Improving Chucking Accuracy and Repeatability by Reducing Kinematic Redundancy

2008 ◽  
Author(s):  
Jeongmin Byun ◽  
C. R. Liu
Keyword(s):  
Hard Turning ◽  
Roller Bearing ◽  
Diameter Ratio ◽  
Kinematic Redundancy ◽  
Positioning Accuracy ◽  
Long Time ◽  
Cylindrical Workpiece ◽  
Finish Hard Turning ◽  
Taper Roller Bearing ◽  
Accuracy And Repeatability

In this paper, the effect of kinematic redundancy on chucking, especially, on the positioning accuracy of a cylindrical workpiece was investigated. No previous research on the effect of kinematic redundancy on the positioning accuracy and the repeatability of a workpiece in chucking has been reported, even if kinematic principle has been known for a long time. Starting from the description of the issues, a series of systematic experiments were carried out. It was demonstrated that the non-repeatability and the chucking error proportionally increase as the kinematic redundancy increases. Also, it was shown that kinematic redundancy had a significant effect on the positioning accuracy of chucked workpieces, especially the workpieces with a relatively higher length/diameter ratio. The contact area between the workpiece and the jaws was reduced to the extent which does not hurt the chucking rigidity and safety to reduce kinematic redundancy. It was shown that the concentricity of the workpieces was improved as much as 10 times by just minimizing the kinematic redundancy in the finish hard turning of the rings of a taper roller bearing.

Improving Chucking Accuracy and Repeatability by Reducing Kinematic Redundancy

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Jeongmin Byun ◽  
C. R. Liu
Keyword(s):  
Hard Turning ◽  
Roller Bearing ◽  
Diameter Ratio ◽  
Kinematic Redundancy ◽  
Positioning Accuracy ◽  
Long Time ◽  
Cylindrical Workpiece ◽  
Finish Hard Turning ◽  
Taper Roller Bearing ◽  
Accuracy And Repeatability

In this paper, the effect of kinematic redundancy on chucking, especially, on the positioning accuracy of a cylindrical workpiece was investigated. No previous research on the effect of kinematic redundancy on the positioning accuracy and the repeatability of a workpiece in chucking has been reported, even if kinematic principle has been known for a long time. Starting from the description of the issues, a series of systematic experiments was carried out. It was demonstrated that the nonrepeatability and the chucking error proportionally increase as the kinematic redundancy increases. Also, it was shown that kinematic redundancy had a significant effect on the positioning accuracy of chucked workpieces, especially the workpieces with a relatively higher length/diameter ratio. The contact area between the workpiece and the jaws was reduced to the extent, which does not hurt the chucking rigidity and the safety to reduce kinematic redundancy. It was shown that the concentricity of the workpieces was improved as much as ten times by just minimizing the kinematic redundancy in the finish hard turning of the rings of a taper roller bearing.

Selection of Major Locating Surface for Improving Chucking Accuracy

2009 ◽  
Author(s):  
Jeongmin Byun ◽  
C. R. Liu
Keyword(s):  
Systematic Study ◽  
Cylindrical Surface ◽  
Hard Turning ◽  
Diameter Ratio ◽  
Positioning Accuracy ◽  
Cylindrical Workpiece ◽  
Finish Hard Turning ◽  
Accuracy And Repeatability ◽  
Selection Of ◽  
Length To Diameter Ratio

Two different types of surfaces are available as a major locating surface for the chucking of a cylindrical workpiece in turning operation — a flat surface and a cylindrical surface. No systematic study on the selection of a major locating surface has been reported while an appropriate selection considering the geometry of jaws and workpieces results in the significant improvement in the positioning accuracy and repeatability of a range of chucked workpieces. This research covers the most common clamping situation where a cylindrical workpiece is overhung clamped and machined with more than one set-up for finishing. In general, a workpiece with a lower length to diameter ratio should be clamped using an end face as a major locator while using a cylindrical surface can produce better positioning accuracy and repeatability for workpieces with higher length to diameter ratio. Recent studies have demonstrated the benefits of hard turning over abrasive machining processes in terms of surface integrity. A strong need currently exists for improving chucking accuracy since it work a major bottleneck in the implement finish hard turning for the production of precision, load-carrying mechanical components, such as bearings and shafts. This paper presents part of a systematic study on improving chucking accuracy for the implementation of finish hard turning, focusing on the development of criteria on the selection of a major locating surface. First, an analysis on the factors affecting the positioning accuracy for each locating surface is carried out. Then the criteria and guidelines for the selection of a major locating surface were constructed. Finally, systematic experiments were carried out to test the criteria and guidelines. The results showed that the positioning accuracy of the chucked workpieces improved significantly when following the guidelines developed in this study.

