An Effective Approach to Approximating 2-D Free-Form Curve Offsets for B-Spline NC Tool Paths With Offset Error Globally Bounded

2010 ◽  
Author(s):  
Maqsood A. Khan ◽  
Zezhong C. Chen
Keyword(s):  
Computer Aided Design ◽  
Tool Path ◽  
Error Function ◽  
Industrial Applications ◽  
Cnc Machining ◽  
Free Form ◽  
Control Points ◽  
Base Function ◽  
B Spline ◽  
Tool Paths

The topic of representing the offset of a 2-D B-spline curve in the same form has been under research for a long time, and it has many industrial applications, especially, in NC tool path generation for pocketing. For B-spline tool paths, it is often required that the tool paths have fewer control points, lower base function degree, and higher geometric accuracy. However, the existing methods often generate the offsets of 2-D free-form curves in the form of B-spline curves with high function degree and many control points. Although these offsets are useful in computer-aided design, they are inappropriate for the use of CNC machining. To address the problems in order to generate high quality B-spline tool paths, this original work formulates an error function of the offset approximation and then constructs a NURBS curve to globally bound the errors. By checking the maximum coefficient of the bounding curve, the upper bound of all the approximated offset errors is found and the errors can be reduced by adding more offset points at the appropriate locations. The proposed new approach is more efficient, and the resulting offsets in B-spline are more accurate with fewer control points and lower function degree. It is useful to generate B-spline tool paths for CNC pocketing, and has potential for other applications in industry.

Adaptive Tool Path Planning Strategy for 5-Axis CNC Machining of Free Form Surfaces

2019 ◽  
Author(s):  
Hrishikesh Mane ◽  
S. S. Pande
Keyword(s):  
Tool Path ◽  
Cnc Machining ◽  
Memory Storage ◽  
Free Form ◽  
Cnc Machine ◽  
Planning Strategy ◽  
Part Quality ◽  
Tool Paths ◽  
Path Topology ◽  
Free Form Surfaces

Abstract This paper presents a curvature based adaptive iso-parametric strategy for the efficient machining of free form surfaces on 5-axis CNC machine using the flat end mill tool. One iso-parametric boundary of the surface is selected as the initial tool path. Set of cutter contact (CC) points are chosen adaptively on the initial tool path considering desired profile tolerance. Adjacent iso-parametric tool paths are computed adaptively based on the scallop height constraint unlike the traditional iso-parametric approach. The path topology is post-processed to generate the part program for 5-axis CNC machine in ISO format. The system was rigorously tested for various case studies by comparing the results with the traditional 5-axis iso-parametric tool path strategy, iso-scallop strategy and iso-planar strategy of a commercial software. Our system was found to generate efficient tool paths in terms of part quality, productivity and memory storage compared to the conventional strategies.

Boundary-conformed machining of turbine blades

2005 ◽  
Vol 219 (3) ◽  
pp. 255-263 ◽  
Author(s):  
S Ding ◽  
D C H Yang ◽  
Z Han
Keyword(s):  
Computer Aided Design ◽  
Tool Path ◽  
Flow Line ◽  
Turbine Blades ◽  
Free Form ◽  
Implementation Processes ◽  
Tool Marks ◽  
Tool Paths ◽  
Continuous Boundary ◽  
Free Form Surfaces

Boundary-conformed machining is a new method to mill free-form surfaces with tool paths that reflect the natural shapes of the surfaces. It is suitable for the machining of turbine blades taking into account the direction of tool marks left on the vanes. To facilitate this type of machining, this paper introduces an application of the ‘boundary-conformed algorithm’ to generate continuous boundary-conformed flow line tool paths for the milling of blade surfaces. With this approach, the initial segment of the flow line tool paths is along the top edges of the blade while the final segment follows the intersection curves between the blade and the hub surface. The intermediate segments cover the surface by changing smoothly from the initial tool path to the final tool path. The two opposite sides of the blade, which are two trimmed surfaces, are machined together continuously from top to bottom with these continuous boundary-conformed tool paths. This method has been successfully integrated into an industrial computer-aided design and manufacture system (Pro/Engineer) by using Pro/Toolkit. A detailed algorithm and implementation processes have been introduced.

