US-12623297-B2 - Method for producing a thread on at least one end of at least one metal tube and thread-cutting facility

US12623297B2US 12623297 B2US12623297 B2US 12623297B2US-12623297-B2

Abstract

A method for producing a thread on at least one end of at least one metal tube ( 3 ) by machining the metal tube ( 3 ) in at least one CNC-controlled machine tool ( 2 ) comprises an optical measurement of the thread during the thread-cutting process and/or following the thread-cutting process, and the electronic detection and evaluation of the measurement data of the thread profile and/or of a sealing lip ( 6 ) of the thread, and the derivation of control commands for controlling the machine tool ( 2 ) from the measurement data with use of at least one closed-loop control unit coupled to the machine tool ( 2 ). A corresponding thread-cutting facility is also disclosed.

Inventors

Jochen Schmitz
Frank d'Hone
Tim Küppers
Helge Dähndel

Assignees

SMS GROUP GMBH

Dates

Publication Date: 20260512
Application Date: 20210915
Priority Date: 20201022

Claims (19)

1 . A method for producing a thread on an end of a metal tube ( 3 ) by machining the metal tube ( 3 ) in a CNC-controlled machine tool ( 2 ), the method comprising: optically measuring the thread during a thread-cutting process and/or following the thread-cutting process; electronically detecting and evaluating measurement data of a thread profile and/or of a sealing lip ( 6 ) of the thread; and deriving control commands for controlling the machine tool ( 2 ) from the measurement data by a closed-loop control unit coupled to the machine tool ( 2 ), wherein optically measuring the thread is performed by a measurement head with two opposing legs, each of the two opposing legs comprising a U-shaped frame arranged around the metal tube, with a camera and a light source positioned opposite the camera being arranged in each of the two opposing legs to form a respective measuring section across each U-shaped frame, wherein optically measuring of the thread is carried out following the thread-cutting process, in a production line that is configured for serial processing of a plurality of metal tubes ( 3 ) two or more cycles after the thread-cutting process.
2 . The method according to claim 1 , wherein the closed-loop control unit comprises a self-learning algorithm for deriving the control commands.
3 . The method according to claim 1 , wherein the thread is a conical external thread ( 4 ) suitable to form a pressure-resistant, gas-tight and/or liquid-tight connection with a complementary internal thread of a further metal tube ( 3 ).
4 . The method according to claim 1 , wherein optically measuring of the thread is carried out by a measuring head ( 10 ) guided on a manipulator and having an optical measuring section ( 16 ).
5 . The method according to claim 4 , wherein the measuring head ( 10 ) is configured for the measurement of conical threads with undercut thread flanks ( 5 ).
6 . The method according to claim 4 , further comprising calibrating the measuring head ( 10 ) by a reference component arranged in a measurement station ( 7 ).
7 . The method according to claim 4 , further comprising: fixing the metal tube ( 3 ) in a defined measuring position within a measurement station, positioning the measuring head ( 10 ) relative to the metal tube ( 3 ) with a system for position recognition of the measuring head ( 10 ), aligning the measuring section ( 16 ) with respect to a tube axis, and traversing the thread profile and/or the sealing lip ( 6 ) of the metal tube ( 3 ).
8 . The method according to claim 1 , wherein the control commands are selected from the group consisting of a position correction of a tool relative to the metal tube to be machined in case of incorrect setting parameters or for wear compensation, a change of a tool due to wear, a selection of a tool due to predetermined geometric requirements on the thread profile, an adjustment of a speed and/or torque of a chuck of the machine tool ( 2 ), and a change of a cycle time of the machine tool ( 2 ).
9 . The method according to claim 1 , wherein the thread to be cut is configured in a software program by configuration data, and wherein the configuration data is compared with the measurement data.
10 . The method according to claim 1 , wherein the measurement data are stored in a quality database with a unique identification and assignment of the metal tube ( 3 ).
11 . A thread-cutting facility for producing threads at ends of metal tubes, comprising: a CNC machine tool ( 2 ) for machining a metal tube ( 3 ) to be provided with threads; a control device for implementing control commands to the machine tool ( 2 ); a device for optical measurement of the cut thread; a closed-loop control unit for deriving control commands from measurement data generated by the device for optical measurement, wherein the device for the optical measurement is coupled to the control device, and wherein the device for the optical measurement includes a measurement head with two opposing legs, each of the two opposing legs comprising a U-shaped frame arranged around the metal tube, with a camera and a light source positioned opposite the camera being arranged in each of the two opposing legs to form a respective measuring section across each U-shaped frame, wherein the measuring head is linearly movable, by a recirculating ball screw or a lantern pinion, relative to a carrier and pivotable about at least one axis, and wherein a first of the two legs of the measuring head is stationary relative to the measuring head and a second of the two legs is adjustable relative to the first of the two legs.
12 . The thread-cutting facility according to claim 11 , wherein the machine tool ( 2 ) is a lathe, a turn-mill center, a thread-cutting machine, or a sleeve-cutting machine.
13 . The thread-cutting facility according to claim 11 , wherein the machine tool ( 2 ) comprises a rotatable chuck for clamping the metal tube ( 3 ) and a tool holder that can be fixed and positioned relative to the chuck and has a tool.
14 . The thread-cutting facility according to claim 11 , wherein a machining station and a measurement station ( 7 ) are arranged one behind the other in a process line, the machining station comprising the machine tool ( 2 ) and the measurement station ( 7 ) comprising the device for optical measurement of the cut thread.
15 . The thread-cutting facility according to claim 11 , wherein the device for the optical measurement is a measuring head ( 10 ) with an optical measuring section ( 16 ), which is mounted on a manipulator and which is configured to move the measuring head ( 10 ) relative to the metal tube ( 3 ) for measuring a thread profile and/or a sealing lip ( 6 ) of the thread.
