Method and device for automatic thread testing

Abstract

Method for testing a thread of a test specimen (09), comprising the following process steps: - Pick-up of the test specimen (09) by a delivery device, (02) in particular a multi-axis robot; - Transferring the test specimen (09) into an approach position in which there is contact or a slight distance between the test specimen (09) and a test mandrel (04) of a test unit; by transferring the test specimen (09) from the delivery device (2) into the approach position; - Transferring the test specimen (09) and the test mandrel (04) to an initial position, for which purpose the feed device (02) applies a predetermined force to the test specimen (09) linearly, in particular vertically, against the test mandrel (04) and the test mandrel (04) retracts in the direction of the force application until the initial position is reached; - Screwing the test mandrel (04) into the test specimen (09) via a drive (05) connected to the test mandrel (04); - Unscrewing the test mandrel (04) from the test specimen (09); - Recording of measured values ​​regarding feed rate and / or torque of the test mandrel (04) at least during the screwing in and / or screwing out of the test mandrel (04) by at least one measuring transmitter; - Transfer of the test specimen (09) to a storage position by the delivery device (02).

Description

[0001] The present invention relates to a method for testing a thread of a test specimen.

[0002] Various approaches for testing threads on components or test specimens are known from the state of the art. On the one hand, there are thread testing units that can be manually inserted and / or used by an operator. One such thread testing unit is known, for example, from DE 20 2018 102 259 U1. These devices require significant personnel effort and are only partially suitable for testing large series or large quantities of test specimens. The known thread testing devices for manual use are more suitable for testing small or very small series, as well as for random testing of test specimens.

[0003] Semi-automated or fully automated thread testing systems are also known. For example, DE 10 2015 102 787 B4 describes a device and method for thread testing in which a multi-axis adjustable testing unit is moved toward the test specimens to be tested, performs the thread test, and is then moved to the next test specimen. Such approaches have the disadvantage that the control or activation of the testing unit is complex and requires the highest precision. Furthermore, relatively complex system technology is required, which requires considerable resources both in acquisition and in operation and maintenance. Due to its complexity alone, it also results in a relatively high susceptibility to errors.

[0004] Two product videos from the ERLO Group, "ERLO Group's revolutionary thread quality checking system, the Interceptor" and "Testing the INTERCEPTOR, thread checking system," showcase an automated thread testing system from the ERLO Group. A thread testing mandrel is movably mounted in the work area and moved toward the threaded holes to inspect them. The videos are published online at https: / / www.youtube.com / watch?v=Heuk3SgNHIg and https: / / www.youtube.com / watch?v=STbUVolzyy8

[0005] DE 10 2018 008 841 A1 describes a cleaning system for workpieces with a centrally located robot for handling the workpieces. At least one device is provided for measuring or testing the cleaning results.

[0006] DE 10 2014 005 434 A1 describes a control device for a robot which uses force measurement to detect the position and orientation of workpieces on the robot tool after a so-called reach into the box.

[0007] DE 10 2018 006 060 A1 describes a universally applicable thread cutting, thread forming and thread testing device.

[0008] DE 32 42 532 A1 describes a device for the automated testing of workpieces and the electro-optical test probes used for this purpose. These optical probes are said to offer great flexibility in application.

[0009] Based on this prior art, it is therefore the object of the present invention to propose a method for testing a thread of a test specimen and a corresponding thread testing device which overcomes the disadvantages of the prior art and in particular enables a largely fully automatic thread testing with a simple system technology.

[0010] This object is achieved with the features of the method according to claim 1.

[0011] Advantageous embodiments are the subject of the dependent claims, the description, in particular the description of the figures and the associated figures.

[0012] Overall, and also to avoid unnecessary repetition, features disclosed by the device should be considered as correspondingly disclosed and claimable by the method, and vice versa.

