Maıerials Science Forum Vols. 510-511 (2006) p[flM'J-fl3989, 5 sayfaOnline available since 2006/Marl15 al www.scientific.net© (2006) Trans Tech Publicaıions, Swiızerlanddoi: LO. 4028/www.scientijic.nel/MSF. 510-511.242

Chipless Forming Process Using RotarySwaging Machine with Four-Oies

Seong-Joo Lim1,2, a , Kyoung-Hoan Na2. b and Chi-Hwan Lee3. c

1 Department of Advanced Precision Engineering, Inha University, 253, Yonghyun-dong, Nam-gu,Incheon 402-751, Republic of Korea

2 Digital Production Processing & Forming Team, Korea Institute of Industrial Technology, 994-32,Dongchun-dong, Yeonsu-gu, Incheon 406-130, Republic of Korea

3 Division of Materials Science and Engineering, Inha University, 253, Yonghyun -dong, Nam-gu,Incheon 402-751, Republic of Korea

alim@kitech.re.kr, bkhna@kitech.re.kr, cinhalee@inha.ac.kr

Keywords: Rotary swaging process; Forming speed; Reduction of diameter; Dimensional precision;Surface roughness; Environment-friendly forming process.

Abstract. The rotary swaging process for producing solid bars, tubes or wires is often used toobtain the chipless forming process compared with the conventional process such as the machiningand welding operation. Furthermore, machined chip, dust particles, harmful gas, and surfacecontamination to be commonly generated at hot working during the conventional process could beeliminated as the swaging process is applied and conducted at room temperature. Experiments forswaged product were performed to analyze the influence of the swaging process on the mechanicalproperties and dimensional precision in terms of surface roughness, surface hardness, and deviationof formed dimension. The changes of dimensional precision in swaged product are also checked outand considered for various process parameters such as the forming speed and the reduction in theouter diameter. Based on the experimental results, the surface roughness is improved under theswaging process. The weight of rod shift is reduced by about 15 % from 223.5 g to 190.2 g. Thusthe number of operations to produce the final product under the conventional process is larger thanthat under the swaging process to be able to omit the machining and welding operation, ete. Thispaper demonstrates that a rotary swaging process turns out to be an envirorıment-friendly formingprocess or chipless forming process without the machined chip.

Introduction

A rotary swaging process has been used for reducing the cross-sectiorıal area or for changing theshape of solid bars, tubes or wires by repeated radial blows with one or more pairs of opposed dies[1]. In particular, the formed parts after the swaging process have good mechanical properties suchas surface hardness, elastic Iimit, tensile strength, compressiye strength, and bending strength sincethe microstructures offormed materials show fiber structures.

The utilization of rotary swaging process was first investigated and developed in Germany toform complicated profiles from holIow cylindrical workpiece. Kegg [2] studied a theory of themechanics of rotary swaging process to predict the relative rotational motion between dies andworkpiece, as well as the various movements and velocities of workpiece by employing the headstock mechanism. Ovens et aı' found [3] that greater cold strengthening is achieved by rotaryswaging rather than by rolling with respect to the same reduction of cross sectional area owing toredundant working during successive die blows of rotary swaging. Piela [4] analyzed the rotaryswaging process using the finite element method and predicted the deformation profile andtemperature distribution of cross-sections. Especially compared with the conventional process suchas machining, welding, sawing and grinding process, the rotary swaging process seems to be anenvirorıment-friendly process without harmful dust, hazardous fumes, and surface contarnination.Furthermore, the dimensional accuracy and surface properties such as surface roughness andsurface hardness are improved under the rotary swaging process conducted at room temperature.

All rights reserved. No part of contents of this paper mav be reproduced or transmitted in any form or by any means without the writıen permission of TIP,www.tıp.net. (ID: 193.140.83.1-18/05/12,08:36:18)

Materials Science Forum Vols. 510-511 243

Figure 1 shows the rotary swaging machine with four dies and out rotor, which is named asmodel KRSM25 [5]. Figure 2 presents the some products including cross-sectional view of tubewith a shape ofaxisymmetric bar made by feed-in rotary swaging operation.

