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Moldmaking in Russia: modern problems  #3 (25), 2005

 
Vladimir Braginsky,
Cand. Tech. Sc., senior lecturer
 

Moldmaking in Russia: modern problems Any technological process requires for its realization corresponding technological equipment (machines, installations, lines) and molding instrument functionally connected with it. It is molding instrument that successively carries out all the stages of molding a product, all the phases of processed material transformations (or mold alteration of an intermediate product), which results into a manufacture of wares of demanded quality. That is why molding instrument is essentially the main working part of a technological system - it is a place of birth of a product, a place where all its functional parameters and properties are formed.

Basic technological differences of various types of molding equipment for plastic wares production are connected with two factors: modular condition of the material processed and geometric shape of the product (volumetric piece-production or continuous, strip-molded), see table 1.
Table 1
Types of molding instrument Modular state of the material processed Material transformation process by molding
Instrument of discrete operation, closed molding zone, volumetric, piece wares
Mold Viscous-fluid (melt) Hardening of thermosetting
Casting mold Viscous-fluid (melt) Hardening of thermosetting
Injection mold Viscous-fluid (melt) Consolidation of thermoplastic,
hardening of thermosetting
Rotation mold Viscous-fluid (melt) Consolidation of thermoplastic
Thermoforming molds
(vacuum-, pneumo-, mechanical
pneumoforming molds)
High-elasticity
(blank - sheet, film)
Consolidation of thermoplastic
Tableting-mold Solid (powder, fiber material) Densification of material to solid state
Instrument of continuous operation, opened molding zone, continuous, strip-molded wares
Extruder head Viscous-fluid (melt) Cooling to high-elasticity state of thermoplastic
Calibration head (assembly, installation) High-elasticity Consolidation of thermoplastic
Molding transport Solid Orientation, crystallization
* The term "mold" showing no technological content of an object is used now without reason for practically all types of molding instrument with closed molding zone; it is used in normative and technical literature, in standards; in foreign literature it is used only in its direct meaning, as in this table.
The information given does not reveal the whole variety of peculiarities of molding instrument and technologies for plastic wares production, but it lets us imagine the real importance of molding instrument production and operation, which means:

