An Efficient, Accurate Approach to Representing Cutter-Swept Envelopes and Its Applications to Three-Axis Virtual Milling of Sculptured Surfaces

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Zezhong C. Chen ◽  
Wei Cai
Keyword(s):  
Tool Path ◽  
Basic Mechanism ◽  
Cnc Milling ◽  
Sculptured Surfaces ◽  
Machining Error ◽  
Tool Paths ◽  
Virtual Machining ◽  
Machining Errors ◽  
Computer Numerically Controlled ◽  
Swept Volume

To address a major technical challenge in simulating geometric models of machined sculptured surfaces in three-axis virtual machining, this paper presents an efficient, accurate approach to representing the 3D envelopes of a cutter sweeping sequentially through cutter locations; these envelopes embody the furrow patches of the machined surfaces. In our research, the basic mechanism of removing stock material in three-axis computer numerically controlled (CNC) milling of sculptured surfaces is investigated, and, consequently, an effective model is proposed to represent the 3D envelopes (or furrow patches). Our main contribution is that a new directrix (or swept profile) of the furrow patches (mathematically, ruled surfaces) is identified as a simple 2D envelope of cutting circles and is formulated with a closed-form equation. Therefore, the 3D cutter-swept envelopes can be represented more accurately and quickly than the existing swept-volume methods. With this innovative approach, a method of accurate prediction of the machining errors along tool paths in three-axis finish machining is provided, which is then applied to the optimization of tool-path discretization in two examples. Their results demonstrate the advantages of our approach and verify that the current machining-error-prediction methods can cause gouging in three-axis sculptured surface milling.

A Generic, Geometric Approach to Accurate Machining-Error Predictions for 3-Axis CNC Milling of Sculptured Surface Parts: Part II — Applications and Analysis

2006 ◽  
Author(s):  
Zezhong C. Chen ◽  
Wei Cai
Keyword(s):  
Tool Path ◽  
Geometric Approach ◽  
Sculptured Surface ◽  
Cnc Milling ◽  
Sculptured Surfaces ◽  
Machining Error ◽  
Tool Paths ◽  
Machining Errors ◽  
Tool Surface ◽  
Cam Software

As sculptured surfaces are widely used in mechanical design, machining sculptured surface parts accurately is highly demanded in industry; however, it is quite challenging to meet their demand. Due to the geometric complexity of these surfaces, the tool-surface geometric mismatch always causes machining errors when the tool cuts along the tool paths. To prevent surface gouging, where the machining error is greater than the part tolerance, state-of-the-art CAM software usually determines cutter contact (CC) points on the tool paths first, and then simulates the machining to check the errors caused by this tool-surface mismatch. If surface gouging occurs, the CC points are adjusted using the CAM software. But this established method is quite time consuming and sometimes ineffective. To overcome these problems, a new system, based on the accurate predictions of machining errors, is proposed in this research paper for the optimization of CC points on the tool paths. First, two established CC point generation methods, the chordal deviation method and the circular arc approximation method, are introduced; and their limitations are addressed. Second, a sensitivity study of the machining errors with respect to the cutting tools is conducted. Then a system implementing the generic, geometric approach to accurate machining-error predictions is proposed to optimize CC points on the tool paths. Finally, this CC point optimization system is applied to two practical parts to demonstrate its advantages over the two established methods. This proposed work provides a profound understanding of the machining errors caused by the tool-surface mismatch and contributes to tool path planning for 3-axis CNC milling of sculptured surface parts.

scholarly journals Precision Sculptured Surface CNC Machining Using Cutter Location Data

2016 ◽  
Vol 686 ◽  
pp. 224-233
Author(s):  
Nikolaos A. Fountas ◽  
Nikolaos M. Vaxevanidis ◽  
Constantinos I. Stergiou ◽  
Redha Benhadj-Djilali
Keyword(s):  
Tool Path ◽  
Low Cost ◽  
Cnc Machining ◽  
Sculptured Surface ◽  
Sculptured Surfaces ◽  
Rough Machining ◽  
Machining Error ◽  
Location Data ◽  
Tool Paths ◽  
Cutter Location Data

