METHOD FOR BENDING PIPES

Abstract: A method for bending pipes, where there is created a file containing known spring-back and extension properties of various pipe materials and sizes at different angles of bend; the routing of the pipe is determined on the intended site of installation of the pipe, for instance by defining the coordinates of the bending points, or by directly measuring the lengths as well as angles and planes of bend of the straight parts of the pipe; on the basis of the predetermined pipe routing, there is defined the geometrical information for the pipe, this information including the lengths of the straight parts, and the radiuses and planes of bend of the pipe angles; bending instructions for bending the pipe are created on the basis of this material information, including extension and spring-back information, calculated or measured geometrical information of the pipe as well as information of its size; and the pipe is bent according to the created bending information.

Description: METHOD FOR BENDING PIPES The present invention relates to the method defined in the introductory section of patent claim 1. The methods known in the prior art for bending metal pipes and for determining their bending points are based on the planning of pipe routes, where the routing of the pipe is at the first stage defined on geometrical grounds only. A drawback with the prior art methods is that they are inaccurate and time-consuming, because the geometrical definition of the pipe's routing does not alone secure the dimensional accuracy of the final bent pipe. Therefore, owing to the extension and spring-back taking place during the bending process, roughly 60 - 70 % of the time consumed in the preparation of the production is used for corrections, where the pipe plans are adapted to suit the production. An iterative com¬ puter aided bending method has also been used. Another drawback with the prior art methods is that, owing to their complicated nature, they offer chances to several human errors. The object of the method of the present inven¬ tion is to eliminate the above mentioned drawbacks. A particular object of the invention is to introduce a method which enables automatization at the planning and production stages of pipe bending. Another object of the invention is to intro¬ duce a method which utilizes real, experimental informa- tion of the behaviour of the pipe while bending. Yet another object of the invention is to introduce a method which remarkably speeds up the plann¬ ing and bending of a pipe. The method of the present invention is charac- terized by the novel features enlisted in the patent claim 1. According to the method of the invention, - there is created a file containing the known spring- back properties and extension properties of different pipe materials and sizes, at different angles of bend of the pipe; - the geometrical routing of the pipe is determined on the intended site of installation of the pipe; - on the basis of the predetermined routing of the pipe, there is defined the geometrical information for the pipe, such as the lengths of the straight parts and the bending radiuses and planes of the pipe angles; - there are created bending instructions for the pipes on the basis of the material information recorded in the file, such as extension and spring-back information, calculated or measured geometrical information and information of the pipe size ' s; and the ' pipe is bent according to the created bending instructions. The geometrical routing of the pipe is deter¬ mined by defining the coordinates of the bending points on the site of installation, or by directly measuring the lengths of the straight parts of the pipe, as well as the angles and planes of bend. A separate file can be created of the routing of the pipe. Naturally the instructions can be presented in any suitable form, for instance as a programme of an automatic bending machine, or as a diagram. In a preferred application of the method, the geometrical routing of the pipe is determined by means of vector operations, on the basis of the coordinates of the bending points. In another preferred application of the me¬ thod, the geometrical routing of the pipe is determined by first defining the coordinates of the bending points, and by then calculating, on the basis of these, the lengths of the straight parts, the angles of bend, the bending plane vectors, the angles between the bending planes, the handedness of the planes and the total sum of the angles of rotation of the bending planes. In another preferred application of the me¬ thod, the file is created on the basis of bending ex¬ periments, carried out with various size groups of pipes, various wall thicknesses and various bend angles, in order to determine the correlation between the actual bend angle and the target angle, as well as the spring- back. In another preferred application of the me- thod, the file is created on the basis of bending ex¬ periments with various pipe sizes, various wall thick¬ nesses and various angles of bend, in order to deter¬ mine the correlation between the initial length of the pipe blank and the length after the bending, as well as the bending extension. In another preferred application of the me¬ thod, in order to form the bending instructions, a bending radius is chosen for the bending tool of the bending machine, and the real angle of bend for the chosen bending tools is defined on the basis of the desired angle of bend and the chosen pipe size and wall thickness, by utilizing the recorded spring-back infor¬ mation, corresponding to the pipe size and thickness, and the desired angle of bend. In another preferred application of the me¬ thod, for any pipe sizes and/or wall thicknesses that fall in between and/or outside the recorded sizes, the spring-back readings recorded in the file are interpo¬ lated and/or extrapolated. In another application of the method, in order to create the bending instructions there are calculated the successive real bending points for the bending machine by taking into account the extension information recorded in the file with respect to the pipe size and wall thickness, as well as to the desired angle of bend. In another preferred application of the me¬ thod, for any pipe sizes and/or wall thicknesses that fall in between and/or outside the recorded sizes and/or wall thicknesses, the spring-back readings recorded in the file are interpolated and/or extrapolated. In another preferred application of the me- thod, the total length of the straight pipe blank is calculated in order to create the bending instructions. In another preferred application of the me¬ thod, the locations of the limiterε to be programmed for the bending machine are calculated in order to create the bending instructions. In yet another preferred application of the method, - on the intended site of installation of the pipe, the coordinates of the branching and/or flanging points are determined; - on the basis of the recorded material information, such as extension and spring-back information, calcu¬ lated or measured geometrical information of the pipe, pipe size information and predetermined coordinates of the branching and/or flanging points, there are defined the actual locations of the holes for the branching and/or flanging points in the straight pipe blank prior to bending the pipe in order to form holes in the straight pipe blank. An advantage of the invention is that both the planning of the bending of the pipe, as well as the bending itself, can be automated. The created files