- enormous nomenclature of plastic wares (ever being renewed, duplicated and repaired), and therefore, of molds necessary for plastics processing industry;
- great, constantly growing need for metal, especially for high-alloy high-quality steels and alloys, metal-working equipment and cutting tools, for electric power and so on;
- certain shortage of professionally trained staff at industrial enterprises, in spite of hundred thousands of workers occupied with elaboration and production of molding instrument.
Molding instrument, being a part of technological system, is connected with all other parts of it. With a rare exception, processing machines (injection molding and thermosetting machines, presses, extruders and other) are multi-purpose, meant for production not a single but quite a wide range of size types of products of similar and various kinds. That is why molding instrument is worked out and manufactured for production of a certain product. It is a separate independent object but its tactical and technical as well as functional features should be always coordinated with corresponding documented parameters of equipment. In the first and so far the only officially approved text-book for institutions of higher education [1] you can find principles of such coordination. As a rule, molding instrument should be projected for a strictly certain model of equipment; on the contrary, it is always difficult to find equipment for ready-made molding instrument, often it turns out to be impossible.
Anyway it is necessary to provide best application of functional features of certain equipment with the help of molding instrument (for production of a necessary product out of the material selected, providing that all the requirements to the product are fulfilled). It is necessary to provide short- (for discrete processes - from cycle to cycle) and long-term (for the period of carrying out the whole program) operating reliability of molding instrument. It is also essential to provide most available capacity of molding instrument, which is especially urgent for the most wide-spread processes - pressing and injection molding carried out on technological machines of periodical, discrete operation with the so called non-dense and extremely non-dense operating cyclograms. On the whole capacity is determined by the length of one molding cycle, which depends in its turn on duration of the material transformation process in a closed mold (see the table). Therefore, speed of the processes mentioned would be directly influenced by constructive and technological peculiarities of functional systems of molding instrument (heating - for thermosetting machines, cooling for injection molding machines) and other factors.We should point out one characteristic tendency of modern moldmaking that established itself due to the necessity of production of complicated large-scale plastic wares of crucial purpose (such as spare parts for cars, aircrafts and other). This tendency includes compulsory conducting of complex project calculations on new constructions and at the same time prototyping of wares and molding parts of instrument. Thanks to such engineering preparations it becomes clear why many world-known producers of molding instrument are so convinced that nowadays there is an opportunity to lift any restrictions on complexity of plastic wares construction by production of a necessary mold.
Complex project calculation should include solution of the following problems: thermostating which means ensuring the same temperature areas in molding instrument and economical power consumption; hydrodynamics (efficient filling of a closed mold cavity - for instrument of discrete operation; melt flow speed factors consideration in order to provide maximum capacity or necessary degree of material orientation - for instrument of continuous operation); durability, which means providing rational material capacity of the construction, taking into account dangerous tension in the most loaded parts; mutual substitution and accuracy, that is well-grounded choice of conjugate parts positions and size acceptance criteria; reliability and longevity; safety of operation; patent expertise and cleanness [2-6].
In elaboration of the majority of molding instrument it can be enough to make verifying calculations and to estimate the correctness of the solutions chosen. It is necessary to do also when standardized assemblies parts and elements are widely used in a construction. Such projecting and "production - assembling" is also a characteristic modern tendency. In Russia "first steps" are being made in this direction (actually there are no storehouses and so on), but it is a promising direction, thanks to which it is possible to reduce sufficiently labor consumption of work of design, to raise speed of production process and to improve quality of molding instrument.
In the late decade the role of prototyping technologies has changed significantly - both in analysis of plastic wares (of "informational basis" for elaboration of molding instrument) and in preparation of instrument production. Prototyping used to be a subsidiary technological method, device, now it has become an obligatory stage of preparation for production (just like application of computers and software technologies became obligatory in engineering work at its time). Unfortunately, in Russia there is no wide and various applications of opportunities offered by prototyping: it reduces production cycle of complicated molding instrument manufacture by 30-40%.
It is common knowledge that a plastic ware, a product is a result of efforts of chemists, technologists, designers, machinists, instrument production specialists, quality control experts, and at the same time it is a product expected by consumers. That is why molding instrument and everything connected with its manufacture in general - information about the state and scale of production and its level of equipping - constantly arouses attention and interest of various specialists, businessmen, as well as investors who feel relatively favorable market situation in the industry, in plastics processing enterprises. We should mention however the following: nowadays molding instrument market in Russia is not developed; investments into development and/or into establishing of instrument production are insufficient, and state capital investments could not be expected; the levels of operating instrument production (machine depot, technologies of preparations for production, main and auxiliary processing operations, methods and means of control) differ considerably (as a comparison - specialized orders-oriented manufactures, such as automotive industry, and instrument production of relatively small capacity with "little" equipped material basis that arouse everywhere and fulfill various orders); methods and practice of price-making in molding instrument production are not perfect; mechanisms of cooperative ties are rather loose and are little used; corporative interests, especially in conditions of competitive market economy, require specific registration and protection; problems of staff enlargement and its training, as it was mentioned above, are nearly the most urgent in instrument production for almost every enterprise:
General state of things should impel to active action, especially in comparison to achievements annually presented at specialized international exhibitions, and first of all - at Euromold Exhibition. It has been conducted since 1994, but only since 1997 this exhibition has been attended by Russian specialists, then by the whole groups. In recent years up to 1000 people have visited it, and only two companies were exponents of the exhibition in 2000 and 2001. Russian businessmen and companies" directors do not feel the necessity to introduce their products, technological opportunities and services to the world community. But exhibition should be used as a unique source of knowledge and experience; there is no other way nowadays as to take some known path developing their own companies and industry. It seems to be of a great importance to combine efforts of specialists, businessmen and investors to put into life such offers, for instant, as creating on cooperative basis: an internet-portal - storage of standardized spare parts, functional assemblies and blocks; a library of standards; news site; bank of maintenance (services); centers of collective use for computerized analysis of molding instrument, prototyping, unique technologies for parts processing; specialized schools for designers, technologists, organizers of production and so on.
Articles selection for the topic of the issue, which is now offered to the readers, relates to "particular" side of the problem; it seems expedient to have such materials published in other issues as well. The topic "Molds: tendencies" may be enlarged to "Molding instrument: market problems", for example. There are constant technical and scientific seminars under this name in St.-Petersburg.
In the sphere under consideration any actions should conduct to high-quality, efficient and certainly accurate - by the time agreed - production of molding instrument, its reliable operation with stable reproduction of the products quality.

 

Bibliography

1. Басов Н.И., Брагинский В. А., Казанков Ю.В. Расчет и конструирование формующего инструмента для изготовления изделий из полимерных материалов. - М., "Химия", 1991.
2. Демин Е.Н. Справочник по пресс-формам. - Л., "Лениздат", 1967.
3. Дубов К.Х. и др. Литьевые формы для деталей из термопластов. - М., ЦНИИТЭ, 1978.
4. Видгоф Н.Б. Основы конструирования литьевых форм для термопластов. - М., "Машиностроение", 1979.
5. Дубов К.Х. и др. Технологическая оснастка для переработки термопластов. - М., ЦНИИТЭ, 1983.
6. Пантелеев А.П., Шевцов Ю.М., Горячев И.А. Справочник по проектированию оснастки для переработки пластмасс. - М., "Машиностроение", 1986.

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