the axial movement of the collet, wherein at least one sensor directly or indirectly detects the axial position and / or the radial extension of the collet in the collet holder.

[0011] The collet is designed either as a pull collet or as a double cone collet.

[0012] Indirect detection of the axial position of the collet is preferably achieved by the sensor detecting the position of the actuator relative to the guide bushing. This, of course, assumes that the collet is firmly connected to the actuator.

[0013] The measurement of the radial expansion of the collet is preferably carried out by the sensor detecting the gap between the inner diameter of the collet holder and the outer diameter of the collet.

[0014] With the aforementioned guide bushing design, a control system is advantageous that is configured to emit an alarm signal when a predetermined value detected by at least one sensor is exceeded or undershot. This value can, for example, relate to the radial extension and / or axial position of the collet in the holder or the axial position of the actuator. However, the value can also be a derived variable, such as the remaining travel distance of the actuator.

[0015] Additionally or alternatively, the control is configured in such a way that it acts on the actuator when a predetermined value detected by at least one sensor is exceeded or undershot.

[0016] Preferably, the control unit and the guide bushing are connected wirelessly. In particular, wireless communication between the control unit and the guide bushing also allows the control unit to be connected via tablet computers or smartphones.

[0017] Furthermore, a machine tool with a guide bush as explained above is presented.

[0018] The sensors used are primarily distance sensors. Alternatively, switches, such as limit switches, can be used, which trigger an alarm and / or stop the machine when a predetermined position of the collet or actuator is reached. The use of other sensors to determine the position of the collet or actuator is possible.

[0019] Finally, a method for controlling such a machine tool is also provided, which comprises the following steps: clamping a material bar in the guide bush, detecting the axial position and / or the radial extension of the collet in the collet holder, and upon detection of a value exceeding or falling below a predetermined position and / or a predetermined radial extension, issuing an alarm and / or acting on the actuator until the exceeded or fallen below value is again exceeded or switched off the machine tool.

[0020] The invention is explained in more detail below with reference to a particularly preferred embodiment shown in the attached drawing.

[0021] Fig.Figure 1 shows a guide bushing 10 for guiding a material bar (not shown). The guide bushing 10 has a collet chuck holder 20 and a collet chuck 30 mounted axially displaceably therein. The collet chuck 30 is designed as a double-cone collet, with the preload of the collet chuck 30 being applied by a pneumatic piston acting on the collet chuck holder 20 via the actuator 40.

[0022] The collet 30 is axially displaced by a pneumatically driven actuator 40, allowing the collet 30 to exert varying clamping forces by running onto the conical seating surfaces. The screw-in depth of the actuator (40) determines the presetting of the collet (30).

[0023] In the example shown, a sensor 50 is provided, which is fixed in the guide bushing 10 and detects the distance between an axially immovable part in the guide bushing 10 and the pneumatic piston or actuator 40. For this purpose, the actuator 40 can, for example, have a flange.

[0024] Using sensor 50, the axial position of collet 30 in collet chuck 20 is determined indirectly by determining the position of actuator 40 relative to guide bushing 10. At the same time, the maximum available travel of actuator 40 and the resulting clamping capacity of collet 30 can be determined. Taking into account the material properties of the material bar, for example, maximum or minimum achievable values ​​can be specified, which must not be exceeded or undercut to avoid damage to the material.

Claims

[1] Guide bush (10) for guiding a material bar, with a collet (30) mounted axially displaceably in a collet holder (20) and an actuator (40) designed for the axial movement of the collet (30), characterized by at least one sensor (50) which directly or indirectly detects the axial position and / or the radial extent of the collet (30) in the collet holder (20). [2] Guide bush (10) according to claim 1, characterized by that the sensor (50) detects the position of the actuator (40) relative to the guide bush (10), wherein the collet (30) is firmly connected to the actuator (40). [3] Guide bush (10) according to one of the preceding claims, characterized by that the sensor detects the gap between the inner diameter of the collet holder (20) and the outer diameter of the collet (30). [4] Guide bush (10) according to one of the preceding claims, characterized bythat the collet (30) is a pull collet or a double cone collet. [5] Guide bush (10) according to one of the preceding claims, characterized by a control system that emits an alarm signal when a predetermined value detected by at least one sensor is exceeded or undershot. [6] Guide bush (10) according to one of the preceding claims, characterized by a control acting on the actuator (40) when a predetermined value detected by at least one sensor is exceeded or undershot. [7] Guide bush (10) according to one of claims 5 and 6, characterized by that the control is wirelessly connected to the guide bush (10). [8] Machine tool with a guide bush according to one of the preceding claims. [9] Method for controlling a machine tool with the features of claim 8, characterized by the steps: - Clamping a material rod into the guide bush (10), - detecting the axial position and / or the radial extension of the collet (30) in the collet holder (20), and - upon detection of a value exceeding or falling below a predetermined position and / or a predetermined radial extent, issuing an alarm and / or acting on the actuator (40) until the exceeded or fallen below value is again exceeded or switched off the machine tool.

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