Simulation of the Metal Spinning Process by Multi-Pass Path Using

AutoCAD/VisualLISP

Alexandru C. FILIP, Ion NEAGOE

Department of Manufacturing Engineering

University TRANSILVANIA of Brasov

Bdul Eroilor nr.29, 500036-BRASOV

ROMANIA

filipal@unitbv.ro, neagoe_ion@unitbv.ro

Abstract: - Metal spinning on NC machine-tools is a complex flexible manufacturing method with high efficiency for

small and single series of parts. The algorithms which describe the roller trajectory during the process are complicated

and hard to understand. This paper presents an application developed under Visual LISP environment which simulates

the metal spinning process by multi-pass path for rotational sheet parts, cylinders and cones. The simulation is based on

some algorithms created by the authors in previous research and is a convenient tool for professionals to test the

manufacturing process before the real production. The application is user-friendly, simple and intuitive.

Key-Words: - Metal spinning, simulation, Multi-pass, Hollow parts, VisualLISP

1 Introduction Among the available CAD tools used today in

engineering [1], [2], [9] the computer simulation is a

versatile tool for developing applications to check the

correctness of the theoretical approaches of a certain

engineering issue. When manufacturing parts, the

computer simulation determines the possible defect of

the predicted technology before the part is really

manufactured, reducing the costs of preparing

production.

The basic scientific method of simulation is the

numerical one, e.g. FEM, which is very used also in

metal spinning [3], [4], [5]. But this method is a rather

complicated one, which demands good knowledge of

plastic behaviour of materials, mathematics etc. and it

needs a relatively expensive dedicated software.

This paper proposes a simplified graphical simulation

of the roller’s trajectory, during the process of metal

spinning by multi-pass path.

The simulation is based on previous research,

developed by the authors [6], [7], [8], for the

manufacturing process of metal spinning of hollow parts.

The authors chose for the simulation the AutoCAD

environment, because it is one of the most known basic

CAD software. Besides the drawing possibilities, this

software provides an integrated programming

environment, VisualLISP, which allows developing user

applications.

The manufacturing of rotational hollow parts by

spinning is a method with high technological flexibility.

The method can be applied on common machine-tools

(like lathes) or on modern ones, like NC lathes. It has a

high efficiency for small and very small series of parts.

The NC lathes can provide different complex trajectories

of the forming tools, for any configuration of the

rotational hollow part. Usually, these equations are

complicated and their accuracy is hard to establish by

other methods than by computer simulation.

The most complex method of metal spinning is the

multi-pass one. Therefore, this method was chosen to be

implemented in the application, based on some

algorithms for calculating the successive positions of the

forming roller, previously tested by the authors of the

present research. The shape of the parts can be

cylindrical or conical as well.

2 Algorithms used for metal spinning by

multi-pass path

2.1 Case of cylindrical parts When manufacturing metal cylinders by spinning

with a multi-pass path, the roller’s trajectory is

established depending on the shape and dimensions of

the part. It implies the calculus of the coordinates of the

specific points of the inner profile of the part at each

passing of the roller and the calculus of the coordinates

of the specific points of the equidistant profile, which is

the trajectory of the roller’s radius centre.

Cylindrical parts are in two types – flangeless or with

a flange. The process of spinning of flangeless parts is

simpler, as there is no risk of interference between the

roller and the flange during the forming stage. In this

case, the most used algorithm for a multi-pass path is the

one when the part is formed at both the direct and the

return travel of the roller (fig.1).

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The spinning of cylindrical parts with a flange is

done [6] in two stages of processing (fig.2):

a) during the first stage, the cylindrical wall of the part

is formed on the mandrel, both at direct and return

travel of the roller, using a trajectory similar with

the one used for manufacturing flangeless parts.

This stage takes place until the preformed flange

makes collision with the second step of the

mandrel. So, the last travel of the roller, during this

stage, (fig.2), will be 1rn1 → 2rn1;

b) during the second stage, the flange is formed, only

at the return travel of the roller, towards the

mandrel. The starting point, for all steps, is the

point 2rn1. The direct travel of the roller is, in fact, a

free one, towards the point 2rn1.

