Addressing Cam Wear and Follower Jump in Single-Dwell Cam-Follower Systems With an Adjustable Modified Trapezoidal Acceleration Cam Profile

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Forrest W. Flocker
Keyword(s):  
Additional Benefit ◽  
Factors Affecting ◽  
Large Separation ◽  
A Value ◽  
Cam Follower ◽  
Cam Profile ◽  
Interface Forces

Presented is a modified trapezoidal cam profile with an adjustable forward and backward acceleration. The profile is suitable for single-dwell cam and follower applications. The main benefit of the profile is that it allows cam designers to choose easily a value for the maximum forward or maximum backward acceleration to achieve design objectives. An additional benefit of the profile is that it has a continuous jerk curve. Follower acceleration is one of the primary factors affecting cam wear and follower jump, two main concerns of cam designers. Large forward acceleration against a load creates cam-follower interface forces that can cause excessive wear. Backward acceleration tends to reduce the cam-follower interface force, and if the backward acceleration is sufficiently large, separation between the cam and follower (“follower jump”) can occur. The cam profile presented in this paper gives cam designers an easy way to adjust the maximum forward or backward acceleration to prevent these problems.

Addressing CAM Wear and Follower Jump in Single-Dwell CAM-Follower Systems With an Adjustable Modified Trapezoidal Acceleration CAM Profile

2008 ◽  
Author(s):  
Forrest W. Flocker
Keyword(s):  
Additional Benefit ◽  
Factors Affecting ◽  
Large Separation ◽  
A Value ◽  
Cam Follower ◽  
Cam Profile ◽  
Interface Forces

Presented is a modified trapezoidal cam profile with adjustable forward and backward acceleration. The profile is suitable for single-dwell cam and follower applications. The main benefit of the profile is that it allows cam designers to choose easily a value for the maximum forward or maximum backward acceleration to achieve design objectives. An additional benefit of the profile is that it has a continuous jerk curve. Follower acceleration is one of the primary factors affecting cam wear and follower jump, two main concerns of cam designers. Large forward acceleration against a load creates cam-follower interface forces that can cause excessive wear. Backward acceleration tends to reduce the cam-follower interface force, and if the backward acceleration is sufficiently large, separation between the cam and follower (“follower jump”) can occur. The cam profile presented in this paper gives cam designers an easy way to adjust the maximum forward or backward acceleration to prevent these problems.

Spline Based Design of Cam Contours for Improved Dynamic Performance

1993 ◽  
Author(s):  
Holly K. Ault ◽  
James C. Wilkinson
Keyword(s):  
Dynamic Performance ◽  
Integrated Design ◽  
Polynomial Functions ◽  
Piecewise Polynomial ◽  
Cam Design ◽  
Piecewise Polynomial Functions ◽  
Cam Follower ◽  
Cam Profile ◽  
Pitch Curve ◽  
Design And Manufacture

Abstract A method for the integrated design and manufacture of radial plate cams is discussed. Currently, a cam-follower system is designed by specifying constraints on the motion of the follower. The physical cam contour or cam pitch curve are not mathematically defined. The cam is manufactured from the discretized follower motion program. A new method for cam design is proposed which will produce a smooth, mathematically defined cam pitch curve while maintaining the proper constraints on the follower motion. Piecewise polynomial functions in the form of rational and/or non-rational splines may be used. Cams will be manufactured using smoothed profiles and tested for improved dynamic performance. The results of initial investigations of cam profile design for this research are presented.

scholarly journals The Delta Variant Had Negligible Impact on COVID-19 Vaccine Effectiveness in the USA

2021 ◽  
Author(s):  
Ben Blaiszik ◽  
Carlo Graziani ◽  
James L. Olds ◽  
Ian Foster
Keyword(s):  
Age Distribution ◽  
Vaccine Effectiveness ◽  
Vaccination Status ◽  
Rt Pcr ◽  
Factors Affecting ◽  
A Value ◽  
Health Authorities ◽  
Public Health Authorities ◽  
The Usa ◽  
Zero Baseline