[0013] The method according to the invention for testing a thread of a test specimen comprises the following method steps: First, the test piece is picked up by a delivery device, in particular a multi-axis robot. Picking up can be accomplished in various ways. On the one hand, other system components, such as conveyors or feeders, can transfer the test piece onto or into a receptacle of the delivery device. Alternatively, the delivery device can also independently or actively effect or cause the pick-up of the test piece, for example, using a gripping device of the delivery device.

[0014] In a subsequent process step, the test specimen is transferred into an approach position in which there is contact or a slight distance between the test specimen and a test mandrel of a substantially stationary or fixed test unit, by the test specimen being transferred from the feed device into the approach position. This already enables various advantages. Since the approach position does not necessarily have to make contact with the test mandrel, the transfer or pickup of the test specimen onto or to the feed device, in particular the multi-axis robot, can conversely also take place with relatively low precision. A further advantage achieved by feeding the test specimen to the test unit is that, as will be explained in more detail below, the test unit can be of correspondingly simple design and requires only a minimum of control or activation.Likewise, for the delivery or movement of the test piece to the test unit, only a simple trajectory with a reasonably precise end point, namely the approach position, needs to be executed by the delivery device, so that this can also be specified and executed relatively easily, requiring relatively little system technology. As already indicated, the delivery device can be designed as a multi-axis robot with a corresponding end-mounted holder for at least one test piece.

[0015] In a subsequent process step, the test specimen and the test mandrel are transferred to an initial position. For this purpose, the feed device applies a predefined force to the test specimen linearly, particularly vertically, against the test mandrel, and the test mandrel retreats in the direction of the applied force until the initial position is reached. This process step also achieves various advantages. On the one hand, the joint transfer of the test mandrel and the test specimen to the initial position can enable a thread test, particularly with regard to the thread depth, based on relative measured values ​​starting from the initial position. Accordingly, the initial position can be used as a reference value for any displacement or depth measurements.This provides a particularly simple way to minimize or completely eliminate the effort otherwise required for the precise arrangement and alignment of the test specimen and test unit before starting the thread test. This also means that the starting position of the test unit and / or the test specimen does not, and need not, represent an absolute or fixed / identically reproducible position with regard to the testing of different test specimens. Instead, the force applied or generated by the feed device to transfer the test specimen and test unit from the approach position to the starting position, in conjunction with the weight of the test unit and, if applicable, other forces, which will be discussed in more detail below, is responsible for the respective starting position reached or approached.This also shows that it is possible to work with relatively simple system technology and correspondingly low precision, since, in particular in the case of a non-absolute or non-fixed starting position and / or an at least partially relative measurement or measurement of the thread to be tested, the force applied by the feed device to move the test unit and test specimen into the starting position can also be provided with a corresponding tolerance or variance.

[0016] After reaching the starting position, a further method step of the method according to the invention involves screwing the test mandrel into the test piece via a drive connected to the test mandrel. This is a generally known method step in thread testing. The drive can be designed as an electric motor, for example. However, a pneumatic drive could also be used. The test mandrel can have an internal or external thread in order to be able to test or measure both internal and external threads on the test piece. In a further method step, which is also known per se or of the generic type, the test mandrel is unscrewed from the test piece.

[0017] In the method according to the invention, measured values ​​are recorded by at least one sensor at least during the screwing in and / or unscrewing of the test mandrel into / out of the test piece. The sensors can advantageously be designed so that they can directly or indirectly measure or record the torque and / or feed rate of the test mandrel. This can preferably be used to check a specified thread depth and / or the accuracy of the thread.

[0018] After the test mandrel is removed from the test piece, the test piece is transferred to a storage position by the feed device. In other words, this means that after the actual inspection of the test piece's thread, the feed device again actively carries out the conveyance or transport of the test piece. If necessary, it can be provided that after the test piece has been transferred to a storage position, another system component, such as a conveyor, a gripper arm, or the like, carries out the further transport or movement of the test piece, possibly also depending on the test result.