The calculus of the coordinates of the characteristic

points, marking the centre of the roller radius, (fig.2) is

done with the following equations:

Rg2

dx

ir1 ++= ; (1)

( ) z1

1 l1isin

cos1Rz

1

ir−−

−=

α

α; (2)

i

ir2 cosR

2

Dx

iα+= ; (3)

( ) ziii

r2 l1isinRctg2

dDz

i−−+⋅

−−= αα . (4)

The equations above are determined considering a

coordinate system XOZ, with the X axis along the part’s

radius and the Z axis along its symmetry axis.

2.2 Case of conical parts The spinning of cones by multiple passes can be

done by several methods. The authors of the present

paper proposed a new path of the roller’s trajectory, [7],

which improved the manufacturing productivity and the

part’s accuracy.

The scheme of manufacturing, based on the new

path, (fig.3) is based on the principle of forming the

part’s wall at both the direct and the return travel of the

roller, by using certain spacing, lz, measured on an axial

direction and a certain decrease rate, ∆α, of the path’s

angle from a direct pass to the next one.

The characteristic points of the path were considered

the points of the roller’s centre of roundness.

The coordinates of the points 1r1 and 2r1 of the roller

path at the first direct travel can be calculated with

similar equations as in the case of cylindrical axi-

symmetric parts, as following:

11 cos21

αRd

xr

+= ; (5)

Fig.2 The scheme of spinning by multi-pass

path of cylindrical parts with a flange

Fig.1 The scheme of spinning by multi-pass path of

flangeless cylindrical parts

Fig.3 The scheme of spinning by multi-pass path of

conical parts

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11 sin1

αRzr= ; (6)

1

12

1r2 cosR

2

Dx

2

Dx

1α∆ +=+= ; (7)

1

1

1222 sin

211α

αR

tg

dDzzz r +

−−=∆+−= . (8)

At a certain pass “i” of the roller, the coordinates of

the start and end points of the path, are calculated with

the following equations:

– for the start points:

( ) ϕ−+= tglixx zrir1

111 (9)

( ) zlizzrir

1111 −−= ; (10)

– for the end points:

ii

2 cosR2

Dx

irα+= ; (11)

( )( ) izi

i Rltgitg

dDz

irαϕ

αsin11

22 +−−+

−−= .(12)

The shape of the trajectory assessed with the above

equations is strongly influenced by the geometrical

shape and dimensions of the part and by some main

technological parameters, such as:

– α1, the roller trajectory’s angle, at the first pass;

– ∆α, the decreasing value of the roller trajectory’s

angle, from one pass to another;

– lz, the roller’s step distance.

The minimum value of the angle α1, meaning the

deviation of the part generatrix at the first passing,

usually [8] depends on the parts’ diameter, the blank’s

diameter, thickness and mechanical properties and on the

feeding rate.

The decreasing value ∆α is, usually, for steel, 1…3°

and for aluminium, 3…6°. The step distance lz influences the number of passings

for a complete processing of the part. If the spacing lz is

too big, the material looses its stability and the part’s

wall wrinckles. The value of the step distance lz depends

[8] on the roller’s radius R and cannot overpass it’s

double, lz≤2R. The maximum value of the step distance

lzmax is calculated with the equation:

Rkkl bgz ⋅⋅⋅= 2max

, (13)

where kg is a coefficient considering the influence of the

material thickness [8] and kb is a coefficient considering

the influence of the planar flange width of the blank [8].

With the equations (1)…(12) a calculus is made for a

certain case of study, giving different values of the main

parameters which have an important influence on the

process. This activity is very laborious and a computer

application will make it easier and more precise.

Besides the advantage of facilitating the engineer

work, a suitable computer application can make data

exchange [9] with the manufacturing equipment or other

entitities such a virtual reality environment.

3 The EduSpin application For simulation purposes there was designed an

integrated application. The user can view a simple

simulation of the process of metal spinning and better

understand the influence of the geometrical and

technological parameters on the roller’s trajectory.

The application was developed under the AutoCAD

environment, which is very suitable for graphic

simulations, because it has drawing capabilities and an

integrated programming language, Visual LISP, which

can be used for designing user applications.

The application, named EduSpin 1.0, integrates three

user functions for the simulation of the roller’s trajectory

in three cases studied by the authors:

– TraCil – for flangeless cylindrical parts;

– TraCilFl – for cylindrical parts with a flange;

– TraCon – for conical parts.

The application has a modular structure. This kind of

programming assures an easy debugging and easier

future developments.

Once the application is launched, a main dialog box

(fig.4) is opened. It contains selection and edit boxes, for

selecting and introducing of all parameters needed for

the calculus and the simulation of the manufacturing

process.

