Profile Tolerance Allocation for Rapid Prototyping of Sculptured Surfaces in a Direct Slicing Process

2012 ◽  
Author(s):  
Ahmad Barari
Keyword(s):  
Rapid Prototyping ◽  
Tolerance Allocation ◽  
Sculptured Surfaces ◽  
Simple Task ◽  
Direct Slicing ◽  
Highly Nonlinear ◽  
Profile Tolerance ◽  
Actual Profile ◽  
Cusp Height ◽  
Deviation Zone

Layer-based manufactured parts and surfaces are inherently subject to stair case effect which can be quantified by cusp height. Cusp height of a layer is the maximum distance measured along a surface normal between the ideal surface and the produced layer. Although calculation of local cusp high is a simple task but estimating the overall deviation zone of the produced surface is a highly nonlinear and complicated problem. This paper presents a practical approach to predict the actual profile tolerances of the surfaces. This prediction is used to allocate profile tolerances for the rapid prototyping process. Also the methodology can be used to select the optimum uniform layer thicknesses that compromise between the number of layers and the desired accuracy of the final surfaces. The unified developed methodologies are capable to analyse complex surfaces and geometries. Variety of experiments is carried out to study the effectiveness and practicality of the presented methodology. The developed methodology can be employed efficiently during design of rapid prototyping parts.

Design for Manufacturing of Sculptured Surfaces: A Computational Platform

2009 ◽  
Vol 9 (2) ◽  
Author(s):  
Ahmad Barari ◽  
Hoda A. ElMaraghy ◽  
Waguih H. ElMaraghy
Keyword(s):  
Computer Aided Design ◽  
Tolerance Allocation ◽  
Design Stage ◽  
Sculptured Surfaces ◽  
Machined Surface ◽  
Minimum Deviation ◽  
Computer Aided ◽  
Design And Manufacturing ◽  
Aided Design ◽  
Deviation Zone

This paper presents a computer aided design for machining (DFMc) platform that enables designers to customize the design for the available machine tools and to estimate the effect of design decisions on the accuracy of the final machined products, particularly those containing sculptured surfaces. The platform contains two modules to model and simulate the actual machined surface and to evaluate the resulting minimum deviation zone compared to the desired geometry. In the first module, based on the configuration of the available machine tool and the limitations imposed by its inherent errors, the machined surface is simulated and presented as a nonuniform rational B-spline (NURBS) surface. In the second module, the minimum deviation zone between the actual and the nominal NURBS surfaces is evaluated when the developed method to do this task efficiently improves the convergence of the resulting optimization process. Utilizing this platform, two different applications are developed; design tolerance allocation based on the minimum deviation zone of the machined surface and adaptation of the nominal design to compensate for the effect of machining errors. Employing these applications during the design stage improves the acceptance rate of the produced parts and reduces the rate of scrap and rework. The DFMc platform and its presented applications can be implemented in any integrated computer aided design/computer aided manufacturing (CAD/CAM) system. The presented methods can be applied to any type of input geometries and are particularly efficient for design and manufacturing of precise components with complex surfaces. Products in this group, such as dies and tools, medical instruments, and biomedical implants, mostly have critical and important functionalities that demand very careful design and manufacturing decisions.

Search-Guided Sampling to Reduce Uncertainty of Minimum Deviation Zone Estimation

2007 ◽  
Vol 7 (4) ◽  
pp. 360-371 ◽  
Author(s):  
Ahmad Barari ◽  
Hoda A. ElMaraghy ◽  
George K. Knopf
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Search Method ◽  
Inspection System ◽  
Search Procedure ◽  
Sculptured Surfaces ◽  
Minimum Deviation ◽  
Geometric Deviations ◽  
Deviation Zone

Integrating computational tasks in coordinate metrology and its effect on the inspection’s uncertainty is studied. It is shown that implementation of an integrated inspection system is crucial to reduce the uncertainty in minimum deviation zone (MDZ) estimation. An integrated inspection system based on the iterative search procedure and online MDZ estimation is presented. The search procedure uses the Parzen Windows technique to estimate the probability density function of the geometric deviations between the actual and substitute surfaces. The computed probability density function is used to recognize the critical points in the MDZ estimation and to identify portions of the surface that require further iterative measurements until the desired level of convergence is achieved. Reduction of the uncertainty in the MDZ estimation using the developed search method compared to the MDZ estimations using the traditional sampling methods is demonstrated by presenting experiments including both actual and virtual inspection data. The proposed search method can be used for assessing any geometric deviations when no prior assumptions about the fundamental form and distribution of the underlying manufacturing errors are required. The search method can be used to inspect and evaluate both primitive geometric features and complicated sculptured surfaces. Implementation of this method reduces inspection cost as well as the cost of rejecting good parts or accepting bad parts.

Generating Spiral Paths for Sculptured Surfaces Machining

2006 ◽  
Author(s):  
Zhiyang Yao
Keyword(s):  
Surface Finish ◽  
End Milling ◽  
Sculptured Surfaces ◽  
Cutting Efficiency ◽  
Final Surface ◽  
Cutter Path ◽  
End Mills ◽  
Cusp Height ◽  
Major Factors ◽  
Final Surface Finish

To machine sculptured surfaces, ball end mills are mainly used to reach the final surface finish requirements. During machining, the cusp height is one of the major factors defining the final surface finish smoothness. A cutter path that maintains a high cutting efficiency as well as a constant cusp height is desired. Spiral curves, with the property of not requiring extra linkage segments between two adjacent arms can be used to generate a smooth cutter path. In this paper, a geometric algorithm for generating spiral cutter paths for ball end milling in machining sculptured surfaces is presented.

Direct slicing of CAD models for rapid prototyping

1995 ◽  
Vol 1 (2) ◽  
pp. 4-12 ◽  
Author(s):  
Ron Jamieson ◽  
Herbert Hacker
Keyword(s):  
Rapid Prototyping ◽  
Direct Slicing ◽  
Cad Models
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