Methods for Improving Chucking Accuracy

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Jeongmin Byun ◽  
C. Richard Liu
Keyword(s):  
Hard Turning ◽  
Machining Process ◽  
Machining Processes ◽  
Positioning Accuracy ◽  
Major Bottleneck ◽  
Series Of Experiments ◽  
Finish Hard Turning ◽  
Major Factors ◽  
Finishing Processes ◽  
Accuracy And Repeatability

Since recent studies have demonstrated the benefits of hard turning over other abrasive machining processes as a finishing process in terms of surface integrity, a strong need has existed to improve the performance of chucking. It is because the poor repeatability and accuracy in the positioning of chucked workpieces became the major bottleneck in the implementation of finish hard turning for precision mechanical components. However, the understanding of chucking has not been adequate nor has any systematic method been reported for improving chucking accuracy. In this paper, all the major factors that affect the positioning accuracy and repeatability of a chucked workpiece have been identified by error budgeting and systematic measurements. In addition, the characteristics of these factors as well as their effect on chucking accuracy were investigated. From the results, a chucking error map that summarizes the relations between these factors and the positioning error of a chucked workpiece was developed. Then, a series of experiments were carried out to test the effectiveness of the error budget. The results demonstrated that the knowledge on these factors was accurate and it could be effectively used to improve the positioning accuracy and repeatability of a range of cylindrical workpieces in chucking. It was also shown that hard turning alone, without any extra machining process, could satisfy the same level of concentricity, which is currently achieved by finish grinding when chucking accuracy was improved by the method developed. Even if this study was originally intended for the implementation of finish hard turning for replacing finish grinding, the methods developed in this study can be used to improve the final form accuracy of cylindrical workpieces in other finishing processes including grinding, if any work holding devices similar to chucks are used to hold the workpieces. The methodology and the procedures for improving chucking accuracy are covered in a pending patent by the authors.

Methods for Improving Chucking Accuracy

2008 ◽  
Author(s):  
Jeongmin Byun ◽  
C. R. Liu
Keyword(s):  
Hard Turning ◽  
Machining Process ◽  
Machining Processes ◽  
Positioning Accuracy ◽  
Major Bottleneck ◽  
Series Of Experiments ◽  
Finish Hard Turning ◽  
Major Factors ◽  
Finishing Processes ◽  
Accuracy And Repeatability

Since recent studies have demonstrated the benefits of hard turning over other abrasive machining processes as a finishing process in terms of surface integrity, a strong need has existed to improve the performance of chucking. It is because the poor repeatability and accuracy in the positioning of chucked workpieces became the major bottleneck in the implementation of finish hard turning for precision mechanical components. However, the understanding of chucking has not been adequate, nor has any systematic method been reported for improving chucking accuracy. In this paper, all the major factors that affect the positioning accuracy and repeatability of a chucked workpiece have been identified by error budgeting and systematic measurements. In addition, the characteristics of these factors, as well as their effect on chucking accuracy, were investigated. From the results, a chucking error map that summarizes the relations between these factors and the positioning error of a chucked workpiece was developed. Then, a series of experiments were carried out, based on the results of the earlier works to test the effectiveness of the error budget. The results demonstrated that the knowledge on these factors was accurate and it could be effectively used to improve the positioning accuracy and repeatability of a range of cylindrical workpieces chucked for machining. It was also shown that hard turning alone, without any extra machining process, could satisfy the same level of concentricity which is currently achieved by finish grinding in the machining of different types of cylindrical workpieces. Even if this study was originally intended for the implementation of finish hard turning that can replace finish grinding, the methods developed can be used to improve the final form accuracy of cylindrical workpieces in other finishing processes including grinding if any workholding devices similar to chucks are used to hold the workpieces. The methodology and the procedures for improving chucking accuracy are covered in a pending patent by the authors.

