Diapositiva 1

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Machining errors in turning of a multi-diameter
workpiece G. Giorleoa, W. Polinib, U.
Priscoa aDipartimento di Ingegneria dei
Materiali e della Produzione, Università di
Napoli, 80125 Napoli, Italy bDipartimento di
Ingegneria Industriale, Università di Cassino,
03043 Cassino, Italy The 2007 IPROMS
Conference on Innovative Production Machines and
Systems (2-13 July 2007) Special Session
Intelligent and Competitive Manufacturing
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• Sources of manufacturing errors in turning
• workpiece deflection
• non-infinite stiffness of the tool-machine-workpi
  ece system
• unknown geometry of the raw part
• thermal deformations
• vibrations of the machining system
• tool wear
• Workpiece deflection is recognized as one of the
  main source of dimensional and geometric errors
  in precision machining. The subject was also
  addressed by CIRP working group Modelling of
  Machining Operation

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• Mathematical model
• cutting forces
• workpiece deflection
• tool compliance
• workpiece holder compliance

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Cutting force model
A scheme of a lathe type cut by a
triangular-shaped tool on Pr
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Cutting force model
Overall deflection of workpiece axis w(z) on a
plane perpendicular to Pi
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Workpiece elastic deflection
The orientation of Pi depends on the values of
Ftan and Frad by
The displacement w(z) of the workpiece axis from
the z reference axis may be expressed as
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Elastic deflection of the workpiece holder The
holder shifts take place in the plane Pi, since
the constraining force acting on the chuck and
the tailstock belong to this plane.
tailstock shift
spindle shift
Where
inverse of the chuck stiffness
inverse of the tailstock stiffness
reaction force of the fixture in Pi for tailstock
reaction force of the fixture in Pi for spindle
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Tool holder compliance Tool holder deflection
along x and y axes 6 are defined by the
corresponding force components
Where
inverse of the tool holder radial stiffness
inverse of the tool holder tangential stiffness
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Cantilever mounting, 1
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Cantilever mounting, 2
Diameter error vs. z/L for cantilever mounting
configurations
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Cantilever mounting, 3
Forces vs z/L for cantilever mounting
configurations
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Between-centres mounting, 1
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Between-centres mounting, 2
Diameter error vs. z/L for between centres
mounting configurations
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Between-centres mounting, 3
Diameter error vs. z/L for the four
configurations involving different workpiece
length
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Between-centres mounting, 4
Diameter error vs. z/L for the three
configurations with different diameters.
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Chuck-Centre mounting
Diameter error vs. z/L for chuck-centre mounting
configurations