[0019] As already stated above, the basic idea of ​​the invention is based on a concept in which the test specimen is actively moved or delivered to a substantially static or stationary test unit by an adjustment device and the test unit, in particular before the start of the actual test, carries out a compensating movement together with the test specimen, which compensates for or overcomes tolerances or inaccuracies in the delivery of the test specimen, so that only minimal plant engineering expenditure has to be incurred for the test unit and a relatively simple delivery device, for example a multi-axis robot with a corresponding end-side holder or holder for test specimens, enables a thread test of the test specimen.This enables largely automated or almost fully automated thread testing with minimal equipment requirements as well as minimal effort for setting up and maintaining the thread testing system and the process for testing threads.

[0020] In a first advantageous embodiment of the method, it can be provided that the test specimen remains or is held in the starting position while the test mandrel is being screwed in and / or unscrewed. Conversely, this also means that in this embodiment the test mandrel is lowered when screwed into the test specimen and, conversely, is raised again when screwed out of the test specimen. However, since the testing unit or parts of the testing unit, in particular the test mandrel, are designed to move back from the approach position to the starting position when transferred, the test mandrel can perform the corresponding up and down movement even if the position of the test specimen remains unchanged. On the one hand, this allows for simple control and operation of the feed device, which can remain in the starting position after reaching it.Furthermore, as will be explained in more detail later, this allows the thread depth test to be determined via the height difference of a reference point of the test mandrel between the initial position and the position at which switching takes place between screwing into the test piece and unscrewing from the test piece, since in a fixed or unchanged test piece this height or height difference corresponds to the thread depth.

[0021] In an advantageous embodiment, it can further be provided that the measured values ​​are recorded via a measuring probe as a measuring transducer, which measures the stroke of the test mandrel in the direction of the force application. The measuring probe can be designed as a displacement sensor and, for example, determine the stroke of the test mandrel relative to a stationary or fixed base of the testing unit. As already indicated, the relative displacement difference between the initial position of the measuring probe, on the one hand, and the position of the measuring probe when reaching the end of the thread or for switching between screwing in and unscrewing the test mandrel is advantageously measured or determined.

[0022] In an alternative or additional, particularly preferred variant of the method, it can be provided that the measured values ​​are recorded via the drive of the test mandrel as a measured value sensor, if necessary in conjunction with a corresponding evaluation unit. This is sometimes particularly advantageous because the measured values ​​can then be taken directly from a corresponding control and evaluation unit as drive parameters of the drive, and no further sensors need to be provided in addition to the drive itself. It is particularly advantageous to use the drive parameters, for example the current consumption of an electrical or electromagnetic drive, to infer or calculate the torque of the test mandrel, so that a torque measurement can be carried out using the drive parameters themselves.The determined or measured torques can then be used to determine whether the thread is free from defects, for example, if a first torque limit is not exceeded. Furthermore, the measured torques can also be used to identify the end of the thread and / or thread damage. Appropriate limit values ​​can also be defined for this purpose. In an advantageous embodiment, such a limit value can also be used to automatically switch the drive direction of the test mandrel, thus triggering the transition between screwing in and unscrewing the test mandrel.

[0023] In addition to or as an alternative to a measuring probe that records the stroke of the test mandrel, the thread depth can also be measured or calculated using the drive as a measuring sensor and a determination or measurement of the rotations or revolutions of the test mandrel in conjunction with knowledge of the pitch of the thread to be tested or of the test mandrel.

[0024] In a further, particularly advantageous embodiment, as already indicated above, it can be provided that the starting position is detected, recorded, or recorded as a relative reference point for measuring the stroke of the test mandrel. This allows a displacement measurement or stroke measurement of the test mandrel to be performed, regardless of the actual or absolute position of the starting position, in response to the force applied to the test mandrel and the test specimen by the feed device, and thus, for example, the thread depth can be measured.

[0025] In a further, particularly preferred embodiment of the method, it can be provided that the test mandrel and / or the drive are prestressed against the weight force via an elastic prestressing element, in particular a spring unit, and the transfer of the test mandrel into the initial position takes place while the prestressing element is relaxed.

