Maximum Allowable Tolerance Research Articles

Tolerance optimization for sheet metal parts based on joining simulation

In the industrial production process, the tolerance design of product is directly related to the product and production cost. This paper proposes an optimization method for the geometrical tolerance design of sheet metal parts based on joining simulation. Finite Element Method (FEM) is applied to simulate the influence of Body In White (BIW) joining process on the assembly deviation. Because the profile tolerance is widely used in the BIW sheet metal parts as the manufacturing requirements for the single parts as well as the assemblies to ensure the dimensional quality of the product, this type of tolerance on parts are mapped on the FE meshes in this work subjected to the Product Manufacturing Information (PMI). A sensitivity analysis is implemented to rank the tolerances by constructing meta-models. Without compromising the dimensional stability of the assembly, the geometrical tolerances of the single parts are optimized through a two-level optimization system. An automotive reinforcement assembly is studied to illustrate the proposed method. The maximum allowable tolerance ranges of the reinforcement part are adapted with respect to a pre-defined process capability index. The result provides a quantitative tolerance optimization strategy for BIW parts in an early development phase.

Costs of mandatory cannabis testing in California

Every batch of cannabis sold legally in California must be tested for more than 100 contaminants. These contaminants include 66 pesticides, for 21 of which the state's tolerance is zero. For many other substances, tolerance levels are much lower than those allowed for food products in California. This article reviews the state's testing regulations in context, including maximum allowable tolerance levels — and uses primary data collected from California's major cannabis testing laboratories and several cannabis testing equipment manufacturers, as well as a variety of expert opinions, to estimate the cost per pound of testing under the state's framework. We also estimate the cost of collecting samples, which depends on the distance between cannabis distributors and laboratories. We find that, if a batch fails mandatory tests, the value of cannabis that must be destroyed accounts for a large share of total testing costs — more than the cost of the tests that laboratories perform. Findings from this article will help readers understand the effects of California's testing regime on the price of legal cannabis in the state — and understand how testing may add value to products that have passed a series of tests that aim to validate their safety.

Optical system to detect volume of medical samples in labeled test tubes

A novel system for liquid-level detection is reported. The system uses two different wavelengths of light to detect the liquid level of medical samples in tubes that are covered by an unknown number of paper labels. By measuring the intensity of the transmitted light at two distinct wavelengths and computing their ratio, which is compared to a threshold value, a system was developed that is self-compensating for the number of tube labels and the type of medical sample to be analyzed. A laboratory prototype was built, and the test results were analyzed using different types of medical samples. Based on a series of experiments, the system was found to detect the liquid level of 0.4 mL with a maximum allowable tolerance of ±0.1 mL with better than 99.73% reliability and a total test time of 0.5 s. These results were achieved with test tubes that had up to six layers of labels attached to the outside of the tube, thereby making the tube completely opaque.

Computer simulation of beam crystallization under non-ideal fields and perturbations in a storage ring

In this paper, we have studied the ion beam crystallization in a storage ring, by taking into account a non-ideal field and perturbations, with the help of computer simulations. The results show that crystalline structures can still be obtained with realistic tolerances, though a longer crystallization time seems to be required. Due to close orbit distortions, the crystalline structures obtained are shifted away from the reference orbit. The maximum allowable tolerances for crystalization are also estimated.

Inverse Error Analysis for Multi-axis Machines

This paper discusses the problem of tolerance distribution among the links and joints of a multi-axis machine. By defining the maximum allowable tolerances for the position and orientation of the tool in the machine’s workspace, the allowable error tolerance limits of the link parameters and of the error motions of the joints are obtained. The solution of this problem, to be referred to as inverse error analysis, is of fundamental importance during the design stages of a new machine.

Dispersion limited production tolerances of single-mode fibers

Based on profile-independent expressions, optimum values of the dispersion slope at the zero-dispersion wavelength for single-mode fibers are given, as a function of production tolerances. This optimum value minimizes the spread in dispersion or maximizes the usable wavelength interval of the fiber. Maximum allowable tolerances for dispersion-flattened fibers are found.