The SARS-CoV-2 Delta variant (B.1.617.2) was initially identified in India in December 2020. Due to its high transmissibility, its prevalence in the U.S.A. grew from a near-zero baseline in early May 2021 to nearly 100% by late August 2021, according to CDC tracking. We accessed openly available data sources from the public health authorities of seven U.S. states, five U.S. counties, and the District of Columbia on RT-PCR COVID-19 tests split by the COVID-19 vaccination status of individuals tested during this period. Together, these time series enable estimation and tracking of COVID-19 vaccine effectiveness (VE∗) (against RT-PCR diagnosed infection) concurrently with the growth of Delta variant prevalence in those locations. Our analyses reveal that in each locality the VE∗ for the combined set of all three US vaccines remained relatively stable and quite well-performing, despite the dramatic concurrent rise of Delta variant prevalence. We conclude that the Delta variant does not significantly evade vaccine-induced immunity. The variations in our measured VE∗ appear to be driven by demographic factors affecting the composition of the vaccinated cohorts, particularly as pertains to age distribution. We report that the measured VE∗, aggregated across the collected sites, began at a value of about 0.9 in mid-May, declined to about 0.76 by mid-July, and recovered to about 0.9 by mid-September.SummaryWe estimated local COVID-19 vaccine effectiveness using RT-PCR COVID-19 test data broken out by vaccination status from select localities in the U.S.A. between 15 May and 15 September 2021 while the SARS-CoV-2 Delta variant (B.1.617.2) was ascending from essentially zero prevalence to total dominance of the genome, and showed that the rise of the Delta variant had negligible effect on vaccine effectiveness.

Valve Gear Refinement

2000 ◽  
Vol 124 (1) ◽  
pp. 86-90 ◽  
Author(s):  
Jurij Avsec ◽  
Milan Marcic ◽  
Maks Oblak
Keyword(s):  
Mathematical Model ◽  
Cam Design ◽  
Cam Follower ◽  
New Type ◽  
Cam Profile ◽  
Profile Design ◽  
Comparison Of The Results ◽  
The Mathematical Model ◽  
Valve Gear ◽  
Lubrication Properties

This paper describes a new type of valve gear cam—MULTICAM—which consists of seven curves and allows an optimum cam profile design. In order to calculate the cinematic and dynamic values and to assess the minimum oil film thickness in the valve gear, the mathematical model of an ideal valve gear was used. In addition, the comparison of the results between the polysine cam and the new MULTICAM cam design was made. By means of the new cam design the Hertz pressures were reduced at the point of contact between the cam and the cam follower and the lubrication properties at the top of the cam improved.

Synthesis of cam profile using classical splines and the effect of knot locations on the acceleration, jump, and interface force of cam follower system

2011 ◽  
Vol 225 (12) ◽  
pp. 3019-3030 ◽  
Author(s):  
U Chavan ◽  
S Joshi
Keyword(s):  
Displacement Function ◽  
Physical Parameters ◽  
Spline Curves ◽  
Design Variables ◽  
Negative Acceleration ◽  
Positive Acceleration ◽  
Large Jump ◽  
Cam Follower ◽  
Displacement Profile ◽  
Cam Profile

Large positive acceleration against a load creates cam follower interface force that can cause excessive wear. Negative acceleration tends to reduce the cam follower interface force, and if the negative acceleration is sufficiently large, jump between the cam and follower can occur. Hence, these are the two main concerns of cam designers. This study presents a new approach to adjust the acceleration, interface force, and jump in the early phase of cam design. Knot locations of polynomial pieces of spline curves are considered as design variables which gives variety of cam profiles. Here, design process starts from displacement profile and there is no need for predefined acceleration curves. A single dwell cam displacement function is defined by classical spline curve, made up of four polynomial pieces that are tied together at their ends, called knots. Specifications of these knots are considered for synthesis and analysis of cam follower system. Mathematical relation between interface force and knot locations is presented as wear and jump models. These models are useful to reduce wear and jump by proper placement of the knots on the basis of interface force. By dynamic simulation of cam follower system, cam curves are drawn for different cases of knot locations and good resemblance was found with theoretical curves. This study suggests the cam designers have the added option to control the kinematic and dynamic quantities without changing the physical parameters of cam follower system.

A Versatile Cam Profile for Controlling Interface Force in Multiple-Dwell Cam-Follower Systems

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Forrest W. Flocker
Keyword(s):  
Closed Form ◽  
High Speed ◽  
Maximum Magnitude ◽  
Design Objective ◽  
Standard Equation ◽  
Negative Acceleration ◽  
Cam Follower ◽  
Cam Profile ◽  
Harmonic Analyses ◽  
Spreadsheet Software

Cam follower systems are widely used in manufacturing because of their precise motion and ability to easily dwell. The cam typically drives a follower in some precise motion needed to accomplish a manufacturing task. Presented in this paper is a closed-form modified trapezoidal cam motion function with adjustable positive and negative acceleration. The profile is suitable for multiple-dwell cam and follower applications. The profile is particularly applicable to high-speed cams in which the follower acceleration is a primary design objective. The main benefit of the profile is that it allows cam designers to easily set limits on the positive and negative acceleration to achieve design objectives. Additional benefits are that the cycle jerk is continuous and that the cam designer can control the maximum magnitude of jerk. The motion program is presented in closed-form for easy implementation in standard equation-solver or spreadsheet software. Dynamic and harmonic analyses are presented to illustrate the benefits of the profile.