Industrial parts with sculptured surfaces are typically, manufactured with the use of CNC machining technology and CAM software to generate surface tool paths. To assess tool paths computed for 3-and 5-axis machining, the machining error is evaluated in advance referring to the parameter controlling the linearization of high-order curves, as well as the scallop yielded as a function of radial cutting engagement parameter. The two parameters responsible for the machining error are modeled and corresponding cutter location data for tool paths are utilized to compare actual trajectories with theoretical curves on a sculptured surface assessing thus the deviation when virtual tools are employed to maintain low cost; whilst ensuring high precision cutting. This operation is supported by applying a flexible automation code capable of computing the tool path; extracting its CL data; importing them to the CAD part and finally projecting them onto the part’s surface. For a given tolerance, heights from projected instances are computed for tool paths created by changing the parameters under a cutting strategy, towards the identification of the optimum tool path. To represent a global solution rough machining is also discussed prior to finish machining where the new proposals are mainly applied.

The Study of Five-Axis Graphic Simulation by Swept Volume Algorithm

2008 ◽  
Vol 375-376 ◽  
pp. 569-573
Author(s):  
Li Qiang Zhang ◽  
Yu Han Wang ◽  
Ming Chen
Keyword(s):  
Processing Time ◽  
Tool Path ◽  
Machining Error ◽  
Machining Errors ◽  
Tool Interference ◽  
Volume Algorithm ◽  
Swept Volume ◽  
Tool Motion ◽  
Five Axis ◽  
Windows Xp

Five-axis NC machining tools can improve the efficiency and accuracy obviously in today’s machining industries, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the verification of the tool path is very important and necessary before machining the part. A new algorithm for 5-axis machining verification based on the swept volume has been presented in the paper. Based on the machine tool path and the cutter geometry, the cutter’s instantaneous swept profile is determined. By integrating the intermediate swept volume, the cutter’s swept envelope can be constructed and applied to NC verification. The algorithm has been implemented through Visual C++ and OpenGL language on Windows XP platform; a few examples are to verify the reliability of the proposed algorithms effectively. The experiment results indicate that the proposed method is superior to the traditional methods on the processing time and image quality. This proposed algorithm can be further applied to machining error analysis, collisions interference and NC path optimization, etc.

A Generic, Geometric Approach to Accurate Machining-Error Predictions for 3-Axis CNC Milling of Sculptured Surface Parts: Part I — Modeling and Formulation

2006 ◽  
Author(s):  
Zezhong C. Chen ◽  
Wei Cai
Keyword(s):  
Tool Path ◽  
Cutting Tool ◽  
Geometric Model ◽  
Research Work ◽  
Geometric Approach ◽  
Cnc Machining ◽  
Sculptured Surface ◽  
Machining Error ◽  
Machining Errors ◽  
Tool Surface

In CNC machining, machining errors are usually caused by some of the sources such as cutting tool deflection, cutting tool wear, machine tool vibration, improper coolant/lubrication, and negative thermal effect. To increase product accuracy, much research has been carried out on the prediction of machining errors. However, in milling of sculptured surface parts, due to their curved shapes, the geometries of cutting tools do not match the parts’ surfaces well if the tools cut along the tool paths on the surfaces in a point-to-point way. As a consequence, machining error is inevitable, even if there is no other source of error in ideal machining conditions. To predict machining errors caused by this tool-surface mismatch, several methods have been proposed. Some of them are simple, and some represent the geometry of machined surfaces using cutter-swept surfaces. But none of these methods is accurate and practical. In this research work, a generic, geometric approach to predicting machining errors caused by the tool-surface mismatch is proposed for 3-axis sculptured surface milling. First, a new geometric model of the furrow formed by an APT tool moving between two neighboring cutter contact (CC) points is built. Second, the mathematical formula of cutting circle envelopes is derived. Then an algorithm for calculating machining errors in each tool motion is provided. Finally, this new approach is applied to two practical parts for the accurate machining-error predictions, and these predictions are then compared to the inaccurate predictions made by two established methods to demonstrate the advantages of this approach. This approach can be used in tool path planning for high precision machining of sculptured surface parts.

