JP2011508674A - How to bend a pipe - Google Patents

Abstract

A method for bending a pipe (T) or similar elongated element in a pipe bending machine. This machine captures and moves the pipe itself, a seat for positioning the pipe (T), a forming roller (R) having a predetermined radius (RR) along which the pipe is bent, and the pipe itself. And appropriate means.
[Selection] Figure 2

Description

  The present invention relates to a method for bending a pipe.

  In particular, the invention relates to a method for bending a pipe in a numerical control machine for bending a pipe.

  The method according to the present invention can be applied to all operations that cause deformation of a manufactured product (rod, sheet, bar, etc.) by bending.

  According to the prior art, pipe bending machines are used according to a “step-by-step” method. That is: After setting the pipe bending machine according to the data indicated in the drawing defining the grooving parameters, the operator manufactures the first part and controls the result.

  Due to the elastic effects of the pipe undergoing bending, the results obtained are usually different from those desired depending on the tolerances required according to the drawing.

  Pipe bending occurs by plastic machining. Therefore, after bending a pipe according to the drawing instructions, such a pipe is released, but the pipe loses some of the given bend due to the springback effect.

  To meet the requirements of the project, the operator usually-according to his experience-resets the machine with suitably modified data, and on average after 3 trials he gets the required bend It becomes possible. When manufacturing the original pipe, this method of operation involves about 75% waste, while when producing continuous pipe, it is about 15% waste.

  The Applicant has considered how to overcome this type of drawback, namely resetting the machine (entering different bending parameters multiple times) to obtain the correct bending in the next few steps. Furthermore, the applicant intends to be able to control the springback of the pipe, thus increasing the bending angle and making it possible to manufacture the pipe in the first operation according to the drawing.

  In particular, Applicants have understood that bending errors are usually due to structural changes to which the pipe is exposed in a straight section immediately adjacent to the bent section. This bent area remains partially straight. On the contrary, this part should already be bent according to the project theory data.

  Thus, the solution takes into account such upstream structural changes (and therefore prior to bending) the correct positioning of the pipe, i.e. the calculation and positioning of such backward movement and bending the pipe in the correct manner. Consists of.

  One form of the invention relates to a method for bending a pipe or similar elongated element according to the appended claim 1.

  Further objects and advantages of the present invention will become apparent from the following description and accompanying drawings, given strictly for illustrative and non-limiting purposes.

I draw a project diagram of a pipe. Fig. 2 represents a pipe during a bending process on a roller of a pipe bending machine. 1 depicts a chart of parameters calculated by the present invention.

  Typically, the pipe bending machine comprises a seat for positioning the pipe T, a forming roller R along which the pipe is bent, and suitable means for capturing and moving the pipe itself. From such a seat, the capture means is responsible for picking the pipe and the moving means rotate the pipe, i.e. move axially longitudinally and place the pipe itself around the roller. Responsible for that. The bending parameters set in the pipe making machine are substantially three: the bending angle around the roller (bending rotation) and the distance between one curve and the following (axial forward movement) And the rotational frequency around the axis of the pipe (axial rotation). The axial forward movement helps to position the pipe at the bending start point. Axial rotation helps to give the pipe the correct orientation on the bending surface. Bending rotation helps to set the correct angle for bending the pipe.

  Given these three parameters, it is possible to produce a pipe starting from a preset “three-dimensional” drawing. The electronic processing unit (eg PLC or microprocessor card) of the pipe bending machine commands and controls the moving and capturing means according to a preset program. It also applies to measuring the bending done through a suitable sensor.

  The method according to the invention can be advantageously applied to metal pipes (for example titanium) used, for example, in aircraft hydraulic systems. However, the present invention is applicable to all elongate elements (pipes and other similar elements such as rods, sections, drawn products, etc.) that require bending in accordance with such preset drawings. .

  In particular, FIG. 1 shows an example of such a preset drawing, in which a pipe is drawn, in which a plurality of critical points (nodes) near the bend are identified and highlighted by letters. ing.

  The origin of the reference system in that space (X, Y, Z) is fixed at the starting point A of the pipe, and the other points are given as triple values for such system (roller diameter, bent). 1 can also be observed in the table of FIG. 1 which also shows the length of the pipe and the distance between the start and end of the pipe).

  Beginning with such data, the processing program stored in the pipe bending machine is used to store the data present in the preset drawing of the pipe, which is then stored in a database that can be associated with the machine processing unit. It is possible to convert into such bending parameters.

  The calculation of such parameters in the method according to the invention is such that at least a pair of calibration bends are performed on a test pipe having the same diameter as the pipe to be produced, in a preliminary process relating to the actual start of the pipe bending process. provide. This is done in such a way that it is possible to calculate two basic factors that are adapted to subsequently determine the correct bending parameters of the pipe bending machine.