16 . The thread-cutting facility according to claim 15 , wherein the measuring head ( 10 ) comprises means for cleaning the thread to be measured.
17 . The thread-cutting facility according to claim 16 , wherein the means for cleaning the thread is a cleaning device acting mechanically and/or with a cleaning fluid.
18 . A thread-cutting facility for producing threads at ends of metal tubes, comprising: a CNC machine tool ( 2 ) for machining a metal tube ( 3 ) to be provided with threads; a control device for implementing control commands to the machine tool ( 2 ); a device for optical measurement of the cut thread; a closed-loop control unit for deriving control commands from measurement data generated by the device for optical measurement, wherein the device for the optical measurement is coupled to the control device, and wherein the device for the optical measurement includes a measurement head with two opposing legs, each of the two opposing legs comprising a U-shaped frame arranged around the metal tube, with a camera and a light source positioned opposite the camera being arranged in each of the two opposing legs to form a respective measuring section across each U-shaped frame, and wherein the measurement data used for deriving the control commands is obtained two or more cycles after machining the metal tube in the CNC machine tool.
19 . The thread-cutting facility according to claim 11 , wherein the camera includes a telecentric optics.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a national stage application, filed under 35 U.S.C. § 371, of International Patent Application No. PCT/EP2021/075267, filed on 15 Sep. 2021, which claims the benefit of German Patent Applications No. 10 2020 213 347.6, filed 22 Oct. 2020 and No. 10 2021 202 211.1 filed 8 Mar. 2021. TECHNICAL FIELD The disclosure relates to a method for producing a thread on at least one end of at least one metal tube by machining the metal tube in at least one CNC-controlled machine tool, comprising an optical measurement of the thread during the thread-cutting process and/or following the thread-cutting process. The disclosure further relates to a thread-cutting facility for producing threads on the ends of metal tubes, and in particular for carrying out the method. BACKGROUND The threads of tubes used for transporting pressurized fluids, such as natural gas or crude oil, which are bolted together in a pressure-resistant, gas-tight and liquid-tight manner, are subject to stringent requirements for leak-tightness. With such OCTG (oil country tubular goods) tubes as casing tubes or riser tubes for oil or gas exploration wells or natural gas or oil production pipelines, conical threads with undercut thread flanks are typically used. A sealing lip is usually attached to the threads on the front side of the tube. Both the thread and the sealing lip must meet the highest precision requirements. In the prior art, in principle it is known to optically measure the threads for quality control of the tubes. A method and a device for the optical measurement of the external thread profile of tubes is known, for example, from WO 2019/09371 A1. The device comprises a support for the tube to be measured and an optical measurement unit with at least one measuring device comprising a light source and a camera arranged in the beam path of the light source for recording a shadow image of the external thread profile, wherein the optical measurement unit is rigidly arranged on a support element that is held pivotably about three spatial axes, wherein furthermore the optical measurement unit has at least two measuring devices whose beam paths cross one another. The method comprises arranging the tubes to be measured on a support, such that the spatial axis runs transversely with respect to a measuring plane of the measurement unit and the external thread is arranged in the beam path between the light sources and the associated cameras, aligning the measurement unit in such a manner that the measuring plane encloses a right angle with the spatial axis, recording shadow images of the external thread by means of the camera of at least one measuring device, and evaluating the shadow images. Another device for measuring a thread is known, for example, from EP 3 465 079 B1. The device comprises a holder for releasably holding a tube, wherein the thread is formed at one end of the tube, a first optical measuring section having a first optical sensor, wherein the first optical measuring section is mounted on a manipulator of the device, which is configured to move the first measuring section relative to the tube, and wherein the first optical measuring section is adjustable about a first adjustment axis relative to a thread axis of the thread, wherein a second optical measuring section of the device with a second optical sensor is arranged on the manipulator, wherein the optical measuring sections altogether form a measuring channel for simultaneous measurement of opposite sides of the thread. The device is characterized in particular by the fact that the measuring channel can be tilted by means of the manipulator about at least a second adjustment axis relative to the thread axis, such that the measuring channel can be freely aligned within a solid angle interval. The measurement data obtained with the known devices and methods are usually detected on a random basis in order to derive findings from this with regard to the wear of the tools for cutting the threads. Moreover, the measurement results are used to record quality assurance data. SUMMARY The disclosure is based on the object of providing a method and a device for producing threads on metal tubes that are improved with regard to the feedback of measurement data from a quality check. The object is achieved by a method as disclosed and claimed and by a thread-cutting facility as disclosed and claimed. One aspect relates to a method for producing a thread on at least one end of at least one metal tube by machining the metal tube in at least one CNC-controlled machine tool, said method comprising an optical measurement of the thread during the thread-cutting process and/or following the thread-cutting process, and the electronic detection and evaluation of the measurement data of the thread profile and/or of a sealing lip of the thread, and the derivation of control commands for controlling the machine tool from the measurement data with u