DE102020215167A1 - Method for determining a final tightening torque or a final tightening angle for screws in a screw connection - Google Patents

Abstract

Method (100) for determining a final tightening torque and/or a final tightening angle for a screw in a screw connection, comprising the steps of:- detecting (101) at least one measured variable during the production of the screw connection with the screw;- deriving (102) a final tightening torque and/or a final tightening angle for the screw of the screw connection as a function of the recorded at least one measured variable.

Description

In a first aspect, the present invention relates to a method for determining a final tightening torque or final tightening angle for a screw in a screw connection and a corresponding computer program, machine-readable storage medium and electronic control device.

In a second aspect, the present invention relates to a method for producing a screw connection and a corresponding device.

State of the art

According to the current state of the art, screw connections or screw connections are tightened under torque control, angle of rotation control or distance limit control. The disadvantage of all these methods is the scatter in the preload force of the screws. These mainly result from screw or screw-in thread-specific scattering (e.g. scattering of the coefficient of friction or scattering of geometrical features of the screw or thread).

Disclosure of Invention

• Erfassen mindestens einer Messgröße während des Herstellens der Schraubverbindung mit der Schraube.

Against this background, the present invention creates a method for determining a final tightening torque or a final tightening angle for a screw in a screw connection. The procedure includes the steps:

• Detecting at least one measured variable during the production of the screw connection with the screw.

Deriving a final tightening torque or a final tightening angle for the screw of the screw connection as a function of the recorded at least one measured variable.

With the aid of the method according to the present invention, the scattering of the prestressing force in screw connections or screw connections can be reduced.

The invention is based on the finding that measured variables that occur and are recorded during the production of a screw connection can be used to use a mathematical method in general or a method of machine learning (ML method) in particular to a screw-specific final tightening torque or a screw-specific final tightening angle.

This results in e.g. the advantages that the spread of the preload forces can be minimized. As a result, the costs for material or screw size can be saved accordingly. And furthermore, the robustness and reliability of the screw connection can be increased.

According to an embodiment of the method of the present invention, the derivation is performed using an artificial neural network. The artificial neural network can be an autoencoder.

When an autoencoder is used as an artificial neural network, the input data and the output data are those that occur and are recorded during the screwing process up to a predetermined point in time or progress. The architecture of an autoencoder, which has a so-called "bottleneck", allows the artificial neural network to learn and extract important features in the measured variables unmonitored or self-monitored. From the result, which is a compressed representation of the input data, an assignment to the optimal final tightening torque or final tightening angle can be created by initially comparing a small number of measured screwing processes. This assignment can be done manually or with an additional neural network.<>

According to an embodiment of the method of the present invention, the artificial neural network has been trained with data accumulated during the making of bolted connections with bolts.

According to one embodiment of the method of the present invention, the at least one measured variable comprises less than 100% of the data occurring during the production of the screw connection.

The at least one measured variable can include more than 80% or at most 90% of the data generated during the production of the screw connection.

A further aspect of the present invention is a computer program which is set up to carry out all the steps of the method according to the present invention.

Another aspect of the present invention is a machine-readable storage medium on which the computer program according to the present invention is stored.

A further aspect of the present invention is an electronic control unit which is set up to carry out all steps of the method according to the present invention.

The electronic control unit can be a Field Programmable Gate Array (FPGA). By using an FPGA as an electronic control unit, which is set up to carry out all steps of the method according to the present invention, it is possible to improve the processing time for determining the final tightening torque or final tightening angle.

A further aspect of the present invention is a manufacturing method for producing a screw connection with a screw.

• Herstellen der Schraubverbindung mit der Schraube und Erfassen mindestens einer Messgröße während des Herstellens der Schraubverbindung.

The procedure includes the following steps:

• Establishing the screw connection with the screw and detecting at least one measured variable during the establishment of the screw connection.

Determining a final tightening torque or a final tightening angle for the screw in the screw connection by means of a method according to the present invention as a function of the at least one measured variable recorded.

Application of the specific final tightening torque or the specific final tightening angle.

A further aspect of the present invention is a device for producing a screw connection, which is set up to carry out all the steps of the method according to the further aspect of the present invention.

character list

Further features and advantages of the aspects of the present invention are explained below using embodiments with reference to the figures.

• 1 ein Ablaufdiagramm des Verfahrens gemäß dem ersten Aspekt der vorliegenden Erfindung;
• 2 ein Ablaufdiagramm des Verfahrens gemäß dem zweiten Aspekt der vorliegenden Erfindung;
• 3 ein Diagramm mit erfassten Messgrößen während des Herstellens einer Schraubverbindung.

Show it:

• 1 a flowchart of the method according to the first aspect of the present invention;
• 2 a flow chart of the method according to the second aspect of the present invention;
• 3 a diagram with measured variables recorded during the manufacture of a screw connection.

