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Automatic mandrel design for cold pilger mill using CATIA v5 CAD/CAM/CAE integrated software.

Abstract: In the cold pilger rolling process, the pipe ingots are rolled out by means of a fixed conical mandrel and two rollers arranged in a roller assembly. The outer diameter and wall thickness of the pipe ingots are reduced by the forward and backwards movement of the roller assembly within the cold rolling machine. The tooling design method is very important in order to form a shaped tube it is well known that the inside finishing of the resulted pipe depend on the mandrel profile. The optimum design of a high precision and complex contour tooling is obtained by computer aided design technology. Using CAD/CAM method, we can shorten the design time and reduce expenses for manufacturing and set up.

Key words: CAD, pilger mill, mandrel design.

1. FUNDAMENTAL PRINCIPLES OF THE PILGER METHOD

The pilger rolling process that rolls the pierced hollows into thinner-walled tubes of great length was developed by Max Mannesmann in the early 1980s. In the pilger rolling stand, a pair of conical-shaped rolls--one arranged above the other--operates in the opposite direction to the material flow as shown in Fig.1. The thick-walled hollow body, with a cylindrical mandrel inside it, is guided towards the pilger rolls. As soon as it is gripped by the tapered portion of the work pass, a small material wave is sheared off the hollow. This wave is forged to the desired wall thickness on the pilger mandrel by the smoothing portion of the work pass, with the hollow body plus mandrel moving backwards in the same direction as the rolls are rotating--i.e. in the opposite direction to the rolling--until they reach the idler pass of the rolls and are released. As the hollow is rotated it is once again pushed forward between the rolls, and a new rolling cycle begins. Since each piece of material undergoes several rolling passes, the resulting pipe has a uniform wall thickness and a perfectly round cross section. At the end of the process, the pipe is pulled off the pilger mandrel and the unfinished areas at the pipe ends are cut off.

[FIGURE 1 OMITTED]

Cross section reductions of up to 85 % are possible. In order to achieve such good performances the profile of the deforming tools must follow a certain curve. For low deformation conic mandrel are used which are very easy to manufacture on common lathes. The problem appears in the case of high cross section reductions where the material flow must follow a parabolic curve. Those parabolic mandrels are the main goal of our study.

2. TEORETICAL METHOD

The inside dimension of the finite pipe results from the outside diameter of the mandrel while the rolling die give the outside diameter of the pipe. Consider this for each set of diameter a different mandrel and a different set of rolling die are used. This paper is focused on the design of the mandrel but the same technique can be used for the automatic design of the pilger rolls. The first step of automatic tool design process consists in the calculation of mandrel profile.

In order to define the parabolic profile the working zone of the mandrel was divided into 40 sections, and for each section the diameter must be calculated. There are several methods used for calculating those dimensions.

For this case study the following relation was used:

DxD = [d.sub.F] + [C.sub.z] x ([d.sub.l] - [d.sub.F] - z [l.sub.i]) + x/l x z (1)

Z = [z.sub.ref] x L/100 (2)

where:

DxD is the diameter corresponding to section x (from 1 to 41) [d.sub.F] is the inside diameter of workpiece pipe [d.sub.1] is the inside diameter of the finite pipe [C.sub.x] is a constant related to the material flow as shown in table 1 [l.sub.i] is the clearance between mandrel and inside diameter of workpiece L is the working length of the mandrel [z.sub.ref] is the reference tapering

Using a Visual Basic form, the input dimensions are entered. The program then calculates the DxD values that are used for the 3D product design.

[FIGURE 2 OMITTED]

For the automatic design process, a parametrical model of the mandrel is used. There are two possibilities to enter and to calculate the values for the parametrical model. The first method is using Visual Basic for CATIA, this way the main parameters are automatically modified by the program, the other consist in using VB for Microsoft Excel and a design table, in this case the user must select a set of parameters from a list of configurations stored in the design table.

The advantage of using excel and VBA for excel is that for every set of input data (inside diameters of workpiece pipe and finite pipe) a new line is created in the working sheet of the design table so that it is not necessary for the user to calculate two times the same profile. The main disadvantage of this method is that the user must have a separate license for Microsoft Office

3. CASE STUDY

The case study was made for the KPW-75 cold pilger produced by the Mannesmann-Meer Company.