The objective of this study is to show that the rotary swaging process is a useful and eco-friendlyprocess as chipless forming process without some harmful effects and machined chip. Based on theexperiment the effect of rotary swaging operation on surface roughness and dimensional accuracy isinvestigated and analyzed. Also, the forming characteristic through the cold rotary swaging processare summarized briefly for considering reasonable experimental conditions such as the formingspeed and reduction in outer diameter oftube.

~.Fig. 1 Rotary swaging machine (KSRMA25) Fig. 2 Rotary-swaged products

Analysis of Rotary Swaging Process as Chipless Forming Process

In general, complex parts used in established industries are manufactured through the combinationof many processes such as are welding, machining, sawing and grinding. Usually welding methodas the most useful process making a structure has been applied to manufacture joining parts such asa rod shift of automobile steering part. In this study a rod shift is manufactured and improved by thecold rotary swaging operation without welding operation. Figure 3(a) shows a rod shift using the arewelding process for joining solid bar and tube and Fig. 3(b) presents one using the rotary swagingprocess as monoblock tube.

Fig. 3 Rod shift using (a) welding process and (b) rotary swaging process

Under are welding operation ultra violet and infra-red rays are able to cause sunbum on thehuman skin and severe bums to the eyes in a short exposure time. Besides there is added danger thatthe small globules or droplets of molten metal might leave the are and fly in all directions. Butrotary swaging process without welding operation gives better condition that electric safety accidentand harmful fumes might not be generated.

During routine machining, grinding and sawing operation for manufacturing final product dustgenerated might cause mechanical irritation of skin, eyes, nose and throat. However rotary swagingprocess does not produce some dusts and machined chips. Hot working is performed as workpartshape could be significantly formed in high temperature and lower force/power is required. In spiteof these advantages cold working is commended for final products with better accuraey, improvedstrength and better surface quality without hazardous factors such as harınful gas, surfacecontamination and lower dimensional accuracy generated at hot working. Weight of rod shift usingrotary swaging process is reduced by about 15 % from 223.5 g to 190.2 g. Weight reduction of finalproduct as an automobile part is useful to reduce fuel consumption and to restrict the occurrence ofCO2. Of course cold rotary swaging process is preformed at room temperature and thus is named aserıvironment-friendly forming process or a chipless forming process.

2,44 Eco-Materials Processing & Design Vii

Preparation for Experiment and Analysis

The experiments und er cold rotary swaging process are carried out to investigate and analyze thechange in dimensional accuracy and surface properties of swaged tube such as surface roughnessand hardness. In addition the cold experiments are preformed to know the influence of someparameters such as forming speed and the percent reduction of outer diameter on microstructures,surface hardness and dimensional precision of tube before and after the rotary swaging process.

The material used in the experiment is STKMl lA (KS) with 0.12C-0.35Si-0.6Mn-0.04P-0.04S(wt%). The cylindrical tubes with initial diameter of 019.0 mm is cut in the length of about 500mmand chamfered at the ends. Forming speed and percent reduction in diameter are considered andselected as important process parameters for cold experiment under rotary swaging process. Processparameters used in experiment are summarized in Table 1.

Table 1 Main process parameters used in experimentParameter ValueForming speed (mm/rev) 0.5, 1.0, 1.5,2.0

Reduction in outer diameter of tube (%) 30,45,55

Deviation of formed dimension (DFD) to analyze change of the dimension precision in outerdiameter of tube und er the rotary swaging process is defined as foIlows.

DFD=(D1-Do)/DoxlOO (%). (1)

where Do is the desired outer diameter of swaged product and Dı is the measured outer diameterof swaged product after rotary swaging operation.

Results and Discussion

Figure 4 presents the change in microstructures of tube to examine metal flow pattern after andbefore swaging process under 55% reduction of diameter and forming speed of 1.0 mm/rev.

Process Position Microstructure

Before

After

Fig. 4 Microstructures of tube before and after rotary swaging process

it is obviously observed from the figure that the number of srnall and elongated grain boundaryincreases after the rotary swaging process. The figure also notes that the grain size becomes smaIleras more far from surface during the rotary swag process. Thickness of tube changes from 2.3 mm(t.) to 3.75 mm (t2) and strength ofswaged product is improved before and after the process.