Analysis on Finish Hard Turning of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy

2009 ◽  
Vol 626-627 ◽  
pp. 225-230 ◽  
Author(s):  
Wei Wei Ming ◽  
Ming Chen ◽  
Bin Rong
Keyword(s):  
Corrosion Resistance ◽  
Elevated Temperature ◽  
Tool Wear ◽  
Hard Turning ◽  
Density Ratio ◽  
High Strength ◽  
Excellent Performance ◽  
Good Corrosion Resistance ◽  
Tool Wear Mechanism ◽  
Finish Hard Turning

Titanium alloys are extensively applied in aerospace, automotive, biomedical, and chemical industries owing to their excellent performance combining high strength-to-density ratio, good corrosion resistance, and high strength at elevated temperature. Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) alloys are used to replace the most common Ti-6Al-4V in some important applications such as some parts in aerospace engine. The purpose of this paper is to evaluate the machinability of TC11 alloys in the finish hard turning conditions. The paper presents the machinability results of TC11 alloys compared with Ti-6Al-4V, and analyzes the variables such as cutting force, surface integrity, and tool wear mechanism in the experiments.

Effect of Workpiece Hardness on Surface Microgeometry when Hard Turning with Ceramic Inserts

2013 ◽  
Vol 581 ◽  
pp. 176-181 ◽  
Author(s):  
Ildikó Maňková ◽  
Jozef Beňo ◽  
Marek Vrabel'
Keyword(s):  
Surface Roughness ◽  
Hard Turning ◽  
Surface Profile ◽  
Surface Finishing ◽  
Oxide Ceramic ◽  
Part Surface ◽  
Cutting Force Components ◽  
Finish Hard Turning ◽  
Force Components ◽  
Mixed Ceramic

Hard turning provides an alternative to grinding in some finishing operations. This paper deals with analysis of part surface finishing when turning hardened steel heat-treated on hardness of 46, 55 and 60 HRC with mixed oxide ceramic inserts. Average surface roughness Ra has been widely used in industry it is known that the single parameter Ra is inadequate to define the functionality of a surface. Two different surfaces with similar values of Ra can behave differently under loading conditions. The surface profile 2D and 3D parameters are assessed. The influence of workpiece hardness on surface roughness parameters and cutting force components is investigated. Results show that finish hard turning with mixed ceramic tool produces surface profile comparable to those produced by grinding.

Effect of Cutting-Edge Geometry and Workpiece Hardness on Surface Residual Stresses in Finish Hard Turning of AISI 52100 Steel

1999 ◽  
Author(s):  
Jeffrey D. Thiele ◽  
Shreyes N. Melkote ◽  
Roberta A. Peascoe ◽  
Thomas R. Watkins
Keyword(s):  
Residual Stresses ◽  
Hard Turning ◽  
Cutting Edge ◽  
Phase Changes ◽  
Edge Geometry ◽  
Surface Residual Stresses ◽  
Aisi 52100 ◽  
High Feed ◽  
Aisi 52100 Steel ◽  
Finish Hard Turning

Abstract An experimental investigation was conducted to determine the effects of tool cutting-edge geometry and workpiece hardness on surface residual stresses for finish hard turning of through-hardened AISI 52100 steel. Polycrystalline cubic boron nitride (PCBN) inserts with representative types of edge geometry including “up-sharp” edges, edge hones, and chamfers, were used as the cutting tools in this study. This study shows that tool edge geometry is highly influential with respect to surface residual stresses, which were measured using x-ray diffraction. In general, compressive surface residual stresses in the axial and circumferential directions were generated by large edge hone tools, for longitudinal turning operations. Residual stresses in the axial and circumferential directions generated by small edge hone tools are typically more tensile than stresses produced by large edge hone tools. Microstructural analysis shows that thermal effects are significant at high feed rates, based on the presence of phase changes on the workpiece surface. At high feed rates, compressive stresses correlate with continuous white layers and tensile stresses correlate with over-tempered regions on the surface of the workpiece. Mechanical effects play a larger role at low feed rates, where phase changes are not observed to a significant degree. For these cases, large edge hone tools generally produce more compressive values of residual stress than small edge hone tools.

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