scholarly journals Cam Mechanisms Reverse Engineering Based on Evolutionary Algorithms

Electronics ◽  
2021 ◽  
Vol 10 (24) ◽  
pp. 3073
Author(s):  
Monica Tiboni ◽  
Cinzia Amici ◽  
Roberto Bussola
Keyword(s):  
Genetic Algorithm ◽  
Reverse Engineering ◽  
Dynamic Time Warping ◽  
Automated Manufacturing ◽  
Time Warping ◽  
Planning Techniques ◽  
Innovative Method ◽  
Cam Follower ◽  
Cam Profile ◽  
Dynamic Time

Cam follower mechanisms are widely used in automated manufacturing machinery to transform a rotary stationary motion into a more general required movement. Reverse engineering of cams has been studied, and some solutions based on different approaches have been identified in the literature. This article proposes an innovative method based on the use of an evolutionary algorithm for the identification of a law of motion that allows for approximating in the best way the motion or the sampled profile on the physical device. Starting from the acquired data, through a genetic algorithm, a representation of the movement (and therefore of the cam profile) is identified based on a type of motion law traditionally used for this purpose, i.e., the modified trapezoidal (better known as modified seven segments). With this method it is possible to estimate the coefficients of the parametric motion law, thus allowing the designer to further manipulate them according to the usual motion planning techniques. In a first phase, a study of the method based on simulations is carried out, considering sets of simulated experimental measures, obtained starting from different laws of motion, and verifying whether the developed genetic algorithm allows for identifying the original law or approximating one. For the computation of the objective function, the Euclidean norm and the Dynamic Time Warping (DTW) algorithm are compared. The performed analysis establishes in which situations each of them is more appropriate. Implementation of the method on experimental data validates its effectiveness.

The Design of Disk Cam Mechanisms With a Translating Follower Having an Added Dual-Roller Intermediate Link

2020 ◽  
Author(s):  
Kuan-Lun Hsu ◽  
Sun-Liang Chou
Keyword(s):  
Contact Stress ◽  
Normal Force ◽  
Design Procedures ◽  
Cam Mechanism ◽  
Working Cycle ◽  
Cam Follower ◽  
Cam Profile

Abstract This paper provides a methodology to design a disk cam mechanism that has a translating follower with dual rollers. Dual rollers are joined by an oscillating link and can contact cam profile simultaneously throughout working cycle of cam rotation. The application of this novel follower can offer two engagements in cam-follower pair to spread the induced normal force and reduce the contact stress between cam and follower. Two examples are worked to demonstrate application of design procedures and to illustrate the capability of reducing contact stress of this novel follower. The results show that the contact stress of such a cam mechanism can be reduced by 28.85% in comparison with that of the cam mechanism with a common translating roller follower.

Factors affecting the ethanol stability of bovine skim milk

1986 ◽  
Vol 53 (3) ◽  
pp. 407-417 ◽  
Author(s):  
David S. Horne ◽  
Thomas G. Parker ◽  
William J. Donnelly ◽  
D. Thomas Davies
Keyword(s):  
Skim Milk ◽  
Original Data ◽  
Early Lactation ◽  
Ph Profile ◽  
Obvious Effect ◽  
Factors Affecting ◽  
A Value ◽  
Alkaline Shift ◽  
Autumn And Winter ◽  
Ethanol Stability

SUMMARYMilk samples from three groups of cows were taken at frequent intervals throughout lactation following autumn-, winter- or spring-calving. The ethanol (EtOH) stability/pH profile was determined for each sample and its characteristic parameters calculated. The lactational trends in these parameters were examined. Asymptotic maximum EtOH stability (Smax) was low in early lactation but rose rapidly to a value which showed no further lactational trends. Asymptotic minimum stability (Smin) for samples from autumn- and winter-calving cows showed a decrease which could be associated with the transition to summer grazing but no obvious lactational effects. The slope parameter increased slowly during lactation. The profile pK value decreased in early lactation, but thereafter increased throughout lactation giving the most obvious effect observed in direct measurement, namely an alkaline shift in the profile as lactation progressed. The EtOH stability calculated at a fixed pH of 6·6 passed through a maximum, characteristic for each cow, in the first weeks of lactation but declined steadily thereafter. This behaviour mirrors the lactational behaviour of the soluble salt balance ratio calculated from the original data of White & Davies (1958).

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