are most advantageously processed by using the process¬ ing and calculation programme designed according to the present invention. This programme checks all steps of the method one by one in order to obtain the instruc¬ tions for bending the pipe, i.e a pipe route or part thereof, and further in order to realize the same. This procedure reduces the chances of human errors down to a minimum and speeds up both the planning and produc¬ tion processes. Another advantage of the invention is that after bending, the ready-made pipe can be transported to the site of installation and installed without having to make any modifications. In the following the invention is explained in detail with reference to the appended diagram of opera¬ tion, which goes through the various steps of the method. On the basis of this diagram of operation, there can be built a processing and calculation programme for realizing the method in practice. In order to achieve accurate bending of a pipe, there is required information of the pipe to be used, which pipe is made of a certain material, has a certain diameter and certain wall thickness; the required infor¬ mation relates to the actual behaviour of this kind of pipe while bending it at various angles of bend. When a pipe is bent, it is always somewhat extended, and the size of the extension depends on the diameter and wall thickness of the said pipe, as well as on the employed angle of bend. While bending, some spring-back is also bound to happen, and in similar fashion the extent of the spring-back depends on the diameter and wall thick¬ ness of the pipe, as well as on the employed angle of bend. The spring-back means, that in order to achieve the target angle, the actual angle of bend must be larger than the target angle. Consequently, as a preliminary operation there are carried out experiments for various pipe size clas¬ ses with various wall thicknesses and varying angles of bend in order to determine the correlation between the actual angle of bend and the target angle, as well as the extent of the spring-back and extension. The obtained experimental results and possible other standard information are combined into a file, for instance a database or a table, most advantageously of a type which can be stored into a computer's memory, to be used by a suitable processing and calculation programme. Advantageously the file is created only once and updated thereafter. If required, the experiments can always be carried out anew, for instance with new pipe sizes, and the file updated. In order to find out correct routing for the pipe, the coordinates of the bending points of the pipe are measured on the intended site of installation by means of theodolite measurement, and recorded in the memory of the measuring computer. Thereafter the coor- dinate readings are transmitted from the measuring computer to the processing computer proper, for instance directly from the site of measurement by means of a modem connection or data communications, on a datacar- rier such as a diskette, or in some other suitable fashion. For a start, the standard information is re¬ corded in the tables (pipe sizes, respective spring- backs and extensions at different angles of bend) . According to the situation in question, the following options can be chosen from the main menu of the system: 1. Calculate with new manually fed readings; 2. Search an old pipe measurement from file; 3. Search initial readings and coordinates from file, or 4. Exit. Accordingly, in the beginning stage of the system, the initial readings can be obtained in many different ways. If we choose option 1, "Calculate with new manually fed readings", we come to a step where the pipe information, the basic initial readings, can be fed into the programme in two alternative ways: 1. On the basis of the lengths + angles and planes of the straight parts, or 2. On the basis of the coordinates. While choosing option 1, the lengths as well as angles and planes of bend of the straight parts are inquired, whereafter the calculation of the bending points is started. While choosing option 2, the measured coor¬ dinates of the bending points are fed into the system, whereafter there are carried out some vector opera¬ tions, i.e. the lengths of the straight parts, the angles of bend, the vectors of the planes of bend, the angles between the planes of bend, the handedness of the planes and the summed-up angles of rotation of the planes of bend are calculated directly from the coordi¬ nates. Thereafter begins the calculation of the bend¬ ing information, and there is first chosen the radius of the bending disk of the bending machine. Then the influence of the spring-back in the angle of bend is taken into account by utilizing the experimentally predetermined values recorded in the file. The actual angle of bend for the chosen bending tool is defined on the basis of the desired angle of bend, as well as the chosen pipe size and wall thickness, with reference to the recorded spring-back information corresponding to the pipe size and wall thickness, as well as to the desired angle of bend. If the desired target angle is not found in the file as such, the corresponding values can be obtained by interpolating or extrapolating the recorded readings. Moreover, there are calculated the successive actual bending points for the bending machine by taking into account the recorded extension information with respect to the pipe size and wall thickness, as well as to the desired angle of bend. The intermediate and/or external readings are obtained as above, by means of interpolating or extrapolating the readings recorded in the file. Then it is tested whether the first and last elements of the pipe are sufficiently long, so that the limitations of the bending machine in question should not hinder bending. If they are not long enough, the lengths are increased. Now the required total length of the pipe blank is calculated. Then there are calculated the locations of the li iters to be programmed for the bending machine. Thereafter it is checked, on the basis of the calculated geometrical information of the pipe and the known limitations of the bending machine, the obstacles of bending, such as possible hitting of the pipe against the floor or against the structures of the bending machine. If the pipe contains junctions or flanges, they are treated separately. This is explained below. If the pipe does not contain junctions or flanges, the bending data is written out and recorded (for example in the memory of a computer) and the iso¬ metric images are drawn on a display screen or on paper by a plotter. Because the dimensions of the actual pipe routing are now determined, a list of required supplies can be created and written out, whereafter we can return to the main menu. The various steps of the method have now been gone through, and it is checked whether the created bending information is recorded. If not, it can be recorded, and the processing of the matter can be finished. If the pipe contains flanges or branches, i.e. junctions, their accurate locations can be defined beforehand for production so that the holes can be bored directly in the pipe blank, exactly on the right spots prior to the bending of the pipe blank. Without the above described knowledge of the behaviour of the pipe while bending this would not be possible. The invention is not limited to the above described preferred applications only, but many modifi¬ cations are possible without departing from the scope of the inventional idea defined in the appended patent claims.

