Precisionforming_省略_rosswedgerolling_.pdf

Science in China Series E Technological Sciences 2009 SCIENCE IN CHINA PRESS Citation Song Y Q Li Z G Wang M H et al Precision forming machine with rolling plate cross wedge rolling Sci China Ser E Tech Sci 2009 52 11 3117 3121 doi 10 1007 s11431 009 0339 2 Precision forming machine with rolling plate cross wedge rolling SONG YuQuan LI ZhiGang WANG MingHui accepted August 3 2009 doi 10 1007 s11431 009 0339 2 Corresponding author email syq Supported by the National Scientific and Technological Project Grant No 2003BA 212C and the 985 Project of Jinlin University 3118 Song Y Q et al Sci China Ser E Tech Sci Feb 2009 vol 52 no 11 3117 3121 equipment provides important means for implementation of new technology The development of equipment and technology by supplementing each other forms the his torical trunk of the whole manufacture industry The development of cross wedge rolling is no exception ei ther Based on the route the paper firstly analyzes the advantages and disadvantages of the existing roller CWR and plate CWR machine and then puts forward the working principle and structural principle of the pre cision forming machine with rolling plate cross wedge rolling CCWR and subsequently describes its design and working process and finally gives a brief discussion and conclusion 1 Overview of the existing CWR ma chines In the world CWR machines mainly have three basic types One roll arc wedge CWR machine roller CWR machine and plate CWR machine 2 However the two classes involving roller CWR and plate CWR are com monly used at present 1 1 Roller CWR machine The elemental structure and working principle of a roller CWR machine is shown in Figure 1 3 The top and bot tom rollers are fixed between left frame and right frame with bearings The top and bottom sector wedge dies are fixed on the top and bottom rollers respectively When the top and bottom rollers rotate in the same direction a cylindrical billet is inputted in the die cavity between the top sector die and bottom sector die using conducting plate and formed into axial rotary workpieces or stepp ed shaft through successive partial compression defor mation in radial direction and successive partial exten sion deformation in the axial direction Because the axes of the top and bottom rollers of the roller CWR machine lie in the same vertical plane as the centerline of the workpiece which makes the resistance force for forming Figure 1 Roller CWR machine 1 Power and transmission system 2 gimbal symmetric 3 frame symmetric 4 roll symmetric 5 fan wedge rolling die antisymmetry 6 conducting plate 7 workpiece workpiece directly act on the top and bottom rollers and transfer to the frame through the rollers the machine is in a good stress state The diameter of the rollers will proportionally increase in dimension with the increasing size of the workpiece and the rollers are supported by the frame and these ensure that the machine has large rigidity In addition power transmission systems are separated from the main structure and connected with the shafts of rollers through the gimbal couplings So the main structure of the machine is compact These are important advantages of the roller CWR machine However the shape of dies mounted on rollers is sector which is difficult to process Due to the limit of the di ameter of rollers a roller CWR machine has no capabil ity of forming the workpiece with large size large radial compression ratio or large axial elongation Moreover due to the gripping of billets by conducting plate its accuracy varies significantly These are the long term problems which are difficult to solve 1 2 Plate CWR machine The working principle of a plate CWR machine is shown in Figure 2 4 The identical wedge shaped flat dies are antisymmetrically installed on the top and bot tom rolling plates which can move in parallel relatively to each other When the upper and lower flat dies are moving relatively to each other the cylindrical billet laid into die cavity between the upper flat die and the lower flat die is formed into workpiece through compression deformation in the radial direction and extension defor mation in the axial direction The successive partial plastic forming is carried out for axial rotary workpiece There are guide grooves on the main frame and auxiliary frame and guides are installed on the rolling plates The guides make sliding fit with guide grooves During roll ing the top and bottom rolling plates are moving in par allel relatively to each other and the rolling force is added to the rolling plates and the frame The bottom rolling plate is driven by the piston of oil cylinder for Figure 2 Plate CWR principle 1 Cylinder 2 rolling plate 3 auxiliary frame 4 main frame 5 rack symmetric 6 gear symmetric 7 guide groove symmetric 8 guide symmetric 9 flat dies 10 