  As illustrated in FIG. 2, a pipe section having a known diameter is subjected to a first bend of a theoretical angle AT1 (120 ° in the illustrated example). In practice, this pipe is exposed to an actual bending angle AR1, which is smaller than the theoretical bending angle, due to the elastic-plastic behavior of the material. In particular, for a 120 ° theoretical bend, the actual bend is calculated to be 105.98 (manually or by such a sensor).

  Similarly, the second bending of the theoretical angle AT2 (30 ° in the illustrated example) is performed. In practice, this pipe is exposed to an actual bending angle AR2, which is smaller than the theoretical angle, due to the elastic-plastic behavior of the material. In particular, for a 30 ° theoretical bend, the actual bend is calculated to be 21.50 °.

  Such calibration measurements are preferably made in a manner that simulates acute and obtuse bends, starting with different theoretical bend angles, preferably less than 90 ° and greater than 90 °.

  From such a calibration measurement for a pipe of a given diameter, it is possible to calculate two basic bending parameter values, the so-called fixed springback RF and proportional springback RP.

According to the present invention, the term proportional springback is used to indicate the value of an angle that is added to each of the set theoretical angles to obtain the desired bending of the pipe. In particular, such a proportional springback RP is obtained from the following equation:
[Equation 1]
RP = ((AT1-AT2)-(AR1-AR2)) / (AR1-AR2)

According to the present invention, the term fixed springback is used to indicate the value of the angle that is added to the theoretical degree of bending in order to obtain the desired bending of the pipe. In particular, such a fixed springback RF is obtained from the following equation:
[Equation 2]
RF = AT-AR (1 + RP)
Where AT represents the set theoretical angle, and AR represents the actual angle measured and generated in the pipe when setting such theoretical angle in a pipe bending machine.

  When such two parameters are calculated as indicated in advance, for a pipe of known diameter according to the invention, the bending angle actually set in the machine (with respect to the theoretical angle shown in the drawing of the pipe) And the desired bend is obtained without error.

In particular, the correct bend angle API set in the machine is calculated as follows.
[Equation 3]
API = AT (1 + RP) + RF
However, AT is a theoretical angle set according to the drawing.

  As described above and shown in FIG. 2, the parameter required to produce a pipe having at least a straight section surrounded by two curves is the length of the straight section itself. In fact, for pipes that need to undergo only one bend, all that is required is to calculate the two aforementioned proportional and fixed springback parameters. The theoretical length X between the two curves is obtained from the drawing (as depicted for illustration purposes in FIG. 1). Applicants have understood that such a theoretical length X results in poorly performed operations when set directly on a pipe bending machine without considering the behavior of the pipe being formed. The result is not as desired, i.e. according to the drawing. In particular, the theoretically calculated straight section is too long and does not take into account deformations that occur in the pipe when performing the forming operation.

The radius of curvature of the pipe depends on the radius RR of the roller on which the curve is formed and the proportional springback, in particular the bending radius of the pipe is calculated as follows:
[Equation 4]
RA = (1 + RP) * RR

  According to the present invention, it is necessary to consider the radius of curvature of the pipe as well as the fixed springback RF in order to obtain the actual forward movement to be performed on the pipe in the machine. These are parameters that adjust the proper axial forward movement of the pipe to position it at the beginning of the next bend. An arc can be approximated to a straight section. In this section, at the end of the process of bending the pipe, such an arc-due to the elastic effect-returns to a straight line and becomes an integral part of the straight part between the two curves. Such a section is determined by the angle corresponding to the fixed springback RF on the circumference CI of a radius equal to the radius RR of the roller on which the pipe is bent, and forward movement or the theoretical distance or straight line between the two curves It represents such a factor (backward movement Y) that is further subtracted from the interval.

As a result, once the radius of curvature is obtained, backward movement corresponding to the following equation is obtained.
[Equation 5]
Y = RA * RF2π / 360

  What was obtained in the example depicted in FIGS. 2 and 3 using a calibration bend performed twice (30 ° and 120 °) has a fixed springback RF of 4.80 degrees and a proportional springback The RP is 0.0909 per degree of curvature.

  As a result, in order to make a 90 ° curve, it is necessary to set a bending angle API = 102.98 with a pipe bending machine.

  Starting with a forming roller radius of 57.15 °, a pipe radius of 62.34 ° is obtained.

  In short, the method according to the present invention includes the following steps performed one after another.

・ Supply test pipes with the same characteristics as pipes to be bent to pipe bending machines,

A pair of bending operations are performed on the machine to set a predetermined theoretical angle (AT1, AT2) for a test pipe having the same diameter as the pipe to be bent, and the resulting bending angles (AR1, AR2) are measured,

-Proportional springback (RP) defined as the value of the angle added at each degree of the set theoretical angle (AT)-starting from such set theoretical bend value and measured actual bend value- To calculate the correct bending angle (API) of the pipe set in the machine,

Fixed springback (RF), defined as the value of the angle intended to be added according to the theoretical bending degree-starting from the calculated proportional springback and starting from such theoretical and measured actual values- To calculate the correct bending angle (API) of the pipe set in the machine,

The correct bend angle (API) of such a pipe set in the machine is the fixed springback (RF) value and the proportional springback (RP) multiplied by the theoretical bend angle (AT). -In addition to the theoretical bending angle (AT)-calculate,

Supply the actual pipe to be bent into the pipe bending machine;

Set the correct bending angle (API) of such pipes in the machine,

• Bend the pipe around a roller of known radius on the bending machine.