Piecewise B-Spline Tool Paths With the Arc-Length Parameter and Their Application on High Feed, Accurate CNC Milling of Free-Form Profiles

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Zezhong C. Chen ◽  
Maqsood A. Khan
Keyword(s):  
Tool Path ◽  
Free Form ◽  
Arc Length ◽  
Cnc Milling ◽  
B Spline ◽  
Tool Paths ◽  
High Feed ◽  
Genuine Solution ◽  
Cnc Controller ◽  
Very High

To conduct B-spline curve machining, first, B-spline tool paths with feed rates are planned; and second, the B-spline interpolator generates tool trajectories in real-time based on the paths fed into the computer numerically controlled (CNC) controller. Currently, the paths are often planned geometrically with a nonarc-length parameter. Literally, the interpolator can process B-spline paths with the arc-length parameter well, while it sometimes is challenged to work with the nonarc-length parameterized B-spline paths. As a consequence, it is difficult to ensure high accuracy of the tool trajectories in B-spline machining in terms of their corresponding paths; especially, if the feed is very high, smooth tool kinematics cannot be well maintained. To root out these problems, a new type of tool path—piecewise B-spline tool paths with the arc-length parameter—is first proposed in this work. Given a B-spline path with a nonarc-length parameter, it is accurately converted into a B-spline path with an arc-length parameter before sending it into the CNC controller. Furthermore, if the prescribed feed rate is very high and the arc-length parameterized B-spline path is disqualified, it is split into pieces represented with distinct arc-length parameterized B-spline paths in different feed rates. The main advantage of these piecewise paths is that they can eliminate the problems encountered by the existing B-spline interpolator with input of nonarc-length parameterized B-spline paths. Therefore, the piecewise arc-length parameterized B-spline paths are a genuine solution to high feed-and-accuracy B-spline machining.

An Automated and Optimal Tool Path Planning System for the 3-1/2-1/2-Axis CNC Maching of Sculptured Parts

2002 ◽  
Author(s):  
Zezhong C. Chen ◽  
Zuomin Dong ◽  
Geoffrey W. Vickers
Keyword(s):  
Path Planning ◽  
Tool Path ◽  
Cnc Machining ◽  
Planning System ◽  
Surface Patch ◽  
Free Form ◽  
Tool Path Planning ◽  
Tool Paths ◽  
Sculptured Parts ◽  
Machining Scheme

Some sculptured parts with complex free-form surfaces usually require expensive 5-axis CNC machining. In this work, a cost-effective and practical solution to the 5-axis sculptured part machining – 3-1/2-1/2-axis CNC machining scheme – is discussed. An automatic and optimal tool path planning system for 3-1/2-1/2-axis CNC machining is introduced. The system uses fuzzy pattern recognition method and Voronoi diagram to subdivide a complex sculptured surface into an optimal number of uniform surface patches, finds the optimal cutter/part orientation for each surface patch, and plans 3-axis CNC tool paths for them. This type of machining is carried out by rotating the part to the cutter/part orientations discretely and sequentially using a tilt-rotary table attached to the 3-axis CNC machine. Under each orientation, the corresponding surface patch is machined using the 3-axis CNC tool paths. This tool path planning system can automatically generate efficient tool paths for sculptured parts and make the 3-1/2-1/2-axis CNC machining scheme as an applicable alternative of 5-axis CNC machining method.

scholarly journals A chord error conforming tool path B-spline fitting method for NC machining based on energy minimization and LSPIA

2015 ◽  
Vol 2 (4) ◽  
pp. 218-232 ◽  
Author(s):  
Shanshan He ◽  
Daojiang Ou ◽  
Changya Yan ◽  
Chen-Han Lee
Keyword(s):  
Tool Path ◽  
Control Point ◽  
Control Points ◽  
Numerical Instability ◽  
Energy Term ◽  
Chord Error ◽  
B Spline ◽  
Tool Paths ◽  
Spline Fitting ◽  
Fitting Method

Abstract Piecewise linear (G01-based) tool paths generated by CAM systems lack G1 and G2 continuity. The discontinuity causes vibration and unnecessary hesitation during machining. To ensure efficient high-speed machining, a method to improve the continuity of the tool paths is required, such as B-spline fitting that approximates G01 paths with B-spline curves. Conventional B-spline fitting approaches cannot be directly used for tool path B-spline fitting, because they have shortages such as numerical instability, lack of chord error constraint, and lack of assurance of a usable result. Progressive and Iterative Approximation for Least Squares (LSPIA) is an efficient method for data fitting that solves the numerical instability problem. However, it does not consider chord errors and needs more work to ensure ironclad results for commercial applications. In this paper, we use LSPIA method incorporating Energy term (ELSPIA) to avoid the numerical instability, and lower chord errors by using stretching energy term. We implement several algorithm improvements, including (1) an improved technique for initial control point determination over Dominant Point Method, (2) an algorithm that updates foot point parameters as needed, (3) analysis of the degrees of freedom of control points to insert new control points only when needed, (4) chord error refinement using a similar ELSPIA method with the above enhancements. The proposed approach can generate a shape-preserving B-spline curve. Experiments with data analysis and machining tests are presented for verification of quality and efficiency. Comparisons with other known solutions are included to evaluate the worthiness of the proposed solution. Highlights The presented B-spline tool path fitting method is chord-error conforming. It is numerically stable and hence industrial-strength. The proposed ELSPIA algorithm incorporates stretching energy into LSPIA algorithm. Includes actual machining experiments to validate the worthiness.

