5-Axis Test-Piece: Influence of Machining Position...1 5-Axis Test-Piece: Influence of Machining...
Transcript of 5-Axis Test-Piece: Influence of Machining Position...1 5-Axis Test-Piece: Influence of Machining...
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5-Axis Test-Piece:Influence of Machining Position
Michael Gebhardt, Wolfgang Knapp, Konrad Wegener
Institute for Machine Tools and Manufacturing (IWF), Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
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1 Introduction2 Test pieces for 5-axis machine tools3 Simulation of axes motion4 Machining of test-pieces5 Interpretation of machined test-pieces6 Conclusions7 Education, Future Steps
Overview
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IWF/inspire research on 5-axis machine tools geometric testing dynamic testing thermal testing compensation
since begin of 2010 new5-axis machining center with swiveling rotary
table vertical machining center
t-(C)-Z-X-Y-b-B-C-w
strong integration into student’seducation
Introduction
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5-Axis Test-Pieces
Introduction
Truncated square pyramid test-pieceCone frustum test-piece
Two 5-Axis test-pieces were presented in ISO/CD 10791-7: 2010-10-06
Current version of ISO/DIS 10791-7:2012-02-14 only includes the conefrustum test-piece
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Alternative test-piece: truncated square pyramid
Milling is possible with just two axes in motion,but tool path can be reconstructed optically
Contact length of the tool is not constant,this results in a not constant process force
CMM is necessary for evaluation(Parallelism / Squareness)
Reversal movement in air(No start- / stop – marks)
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Influence of machining position on accuracy of conical test-piece
Four positions were considered for simulations and machining experiments:
- Basis location:BM (Bottom, Middle)
- Radial offset to C:BO (Bottom, Outside)
- Radial offset to B:TM (Top, Middle)
- Combination of two offsets:TO (Top, Outside)
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Realization of different heights
Reference cornerfor probing Test-piece
Different tube elementsrealize a variable heigth
Fixture in slots of machine tool (variable radial offset)
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Measurements were carried out with capacitive sensors FEM simulation and measurements
show a displacement within 1.5 mat top of the fixture due to gravityat B=90°
Process forces Only radial comp. to test-piece Constant except start / stop Small (~3 µm) change of circularity
of cone
Bending of fixture (FEM calculation and measurement)
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Ben
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in
m
B-Rotation in °FEM simulation of bending due to gravity
Measurements withcapacitive sensors(1 measuring point per 5°)
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Different locations lead to different axis motions – example: X-axis
Simulation of axis motion
For all positions: B-Axis: 60°- motion C-Axis: 360°- motion
Position BM: just 4-axis motion!
X-axis motions
Axes ranges for different locations of theconical test-piece
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Simulations – Position TO (Top, Outside),Different inclination angles (1)
Inclination angle = -30°Offset to B-axis: 220 mmOffset to C-Axis: 160 mm
Inclination angle: = 30°Offset to B-axis: 220 mmOffset to C-Axis: 160 mm
Ranges:
84 mm
360 mm
16 mm
60°
360°360°
60°
410 mm
280 mm
410 mm
= REVERSAL POINTS
C-A
xis
C-A
xis
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Simulations – Position TO (Top, Outside),Different inclination angles (2)
Inclination angle = -30°Offset to B-axis: 220 mmOffset to C-Axis: 160 mm
Inclination angle: = 30°Offset to B-axis: 220 mmOffset to C-Axis: 160 mmC
-Axi
s
C-A
xis
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Machining test-pieces
NC-programming and simulation in ESPRIT®
Following machining sequence wasrealized:
(1) Face milling of upper surface(2) Milling of groove in upper surface(3) Flank milling of cylinder (4) Flank milling of cone
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Analysis of milled test-pieces (1)
Measurement on a Talyrond 265 roundnessmeasuring machine
Radial probing for cylinder and cone
machine axis X
machine axis Y
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Analysis of cylinder (circularity):Comparison of four different positions
Positioning error, EXX = EYY
Squareness XY,C0Y = 0
X-Reversal < 5 m
Y-Reversal < 1 m
X-Reversal < 5 m
Y-Reversal < 1 m
EYY > EXX, pitchof Y EAY
X-Reversal < 7 m
Y-Reversal < 1 m
Positioning error, EXX = EYY
Squareness XY,C0Y = 0
X backlash and pitch of X, EBX atreversal point
EYY > EXX, pitchof Y EAY
X-Reversal < 7 m
Y-Reversal < 1 m
X backlash and pitch of X, EBX atreversal point
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Analysis of cone (circularity):Comparison of four different positions (=-30°)
From Cylinder:EXX = EYY, COY ~ 0From Simulation:Z=0
Form errorcaused by B and/or C Axis reversalcaused by X and/or B
From Cylinder:EXX = EYY, COY ~ 0 Form errorcaused by Z, B and/or C Axis reversalcaused by X, Zand/or B
From Cylinder:EXX, EYY, COY ~ 0
From Cylinder:EXX, EYY, COY ~ 0 Additional formerror caused by Z, Band/or C Axis reversalcaused by X, Z and/or B
Additional formerror caused by Z, Band/or C Axis reversalcaused by X, Z and/or B
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Analysis:Special phenomena (1)
Peaks at position BM which do not appear at position BO (tagged red)Possible reason: reversal points of Y-axis
Amplitude of «noise» in roundness measurement at position BO larger thanat position BMPossible reason: influence of angular positioning of C-Axis(Resolution C-Axis: 0.001°, 2x resolution * offset ~1.2 m)
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Analysis: correlation between measurements and Monte Carlo Simulation
Monte Carlo Simulation:Mean values and twice the standard deviation
Measurements:Mean values and twice the standard deviation
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Conclusions
investigation of influence of machining position- a variable setup to realize different machining positions was built.- for every position, several cone frustum test-pieces were milled. - axis movement and form deviation were simulated.
analysis of test-pieces- cylinder and cone were analyzed on a roundness measuring machine.- machine tool characteristics as axis reversal, pitch or squareness could be
identified.
special phenomena- “amplitude of noise” increases with increasing offset of milling position to C-axis.- sporadic occurrence of peaks looking like lubrication impulses. further measurements required
comparison of measurements and simulation- large circular form errors come along with large axis motion - Monte Carlo simulations of form deviation and measurements of milled test-pieces
show form deviations of similar range
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machine tool used for demonstrations and practical exercises in the following lectures:
practical course ‘from the idea to the workpiece’machining examples, machining of landscape topographie
machine tool metrologymeasurement of positioning accuracy with laser interferometer on NMV5000DCGmeasurement of straightness with straightedge on NMV5000DCGmeasurement of tool spindle with spindle analyzer on NMV5000DCG
manufacturing processes 1 and 2NC programming, milling
production machines 1 and 2design of machine tools, components of machine tools, machine tool performance (DCG), modeling of machine tools
Use of machine tool for education
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machine tool used for following thesis / student projects:
semester thesis ‘Measuring on machine tool’measurements and manufacture on NMV5000DCG
student focus project ‘sun car’manufacturing of key parts on NMV5000DCG
Use of machine tool for education
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Thermal testing including rotary axescompensation for thermal distortion of rotary axes
Future Activities
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Acknowledgement
IWF/inspire thanks MTTRF and MoriSeikifor generous support of research for 5-axis machining centers.