Systems of cоmputer aided design of axial cutting tool
The maintenance
- NTRODUCTION
- Main principles of creation of CAD system of CT
- Conclusion
- References
INTRODUCTION
Deriving of holes with increased requirements on exactitude by means of end measured multitoothed tools is rather difficult technological problem. In practice, as a rule, at projection of master schedules process men use the various help data which is rather averaged and not considering feature of concrete process. At the same time, in these materials there is no data about negative influence of vibrations, the geometrical sizes, modes of manufacture of the cutting tool on exactitude forming of holes though in a number of references that the specified parametres make essential impact on cutting of metals as a master schedule is specified. At the same time calculation of the tool with all specified parametres and selection of optimum parametres is a difficult, labour-consuming problem which are extremely difficult for fabricating manually. Therefore the increasing spreading is received by systems of computer-aided design of the cutting tool (CAD system of CT).
Main principles of creation of CAD system of CT
Last two decade computer-aided design systems get more and more distribution. Such systems allow reducing considerably time of projection and introduction in maintenance the widest spectrum of production: from architectural projects to topology of microcircuits. CAD system systems allow solving the most different problems, and are applied in the most different branches. In particular, in machine industry two aspects of a CAD system are most spreaded: systems of projection of technological processes and system of solid-state simulation. The last allow to spend strength probes of details and the designer assaying of nodes and gears at a design stage and to make reparations directly on an analysis stage
For today several directions in systems of solid-state modeling are developed. The most widespread are lower listed:
- CAD-systems - are intended for direct creation of model.
- CAE-systems - are intended for the automated calculation of a detail.
- CAM-systems - are intended for the automated writing of the operating program for NC machine.
Рicture 1 – types of CAD
Leading firms CAD-makers let out the software products including listed above system, which does their more attractive to the enterprises using CAD-systems at designing.
As a result of crisis of 2008 on the market of the metalcutting equipment a considerable quantity of NC machines has arrived, which become outdated morally, but not developed the resource has arrived. Such situation has promoted increase in number of the small firms, specializing on metal working. Specificity of such enterprises consists in wide listed products at their low seriality. There is a necessity for short terms to develop or choose from offered a configuration of the equipment and a tool design. As consequence, during this period there were some new, specific directions of CAD-systems. One of such directions - CAD the cutting tool.
CAD of the cutting tool can be used in many branches of mechanical engineering. Uniting all requirements to similar CAD it is possible to allocate four primary goals, connected with designing and using of the cutting tool:
- Designing of the normalized tool - the typical problem facing the designer-toolmaker. At its decision the wide range of various state and branch standards is used.
- The Choice of the tool for the set production from available - today this problem receives the increasing urgency owing to increase in a share of small-scale manufacture in mechanical engineering total amount.
- Designing of the special tool - designing of the tool, different in service conditions or in geometrical parameters (the form, the sizes). In a similar case as various recommendations, however process are widely used demands the creative approach to a choice of parameters.
- 4. Working out of essentially new tool – the most difficult challenge demanding the creative approach, a wide experience and knowledge from the designer, and access to applications of modern heuristic methods and the big electronic databases.
Рicture 2 – diagram of output made by а - large, б - small companies
Methodological base for any of the resulted cases is step-by-step designing principle [8]. The principle essence consists that the tool is considered, like set of elements, each of which carries out own function. Each element can have some variants of a design that allows to create the designs most suitable to set working conditions. Besides the method divides designing process into some stages. In the beginning of designing the tool represents a minimum of the geometrical primitive things, connected so that most precisely to repeat the basic form of the tool. At each following stage the model becomes complicated until will take a form of the real tool with all necessary geometrical parameters. Such approach allows unifying all process of modeling.
The second important point in working out of CAD of cutting tool is parameterization of elements of model. Parametrical models can be constructed both in the form of the separate program, and in the form of the separate subroutine (module) or even a set of commands-macros or databases.
It is possible to carry following factors to advantages of the subroutine as a variant of such system of the tool of calculation:
- Possible to use developed enough logic and mathematical devices - allows to carry out difficult enough calculations and to carry out difficult operations.
- Possible of creation of the interface of the subroutine, friendly to the user - allows to simplify development and subroutine use considerably.
However a lack of such variant is that it is necessary to co-ordinate work of the module with work of other program - that is in case of working out of the new design which prototype is not present in base, work seriously becomes complicated necessity of export-import of model or becomes at all impossible.
In favour of a variant of use of macros it is possible to carry following factors:
- Work directly in the CAD-program.
- Possible to create the model, as element of more difficult model.
- Possible to edit the commands of a macro the user.
- Possible to use a "network" principle - a principle of construction of the program at which the program consists not of one general executive file, but from the several specialized. It allows updating directly necessary files-macros, instead of all program as a whole.
- Available of a code of the initial program to an application writing - is not present necessity for "an open" code of the initial CAD-program.
However, analyzing the principles underlying in CAD of the cutting tool, it is possible to note the following: with increase of level of detailed elaboration of model, the labour-input of its creation and the requirements shown to the computer increases. Besides, some geometrical parameters inherent in real object cannot be displayed on its solid-state model. The roughness, radial and face palpation, an error of the sizes, etc for example. Thus such detailed parameters are not always needed to carry out calculations .Considering all listed, there is an actual question on definition of rational level of detailed elaboration of model at which the model will give a comprehensible error of calculations or can form the basis for a constructive choice. The assaying of sources has displayed that the given theme practically is not opened. At the same time accurate criteria for definition of similarity of a model and a real tool are an important component at projection of solid-state model of the cutting tool. For definition of such criteria it is necessary to compare to the real tool a solid-state model at different levels of detailing. As the fundamentals for numerical comparison of such sample pieces can serve strength calculations with finite element method application.
Рicture 3 – example of step-by-step design method
whole drillConclusion
In modern mechanical engineering various CAD-SYSTEMS start to play the increasing role. With their help the period of development of the project from initial sketches to finished articles is lowed to several days or even hours. The important role in this process is played by manufacture preparation, namely: an equipment choice, appointment of cutting modes, definition of sequence of processing of surfaces, a tool choice. Last of listed is many-sided problem, comparable with a choice of a design of the detail. In particular, the tool choice can include various strength calculations, temperature calculation, dynamic calculation and many other things. To make all these calculations manually it would be rather difficult, therefore a wide circulation receive CAD of the cutting tool which allow to carry out all calculations with computer. As base for such calculations the standard techniques finished taking into account their use on the computer for solid-state modeling of the cutting tool can serve.
Important problem for development CAD is development of criteria of similarity of model and the real tool. The program tools allowing numerically to compare levels of detailed elaboration of models are necessary for the decision of this problem and to define the optimum. For creation of such tools following techniques most approach: step-by-step designing, a method of final elements, parametrical construction of solid-state models of the tool. Besides, the resulted techniques and approaches can be used and for creation of working CAD of cutting tool.
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