Method for adjusting the energy consumption of two tools during the machining of pipe section ends

Abstract

A method for machining a longitudinal profile section having an actual length and a first and a second end, wherein the first and the second end are machined using respectively a first and a second tool head and material is continuously abraded by the first and second rotating tool head during a machining period, the machining period is divided into time increments (ti), a torque (M(ti,) M(ti)) of the tool head is measured for each time increment (ti) and an individual energy consumption (E(ti), E(ti)) is determined for each time increment (ti), said individual energy consumption corresponding to an individual quantity of material abraded during the time increment (ti), and a total energy consumption (E(t), E(t)) both of the first and of the second tool head is determined from the individual energy consumptions (E(ti), E(ti)), said total energy consumption corresponding to the total quantity of abraded material.

Claims

1. A method for machining a longitudinal pipe section (1) having a first and a second end (3, 3), comprising the steps of: utilizing a first and second rotating tool head (6, 7) to machine the first and the second end (3, 3), wherein the first and second tool head rotate simultaneously and in opposite directions on a same axis of rotation R and each of the tool heads (6, 7) forms an outside chamfer (8, 8), an inside chamfer (9, 9) and a flat face (10, 10) on each of the two pipe section ends (3, 3); abrading a material continuously by the first and second rotating tool head (6, 7) during a machining period (t); dividing the machining period (t) into time increments (ti); measuring a torque (M(ti,) M(ti)) of the first and second rotating tool head (6, 7) for each time increment (ti); determining an individual energy consumption (E(ti), E(ti)) for each time increment (ti), wherein said individual energy consumption corresponds to an individual quantity of material abraded during the time increment (ti); and determining a total energy consumption (E(t), E(t)) of both the first and of the second rotating tool head (6, 7) from the individual energy consumptions (E(ti), E(ti)), wherein said total energy consumption corresponds to the total quantity of abraded material; adjusting the total energy consumptions (E(t),E(t)) to a predefined ratio; wherein the abraded quantity of material of the first and second end (3, 3) is determined continuously; and wherein the first and second rotating tool heads (6, 7) are controlled that when the total energy consumption E(t) of the first tool head (6) is greater than the total energy consumption E (t) of the second tool head (7), the rate of advance of the second tool head (7) is increased in comparison to the first tool head (6) and in that an angular velocity (ti), (ti) of the tool head (6, 7) is measured during each time increment ti and an individual energy consumption (E(ti),E(ti)) during the time increment (ti) is determined from the angular velocity (ti), (ti) and the torque (M(ti), M(ti)) and the duration of the time increment (ti).

2. The method of claim 1, further comprising the step of: determining a total energy consumptions (E(t), E(t)) of each of the tool heads (6, 7) by summing the individual energy consumptions (E(ti)), E(ti)) of each of the tool heads (6, 7) and determining a total energy consumption (E(t)), E(t)) of each of the tool heads (6, 7).

3. The method of claim 2, wherein the two total energy consumptions (E(t)), E(t)) are adjusted to be equal.

4. The method of claim 1, wherein the longitudinal pipe section (1) is machined symmetrically at its two ends (3, 3).

5. The method of claim 1 further comprising the step: determining in each case the total energy consumptions E(t), E (t) of each of the two tool heads 6, 7 during one operating cycle; wherein when the two total energy consumptions E(t), E (t) differ from one another, the longitudinal pipe section (1) machined in the next working cycle is machined taking into account the total energy consumptions E(t), E (t) of the operating cycle and reducing the difference between the total energy consumptions E(t), E (t).

6. The method of claim 1, wherein the longitudinal pipe section comprises: a pipe section (1); and an inside chamfer (9, 9) and/or an outside chamfer (8, 8) and/or a flat face (10, 10) is abraded at the two ends (3, 3).

