Water Jet Automation

Water jet cutting has been an extremely helpful tool that creates flawless parts with tolerances up to 0.1 mm. During the cutting process, it is important to note that each step must be optimized to create the best finish or maintain the correct tolerance zone. These steps are composed of abrasive mass flow rate, traverse speed, and standoff distance. In order for these optimization techniques to be followed a strict set of rules must be followed to ensure consistent progression. Programs such as MATLAB can be utilized to reduce human error in the calculations. MATLAB files can then be saved to use with other materials and thickness combinations.

Can ISO GPS and ASME Tolerancing Systems Define the Same Functional Requirements?

Geometrical tolerances are defined in the ISO Geometrical Product Specification system that is used worldwide, but on the other hand, the ASME Y14.5 standard is used in American companies to define how far actual parts may be away from their nominal geometry. This paper aimed to investigate whether specifications defining acceptable geometrical deviations in one system can be transformed to specifications in the other system. Twelve selected cases are discussed in the paper. Particularly, two cases of size tolerance, three cases of form tolerances, one case of orientation tolerance, four cases of position tolerance (including position tolerance with MMR for the pattern of five holes) and, finally, two cases of surface profile tolerance (unequally disposed tolerance zone and dynamic profile tolerance). The issue is not only in the several different symbols and a set of different defaults, but also in the different meanings and different application contexts of some symbols that have the same graphical form. The answer to the question raised in the paper title is yes for the majority of indications specified according to ASME Y14.5 when new tools from the 2017 edition of ISO 1101 are applied.

Computer support for the shape formation of helical surfaces with a disk tool

An analytical description of the process of making helical surfaces with a disk tool with a substantiated definition of the objective function is proposed. By analogy with coordinate metrology, it is proposed to adopt a minimum tolerance zone as an objective function. This allows to specify the required solution error and eliminates the need to use normal lines or tangents to the profiles. An example of calculating the profile of a helical groove of a twotoothed end mill, performed with an error of 0.05 mm is presented. Keywords: helical surface, disk tool, computer support, optimization, minimum tolerance. [email protected]

Statistics Based Neural Networks Method for Industrial Image Inspection

Automated industrial image inspection system has attracted a great deal of interest in recent years. In this thesis, a new method is presented by combining a statistics method with a neural networks method, which could reduce the interference of machine dynamics and improve the inspection accuracy. Different from the pixel-based or feature-based methods, the proposed method is based on two indices of an image, which are the variances of the rows and columns of the image. For image inspection, first neural networks are trained using these two indices from a set of good images in order to establish a tolerance zone. Then, the two indices of each inspection image are computed through trained neural networks and compared with the tolerance zone. A defective item is detected if either index falls out of the tolerance zone. The other contributions, such as two-point based image registration method and defect simulation algorithms, also help to improve the performance of inspection. Experimental results demonstrate that the proposed approach has a better performance in comparison with traditional statistics approach.

Statistics Based Neural Networks Method for Industrial Image Inspection

Automated industrial image inspection system has attracted a great deal of interest in recent years. In this thesis, a new method is presented by combining a statistics method with a neural networks method, which could reduce the interference of machine dynamics and improve the inspection accuracy. Different from the pixel-based or feature-based methods, the proposed method is based on two indices of an image, which are the variances of the rows and columns of the image. For image inspection, first neural networks are trained using these two indices from a set of good images in order to establish a tolerance zone. Then, the two indices of each inspection image are computed through trained neural networks and compared with the tolerance zone. A defective item is detected if either index falls out of the tolerance zone. The other contributions, such as two-point based image registration method and defect simulation algorithms, also help to improve the performance of inspection. Experimental results demonstrate that the proposed approach has a better performance in comparison with traditional statistics approach.