Surface roughness and surface hardness are measured on the surface of the tube before and afterrotary swaging process as can be shown in Table 2. The values in the roughness and the hardness oftube are expressed as a symbol of RMAX, namely maximum individual depth of roughness and Hv,

Materials Science Forum Vols. 510-511 245

Vicker's hardness, respectively. In Figs 5 and 6 dimensional errors by using a symbol of DFD areexpressed for various forming speeds and percent reductions before and after the experiment underrotary swaging process. it is indicated from the table and the figure based on experiment results thatthe swaged product has better surface quality and more precise dimension than those before therotary swaging process.

Table 2 Change in surface propertiesltem Surface roughness (RMAX)

Before After

Surface hardness (Hv)

Before After

6.3286.6156.445

2.0861.9772.100

155

151

156

237238240

~ 5.0c:o.v;

4.5c:

"E'i3 4.0.""E 3.5

<2<.-.o 3.0c:'2;; 2.5s'"cı 2.0

--+- Dimension alter swaging

ii. 5.5 .--------------------,

g 5.0

.~ 4.5E'i3 4.0."g 3.5c::: 3.0oc: 2.5'2j 2.0 D· . f .> --+- ımensıon a ter swagıng

cı 15 '---'-~~~~~~_~~_'---'

-Tube· STKMI lA-Reduction of diameter . 55%

-Tube: STKMI lA-Fonning speed : i .Omm/rev

0.5 LO 1.5 2.0Forming speed (mm/rev)

Fig. 5 Change in various forming speeds

30 35 40 45 50 55Reduction of diameter (%)

Fig. 6 Change in various percent reductions

Summary

Us ing the rotary swaging machine developed with an outer rotor, the cold rotary swaging processwas conducted without harmful dust, hazardous fumes, and surface contamination compared withthe conventional process such as welding, machining, grinding and sawing. So the rotary swagingprocess proved to be an environment-friendly process or chipless forming process. Themicrostructure after the rotary swaging process had a greater number of small and elongated grainsthan that before the rotary swaging process. Furthermore, roughness and hardness on the surface ofthe tube was much more improved through the rotary swaging process. The dimensional precisionin the outer diameter of the tube used in the experiment showed good accuracy after the rotaryswaging process. Therefore, this paper provided the available information on the optimal design ofrotary swaging process as chipless forming process or environment-friendly process in someindustries.

References

[1] R. Hebdzynski, S. Kajzer, R Kozik, : Forging on the four-lever arms swaging machine", Journalof Materials Processing Technology, Vol. 64(1997), pp. 199206.

[2] R. L. Kegg, 1964, "Mechanics of the Rotary Swaging Process", Journal of Engineering forIndustry Transactions of the ASME, Vol. 86, pp. 317325.

[3] W. G. Ovens, E. L. Bartholomew, R. R. Biederman, 1976, "Metal jlow two-die Swaging",Journal of Engineering for Industry Transactions of the ASME, Vol. 98, No. 4, pp. 11 2 1 1124.

[4] A. Piela, 1992, "Studies on the applicability of the finite element method to the analysis ofswaging process", Archives of Metallurgy, Vol. 37, No. 4, pp. 425443.

[5] S. 1. Lim, D. J. Yoon, J. H. Lee and K. H. Na, 1997 , "Development of Rotary Swaging Machinewith the Outer Rotor", J. of Korea Institute ofIndustrial Techno., Vol. 2, No. 2, pp. 137144.

Eco-Materials Processing & Design Vii10.4028/www.scientific.netlMSF.51 0-511

Chipless Forming Process Using Rotary Swaging Machine with Four-Dies10.4028/www.scientific.netlMSF.510-511.242

001 References[3] W. G. Ovens, E. L. Bartholomew, R. R. Biederman, 1976, "Metal flow two-die Swaging",ournal of Engineering for Industry Transactions of the ASME, Vol. 98, No. 4, pp. 11211124.doi: 10.1115/1.3439064