1 shows a flow chart of the method 100 for control according to the first aspect of the present invention.

The method 100 occurs during the making of a bolted connection with a bolt.

In step 101, at least one measured variable is recorded during the production of the screw connection with the screw. In principle, the at least one measured variable can be one or more arbitrary measured variables. Central to the invention is that the at least one measured variable is related to the production of the screw connection. For example, the measured variable recorded can be the torque and the current of the drive spindle of the screwing device.

In step 102, a final tightening torque or a final tightening angle for the screw of the screw connection is derived as a function of the at least one measured variable recorded.

2 shows a flow chart of the production method 200 for producing a screw connection with a screw according to the second aspect of the present invention.

In step 201, at least one measured variable is recorded during the production of the screw connection with the screw.

In step 202, a final tightening torque or a final tightening angle for the screw in the screw connection is determined using the method according to the first aspect of the present invention as a function of the at least one measured variable recorded.

For this purpose, the at least one measured variable, for example a value curve of the at least one measured variable or, if several measured variables are recorded, the value curves of the several measured variables are fed to the method for determining a final tightening torque or a final tightening angle according to the first aspect of the present invention and, depending on this, the final tightening torque or the final tightening angle is determined.

In step 203 the specific final tightening torque or the specific final tightening angle is applied to the screw of the screw connection.

It can be attached, for example, by means of a device for producing a screw connection, for example by means of an appropriately designed screwdriver.

3 shows a diagram with measured variables recorded during the manufacture of a screw connection.

The time progress is plotted on the abscissa. The recorded measured variables are plotted on the ordinate. In the example shown, these are the torque (solid curve) and the current of the drive spindle (dashed curve) of the screwing device. The example shown shows a torque-controlled, double tightening process with downstream determination of a load limit.

In the period up to t0, the screw enters the tapping thread. In the period between t0 and t1, the processes of running into the tapping thread, tapping and screwing into the thread take place. A friction can be derived from the detected moment.

At time t1, the first tightening of the screw is complete.

In the period between t1 and t2, the first tightening is released by 360°. In the period between t2 and t3, the re-tightening takes place, which is completed at time t4.

The downstream determination of a load limit begins from point in time t4.

It is clear that the data of the example shown is only available after the screwing process has been completed.

The present invention is based on the finding that the data that accumulates up to, for example, 90% completion of the screw connection, i. H. until the re-tightening is completed, are sufficient to determine the final tightening torque or the final tightening angle.

This determination or "prediction" of the screw-specific final tightening torque or final tightening angle can be carried out by applying a suitable mathematical method to the data generated during the screwing process. The use of a machine learning method (ML method), in particular an artificial neural network, for example in the form of an autoencoder, has proven to be an advantageous mathematical method.

Although the illustrated example shows a double tightening method, the present invention can also be applied to a single tightening method, e.g. H. apply to tightening procedures that are completed after the initial tightening of the bolt.

Before the screwing process is completed, the applied ML method or the autoencoder determines the final tightening torque or final tightening angle for each individual screw, which leads to a minimal deviation from the required preload force.

In order to achieve this, the ML method is taught using measurement curves. For this teaching, a measured or alternatively an estimated value for the preload force resulting from the input data must be available. In this way, the ML process can use the input data, which is generated before the tightening process is completed, to determine how each screw must be tightened individually.

Claims (10)

Method (100) for determining a final tightening torque and/or a final tightening angle for a screw in a screw connection, comprising the steps: - Detecting (101) at least one measured variable during the production of the screw connection with the screw; - Deriving (102) a final tightening torque and/or a final tightening angle for the screw of the screw connection as a function of the at least one measured variable recorded. procedure after claim 1 , whereby the derivation takes place by means of an artificial neural network. procedure after claim 2 , where the artificial neural network is an autoencoder. procedure after claim 2 or 3 , where the artificial neural network was trained with data that arose during the manufacture of screw connections with screws. Method according to one of the preceding claims, wherein the at least one measured variable comprises less than 100% of the data occurring during the production of the screw connection, in particular more than 80%, in particular a maximum of 90% of the data occurring during the production of the screw connection. Computer program which is set up, all steps of the method according to one of Claims 1 until 5 to execute. Machine-readable storage medium on which the computer program claim 6 is saved. Electronic control unit, in particular FPGA, which is set up, all steps of the method according to one of Claims 1 until 5 . Production method (200) for producing a screw connection with a screw, comprising the steps: - producing (201) the screw connection with the screw and detecting at least one measured variable during the production of the screw connection; - Determining (202) a final tightening torque and/or a final tightening angle for the screw in the screw connection by means of a method of one of Claims 1 until 5 depending on the detected at least one measured variable; - Attaching (203) the specific final tightening torque and/or the specific final tightening angle to the screw of the screw connection. Device for producing a screw connection, which is set up, according to all steps of the method claim 9 to execute.

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