An approximated approach for collision check in process planning, an application to spare parts ...

112 Pages·2017·9.34 MB·English

SCHOOL OF INDUSTRIAL AND
INFORMATION ENGINEERING
Master of Science degree in
Mechanical Engineering
An approximated approach for collision
check in process planning, an application
to spare parts production
Supervisor: Prof. Marcello URGO
Master of Science Thesis by:
Antonino CURCIO
ID 858356
Academic Year 2016-2017

Acknowledgements
Vorrei ringraziare chi mi `e stato vicino: facendolo, mi ha reso le
giornate migliori e distratto nei periodi piu` stressanti.
Ma vorrei soprattutto ringraziare chi non mi `e stato vicino:
facendolo, mi ha reso una persona piu` forte.
i

Contents
List of Figures . . . . . . . . . . . . . . . . . . . . . . . vii
List of Tables . . . . . . . . . . . . . . . . . . . . . . . ix
1 Introduction 1
1.1 Problem statement . . . . . . . . . . . . . . . . . 2
1.2 CNC Machining Centers . . . . . . . . . . . . . . 2
1.3 Objectives . . . . . . . . . . . . . . . . . . . . . 4
2 State Of The Art 7
2.1 Skeletonization and garbing: state of the art . . . 7
2.2 Garbing Processes . . . . . . . . . . . . . . . . . . 8
2.2.1 Image-based methods . . . . . . . . . . . . 9
2.2.2 Object-based methods . . . . . . . . . . . 10
2.2.3 M-Reps and variants . . . . . . . . . . . . 12
2.2.4 Application case . . . . . . . . . . . . . . 12
2.3 Collision Detection methods: State of the Art . . 13
2.3.1 Surface properties analysis based methods 13
2.3.2 Vector based method . . . . . . . . . . . . 14
2.3.3 Convex Hull method . . . . . . . . . . . . 14
2.3.4 Bounding volume and space partition method 14
2.3.5 Rolling ball method . . . . . . . . . . . . . 15
2.3.6 Graphics-assisted approach . . . . . . . . . 16
2.3.7 Sweep plane approach . . . . . . . . . . . 18
2.3.8 Synthesis . . . . . . . . . . . . . . . . . . 18
3 The method development 21
3.1 The space reconstruction strategy . . . . . . . . . 22
3.1.1 Part programs . . . . . . . . . . . . . . . . 23
3.1.2 Trajectory derivation from a part program 24
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CONTENTS
3.2 Volume Derivation . . . . . . . . . . . . . . . . . 27
3.2.1 The “2D” approach . . . . . . . . . . . . . 27
3.2.2 The “3D” approach: Ball primitive . . . . 31
3.2.3 The “3D” approach: cylindrical primitive . 33
3.3 Building a new setup . . . . . . . . . . . . . . . . 34
3.3.1 The translation of the G-Code and the NPP 34
3.3.2 The choice of the machining environment . 35
3.4 The collision detection . . . . . . . . . . . . . . . 36
3.4.1 Analytical representation of the swept volume 36
3.4.2 Representation of the workpiece and fixtures 36
3.4.3 The membership test and collision map gen-
eration . . . . . . . . . . . . . . . . . . . . 38
3.4.4 A tool for collision detection tests: the WBB
method . . . . . . . . . . . . . . . . . . . 41
3.4.5 The validation . . . . . . . . . . . . . . . . 44
4 The use case and validation 47
4.1 Basic definitions . . . . . . . . . . . . . . . . . . . 47
4.2 The workflow of the use case . . . . . . . . . . . . 49
4.3 The component description . . . . . . . . . . . . . 51
4.4 The manufacturing cycle description . . . . . . . 57
4.5 The part program creation . . . . . . . . . . . . . 60
4.6 The selection of the machining equipment . . . . 61
4.7 VERICUT(cid:13) simulation and method application . 62
R
4.7.1 First setup . . . . . . . . . . . . . . . . . . 63
4.7.2 Second setup . . . . . . . . . . . . . . . . 70
4.8 Application of the WBB method on the use case . 74
5 Conclusions and future works 79
5.1 Conclusions . . . . . . . . . . . . . . . . . . . . . 79
5.2 Future works . . . . . . . . . . . . . . . . . . . . 80
A Mathematica scripts 83
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List of Figures
1.1 Example of machining centers (from [1]) . . . . . 3
1.2 Representation of axes in a CNC machine tool . . 3
1.3 Human-Machine interaction process (from [2]) . . 4