A Data-Driven Machining Error Analysis Method for Finish Machining of Assembly Interfaces of Large-Scale Components

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Wei Fan ◽  
Lianyu Zheng ◽  
Wei Ji ◽  
Xun Xu ◽  
Lihui Wang ◽  
...  
Keyword(s):  
Error Analysis ◽  
Large Scale ◽  
Tool Path ◽  
Cutting Parameters ◽  
Pso Algorithm ◽  
Data Driven ◽  
Machining Accuracy ◽  
Machining Error ◽  
Spatial Statistical Analysis ◽  
Machining Errors

Abstract To guarantee the final assembly quality of the large-scale components, the assembly interfaces of large components need to be finish-machined on site. Such assembly interfaces are often in low-stiffness structure and made of difficult-to-cut materials, which makes it hard to fulfill machining tolerance. To solve this issue, a data-driven adaptive machining error analysis and compensation method is proposed based on on-machine measurement. Within this context, an initial definite plane is fitted via an improved robust iterating least-squares plane-fitting method based on the spatial statistical analysis result of machining errors of the key measurement points. Then, the parameters of the definite plane are solved by a simulated annealing-particle swarm optimization (SA-PSO) algorithm to determine the optimal definite plane; it effectively decomposes the machining error into systematic error and process error. To reduce these errors, compensation methods, tool-path adjustment method, and an optimized group of cutting parameters are proposed. The proposed method is validated by a set of cutting tests of an assembly interface of a large-scale aircraft vertical tail. The results indicate that the machining errors are successfully separated, and each type of error has been reduced by the proposed method. A 0.017 mm machining accuracy of the wall-thickness of the assembly interface has been achieved, well fulfilling the requirement of 0.05 mm tolerance.

ROUGH MACHINING FOR MULTI-SCULPTURED SURFACES

1999 ◽  
Vol 23 (2) ◽  
pp. 275-286
Author(s):  
A. Vafaeesefat ◽  
H.A. EIMaraghy
Keyword(s):  
Cutting Planes ◽  
Tool Path ◽  
Tool Path Generation ◽  
Parallel Projection ◽  
Geometric Description ◽  
Sculptured Surfaces ◽  
Rough Machining ◽  
Tool Paths ◽  
Rough Milling ◽  
Bounding Surfaces

This paper present a method to generate 3-axis NC programs for rough milling processes. A raster digitizing of the solid volume delimitated by sculptured surfaces to be machined is first created. This is accomplished by using the so-called Z-buffer created from a parallel projection of all surfaces. Conventional rendering software can be used to generate the Z-buffer. This volume is transformed into a 3-D mesh composed of “empty”, “full”, and “mixed” blocks. Machining is preformed from top to bottom in a sequence of horizontal cutting planes. At each level of planar machining, spiral routines are used to generate the tool path. The proposed method is valid for generating tool paths for general cavities bounded by arbitrary surfaces. One of the notable advantages of the proposed method is that the tool path generation is independent from the geometric description of bounding surfaces. An example is used to illustrate the approach and its advantages.