Computer-Aided Design/Tolerancing Integration: A Novel Tolerance Analysis Model of Assemblies With Composite Positional Defects and Deformations of Nonrigid Parts

Nowadays, the tolerancing integration in computer-aided design (CAD) tools remains among the major goals of mechanical manufacturers. In the virtual product development, ideal and rigid models are used in the digital mockup (DMU). Hence, research works developed integrated CAD models for tolerance analysis, while considering manufacturing defects. However, the tolerance analysis in the case of composite positional tolerance for feature patterns, commonly used in the industry, becomes a difficult activity with the consideration of parts deformations. Thus, this paper presents a novel CAD model for the tolerance analysis considering composite positional defect of features set and nonrigid component deformations due to external mechanical loads. The modeling of rigid components with dimensional defects is established based on the numerical perturbation method. Indeed, the relationships between driving and driven dimensions are determined to obtain the configurations in maximum and least material of the CAD model. Thereafter, the geometrical deviations are modeled by face displacements. The modeling of composite positional errors is performed while respecting the feature relating position tolerance zone framework and the pattern-location tolerance zone framework constraints, as well as the maximum or least material condition. The deviations caused by nonrigid part deformations are considered by the integration of finite element results into the CAD model. The realistic configurations of the assembly are obtained after the updating of mating constraints between rigid and nonrigid parts with defects. The composite positional tolerance is analyzed with the simulation of relative motion between parts. A case study is proposed to evaluate the developed tolerancing method.

Interpretation of Modifier Ⓜ “Circle M” in ASME Y 14.5 GD&T: Intuitive or Deceptive?

Geometric Dimensioning and Tolerancing (GD&T) is a system for defining and communicating engineering tolerances by using a symbolic language on engineering drawings that describe nominal (theoretically perfect) geometry of controlled features, as well as their allowable variation in size, other geometrical characteristics (form, orientation and location) and variation between features. Per this language, dimensions and tolerances are selected to suit function and mating relationship of a part and are subject to a unique interpretation. It allows design engineers, manufacturing personnel, and quality inspectors to describe geometry and allowable variation of parts and assemblies in an efficient and effective manner. When compared to coordinate dimensioning, GD&T has the benefits of reducing the manufacturing cost and number of drawing revisions, describing an important functional relationship on a part, saving inspection time by using functional gages, and improving measurement repeatability. However, GD&T has a fairly complex rule-based system, and as a result can be difficult to teach and learn. One such concept relates to the use of modifier circle M. In GD&T, a feature control frame is required to describe the conditions and tolerances of a geometric control on a part’s feature. The feature control frame may consist of up to four pieces of information, (1) GD&T symbol or control symbol for the feature, (2) Tolerance zone type and its size, (3) Tolerance zone modifiers and (4) Datum references (if required by the GD&T symbol). When circle M is used as a feature tolerance zone modifier, it is relatively easy to understand that there is a possibility of getting bonus tolerance, and in turn, a higher total tolerance. However, what is not very intuitive is the size of the feature counterpart on the functional gage to inspect the given feature control frame. Apparently, it is not the Maximum Material Condition (MMC) size of the feature. Rather, the size is what is called a virtual condition (VC) of the feature, which is defined as the theoretical extreme boundary condition of a feature of size (FOS) generated by the collective effects of MMC and applicable geometric tolerance. When circle M is used as a datum feature/reference modifier, it is even more strenuous to calculate the datum boundary or the size of the datum feature counterpart on the functional gage. In this case, it is the Maximum Material Boundary (MMB); a virtual condition of the datum feature governed by a specific rule of GD&T that establishes this VC with respect to the preceding datum in the feature control frame. This would necessitate one to look for a specific applicable geometric tolerance that is an exclusive relationship between the datum feature and its preceding datum in the feature control frame. Even worse, in case of position tolerance (which, often times, is a lumped sum tolerance controlling orientation and location geometric characteristics of the datum feature simultaneously), it is even trickier to find an exclusive relationship between the datum feature and its preceding datum. In this article, authors have made an attempt to clarify the above-mentioned situations through numerous examples. Hopefully, this can be successfully implemented in undergraduate and graduate education reinforcing the premise that a better educated workforce would be able to contribute significantly higher to advanced manufacturing, design, quality tools and advanced metrology.