2.1 The MAT skeleton ; of the shape O with example
of maximum inscribed balls (red), contributing to
M, and not maximum inscribed balls (green), not
contribuiting to M [4] . . . . . . . . . . . . . . . 8
2.2 The ball splatting: naive splatting for parallel pro-
jections, impostor technique for perspective ones . 10
2.3 Representation of a reconstruction using skin sur-
faces. The dashed area is the reconstruction. On
the left s=1, on the right s=0.5 [3] . . . . . . . . 11
2.4 Collision map output of the method proposed by
Wang et al. case a) is a collision, case b) is a non
collision, case c) is a possible collision . . . . . . 17
2.5 Workflow of the approach proposed in [15] . . . . 17
2.6 Representation of the machining environment and
collision check with the sweep plane approach . . 18
3.1 General workflow . . . . . . . . . . . . . . . . . . 22
3.2 Creation of intermediate points along a linear in-
terpolation tool path . . . . . . . . . . . . . . . . 25
3.3 Volume derivation methods . . . . . . . . . . . . 27
3.4 Trajectory of the tool in the analyzed case . . . . 29
3.5 STL format representation of a component . . . 37
3.6 Representation of a component through a points
cloud . . . . . . . . . . . . . . . . . . . . . . . . 38
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LIST OF FIGURES
3.7 Processes of the collision test module . . . . . . . 39
3.8 Example of collision map . . . . . . . . . . . . . 40
3.9 The collision map could be also superimposed to
the STL representation of the component . . . . 41
3.10 Example of bounding boxes filled with a points
cloud with the random function . . . . . . . . . . 42
3.11 Structure of the two-phase collision test using the
bounding boxes . . . . . . . . . . . . . . . . . . . 44
4.1 The workflow of the use case . . . . . . . . . . . 50
4.2 The IMASFLEX-150 line . . . . . . . . . . . . . 52
4.3 Working directions of the 380 component . . . . 53
4.4 Manufacturing features of the 380 component. Im-
age modified from [17] . . . . . . . . . . . . . . . 54
4.5 Precedence graph of the 380 component . . . . . 56
4.6 Tool of the line for MW46 . . . . . . . . . . . . . 58
4.7 Tool of the line for MW43 . . . . . . . . . . . . . 58
4.8 Tool of the line for MW44 . . . . . . . . . . . . . 59
4.9 The selected machine tool: Makino 1010 . . . . . 61
4.10 Setup with many workpieces: on the left the first
setup, on the right the second setup . . . . . . . 62
4.11 Most dangerous condition in setup 1 . . . . . . . 63
4.12 Discretization of trajectory points. Output from
MATLAB(cid:13) code . . . . . . . . . . . . . . . . . 64
R
4.13 Tool (yellow) and toolhoder (blue) swept volumes
for each machining process on one workpiece . . 65
4.14 Representation of the workpieces with the fixtures
in Mathematica . . . . . . . . . . . . . . . . . . 66
4.15 A 3D graphical representation of the whole set of
geometries . . . . . . . . . . . . . . . . . . . . . 67
4.16 Sparse representation of the passage of the tool and
toolholder in the most critical phase . . . . . . . 68
4.17 Extract of the script in Mathematica. As can be
noted, the collision points counter gives 0 as result. 69
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LIST OF FIGURES
4.18 On the left: collision map using points cloud. On
the right: collision map using 3D representation of
components . . . . . . . . . . . . . . . . . . . . . 70
4.19 Collision detected by VERICUT(cid:13) . . . . . . . . 71
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4.20 Mathematica script extract with collision tests for
the second setup . . . . . . . . . . . . . . . . . . 73
4.21 Collision maps for the second setup . . . . . . . . 74
4.22 Bounding boxes . . . . . . . . . . . . . . . . . . 75
4.23 Mathematica extract of WBB application on the
first setup . . . . . . . . . . . . . . . . . . . . . . 76
4.24 Mathematica extract of WBB application on the
second setup . . . . . . . . . . . . . . . . . . . . 77
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