Application of Convex Hull for Tool Interference Avoidance in 5-Axis CNC Machining

1996 ◽  
Author(s):  
Yuan-Shin Lee ◽  
Tien-Chien Chang
Keyword(s):  
Convex Hull ◽  
Tool Path ◽  
Correction Method ◽  
Nc Machining ◽  
Cnc Machining ◽  
Free Form ◽  
Interference Avoidance ◽  
Tool Interference ◽  
Free Form Surface ◽  
Free Form Surfaces

Abstract In this paper, a methodology of applying convex hull property in solving the tool interference problem is presented for 5-axis NC machining of free-form surfaces. Instead of exhausted point-by-point checking for possible tool interference, a quick checking can be done by using the convex hull constructed from the control polygon of free-form surface modeling. Global tool interference in 5-axis NC machining is detected using the convex hull of the free-form surface. A correction method for removing tool interference has also been developed to generate correct tool path for 5-axis NC machining. The inter-surface tool interference can be avoided by using the developed technique.

A New Approach to G1 Biarc Approximations for Making Smooth, Accurate, and Non-Gouged Profile Features Using CNC Contouring

2006 ◽  
Author(s):  
Zezhong C. Chen ◽  
Xujing Yang
Keyword(s):  
Manufacturing Industry ◽  
Cutting Tool ◽  
Minimum Size ◽  
Free Form ◽  
New Approach ◽  
B Spline ◽  
Tool Paths ◽  
The Past ◽  
Approximation Errors ◽  
The Individual

Extensive research on G1 biarcs fitting to free-form curves (i.e., Bezier, B-spline, and NURBS curves) has been conducted in the past decades for various purposes, including CNC contouring to make smooth, accurate profile features such as pockets, islands, and sides. However, all the proposed approaches only focused on the approximation errors and the biarc number, not on the radius of the individual fitting arc; so it could be smaller than the cutting tool, which would cause gouging during machining. This work, based on the tool radius pre-determined by the minimum size of the concavities of the design profile, proposes a new approach to approximating the profile with a G1 biarc curve in order to make smooth, accurate, and non-gouged profile features using CNC contouring. The significant new contribution of this work is a new mechanism that ensures all the concave arcs of the fitting curve are larger than the pre-determined tool and the fitting errors meet the specified tolerance. This approach can promote the use of G1 biarc tool paths in the manufacturing industry to make high precision profile features.

Virtual Model of Tool Path for Milling Machine at Classical Design Base

2013 ◽  
Vol 282 ◽  
pp. 235-241 ◽  
Author(s):  
Ján Semjon ◽  
Peter Demeč ◽  
Jozef Svetlík
Keyword(s):  
Computer Aided Design ◽  
Tool Path ◽  
Milling Machine ◽  
Coordinate Systems ◽  
Machine Model ◽  
Tool Paths ◽  
True Value ◽  
Classical Design ◽  
Ideal Tool ◽  
Aided Design

This article focuses on issue of proposal ideal tool paths for machine tools. Model of machine consists from 6 basic knots where milling machine disposes spindle placed in the horizontal direction are. Based on mathematical analysis we can detect the movement of machine axes for uncertainty investigated. The calculated values can be compared with machine model developed in Computer - Aided Design. Defining the shape of workpiece as well as assigning an appropriate instrument can be determined by true value of precision workpiece. After substituting the values of specific dimensions we get the final position of vectors point for contact in tool coordinate systems at individual model solids.

A New Method for the Generation of Tool Paths for Finishing Near Net Shape Components

2013 ◽  
Author(s):  
Edgar A. Mendoza López ◽  
Hugo I. Medellín Castillo ◽  
Dirk F. de Lange ◽  
Theo Lim
Keyword(s):  
Geometric Modeling ◽  
Tool Path ◽  
Cutting Tools ◽  
Approximation Error ◽  
Cnc Machining ◽  
New Method ◽  
End Mill ◽  
Tool Paths ◽  
Near Net Shape ◽  
Finish Cut

The CNC machining has been one of the most recurrent processes used for finishing NNS components. This paper presents a new method for the generation of tool paths for machining 3D NNS models. The proposed approach comprises two machining stages: rough cut and finish cut, and three types of cutting tools: ball-end mill, flat-end mill and fillet-end mill. The proposed tool path generation algorithm is based on: (1) approximation of the model surfaces by points using slice planes and visibility analysis, (2) accessibility analysis of the tool, (3) approximation error and tolerance evaluation, (4) collision analysis of tool and tool holder. The tools paths generated are exported as a CNC program. The implementation was carried out in C++ using the ACIS® geometric modeling kernel to support the required geometric operations. To prove the effectiveness of the system several models with variable geometric complexity were tested. The results have shown that the proposed system is effective and therefore can be used to generate the tool paths required for finishing 3D NNS components.

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