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.