workpiece Song Y Q et al Sci China Ser E Tech Sci Feb 2009 vol 52 no 11 3117 3121 3119 reciprocating motion and synchronously drives the up per flat die to relatively slide through gear and rack or the top rolling plate is driven by the piston of oil cylin der for reciprocating motion and the bottom rolling plate is fixed on the frame The upper wedge shaped flat die and the lower wedge shaped flat die are installed on the top and bottom rolling plates respectively The rolled piece laid between the upper wedge shaped flat die and the lower wedge shaped flat die is rolled to successive partial compression deformation in the radial direction and successive partial extension deformation in the axial direction The plate CWR has the following advantages simpleness of manufacturing high precision flat dies and making a billet accurately enter into the groove of flat dies without conducting plate by design ing the feeding groove on flat dies which makes plate CWR have a high rolling forming precision in theory During rolling a cylindrical billet between the upper flat die and the lower flat die applies the counterforce di rectly to the rolling plates and bends them so as to lower the forming precision It is the main reason why the plate CWR machine has poor rigidity especially for the forming of the workpieces with large size large radial compression ratio or large axial elongation Because the reciprocating motion of flat dies depends on the cylinder piston drive the machine has complex structure and ocuppies large floor space In addition the matter that oxide skin is not easy to remove also needs to be further solved during hot rolling 2 The design of CCWR machine From the above description the roller CWR machine has high structure rigidity but sector dies are difficult to process and the gripping of workpiece is unstable and its forming precision is poor However the plate CWR machine has poor rigidity and occupies a large floor space and the flat dies are easy to manufacture the feeding of billet is reliable and its forming precision is high By analyzing their structure and mechanical es sence the main matter is that the dies are fixed with the load bearing parts for overcoming deformation resis tance So firstly the sector dies should be separated from the rolling roller of the roller CWR machine and the flat dies should be separated from the rolling plate of the plate CWR machine Then integrate the advantages of both machines into a CCWR machine the rollers merely undertake the resistance force for workpiece forming rather than serve as constraints of workpiece forming and flat dies merely serve as constraints of workpiece forming rather than undertake the resistance force for workpiece forming Thus the advantages involving high rigidity and small floor space of the roller CWR ma chine and high forming precision and simpleness of manufacturing the dies of the plate CWR machine are retained and in turn shortcomings involving difficulty of manufacturing sector dies and poor forming precision of the roller CWR machine and poor rigidity and large floor space of the plate CWR machine are abandoned According to the new idea of mechanical and structural design we have declared the invention intitled the plas tic plate rolling plastic precision forming machine which was later granted for a patent for invention in China 5 Based on the patent the CCWR machine consists of the following parts the power and transmission system the load bearing system the forming and the die installation system the feeding and unloading system This paper will describe the design of CCWR machine and struc ture principle of each part 2 1 Power and transmission system As shown in Figure 3 a the output power of motor 1 is transferred from small belt pulley 2 to big belt pul ley 4 also as the flywheel through belt 3 then through gear pair to big gear 6 also as the flywheel When closing the clutch 14 and opening clutch 8 and arrester brake 9 the power through gear pair 13 2 small belt pulley 3 belt 4 big belt pulley 5 pinion 6 big gear 7 15 gear pair 8 14 clutches 9 arrester brake 10 12 and 12 13 gear pairs 11 transmission shaft 16 main frame 17 gear ring 18 press roller 19 draw rod 20 sliding plate 21 flat die 22 framework of the sliding plate 23 rack 24 guideway 25 guide groove 26 workpiece 27 pedestal 28 gimbal 29 workpiece box 30 filter net of oxide skin 31 retaining nest of the billet 32 workpiece outlet 33 auxiliary frame guideways The gear ring engages with the rack The trapezoidal guideways on the framework of sliding plates make sliding fit with the trapezoidal guide groo ves of the frame The upper and lower sliding plates are eudipleurally installed on the frameworks of their own The upper press roller keeps rolling contact with the upper sliding plate and the lower press roller keeps rolling contact