[0026] Preloading the test mandrel and / or the drive against the weight or against the force vector of the weight results in a portion of the weight of the test mandrel and the drive being compensated or diverted by the preload element and thus not acting on the thread even during a thread test, thereby minimizing the risk of thread damage caused by the test mandrel. Advantageously, the preload element can be designed so that a preload is still present even when the initial position is reached, or in other words, the preload element is not completely released.If, according to the advantageous embodiment described above, the test specimen is held in the initial position by the feed device during the test, this results in the test mandrel having to rotate into the test specimen and lower itself against the preload force of the preload element when screwing into the thread of the test specimen, which accordingly reduces the total weight force of the test mandrel on the test specimen and, in conjunction with the force acting on the test specimen from the feed device, leads to a state of equilibrium in which only a minimal axial force is applied to the test specimen, in particular to the thread, during the test.

[0027] Furthermore, an advantageous pre-tensioning element also makes it possible for the transfer of the test mandrel and / or drive from the approach position to the starting position to be facilitated by the corresponding application of force by the feed device, because the pre-tensioning element supports the movement of the test mandrel and / or drive against the effect of the weight force.

[0028] In a further, particularly preferred embodiment of the method, it can be provided that the transition between screwing the test mandrel into and out of the thread of the test piece and out of the thread of the test piece is controlled based on a comparison of measured values ​​and specified limit values. As already indicated above, for example, a limit value for a torque and / or a limit value for a relative stroke measurement can be defined and specified. Upon reaching or exceeding these values, the transition occurs or a switch is performed, which changes the direction of rotation of the drive and thus the direction of rotation of the test mandrel.

[0029] According to a further, particularly advantageous embodiment of the method, it can also be provided that the test piece remains in a receiving unit of the delivery device during the method, at least between the time the test piece is picked up by the delivery device and the time the test piece is transferred to a storage position. Since no further transfers of the test piece take place, for example into a holder of the testing unit or the like, the system technology can also be minimized. Likewise, a relatively fast thread test is achieved, since no further relocation, transfer, or fastening steps need to be carried out after the delivery device has picked up the test piece, in particular into a receiving unit. The receiving unit can be designed, for example, as a gripping device or a pair of tongs.However, the receiving unit can also be designed as a plate device or a bowl device.

[0030] The above-mentioned object is also achieved by a thread testing device not encompassed by the invention with a testing unit which has a test mandrel which can be driven rotatably by a drive, wherein a feed device, in particular a multi-axis robot, is provided for receiving, holding and moving a test piece which has a thread to be tested, and wherein the testing unit is arranged in a stationary manner and the test mandrel is mounted so as to be displaceable only linearly in the region of a compensating movement relative to the stationary testing unit.

[0031] As already explained above, this device enables thread testing with low technical expenditure, which can also be carried out largely or completely automated or automatically, in that the feed device picks up a test specimen, transfers it to the test unit, holds or positions it during the test and puts it down or transports it away after the test.

[0032] According to an advantageous embodiment, the feed device can be configured to pick up the test piece, feed it to the test unit, hold it during the test, in particular screwing in and out of the test mandrel, and place it there. This also allows for a threading device for automatic thread testing to be realized with minimal equipment complexity, namely preferably only a multi-axis robot with a holding or storage device, which can be arranged at the end, for example, which would otherwise only require a stationary test unit. The test unit and the feed device can advantageously be arranged in a processing cell.

[0033] According to a further, particularly preferred embodiment, it can be provided that the drive, together with the test mandrel, is mounted for linear movement in the region of the compensating movement. In the context of the present disclosure, a stationary test unit is to be assumed if a base of the test unit, which is used, for example, to hold or support the drive and / or the test mandrel, is immobile or stationary. The movable, in particular linearly movable, design of the test mandrel and / or the drive, as well as any other parts of the test unit, does not lead to a contradiction in the sense that the test unit as a whole is not designed or constructed to be stationary.Rather, the stationary arrangement of the test unit is to be understood in such a way that the test unit is not guided to the test object, but that, conversely, the delivery device brings about the transport of the test object to a stationary test unit.