Description

(1) The invention will be described on the basis of an example of embodiment in three figures, in which:

(2) FIG. 1 shows a schematic side view of a pipe section and two chamfering heads,

(3) FIG. 2 shows a graph of the torque as a function of the chamfering duration at a constant angular velocity,

(4) FIG. 3 shows a graph of the energy as a function of the chamfering duration at a constant angular velocity.

(5) FIG. 1 shows the pipe section 1 clamped in a clamping device (not shown). In the form shown by the outer rectangular border in the side view, the pipe section 1 is clamped with an actual length, and during a machining process material is abraded from a region 2 shown by hatching in FIG. 1 and the pipe section 1 is shortened to a production length.

(6) The pipe section 1 is cut to size from a pipe by a pipe cutting machine. As a result of being cut to size, the pipe section 1 has sharp edges at its one pipe section end 3 and at its other pipe section end 3. The pipe section 1 is cut to size in its actual length from the pipe, in particular by sawing or chopping. The actual length corresponds to the longitudinal extension of the pipe section 1 in its rectangular contour in a longitudinal direction L. After being cut to size, the pipe section 1 is machined by means of two tool heads 6, 7, which rotate simultaneously and in opposite directions on the same axis of rotation R. Each of the tool heads 6, 7 forms an outside chamfer 8, 8, an inside chamfer 9, 9 and a flat face 10, 10 on each of the two pipe section ends 3, 3. By virtue of the machining of the two pipe section ends 3, 3 by means of the two tool heads 6, 7, the actual length is shortened to the desired production length L2, which is shorter than the actual length. The production length is achieved by a predefinable distance between the two tool heads 6, 7 at the end of the machining of the two pipe section ends 3, 3. Each of the tool heads 6, 7 has three cutting plates 11, 12, 13 respectively 11, 12, 13 which, as shown in FIG. 1, by a rotational movement of the tool heads 6, 7, form the corresponding outside chamfer 8, 8, the inside chamfer 9, 9 and the flat face 10, 10 on the two pipe ends 3, 3 and in so doing abrade material from the two pipe section ends 3, 3.

(7) A drive of each of the two tool heads 6, 7 generates one torque M(t) and another torque M(t) at the one pipe section end 3 and at the other pipe section end 3. As shown in FIG. 2, the one torque M(t) initially acting on the one pipe section end 3 is zero when the associated tool head 6 is not in contact with the one pipe section end 3. As soon as contact takes place between the tool head 6 and the one pipe section end 3 at an instant ta, the one torque M(t) begins to act on the tool head 6. The further the tool head 6 penetrates into the material of the one pipe section end 3, the larger the surfaces of the one pipe section end 3 machined by the three cutting plates 11, 12, 13 become, and the acting one torque M(t) accordingly increases in a substantially linear manner as shown in FIG. 2. When the one pipe section end 3 at an instant tb has reached its desired external contour by chamfering, that is to say the inside and outside chamfer 9, 8 and the flat face 10 have the desired size, the one torque M(t) no longer changes. The surfaces machined by the tool head 6 have a constant size during the further machining period after the instant tb, so that the one torque M(t) remains constant from an instant tb onwards, as shown in FIG. 2. From the instant tb onwards, only the length of the pipe section 1 becomes shorter.

(8) The same applies to the other pipe section end 3. The above description applies in a corresponding manner to the other torque M(t), the other inside chamfer 9, the other outside chamfer 8 and the other flat face 10, which are produced by material being abraded from the other pipe section end 3 by the cutting plates 11, 12, 13.

(9) It is problematic to keep the abrasion of material as low as possible. Once the external contour has been achieved at the instant tb, the two torques M(t), M(t) do not give any indication as to how far the one or the other tool head 6, 7 is advanced into the respective pipe section end 3, 3 in the longitudinal direction L or respectively counter to the longitudinal direction L.