  According to the present invention, the term “pipe with the same characteristics” is used to indicate that the test pipe has the same diameter, thickness and material as the pipe to be bent.

  Once the initial bending has been performed-if there is more curvature in the pipe project in the drawing-it is then necessary to calculate a straight section surrounded by two subsequent curves. This is done in such a way that the moving means of the machine moves the pipe by the correct distance forward movement.

  Such a correct distance calculation is performed by the following steps.

Calculating the radius of curvature (RA) of the pipe following the calculated straight section, starting from the radius (RR) of the bend roller and from the proportional springback (RP);

Recalculate the length of the straight section between the two curves, replacing the forming roller radius (RR) with the pipe radius (RA) calculated in the previous step;

Calculating a backward movement factor (Y) defined as an arc whose radius is the forming roller radius (RR) and whose angle is a fixed springback (RF);

Set the actual forward travel-to the pipe bending machine-calculated by subtracting such backward travel factor (Y) from the theoretical forward travel value (X) of the pipe that can be obtained from the project data.

Claims (8)

A method for bending a pipe or similar elongate element in a pipe bending machine, the machine comprising a seat for positioning the pipe to be bent and a predetermined radius along which the pipe is bent. Comprising a forming roller and suitable means for capturing and moving the pipe itself,
a. To such a seat, supply a test pipe with the same characteristics as the actual pipe to be bent,
b. A pair of bending operations are performed on the machine to set a predetermined theoretical angle (AT1, AT2) for such a test pipe, and the resulting bending angles (AR1, AR2) are measured,
c. Proportional springback (RP) defined as the value of the angle added for each angle of the set theoretical angle (AT)-the theoretical bending value so set and the actual bending value measured for the test pipe Starting with-calculating the correct bending angle (API) of the pipe set in the machine,
d. Calculate the fixed springback (RF) defined as the value of the angle added to the theoretical bending degree-starting from the proportional springback so calculated for the test pipe and from the theoretical bending value and the actual bending value measured And determining the correct bending angle (API) of the pipe set in the machine,
e. Such a correct bend angle (API) of a pipe set in the machine is expressed by a fixed spring back (RF) value and a proportional spring back (RP) multiplied by a theoretical bend angle (AT) − Calculate in addition to the theoretical bending angle (AT)
f. Supplying the actual pipe to be bent into the pipe bending machine;
g. Set the correct bending angle (API) of the pipe in the machine,
h. A method comprising bending a pipe around such a forming roller of a bending machine. To perform the subsequent bending process,
Calculating the radius of curvature (RA) of the pipe, starting from the radius (RR) of the roller that was being bent and starting from the proportional springback (RP);
Recalculate the length of the straight section between the two curves, replacing the forming roller radius (RR) with the pipe radius (RA) calculated in the previous step;
Calculating a backward movement factor (Y) defined as an arc whose radius is such a radius (RR) of the forming roller and whose corner is a fixed springback (RF);
Setting the actual forward movement calculated by subtracting such backward movement factor (Y) from the recalculated forward movement value (X) of the pipe to the pipe bending machine;
The method according to claim 1, wherein the steps e) to h) of claim 1 are repeated to perform a further bending process.   The method of claim 1, wherein such calibration measurements are made in a manner that simulates acute and obtuse bending, starting with a theoretical bending angle, one less than 90 ° and one greater than 90 °. Such a proportional springback (RP) is given by the following formula:
[Equation 1]
RP = ((AT1-AT2)-(AR1-AR2)) / (AR1-AR2)
The method according to claim 1, wherein AT1 and AT2 are such predetermined theoretical angles and AR1 and AR2 are bending angles obtained as a result of the test bending process. Such a fixed springback (RF) has the following formula:
[Equation 2]
RF = AT-AR (1 + RP)
(However, AT is used to indicate the set theoretical angle, and AR is used to indicate the actual angle measured that occurs in the pipe when setting such theoretical angle in a pipe bending machine. 2. The method of claim 1, wherein the method is calculated according to: The bending radius (RA) of the pipe is given by the following formula:
[Equation 3]
RA = (1 + RP) * RR
3. The method of claim 2, wherein RR is calculated according to (where RR represents the radius of the roller of the pipe bending machine and RP is a proportional springback). Such a backward movement factor (Y) is given by the following formula:
[Equation 4]
Y = RA * RF2π / 360
7. The method of claim 6, wherein RA is calculated according to (where RA is the bend radius of the pipe and RF is the fixed springback).   The method of claim 1, wherein the test angles are 30 ° and 120 °, respectively.

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