Tool Path Generation Using UNIGRAPHICS NX

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Tool Path GenerationUsing UNIGRAPHICS NX

• Course Project for course
• ME 5233

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Abstract

• Chapter1 Introduction UNIGRAPHICS NX
• Chapter 2 Computer Aided Design
• Chapter 3 Computer Aided Drafting
• Chapter 4 Computer Aided Manufacturing And Tool
  Path Generation
• Chapter 5 Tool Path Generation using UNIGRAPHICS

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UNIGRAPHICS NX

• A complete CAD/ CAM/CAE system
• A fully three-dimensional, high precision system
• Accurately describe almost any geometric shape
• Can be used for several application.

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Applications

• Analysis
• Assemblies
• Drafting
• Gateway
• Geometric Tolerancing Module

• Manufacturing
• Modeling
• Quality Control
• Sheet Metal
• Wire Harnes

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Gateway

• Prerequisite for all other interactive
  applications
• The first application
• To open existing part files
• To create new part files
• To save part files
• To import and export various types of files

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Modeling

• To create 2D or 3D wireframe or solid models.

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Types of Modeling

• Features Modelingsupports the creation and
  associative edit of standard design features
• Free-Form Modeling supports the creation of
  complex surface and solid models
• Sheet Metal Feature Modeling supports the
  creation of sheet metal specific features such as
  flanges, ribs

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Application of Parts

• Produce fully dimensioned engineering drawings
• Generate instructions for NC machining
• Generate input for analytical processes such as
  finite element analysis

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Drafting

• To create engineering drawings using the built-in
  curve/sketch tools.
• Supports automatic creation of drawing layouts
• To view orthographic projection, sectioning,
  auxiliary and detail views

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Manufacturing

• Supports the creation and editing of CLSFs for NC
  machining
• Supports the formatting of a tool path to meet
  the input requirements
• Generates the required MDFs.

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Computer Aided Manufacturing

• An effective utilization of computer technology
  in the management control and operation of the
  manufacturing

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Advantages of CAM

• To control machines and machine tools.
• Possibility of performing multiple operation on
  the same machine in one set up.
• A significantly reduced scarp rate.
• The ease of incorporating part design changes.
• Significantly increased production.

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Terms Used in Tool Path Generation

• Part Programming
• CNC Machine Tool
• Motion of Machine Tool
• Classification of Machine Tools
• Cutter Programming
• Modes of Programming
• Topology for Cutter Movement
• Output files (CL DATA Files)
• APT and Postprocessors

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Part Programming

• A part program is a combination of machine tool
  code and machine specific instructions. It
  contains geometric information about part
  geometry and motion information to move the
  cutting tool .

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CNC Machine Tool

• Machine control units (MCU)reads the part
  programming and controls the machine too
• Machine tool

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Motion of Machine Tool

• Each axis of motion is driven by motor generally
  stepper motor.
• Generally Z axis is the axis of the machine tool
  .
• Positive direction of the axis moves the cutting
  tool away from workpiece.
• CNC machines are classified according to the
  capability of machine tool to simultaneously
  control the tool along axes

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Classification of Machine Tools

• Point-to-point (PTP) machining tool performs
  operation at specified point on workpiece .
  Drilling operation
• Continuous path machining tool tool is in
  contact with the workpiece along curve or edge of
  workpiece . Milling operation.

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Cutter Programming

• Cutter center programmingActual diameter of the
  tool is considered. The cutter follows the part
  at a fixed distance away from the part on each
  point on the path. Only one tool can be used
• Zero radius programmingCutter still guide along
  the part contour by a fixed distance equal to
  cutter offset

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Modes of Programming

• Absolute Programming an origin for each axis of
  motion of the machine tool has to be selected
  prier to staring the program. All the distances
  are calculated from the origin .
• Incremental Programming Its not require to set
  origin before and all the distances are
  calculated from the last position.

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Topology for Cutter Movement

• the path that tool takes around the work-piece is
  topology
• Zigzag Cutter will move in horizontal backward
  and forward direction
• Zig In this cutter moves in horizontal direction
  but only in one direction
• Follow part This is suitable for finishing
  operation
• Contour Zig This is combination of follow part
  and zig method

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Output files (CL DATA Files)

• It is the outcome of part program.
• First CC(Cutter Contact) points are computed. The
  CC points are set points that are on the edge of
  the workpiece from which tool is scheduled to
  pass through. Second step is to offset these CC
  points to get CL points. CL points are set of
  points that the center of the tool is schedules
  to pass through.

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APT and Postprocessors

• APT are statements that define part shape and
  tool motion as well as machine tool dependent
  data, such as federates and spindle speeds
• A postprocessor is a computer program which
  converts the APT format CL file output from
  CAD/CAM programs to machine dependent G-code
  format commands

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Steps in Tool Path Generation

• Select Cam set-up
• Create Operation and generate tool path
• Cutter location DATA files and post-processing

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Tool Path Generation for Base Plate

• Milling is machining process for the
  manufacturing of a variety of high precision
  components .
• To produce the part efficiently, the bulk waste
  material is removed from the workpiece during the
  rough cut
• The fine cut, used a small cutting tool, and
  mills the roughly cut workpiece to a finer
  finish.

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Final Steps

• Tool Path Generation Verification
• by animating material removal and tool
  movement option.
• Postprocessor CL data for generated tool path .
  G-code file using CL data file

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Rough Milling Operation

• CAM set-upshop_dimold session and
  shop_mill_contour as a cam setup.
• Orientation of MCS
• Declare part geometry
• Selection of OperationZ-level follow cavity

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Selection of Various Parameters

• Tool Section Base diameter 13mm
• Length96mm
• Flute Length43mm
• Number of Flute4
• Cut Method contour - zig method extra milling
  was occurred only where it was necessary

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Selection of Various Parameters

• Step Over Step over of 50 of tool diameter was
  selected .
• Feed Rates Selected from data base tables.
• Depth Per Cut a high depth of cut of 6 mm per
  cut
• Other parameters spindle and coolant on,
  automatic initial engage and final retrieval of
  tool.

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Finishing Operation

• Tool parameters
• Base radius 3.2 mm
• Length56mm
• Flute Length13mm
• No of flute4
• Cut method follow part, undercut and overcut
  will be at minimum
• Depth per cut 1mm per cut

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Conclusions

• The part and tool path was generated in
  UNIGRAPHICS NX.
• For optimization of machining operation, two
  different programs were created .
• Standard postprocessor was used.
• Tool path was verified by running G code file on
  Bridge Port CNC Machine.

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Recommendations

• Tool path for future new machine be smaller and
  simpler .
• A new machine will require specific
  postprocessor.

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References

• UNIGRAPHICs Documentation.
• Senior Project Report of Collen Hobson submitted
  at UNB in March, 1998
• Automation Production Systems and Computer-Aided
  Manufacturing, Mikell P. Groover ,270.
• Computer Numerical Control Programming, Peter J.
  Amic, 24
• CAD/CAM Theory and Practice, Ibrahim Zeid,1002.

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References

• A new approach to CNC tool path generation,
  article by Chih-Ching Lo in Computer Aided
  Design, Vol. 30, 649
• Numerically Controlled Machine Tools, G.W.
  Vickers, M.H. Ly, R. G. Oetter , 71
• Prediction of Contour accuracy in the end milling
  pickets, article by Kris M. Y. Law, A. Geddam in
  Journal of Material Processing Technology, 2001,7

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References

• A new cutter-path topology for milling machines,
  article by S marshall and J G Griffiths