Dumitru Pop

Aspects Regarding some Simulation Models for Logistic Management

Abstract The main purpose of the paper is to develop a neural network application that could predict supplier problems in terms of stock management, lead time and production. Stocks of goods that manufacturers would classify as raw materials stocks are, in a special sense, goods in early stages of the production process. In a logic-based economic competitiveness, the company which holds the largest stock is underperforming! Technically, the stock is inevitable and in some cases even desirable; economically it is associate with an asset value stock, therefore, it should be minimized. Minimizing the value, the costs will also be minimized.

Productivity of DMUs: A Proposed Framework☆

Abstract In any industry enterprises are continually forced to face market changes and, at the same time, to reach a high level of productivity to be efficient. For this purpose, the managers are always in search of tools or methods to assist in improving productivity. However, in order to improve the productivity, we have to take into account a number of key issues. Besides that it is essential to calculate the businesses productivity through various methods and it is necessary to take into account the qualitative factors affecting the productivity level, factors that can not be included in any calculation method. Many literature studies investigates quantitative or qualitative part of a problem. A research which takes into account both aspects is very difficult and requires a high volume of work and information. This research aims to combine the two issues to encompass a broader range of issues that are related to the enterprise productivity. Thus, using our studies so far, we proposed a way to determine the level of productivity for the qualitative and quantitative factors (PQQF). For this purpose we developed a framework to help improve productive performance in terms of productivity. This framework is a guide of best practices and recommendations for large enterprises managers in mechanical engineering. The proposed framework includes a set of steps leading to the identification of five productivity levels of quantitative and qualitative factors (PQQF), which was reached by the DMUs (Decision Making Units). This level of productivity can be compared to the levels attained by direct market competitors. Improving the productivity of machine building industry enterprises can be done following the reverse path proposed by the developed framework. This reverse path helps identify, step by step, the unproductivity sources that exist within the studied firms.

Demolding Moment Calculation for Injected Parts with Internal Trapezoidal Thread

At the final step of the injection process (of a plastic product with cavities) when the part is on the point to be ejected the adhesion phenomena occurs between the core and the plastic part. The mold adhesion effect has a significant influence on the mold design ejection system and over the whole process. This paper presents a computation methodology of the demolding moment for two cases of plastic injected parts with internal trapezoidal thread. Knowing the value of this moment offer us the possibility to adopt the right design solution of the ejector system and of the entire mold. As further work the author will try to validate this method through a set of practical experiments.

Generation of the Storage Costs Function Using Neural Networks

The main purpose of the paper is to develop a neural network application destined to the raw material stock management, as an performant alternative to the classical models of costs stock management. Stocks of goods that manufacturers would classify as raw materials stocks are, in a special sense, goods in early stages of the production process. The testing was made for three companies from the automotive industry, but it could be applied to any kind of Romanian organization.

STUDIES REGARDING THE OPTIMIZATION OF MILLING PROCESS

Abstract An impediment to improve the performance of milling machines are vibrations. In order to avoid chatter, on line monitoring of the milling process is proposed in conjunction with stability diagrams. These diagrams are determined using the semi-discretization method. An optimisation algorithm was developed to increase feed rate and spindle speed while the cutting process remains in the stable area.