After the data input, the user launches the simulation

and surveys the screen. The speed of the simulation can

be adjusted at any value according to any desire.

Each function draws a simplified version of the

technological scheme (fig.5 and 6) with all the

characteristic points of the path and creates a simple text

file with the values of their coordinates, for future NC

programming purposes.

Fig.4 Main dialog box of EduSpin 1.0 application

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Fig.6 Simulation of metal spinning for conical parts

Fig.5 Simulation of metal spinning for cylindrical parts with a flange

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The calculation of the coordinates of the

characteristic points is done with the equations

determined in the algorithms presented in chapter 2,

namely the equations (1) to (12).

The results of any simulation can be recorded for

further study or distribution via the usual options of

saving files in AutoCAD environment.

For example, when manufacturing parts made of soft

steel DC 04 SR EN 10130 +A1, some values for the

simulation can be according to the following:

• inner cylindrical diameter, d=60…80 mm;

• flange diameter, dfl=100…120 mm;

• part height, h=40…60 mm;

• sheet thickness, g=1…2 mm.

The results of the simulation (fig.5 and 6) can be

viewed and analysed and conclusions can be drawn.

When modifying one or several process parameters, their

influence is easily observed and the process of metal

spinning is better understood even without practical

activities of manufacturing real parts.

4 Conclusion The EduSpin 1.0 application is an example of using a

common CAD environment, like AutoCAD, for

simulation purposes in the domain of industrial

engineering.

Compared to all other methods of simulation of a

deformation process, this application is simple and

intuitive, being a useful tool for engineers to test the

accuracy of the technological design before the real

production, thereby reducing the costs.

The application development under a graphical

environment such AutoCAD allowed the simulation of

the spinning process, according to the values of the

parameters given by the user.

It is worth mentioning that among the range of

applications of simulation of a manufacturing process,

this application is less expensive, being used even in the

process of teaching at the authors’ university.

Further development is foreseen to allow the

application to simulate the metal spinning process for

any shape of symmetrical hollow part and to extend the

simulation to the 3D level. At the same time, this method

is intended to be developed for other cold-forming

operations such as bending or deep-drawing.

References:

[1] Babich, A. Mavrommatis, K.Th. Teaching of

Complex Technological Processes Using

Simulations. International Journal of Engineering

Education. Vol.25, No.2, Tempus Publications, 2010.

[2] Cerra, P.P. Penin, P.A., Diaz, R.G. Morales, R.P.

3D-CAD learning environment through interactive

modular system (AIMECDT-3D, Computer

Applications in Engineering Education, Wiley

Periodicals, Inc., Vol.18, Issue 1, 2009.

[3] Hamilton, S., Long, H. Analysis of conventional

spinning process of a cylindrical part using finite

element methods. Proceedings of the 12th

International Conference on Metal Forming, vol.1,

2008, Cracovia.

[4] Liu, C.H., The simulation of the multi-pass and die-

less spinning process. Journal of materials

processing technology. No.192-193, Elsevier

Science, 2007.

[5] Music, O., Allwood, J.M., Kawai, K., A review of

the mechanics of metal spinning. Journal of

materials processing technology. No.210, Elsevier

Science, 2010.

[6] Neagoe, I., Filip, A.C., Researches on the Roller

Trajectory when Manufacturing Cylindrical Hollow

Parts with a Flange by Spinning. (part two -

Validation by Computer Simulation of the Roller

Trajectory). Sbornik dokladi ot treta Konferentia s

mejdunarodno uceastie “Masinoznanie I masinni

elementi”, 2006, Technical University of Sofia.

[7] Neagoe, I., Filip, A.C. Algorithm and Computer

Simulation of the Roller Working Trajectory for the

Spinning of Cones. The 3nd

International Conference

on Integrated Engineering. Published in the

Academic Journal of Manufacturing Engineering,

vol.6, issue 3/2008, Editura Politehnica Timişoara.

[8] Neagoe, I., Filip, A.C. New Mathematical Models of

the Technological Parameters at Axi Symmetric

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International

Conference on Integrated Engineering. Published in

the Academic Journal of Manufacturing Engineering,

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[9] Oancea, G., Garbacia, F., Nedelcu, A., Software

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Latest Trends on Engineering Mechanics, Structures, Engineering Geology

ISSN: 1792-4294 165 ISBN: 978-960-474-203-5