Exact Constraint Web Handling

1999 ◽  
pp. 135-164
Keyword(s):  
Web Handling ◽  
Exact Constraint

scholarly journals Exact Constraint

2009 ◽  
Vol 131 (09) ◽  
pp. 32-36
Author(s):  
James G. Skakoon
Keyword(s):  
Degrees Of Freedom ◽  
Two Dimensions ◽  
Washing Machine ◽  
Design Engineers ◽  
Successful Design ◽  
Tapered Roller ◽  
Tapered Roller Bearings ◽  
Exact Constraint ◽  
Three Degrees Of Freedom

This article discusses the significance of knowing exact constraint in successful design. Although not traditionally taught in mechanical engineering curricula, and not universally known among mechanical engineers, principles of exact constraint have been around for over a century. Designers of precision instruments have for decades used exact constraint, without which they simply would not achieve the precision required by many devices. Exact constraint has a well-developed theory applicable for design engineers. Applying it improves designs by avoiding over-constraint. Over-constrained designs lead to high stresses, tight tolerances, looseness, binding, and difficult assembly. Exact constraint is easier to picture in two dimensions than in three. In two dimensions, there are three degrees of freedom: two translations and one rotation. Some useful compromises to exact constraint are pinned and bolted connections, ball bearings, and tapered roller bearings. Another is in-situ adjustment of over-constraint as in, for example, the thread-adjusted foot pads of a clothes dryer or washing machine.

Using Exact Constraint to Design Flexure Mechanisms

2000 ◽  
Author(s):  
Douglass L. Blanding
Keyword(s):  
Machine Design ◽  
Qualitative Technique ◽  
Exact Constraint

Abstract This paper presents a qualitative technique, known as “Exact Constraint Machine Design”, for synthesizing and analyzing the design of flexure mechanisms. This technique is presented more fully in the book: Exact Constraint: Machine Design using Kinematic Principles.

Computer Aided Tolerance Analysis of Parts and Assemblies

1989 ◽  
Author(s):  
R. T. Scott ◽  
G. A. Gabriele
Keyword(s):  
Real World ◽  
Probability Distributions ◽  
Three Dimensional ◽  
Tolerance Analysis ◽  
The Real ◽  
Assembly Tolerance ◽  
Computer Aided ◽  
Probability Information ◽  
Exact Constraint

Abstract An exact constraint scheme based on the physical contacting constraints of real part mating features is used to represent the process of assembling the parts. To provide useful probability information about how assembly dimensions are distributed when the parts are assembled as intended, the real world constraints that would prevent interference are ignored. This work addresses some limitations in the area of three dimensional assembly tolerance analysis. As a result of this work, the following were demonstrated: 1. Assembly of parts whose assembly mating features are subjected to variation; 2. Assemble parts using a real world set of exact constraints; 3. Provide probability distributions of assembly dimensions.

Design Optimization Using Genetic Algorithms of Web Handling Systems: The Case of the Pendulum Dancer Mechanism

2007 ◽  
Author(s):  
Marc Vedrines ◽  
Dominique Knittel
Keyword(s):  
Genetic Algorithms ◽  
Design Optimization ◽  
Dynamic Behavior ◽  
Linear Time ◽  
State Space Model ◽  
Software Environment ◽  
Web Handling ◽  
Linear Time Invariant ◽  
Steady State Operation ◽  
Industry Applications

Web systems handling elastic webs are very common in industry. The plant considered in this paper is an industrial winding system with pendulum dancer mechanism. Such a studied dancer moves along an arc of circle. Its utility is double: it imposes the web tension (in steady state operation) and filters the variations of tension mechanically. It is actuated by an air jack with adjustable pressure and has a stiffness and viscous dynamic behavior. Pendulum dancers have been rarely presented and studied in publications. The non-linear model built in Matlab software environment is used as a simulator. Moreover, the state space model useful for modern controller computing can be found thanks to linearization around an operating point. In order to improve the unwinder-winder control performances, the mechanical parameters of the pendulum dancer have to be optimized. The more constant the dynamic behavior over a large frequency band will be, the better the performance of a linear time invariant controller will be obtained. This is the main objective in desensitizing the dancer. The optimization is achieved by using genetic algorithms. The obtained results are discussed and the benefits of this design optimization for industry applications are presented.

Roll-to-roll web handling for membrane inspection

2014 ◽  
Author(s):  
Henry Tan ◽  
Arthur Tay ◽  
Ng Bing Qiang ◽  
Chong Wee Keat ◽  
Kiew Choon Meng ◽  
...  
Keyword(s):  
Web Handling ◽  
Roll To Roll

Viscoelastic Effects in Modeling Web Handling Systems: Unsteady-State Analysis

1998 ◽  
Vol 65 (1) ◽  
pp. 234-241 ◽  
Author(s):  
Xiaofeng Guan ◽  
M. S. High ◽  
D. A. Tree
Keyword(s):  
Steady State ◽  
Deborah Number ◽  
System Response ◽  
Governing Equations ◽  
Web Handling ◽  
Periodic Disturbance ◽  
Start Up ◽  
Viscoelastic Effects ◽  
Unsteady State Analysis ◽  
Predictor Corrector

A model to predict the tension in open spans of web handling systems during transient operations has been developed. Governing equations were developed by using the White-Metzner equation to describe the material response in conjunction with mass and force balances. The governing equations were nondimensionalized and solved via the MacCormack predictor/corrector technique. Two dimensionless parameters emerged from the analysis, the Deborah number, De, and the ratio of the viscous stress to the steady state stress, N. The resulting model is the companion to a previously reported model for steady-state operations (Guan et al, 1995). The model was used to predict the behavior of a web handling system during start-up, transition between steady states, and a periodic disturbance. During start-up and transition, systems responded more rapidly at low De. The system response during a periodic disturbance was correlated to De, the frequency, and the magnitude of the disturbance.

Sign in / Sign up

Export Citation Format

Share Document