The two methods described above are similar. The input form (Fig. 2) and the compute algorithms are the same; the main difference is that the results calculated by the program are differently used. For this case study I used the second method, this way I was able to see the results and to compare them with the one provided by the Mannesmann Company.

As we can see from table 2 the data obtained with this method are comparable with the ones recommended by the producer. The dimension used where 76x4 for the workpiece pipe and 48x2 for the finite pipe.

The notations used in table 2 are: x is the section number DxDc is the diameter calculated by the program corresponding to section x (from 1 to 41) DxDm is the diameter recommended by the producer of KPW-75 cold pilger [DELTA]e % is the error between DxDc and DxDm

4. CONCLUSION

Precision tools development now depends on fast designing and machining. This is the reason why these days tool design depend on CAD/CAM/CAE Systems.

The maximum error that resulted from using this simplified method is 0,05% (x=37). This could be considered a very good result as it does not lower the finite pipe precision.

The obtained model can be further used to generate the blue print of the mandrel, or the code for the NCC Machine Tool.

5. REFERENCES

Randall S., Prieur H. (1967) Tubular Production in the Cold Pilger Machine, Iron and Steel Engineer--August 1967

Stapleton G. (2005) An evaluation of two cold pilger die designs, available from: http://www.dmv-stainless.com/en/ products/manufacturing_processes/, Accessed: 2005.07.12

Stroud R. (2005) Tooling, the key for mill production, Available from: http://www.thefabricator.com/articles/tube_and_ pipe_article?ID=189, Accessed: 2005.07.10

Christofer J. Bockmann, Lars Klander, Lingyan Tang (2002) Visual Basic Programmer's Library, Publisher TEORA, Bucharest 2002

CATIA V5R13 Online Documentation.
Table 1. The values of the [C.sub.x] corresponding to stainless steel

x Cx x Cx x Cx x Cx

1 1 11 0.0378 21 0.081 31 0.006
2 0.918 12 0.337 22 0.067 32 0.004
3 0.841 13 0.3 23 0.055 33 0.003
4 0.768 14 0.265 24 0.045 34 0.002
5 0.7 15 0.233 25 0.036 35 0.001
6 0.637 16 0.201 26 0.029 36 0
7 0.577 17 0.178 27 0.022 37 0
8 0.522 18 0.133 28 0.017 38 0
9 0.470 19 0.113 29 0.013 39 0
10 0.423 20 0.096 30 0.009 40 0

Table 2 Comparison between computed results and
Mannesmann--Meer values

 [DELTA]e [DELTA]e
x DxDc DxDm % x DxDc DxDm %

1 66.2 66.2 0.000 22 51.328 51.327 0.002
2 65.169 65.169 0.000 23 50.87 50.874 0.008
3 64.181 64.18 0.002 24 50.431 50.435 0.008
4 63.226 63.229 0.005 25 50.007 50.009 0.004
5 62.314 62.317 0.005 26 49.592 49.595 0.006
6 61.444 61.442 0.003 27 49.194 49.192 0.004
7 60.599 60.601 0.003 28 48.796 48.799 0.006
8 59.796 59.795 0.002 29 48.414 48.415 0.002
9 59.018 59.021 0.005 30 48.041 48.039 0.004
10 58.281 58.279 0.003 31 47.669 47.67 0.002
11 57.564 57.566 0.003 32 47.304 47.308 0.008
12 56.879 56.881 0.004 33 46.948 46.951 0.006
13 56.228 56.224 0.007 34 46.578 46.598 0.043
14 55.594 55.593 0.002 35 46.252 46.249 0.006
15 54.985 54.986 0.002 36 45.905 45.904 0.002
16 54.401 54.403 0.004 37 45.557 45.58 0.050
17 53.843 53.842 0.002 38 45.218 45.219 0.002
18 53.301 53.301 0.000 39 44.879 44.879 0.000
19 52.785 52.781 0.008 40 44.539 44.539 0.000
20 52.277 52.279 0.004 41 44.2 44.2 0.000
21 51.794 51.795 0.002
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Title Annotation:computer-aided design, manufacturing, and engineering
Author:Parpala, R.C.
Publication:Annals of DAAAM & Proceedings
Article Type:Report
Geographic Code:4EUAU
Date:Jan 1, 2005
Words:1631
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