[0034] In a further preferred embodiment of the thread testing device, it can be provided that the linearly movable bearing of the test mandrel and / or the drive cooperates with an elastic prestressing element, in particular a spring, so that the test mandrel and / or the drive is prestressed against the weight force.

[0035] This facilitates the execution of the evasive movement and can also have advantageous effects when carrying out the thread test, in particular when screwing in and out the test mandrel, and in particular minimizes the risk of damage or injury to the thread to be tested.

[0036] According to a further, likewise preferred embodiment, the testing unit can be provided with a sensor that detects a stroke of the test mandrel and / or the drive along the linearly movable bearing relative to the stationary testing unit. As already explained above, the sensor can detect the thread depth via the stroke of the test mandrel starting from the initial position.

[0037] Furthermore, it can advantageously be provided that an evaluation unit configured to evaluate drive parameters is provided as the sensor. This allows a simple evaluation unit, without the need for additional sensors or measuring units, to perform a measurement based on the evaluation of the drive parameters, for example, a torque measurement and / or a displacement measurement, at least indirectly via the revolutions of the test mandrel and the thread pitch and / or the current consumption.

[0038] In a further, particularly advantageous embodiment, the thread testing device can comprise a machining cell in which the feed device and the testing unit are arranged. Particularly preferably, the testing unit can be arranged stationary in the machining cell, and only the test mandrel and / or the drive are mounted so as to be linearly displaceable relative to the stationary testing unit, so that the feed device picks up the test pieces and feeds them to the stationary testing unit and, if necessary, also effects or causes the removal of the test pieces after testing by the stationary testing unit.

[0039] Individual details of advantageous embodiments and exemplary embodiments of the present invention are explained using the following, purely schematic representations.

[0040] Showing: Fig. 1a to Fig. 1c: a schematic representation of a sequence of a method according to the invention for a thread testing device; Fig. 2: an exemplary test unit for use in a test device not according to the invention and / or a method according to the invention.

[0041] In Fig. 1a schematically shows a thread testing device 01, which is not encompassed by the invention. This can be arranged in a processing cell (not shown) and comprises a feed device 02, which can preferably be designed as a multi-axis robot, and a testing unit 03. The testing unit 03 can, for example, have a test mandrel 04, a drive 05 and a length measuring sensor 06. The testing unit 03 is arranged in a stationary manner. Only the drive 05 together with the test mandrel 04 are mounted for linear movement, in particular in the vertical direction V. For example, a guide carriage 14 is arranged or formed on a stationary base plate 10, which enables the movable mounting of the drive 05 and the test mandrel 04. In this direction of movement V, the movable drive 05 and the test mandrel 04, which can be moved together with the drive 05, are preloaded against the force of gravity by, preferably two, preload elements 07.In the representation of the . Fig. 1a, the feed device 02 has just picked up a test piece 09 with a thread to be tested, for example via an end-side gripping device 08, and begins the feed or feeding to the stationary test unit 03.

[0042] In the presentation of the Fig. 1b, the feed device 02 has moved the test piece 09 into an approach position relative to the test unit 03. In this position, either contact with the test mandrel 04 has already been established or the smallest possible offset in the vertical direction V and the best possible concentric alignment relative to the test mandrel 04 perpendicular to the vertical direction V have been established. Fig. 1a initially shows a situation in which there is still a distance in the vertical direction V between the test specimen 09 and the test mandrel 04.

[0043] In the presentation of the Fig. 1b, an adjustment of the feed device has already been made so that contact has been achieved between the test piece 09 and the test mandrel 04.

[0044] In a subsequent method step, a force is applied to the test unit 03 along the vertical direction V by the feed device 02 together with the test piece 09 held by it, which force causes the test unit 03, in particular the drive 05 and the test mandrel 04, to retreat or retreat along the vertical direction V and, if there was still a distance between the test piece 09 and the test mandrel 04 in the vertical direction V during the previous method step, a contact or mechanical contact is initially established between the test mandrel 04 and the test piece 09.