Service quality assessment model for academic libraries

Purpose The purpose of this paper is to develop a service quality assessment model for academic libraries using SERVQUAL and validate the model surveying teachers, students and researchers. Design/methodology/approach A model was developed, including 28 statements of five dimensions using the SERVQUAL instrument. It incorporated three segments, i.e. minimum service expectation, desired service expectation and actual service performance with a seven-point Likert scale. The minimum service expectation and desired service expectation appear at both ends of the tolerance zone, which represents the range of satisfactory service performance. A performance level upper tolerance zone could delight users, or service performance below the tolerance zone would cause dissatisfaction. A survey was conducted among 552 respondents from ten private university libraries of Bangladesh to validate the model. Findings Several statistical methods like Cronbach’s alpha (0.986), Bartlett’s test (0.001), rotation sums of squared loadings (74.26) in factor analysis, item loading (0.671‐0.839), commonalities (0.579‐0.859), Kaiser–Meyer–Olkin value (0.971), construct reliability (0.862‐0.910) and AVE value (0.510‐0.660) supported reliability and validity of the model. The actual service performance of all dimensions existed within the tolerance zone of the respective dimensions. Besides, the overall service performance (5.11) resided within the tolerance zone (4.73‐5.84), indicating the users were satisfied with the service provided by their libraries. Originality/value The model was developed in the current context of university libraries, which produced appropriate results. It will prompt further research on service quality assessment in academic libraries globally.

Tolerance Zone-Based Grouping Method for Online Multiple Overtracing Freehand Sketches

Multiple overtracing strokes are common drawing behaviors in freehand sketching; that is, additional strokes are often drawn repeatedly over the existing ones to add more details. This paper proposes a method based on stroke-tolerance zones to group multiple overtraced strokes which are drawn to express a 2D primitive, aiming to convert online freehand sketches into 2D line drawings, which is a base for further 3D reconstruction. Firstly, after the user inputs a new stroke, a tolerance zone around the stroke is constructed by reference to its polygonal approximation points obtained from the stroke preprocessing. Then, the input strokes are divided into stroke groups, each representing a primitive through the stroke grouping process based on the overtraced ratio of two strokes. At last, each stroke group is fitted into one or more 2D geometric primitives including line segments, polylines, ellipses, and arcs. The proposed method groups two strokes together based on their screen-space proximity directly instead of classifying and fitting them firstly, so that it can group strokes of arbitrary shapes. A sketch-recognition prototype system has been implemented to test the effectiveness of the proposed method. The results showed that the proposed method could support online multiple overtracing freehand sketching with no limitation on drawing sequence, but it only deals with strokes with relatively high overtraced ratio.

Characteristics оf growth and fluorescence оf certain types оf algae under acclimation to different temperatures under conditions оf cultures

The temperature rate growth dependence and the relative variable fluorescence, (Fv/Fm) of some of marine planktonic algae from the culture collections were investigated. The algae optima temperature growth (Topt), upper and lower limits tolerant zone of species, and in some cases, changes in the dynamics of these parameters outside the tolerance zone were determined. The similarity of species temperature characteristics with vegetation conditions these species in the nature was observed. Prolonged stress exposure to low positive temperature (4–6°C) was reversible; recovery of the growth rate and Fv/Fm was observed immediately after the increase of temperature. At temperatures above Topt on 2–3°C for diatoms was observed gradual degradation of culture, which, depending on the duration of exposure can lead to the death of the algae. Dinoflagellate species of the summer growing season had higher temperature resistance, and remained viable at temperatures above 5–8°C high Topt, due to lower growth rates. Rising part temperature dependence of the rate of growth approximated by a linear relation, the regression coefficient is 0.08–0.13 for diatoms and 0.03–0.11 for dinophyte. The normalized values for this parameter (the relative value of change in the growth rate, %) was 5.3±0.4 for diatoms and 6.4±0.5 for dinophyte at 1°C of temperature change. For dinophyte species were also been observed larger values of the parameter Q10. The value Fv/Fm for most species had high values in the whole temperature range, in which maintained a stable growth of algae. The fall of this parameter was observed in increasing the border of tolerance zone, and was associated with inhibition of thermal growth processes.