(10) According to the invention, for the machining of the one pipe section end 3, a total energy consumption E(t) up to a machining instant t is determined. The total energy consumption E(t) is shown in FIG. 3. It changes continuously throughout the entire machining period, by increasing in a monotonous fashion. The total energy consumption E(t) at the instant t correlates with an abrasion of material at this instant t. Since the two pipe section ends 3, 3 are machined simultaneously, the one E(t) and another total energy consumption E(t) up to the instant t are determined. The comparison of the two total energy consumptions E(t), E(t) is a criterion for the extent to which the two pipe section ends 3, 3 are being machined symmetrically, that is to say the extent to which an equal quantity of material is being abraded from the two pipe section ends 3, 3. The aim is to achieve the most equal possible quantity of abraded material from the two pipe section ends 3, 3 at the end of the machining period.

(11) The determination of the one total energy E(t) will be explained on the basis of the one tool head 6. It can be transferred analogously to the other tool head 7 by replacing the corresponding reference signs.

(12) Individual energy consumptions E(ti) are determined during different time increments ti, i=1, . . . , n. The time increments ti may all have the same length or else different lengths. The time increments ti in this example of embodiment all have an identical length of ti=0.006 sec. The individual energy consumptions E(ti) during the time increment ti are determined by determining a torque M(ti) of the tool head 6 during the time increment ti. The torque M(ti) is measured at an instant ti within the very short time increment ti. The torque M(ti) is substantially constant during the time increment ti. In addition to the torque M(ti), an angular velocity (ti) is determined at the instant ti during the time increment ti. Also with regard to the angular velocity (ti), it is the case that this is substantially constant throughout the duration of the time increment ti and the instant ti can again here be selected at will within the short time increment ti.

(13) The one torque M(t) can be determined in the motor or by means of a torque meter on the rotating tool head 6 itself, and the individual energy consumption E(ti) during the time increment ti is determined from the torque M(ti) at the respective instant ti and the angular velocity (ti) at the instant ti, according to the equation E(ti)=M(ti)*(ti)*ti.

(14) The one total energy consumption E(t) up to the instant t is obtained by summing the individual energy consumptions E(ti) according to the equation E(t)=.sub.i=3.sup.nM(ti)*(ti)*ti where t=.sub.i=0.sup.nti and n-measurements of torque M(ti) and angular velocity (ti). The one total energy consumption E(t) required up to the instant t correlates with the quantity of material abraded from the one pipe section end 3. A correlation between total energy consumption E(t) and abraded quantity of material can be determined empirically and/or numerically.

(15) In an analogous manner, the total energy consumption E(t) of the other tool head 7 is determined at the same time. The two total energy consumptions E(t), E(t) are compared with one another and, if they differ from one another, the rate of advance of the tool head 6, 7 consuming more total energy E(t), E(t) is reduced in comparison to the tool head 6, 7 consuming less total energy E(t), E(t) until the total energy consumptions E(t), E(t) have again equalized. For this purpose, an electronic control of the two tool heads 6, 7 is provided, which is connected to an evaluation unit for evaluating the two total energy consumptions E(t), E(t).

(16) Overall, so much material is abraded that the pipe section 1 is shortened from the actual length to the production length.

LIST OF REFERENCES

(17) 1 pipe section 2 region 3 pipe section end 3 pipe section end 6 one tool head 7 other tool head 8 one outside chamfer 8 other outside chamfer 9 one inside chamfer 9 other inside chamfer 10 one flat face 10 other flat face 11 one cutting plate 12 other cutting plate 13 one cutting plate 11 other cutting plate 12 other cutting plate E(t) one total energy consumption E(ti) individual energy consumptions E(t) other total energy consumption E(ti) other individual energy consumptions L longitudinal direction L1 actual length L2 production length M(t) torque M(t) other torque M(ti) one torque at the instant ti M(ti) other torque at the instant ti (ti) one angular velocity at the instant ti (ti) other angular velocity at the instant ti R axis of rotation t instant ta instant tb instant ti instant ti time increment