[0045] Due to the predetermined force applied by the feed device 02, an initial position is reached for both the test specimen 09 and the test unit 03, in particular the test mandrel 04 and the drive 05, which can be recorded or detected, for example, by the sensor 06. For this purpose, the guide carriage 14 can, for example, be moved relative to the base plate 10 of the test unit 03 along the vertical direction V. A compensating element 15, preferably a compensating head, can advantageously be provided between the drive 05 and the test mandrel 04.

[0046] By lifting the test mandrel 04 and drive 05 against the vertical direction V, the pre-tensioning elements 07 are also released. Fig. 1c shows, for example, a situation after reaching the initial position, in which the test unit 03, in particular the drive 05 and the test mandrel 04, are in a position opposite to the representation of the Fig. 1b has been raised and the pre-tensioning elements 07 have been released. The lifting can be carried out by moving the guide carriage 14 along the vertical direction V.

[0047] Starting from the initial position of test mandrel 04, drive 05 and test piece 09 (as in Fig. 1c), the thread test can then begin by screwing the test mandrel 04 into the test piece 09, in particular into a thread of the test piece 09. For this purpose, the test mandrel 04 can preferably first be driven in a first direction of rotation, which would in itself cause the test mandrel to be unscrewed from the thread in order to determine or establish the thread end of the test piece 09 by the thread ends sliding against one another. From this point, the direction of rotation of the test mandrel 04 can then be reversed and the test mandrel 04 can be screwed into the thread of the test piece 09. In this case, the measuring sensor 06 can measure, for example, the distance traveled by the test mandrel 04 and / or the drive 05. In other words, the movement or translational displacement of the guide carriage 14 relative to the base plate 10 can be determined.Furthermore, for example, the torque with which the test mandrel 04 is screwed into the thread of the test piece 09 can also be recorded by evaluating drive parameters of the drive 05.

[0048] When a target depth is reached and / or when a limit torque or other limit value of a measuring sensor is exceeded, the drive direction of the test mandrel 04 can be switched again via the drive 05, so that either when the thread bottom or thread end of the test piece 09 is reached or when a thread damage of the test piece 09 is encountered, the test mandrel 04 is unscrewed from the thread of the test piece 09. The position reached after unscrewing again corresponds to the representation of the Fig. 1c, since the feed device 02 advantageously holds the test specimen 09 in the initial position during the test.

[0049] Based on the measured values ​​recorded by the sensors, the thread can be classified as faultless or faulty after or in parallel with the test, for example depending on the maximum measured torques and / or the maximum depth reached.

[0050] After the test mandrel 04 has been completely unscrewed, for example by reaching the initial position of the test mandrel 04 and / or the drive 05 again, the test specimen 09 can be removed and / or deposited by the feed device 02. In the meantime, a situation may occur which is related to the representation of the Fig. 1a, in which the test specimen 09 is removed from the test unit 03, possibly on a different trajectory than upon delivery, wherein the removal of the test specimen 09 lowers the test unit along the vertical direction V until the preload force of the preload elements 07 and the weight force of the drive 05 and the test mandrel 04 are in equilibrium or until a guide carriage 14 reaches a lower stop and the preload elements 07 have reached a maximum preload.

[0051] The illustrated thread testing device, which is not encompassed by the invention, and the described method have the advantage that they can be integrated into robot systems without additional control, particularly when the feed device 02 is designed as a multi-axis robot, and can therefore be implemented in a correspondingly small / compact, lightweight and cost-effective manner. In addition, the idle speed of the system can be individually adjusted for the respective thread or thread type to be tested and can be monitored or checked via an output signal from the drive 05. Damage protection for the test mandrel 04 is also made possible by a predefinable or adjustable maximum torque or other drive parameters of the drive 05. Furthermore, the system orthe thread testing device 01 is designed in such a way that no electronic or pneumatic feed of the test mandrel or the testing unit 03 is required, but rather the linearly movable design of the test mandrel 04 and the method, in particular lifting the test mandrel 04 to reach the starting position, ensures that the feed of the testing unit or the feed of the test mandrel 04 is effected by its own weight, in particular of the test mandrel 04 and / or the drive 05. Furthermore, the device and the method allow direct approach to the approach position and the starting position by the feed device 02. Further advantages are that simple control and evaluation of the feed device 02 and the testing unit 03 is enabled.