Improving Rough Cutting Efficiency for Machining of Impellers

2004 ◽  
Author(s):  
Der-Min Tsay ◽  
Chien-Wen Chen
Keyword(s):  
End Milling ◽  
Geometric Model ◽  
Production Costs ◽  
Cnc Milling ◽  
Rough Machining ◽  
Tool Paths ◽  
Cnc Milling Machine ◽  
Computer Numerically Controlled ◽  
Step Interval ◽  
Time Required

A procedure that can be used to generate rough cutting tool paths with minimized variations of material removal rates (MRRs) is developed for 5-axis ball end milling of centrifugal compressor impellers. Based on the geometric model of impellers, the detailed processes in finding the cutter contact (CC) points with equal spacing for step interval between two adjacent tool paths and a constant depth between two neighboring cutting layers are presented. The developed system can considerably improve productivity and lower production costs in rough machining since the time required can be reduced by minimizing the waste tool paths. Simulation and machining tests by a 5-axis computer numerically controlled (CNC) milling machine are performed to illustrate the procedure and its advantages.

Single Point Incremental Sheet Forming of Polymer on Computer Numerically Controlled (CNC) Milling Machine Tool

2014 ◽  
Vol 622-623 ◽  
pp. 420-426 ◽  
Author(s):  
D. Rajenthirakumar ◽  
R. Sridhar
Keyword(s):  
Plastic Deformation ◽  
Sheet Metal ◽  
Failure Modes ◽  
Tool Path ◽  
Single Point ◽  
Research Work ◽  
Milling Machine ◽  
Forming Process ◽  
Tool Paths ◽  
Computer Numerically Controlled

The idea of incrementally forming sheet metal with a single point tool, called ‘dieless forming’, was patented by Leszak [1] well before it was technically feasible. There have been many studies, which have lead to the present situation [2-9]. The new processes are attractive because manufacturing sheet metal can be accomplished by any facility having a three-axiscncmill. Sheet metalspifis an innovative, flexible sheet metal-forming technology that uses principles of layered manufacturing. It transforms the complicated geometry information into a series of parameter of two-dimensional layers and then the plastic deformation is carried out layer-by-layer through the computer numerically controlled. The basic principle ofspif(Fig. 1) is that the forming tool moves around the outline of the part along the predefined tool path and extrudes the sheet metal point by point so that the local plastic deformations occur incrementally [8, 10]. The forming tool paths have a great effect on the surface quality, forming time and dimensional accuracy. Although the movement mode of the forming tool is similar to one of the cutters in thecncmilling machine, the forming process based on the plastic deformation and milling process is totally different, so the requirements for the tool paths are different. As a result, there are some specific characteristics which should be considered in forming tool path generation. The goal of this paper is to evaluate the possibility of producing low-cost polymer sheet components by means ofspif. Three different thermoplastic materials were incrementally formed on a conventionalcncmilling machine. Experiments are conducted to determine the formability, failure modes and significant process parameters. Even though considerable amount of research work has been done in the field, these aspects are not completely defined and only limited number of materials has been tested.

Effect of Feed Rate, Tool-Path and Step over on Geometric Accuracy of Freeform Surfaces when 3 Axis CNC Milling

2019 ◽  
Vol 889 ◽  
pp. 107-114
Author(s):  
Quy Hoang Van ◽  
Tuyen Bui Ngoc
Keyword(s):  
Feed Rate ◽  
Tool Path ◽  
End Milling ◽  
Cnc Milling ◽  
Sculptured Surfaces ◽  
Machining Time ◽  
Freeform Surfaces ◽  
Ball End Milling ◽  
Cad Cam ◽  
Step Over

The use of freeform (sculptured) surfaces in the product design process is accelerating at an exponential rate driven by functional as well as esthetics demands. CAD/CAM software is a must in their design are relatively well-covered, issues still remain when it comes to the actual manufacture of freeform surfaces. The major issues are related to the chosen feed rate, toolpaths and step over that would assure the required surface quality, the minimization of the total machining time, etc. This research presents an experimental study to define the effects of machining’s parameters (including: feed rate; toolpath and step over) for CNC 3-axis ball end milling process. The result shows a model for cutting is formulated and incorporated into the parameters of machining that is compatible with all CAD/CAM systems. This result can be used to choose parameters of optimum including federate, toolpath and step over when machining of other freeform surfaces. Keywords: Freeform surface; tool path; ball end milling

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.

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