Sculptured surface tolerance verification with design datums

2005 ◽  
Vol 43 (7) ◽  
pp. 1465-1482 ◽  
Author(s):  
Y. Li ◽  
P. Gu *
Keyword(s):  
Sculptured Surface ◽  
Tolerance Verification

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.

Automatic Planning for 5-Axis Sculptured Surface Machining

1994 ◽  
Author(s):  
Yuan-Shin Lee ◽  
Tien-Chien Chang
Keyword(s):  
Sculptured Surface ◽  
Sculptured Surfaces ◽  
Design Modification ◽  
Surface Machining ◽  
Sculptured Surface Machining ◽  
Cutter Path ◽  
Automatic Planning ◽  
Five Axis ◽  
Five Axes ◽  
Complete Operation

Abstract In modern product design, sculptured surfaces are commonly used for functional and artistic shape design. Design of sculptured surfaces is evolutionary, consisting primarily of incremental changes to existing part surfaces. Manual operation planning for sculptured surface machining is known to be error-prone and inefficient, which requires considerable checking, verification, and rework. Five-axis machining has higher productivity and better machining quality than 3-axis machining. However, the programming for 5-axis machining is more difficult due to the complex simultaneous cutter movements along the machine’s five axes. This paper presents a systematic methodology to generate operation plans for 5-axis sculptured surface machining. A complete operation plan and the error-free cutter path can be automatically generated from the CAD part design. To achieve design for manufacturing of sculptured surface products, the machining unfeasibility information can be fed back to the designer for further design modification. Results of computer implementation and testing examples are also presented.

Position Tolerance Verification Using Simulated Gaging

1989 ◽  
Author(s):  
F. Etesami
Keyword(s):  
Lagrange Multipliers ◽  
Optimization Problem ◽  
Coordinate Measuring Machines ◽  
Vision Systems ◽  
Dimensional Inspection ◽  
Perfect Form ◽  
Nominal Feature ◽  
Manual Tasks ◽  
Tolerance Verification

Abstract One of the routine manual tasks in dimensional inspection is the assembly verification of circular features by mechanical gaging. With the aid of coordinate measuring machines or vision systems, this task can be performed more efficiently through simulation or soft-gaging. A formulation is presented for interpretation of 2D position tolerance specifications. Simulated gages are constructed from datum features as a set of constraint relationships. The measure of perfect-form position-imperfection is determined as the distance between the measured and the nominal feature positions subject to datum constraint requirements. The derived formulation is applied to an example part with a hole-slot datum-priority-frame. This formulation results in a three-variable optimization problem which is solved by an Augmented Lagrange Multipliers technique. The extension of the formulation to 3D is also discussed, but without reference to a specific representation.

Generalized Abbe Principle: Position Error Propagation in Machine Elements

1996 ◽  
Author(s):  
Joseph Pegna
Keyword(s):  
Error Propagation ◽  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Statistical Characterization ◽  
Physical Limit ◽  
Potential Applications ◽  
Machine Elements ◽  
Tolerance Verification ◽  
Precision Machines

Abstract In the quest for ever finer levels of technology integration, mechanical linkages reach their precision limits at about 5micrometers per meter of workspace. Beyond this physical limit, all six dimensional degrees of freedom need to be precisely ascertained to account for mechanical imperfections. This paper substantiates Wu’s vision of “precision machines without precision machinery.” A formulation and statistical characterization of position and orientation error propagation in rigid bodies are presented for two extreme models of measurement. It is shown that error distribution is uniquely dependent upon the design of the measurement plan. The theoretical foundations presented were evolved in the course of designing precision machinery. Other potential applications include: fixture design, metrology, and geometric tolerance verification.

Measurements and Characterization of Photovoltaic Modules for Tolerance Verification

2013 ◽  
pp. 144-152
Author(s):  
C. Calò ◽  
A. Lay-Ekuakille ◽  
P. Vergallo ◽  
C. Chiffi ◽  
A. Trotta ◽  
...  
Keyword(s):  
Digital Imaging ◽  
Failure Mechanisms ◽  
Matrix Methods ◽  
Energy Prediction ◽  
Photovoltaic Modules ◽  
Pv Module ◽  
Pv Modules ◽  
Tolerance Verification ◽  
Material Tests

One of the most important aspects of photovoltaic modules is reliability for future uses, that is, a certain module will last certain number of years in use (generally 30 or 35 years). Reliability yields from excellent qualification tests on photovoltaic (PV) modules. Testing for reliability identifies unknown failure mechanisms and whether modules are susceptible to known failure mechanisms. This paper illustrates techniques of outdoor measurements and qualification characterization to know PV module conditions for commercial uses. Matrix methods are used for energy prediction. Failure material tests, using digital imaging and thermography, have also been conducted.

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