[0052] In the presentation of the Fig.2 shows an embodiment of a testing unit 03, which is not encompassed by the invention, again in detail. This has a base plate 10, which can be arranged, in particular screwed, in a machining cell (not shown). Furthermore, the testing mandrel 04 and the drive 05 are movably connected to the base plate 10 via a mounting unit 11. The mounting unit 11 can, for example, be mounted so as to be linearly movable in the vertical direction V via the guide carriage 14. The mounting unit 11 and / or the guide carriage 14 can also be coupled to the pretensioning elements 07, so that the drive 05 and the testing mandrel 04 are pretensioned against the force of gravity via these elements.

[0053] Via a projection 12 of the mounting unit 11, contact can be made to a sensor 06, which measures and / or reads the position of the drive 05 and the test mandrel 04 and / or the guide carriage 14 with respect to the base plate 10.

[0054] The test mandrel 04 can be connected to the drive 05 in a replaceable or interchangeable manner. The drive 05 can be controlled and driven via corresponding inputs and outputs 13, and corresponding drive parameters can be read out.

[0055] Reference symbol 01 Thread testing device 02 Delivery device 03 Test unit 04 Test mandrel 05 Drive 06 Length measuring sensor 07 two preload elements 08 Gripping device 09 Candidate 10 Base plate 11 Assembly unit 12 lead 13 exits 14 guide carriages 15 Compensating element V Vertical direction

Claims

[1] Method for testing a thread of a test piece (09), comprising the method steps: - Picking up the test specimen (09) by a delivery device (02), in particular a multi-axis robot; - Transferring the test specimen (09) into an approach position in which there is contact or a slight distance between the test specimen (09) and a test mandrel (04) of a test unit; by transferring the test specimen (09) from the feed device (2) into the approach position; - transferring the test piece (09) and the test mandrel (04) into an initial position, for which purpose the feed device (02) applies a force to the test piece (09) linearly, in particular vertically, with a predeterminable force against the test mandrel (04) and the test mandrel (04) retreats in the direction of the force application until the initial position is reached; - screwing the test mandrel (04) into the test specimen (09) via a drive (05) connected to the test mandrel (04); - Unscrewing the test mandrel (04) from the test piece (09); - Recording of measured values with regard to the feed and / or torque of the test mandrel (04) at least during the screwing in and / or unscrewing of the test mandrel (04) by at least one measuring sensor; - Transferring the test specimen (09) into a storage position by the feed device (02). [2] Method according to claim 1, characterized by that the test specimen (09) is held in the initial position during the screwing in and out of the test mandrel (04). [3] Method according to claim 1 or 2, characterized by that the measured values are recorded via a measuring probe as a measuring sensor (06), which measures the stroke of the test mandrel (04) in the direction of the force application. [4] Method according to one of claims 1 to 3, characterized by that the initial position is recorded as a relative reference point for measuring the stroke of the test mandrel (04). [5] Method according to one of claims 1 to 4, characterized by that the measured values are recorded via the drive as a measuring sensor (06). [6] Method according to one of claims 1 to 5, characterized by that the test mandrel (04) and / or the drive (05) is prestressed against the weight force via an elastic prestressing element (07), in particular a spring, and the transfer of the test mandrel (04) into the initial position takes place while the prestressing element (07) is relaxed. [7] Method according to one of claims 1 to 6, characterized by that the transition between screwing in and unscrewing is controlled by a comparison of measured values and specified limit values. [8] Method according to one of claims 1 to 7, characterized bythat the test specimen (09) remains in a receiving unit of the delivery device (02) during the process, at least between the pickup of the test specimen (09) by a delivery device (02) and the transfer of the test specimen (09) into a storage position.

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