Interdependence Between Tool Fracture and Wear

Wear and fracture are the main causes of tool scrapping. However fracture plays a major role for increasing values of the hardness and brittleness of tool materials or when low-cobalt tungsten carbides are used or in interrupted cutting conditions where it is the most relevant factor for tool scrapping. In order to obtain the optimal values of the cutting speed both these factors should be considered. The hypothesis of stochastic independence among them simplifies the mathematical formulation of the optimization problem; but experimental investigations do not agree with this assumption and, as a matter of fact, the probability density function of tool fracture results to be dependent on the…

Some observations on metal cutting with reference to the mechanical characteristics of working materials

The hypothesis of the minimum work of Merchant is applied to materials with different yield points in traction and in simple compression on the assumption that these materials yield in accordance with the paraboloid yield-criterion. The experimental data obtained from cutting tests like those described in this paper may apparently be in good agreement with theoretical results. But closer examination reveals that the values of the shear angle φ depend largely on the cutting speed and on the feed p. r. All relationship between φ and (λ — γ) (difference between the friction angle on the rake face and the rake angle) must therefore take in account the influence of the above variables.

A Quality Risk Management Model Approach for Cell Therapy Manufacturing

International regulatory authorities view risk management as an essential production need for the development of innovative, somatic cell-based therapies in regenerative medicine. The available risk management guidelines, however, provide little guidance on specific risk analysis approaches and procedures applicable in clinical cell therapy manufacturing. This raises a number of problems. Cell manufacturing is a poorly automated process, prone to operator-introduced variations, and affected by heterogeneity of the processed organs/tissues and lot-dependent variability of reagent (e.g., collagenase) efficiency. In this study, the principal challenges faced in a cell-based product manufacturi…

On Line Tool Life Prediction for Tool Replacement Strategy in FMS Workstation

In FMS environment a large variety of tools are shared resources being employed to process different part type varying the cutting parameters during their useful life. The paper suggests a new methodology to predict the tool life on line using the information deriving from the control station of the production system to gain information about the tool wear.

A RELIABILITY MODEL FOR OPTIMAL ALLOCATION OF SPARE TOOLS IN FMS

ABSTRACT A model for the dynamic management of the tool set of an FMS workstation is developed. The proposed approach processing the on-line recorded tool failure data updates the estimate of the parameters of the probability density functions of tool life and selects, at the occurence of each failure, the code of the tool to be allocated in the workstation storage devices in order to maximize its reliability over a planned horizon.

Lower and Upper Bounds of Manufacturing Cost in FMS

Abstract The use of traditional techniques of product costing, cost control and performance evaluation in advanced manufacturing environment supplies poor results to operations management. In this paper, after a brief review of the major drawbacks of traditional machining economics, a new framework for product costing will be presented. The basis of the proposed approach lies on an analysis of the production process aimed at single out proper cost drivers for the use of the various employed manufacturing resources. As a consequence, the quota of the manufacturing cost of uncertain allocation is drastically reduced. A lower and an upper bound value of the unit production cost are also define…

Cost Analysis of FMS Throughput

Abstract The need for an effective cost planning and control system is stressed in today highly competitive manufacturing environment. The conventional approaches of machining economics to cost analysis are no more able to cope with the new structure of the production costs in the highly automated - highly integrated manufacturing systems. Suitable cost analysis procedures should provide a strong integration between process planning data and overall system performances. The here proposed procedure for the estimate of the unit manufacturing cost in FMSs achieves this integration by using performance evaluation techniques like discrete event simulation or queueing network models.

Machining Economics in FMS by a Fuzzy Approach

Abstract In a conventional manufacturing system, cutting parameters have to be fixed in order to pursue the economical and productive target related to each cutting operation. In a Flexible Manufacturing System (FMS), as a consequence of the unbalanced workload due to the mutual interaction among the shared resources, the optimization of each operation does not allow the optimum of the global production system to be reached. A fuzzy programming model is developed in this paper in order to select cutting speeds of the operations in the production plan as a satisfying compromise solution between single operation and the integrated system targets.

The Effect of Process Evolution on Capability Study

In today manufacturing scenario the trend to produce with lower and lower tolerance and continuously decrease the defectives rate seems to be irreversible. Then the evaluation of system performances is essential to determine if the process is able to respect our tolerances. With the classical approach this evaluation is realised by considering the process in the in control state and evaluating the capability indices and, consequently, the defectives rate. In this paper the evolution of the process is considered in terms of the mean out-of-control-time, and the real defective rate is evaluated by proposing a new capability index.

Analysis of induced shape defects in FSW aluminum lap-joints for automotive applications

Tool-life modelling as a stochastic process

Abstract In a previous paper [G. Galante, A. Lombardo, A. Passannanti, Proceedings of XXXVII Scientific Meeting of the Italian Statistical Society, 1994, p. 553] the Authors proposed to model cutting tool wear behaviour as a stochastic process with independent Gaussian increments plus drift. Such a model implies that the tool-life, i.e. the time to reach a fixed value of flank wear, has an inverse Gaussian probability distribution. The model has several practical and theoretical advantages. In fact, it is based on an easily and cheaply experimentally verifiable wear behaviour hypothesis, it is more flexible because it is not limited to a particular wear level and, finally, the data are bett…