with the lower sliding plate The upper and lower flat dies are antisymmetrically inlaid on the upper and lower sliding plates respectively There is a retaining nest of the billet in the billet entrance between the upper and lower flat dies And there is a workpiece outlet in the workpiece outlet between the upper and lower flat dies The filter net of oxide skin is mounted under the workpiece outlet and there is a workpiece box placed on bottom of the filter net of oxide skin 2 3 CWR forming process In Figure 3 when closing clutch 14 and opening clutch 8 and arrester brake 9 the power is tranferred through the gimbal to the top and bottom press rollers then the top and bottom press rollers slowly rotate in the identical direction With the gear ring driving rack and the trapezoidal guideway making sliding fit with the trapezoidal guide groove the upper and lower flat dies move slowly in the opposite directions Meanwhile a billet is automatically fed into the die cavity of the upper and lower flat dies using the retaining nest to locate the billet Under the pressures of the top and bottom press rollers to the upper and lower flat dies through the upper and lower sliding plates the billet is formed into work piece with cross wedge rolling After finishing the roll ing forming oxide skin is percolated through the filter net of the oxide skin and the workpiece automatically enters into the workpiece box At this time by opening clutches 8 and 14 and closing arrester brake 9 CCWR machine stops working And then by opening clutch 14 and arrester brake 9 and closing clutch 8 the machine quickly returns to the original work position When opening clutches 8 and 14 and closing arrester brake 9 once more the machine at original position can begin the new rolling process 3 Discussion and conclusion 3 1 Discussion Rollers of the traditional roller CWR machine have high rigidity but its sector dies are difficult to manufacture and of poor precision Flat dies of the traditional plate CWR machine are easy to manufacture and of high pre cision but the plate structure has low rigidity These depend on the stress state of the two machines and com Song Y Q et al Sci China Ser E Tech Sci Feb 2009 vol 52 no 11 3117 3121 3121 bination of their dies and structure to a whole In order to incorporate their advantages and abandon their short comings the long standing traditional structures of roller CWR or plate CWR machines must be broken namely for the roller CWR machine sector dies should be separated from rollers and for the plate CWR ma chine flat dies should be separated from the rolling plates Then with rearrangement the precise forming machine with compound cross wedge rolling combining roller and plate CCWR machine is designed The new machine has the advantages including high rigidity for roller CWR machine and high precision for plate CWR machine This is the core idea and innovation in the paper To implement the design of CCWR machine it must be guaranteed that the up and down rollers can under take the resistance force for workpiece forming and the flat dies can constrain the forming shape of workpiece Therefore rolling rollers will be replaced with press rollers and gear rings are symmetrically installed on both ends of the press rollers The racks are installed on both sides of the frameworks of the upper and lower sliding plates and the gear rings engage with the racks There are guideways and guide grooves installed on both sides of the frameworks of the upper and lower sliding plates which make sliding fit with each other When the upper and lower flat dies move in the opposite directions a billet is being formed in the cavity of the flat dies For the designs of the main mechanical struc ture of the machine and the installation structure of the dies presented in the paper it should be guaranteed that the axes of the top and bottom press rollers and the cen terline of billet always keep on an identical vertical plane This point belongs to the research topic of the cross wedge rolling technology and would be specially discussed in another paper In addition although CCWR machine has the filter net of oxide skin in the paper to completely solve the problem that oxide skin is difficult to remove the CCWR machine should be inclined at an angle of over 20 degrees to the ground during installation and at the end of every rolling process the wind auxiliary equip ment is r used to clean the oxide skin randomly Replac ing hydraulic drive system in traditional plate CWR machine with the power drive system can reduce the floor area of the machine and simplify the structure of the machine The retaining nest in flat dies instead of the guide plate in the traditional roller CWR machine can improve the accuracy of feeding billet Because the press roller mainly plays the role of bearing load its diameter is great