Claims: PATENT CLAIMS 1. A method for bending pipes, c h a r a c¬ t e r i z e d in that - there is created a file containing the known spring- back and extension properties of various pipe materials and pipe sizes at different angles of bend, - the geometrical routing of the pipe is determined on the intended site of installation of the pipe; - on the basis of the predetermined pipe routing, there is calculated the geometrical information of the pipe, such as the lengths of the straight parts, and the radiuses and planes of bend of the pipe, - on the basis of the material information recorded in the file, including extension and spring-back informa¬ tion, calculated or measured geometrical information of the pipe as well as information of the pipe sizes, there are created bending instructions for the pipe, and - the pipe is bent according to the created bending instructions. 2. The method of claim 1, c h a r a c t e¬ r i z e d in that the geometrical routing of the pipe is determined by means of vector operations and on the basis of the coordinates of the bending points. 3. The method of claim 2, c h a r a c t e - r i z e d in that the geometrical routing of the pipe is determined from the coordinates of the bending points, and from these coordinates there are calculated the lengths of the straight parts, the angles of bend, the bending plane vectors, the angles in between the bending planes, the handedness of the planes as well as the summed-up angles of rotation of the bending planes. 4. The method of any of the claims 1 - 3, c h a r a c t e r i z e d in that the file is created on the basis of bending experiments with various pipe size classes, various wall thicknesses and angles of bend, in order to define the correlation between the actual angle of bend and the target angle, as well as the spring-back. 5. The method of any of the claims 1 - 4, c h a r a c t e r i z e d in that the file is created on the basis of bending experiments with various pipe size classes, various wall thicknesses and angles of bend, in order to define the correlation between the initial length of the pipe blank and the pipe length after bending, as well as the bending extension. 6. The method of any of the claims 1 - 5, c h a r a c t e r i z e d in that in order to create the bending instructions, there is chosen a bending radius for the bending tool of the bending machine, and the actual angle of bend for the chosen tool is defined on the basis of the desired angle of bend as well as the chosen pipe size and wall thickness, with reference to the recorded spring-back information cor¬ responding to the pipe size and thickness in question, as well as to the desired angle of bending. 7. The method of any of the claims 1 - 6, c h a r a c t e r i z e d in that for any pipe sizes and/or thicknesses that fall in between and/or outside the determined size classes and/or wall thicknesses, the spring-back readings recorded in the file are inter- polated and/or extrapolated. 8. The method of any of the claims 1 - 7, c h a r a c t e r i z e d in that in order to create the bending instructions, there are calculated the successive actual bending points for the bending machine by taking into account the recorded extension informa¬ tion with reference to the pipe size and wall thickneεr, as well as to the desired angle of bend. 9. The method of any of the claims 1 - 6, c h a r a c t e r i z e d in that for any pipe sizes and/or thicknesses that fall in between and/or outside the determined size classes and/or wall thicknesses, the extension readings recorded in the file are interpo- lated and/or extrapolated. 10. The method of any of the claims 1 - 9, c h a r a c t e r i z e d in that in order to create the bending instructions, the total length of the straight pipe blank is calculated. 11. The method of any of the claims 1 - 10, c h a r a c t e r i z e d in that in order to create the bending instructions, there are calculated the locations of the limiters to be programmed for the bending machine. 12. The method of any of the claims l - 11, c h a r a c t e r i z e d in that - on the intended site of installation of the pipe there are defined the coordinates of the branching and/or flanging points, - on the basis of the recorded material information, such as extension and spring-back information, calcu¬ lated or measured geometrical information of the pipe, information of the pipe sizes and the coordinates of the predetermined branching and/or flanging points, there are defined the actual spots of the holes for the branching and/or flanging points in the straight pipe blank, prior to bending the pipe in order to form the holes directly in the pipe blank.

Inventors: TOKOLA JOHANNES, TOKOLA, JOHANNES
Applicants: TOKOLA JOHANNES, TOKOLA, JOHANNES
Application year: 1991
Main classification: B21D7
IPC codes: B21D7, G05B19