Zharkevich O.M., Nurzhanova O.A., Karsakova N. Zh.

Karaganda State Technical University

Diagnosis of the cutting tool in a computer-aided manufacturing

 

Reliability of any technical tools, and the more means working in an automated or automatic mode, is one of the basic properties. This property shows the usefulness of these tools in the workplace.

 Reliability is a property of the object to save time within the established values of all the parameters that characterize the ability to perform the required functions in the set terms and conditions for the use, maintenance, repair, storage and transportation [1].

Reliability consists of a properties combination: reliability, durability, maintainability, and persistence.

Operational control is used during the operation of equipment and final control is used usually after manufacturing as well as repair. The ultimate goal is to correct diagnosis, i.e. elimination of the defect or its consequences. The correction means excluding from the process defective item (broken tools, broken machine, robot, etc.) in relation to flexible manufacturing systems (FMS). Also correction means rearranging process in the case of a parametric failure when FMS unit is functional but its characteristics have changed.  For example, in the case of fixed size tool wear should be changed control part program for the changes in size. Parry of defect can be done through the introduction of a structural or information redundancy (pre-entered in the FMS backup, redundant equipment - transport system, tool shops, etc.).

To improve the performance of automated equipment, provision of specified dimensional accuracy of manufactured products with sufficiently low surface roughness processing device provides for the introduction of diagnosing the cutting process.

When you create a flexible, highly automated production systems must use special diagnostic devices that reliable automatic monitoring of the main components and processes in the metal working machine [2]. Special attention is paid to the cutting tool and its functionality as untimely failure detection of tool may have wide-ranging consequences - from the emergence of a marriage before the crash the machine, etc.

In this regard, it is necessary to provide for the control of the current state of the cutting tool with the replacement of the failed backup tool, and when it is necessary the replacement of rejected billet, which provides normative - technical documentation.

Automatic control of the cutting tool and the reservation can:

- improve the reliability of the process of metal (determine the correctness of its course, the machine automatically recover from failures in the tools;

- reduce the consumption of the tool;

- improve the quality of treatment and reduce the marriage;

- protect machinery and machine components against breakage and premature loss of accuracy;

- improve treatment regimens;

- implement a "deserted technology" [3].

All this leads to the necessity to use automated systems diagnostics tool when working machinery automatic production.

This question can be solved at different levels:

- the creation of systems that control only the integrity of the tool before starting the treatment process;

- monitoring tool breakage during processing;

- monitoring tool breakage during handling and periodic or continuous evaluation indicator for the correction of the tool position and predicting the remaining life performance.

Using a diagnostic system of a certain level depends on the requirements for the reliability of the machine, precision machining, economic indicators, etc.

The choice of methods and means of monitoring and diagnosing the cutting tool is closely connected with the study with the most common failures of the causes and possible consequences. It is important to identify such failures that lead to large equipment downtime and high costs.

Working surface of the cutting tool during cutting exposed various voltages, high temperatures, surface-active cutting fluids (coolant), which reduces the efficiency of the tool due to plastic deformation, damage, wear and tear. There is wear. Follows constructive cutting elements of the tool break the constantly increasing wear on both the rear and at the front surface. In this regard, the defect rate is increased and the processing time increases recovery of operational processing system. The main types of breakages as the cutting tool include: wear, chipping, breakage and splitting off.

As practice shows, and experiments, breakage cause a large number of failures in the beginning and middle of the tool. In the initial period of operation of the tool is increased dimensional wear, then a stable period of normal wear and tear, almost proportional to the cutting path.

The majority of metal-cutting tools malfunction during various processing steps are as follows: 10% - splitting off, 12% - a branch of the cutting part, 21% - breakdowns, 22% - chipping and about 35% - wear. Thus the time required for detection and removal of failed cutting tools comprise about 10% of the working time of cutting systems.

Thus, the diagnosis of tool wear is of great importance for improving the reliability of the automated equipment.

References:

1.                     ГОСТ 27.002-83 Надежность в технике. Основные понятия. Термины и определения

2.                     Ямпольский Л.С., Банашак З. Автоматизация проектирования и управления в гибком производстве. – Киев: Тэхника Варшава – Научно техническое издательство, 1989. - 214с.

3.                     Н.П. Меткин, М.С. Лапин, С.А. Клейменов, В.М. Критский. Гибкие производственные системы. – М.: Издательство стандартов, 1989. – 309с.