Plasticheskie Massy, No. 2, 2006, pp. 3–9

Injection moulding of plastics N. M. Chalaya MIPP-NPO “Plastik” Open Joint Stock Company

Selected from International Polymer Science and Technology, 33, No. 5, 2006, reference PM 06/02/03; transl. serial no. 15623

Translation submitted by P. Curtis On the 7th–8th February 2006, the fifth regularly scheduled “Injection Moulding of Plastics” scientific and practical seminar was held at the M. V. Lomonosov State Academy of Fine Chemical Technology (MITKhT), Moscow. The seminar is traditionally organised and conducted by the editorial board of the journal Plasticheskie Massy together with the “Plastsuper” LLC, the plastics processing department of the MITKhT, and the Interregional Voluntary Organisation of Engineers for the Production, Processing, and Use of Plastics. In the two days, 16 papers were delivered, which can be divided into three topical blocks: • The development and use of composite materials for moulding, examination of the properties of injection mouldings, and questions of the intensification of injection moulding processes. • Modern injection moulding equipment of the leading companies figuring on the Russian market. • The design and manufacture of products and injection moulds. Furthermore, questions of the standardisation of feedstock consumption in the production of injection mouldings from plastics were examined, as well as innovations of the Euromould-2005 exhibition. About fifty specialists from 35 scientific research, industrial, and educational organisations and enterprises of the industry took part in the seminar, from the most varied regions of Russian and countries of the CIS (Moscow and the Moscow region, St Petersburg, Nizhnekamsk, Kazan’, Rostov-on-Don, Kosterevo in the Vladimir region, Ryazan’, Shchekino in the Tula region, Minsk, and so on). In the main, enterprises producing injection-moulded plastic products for the automotive, © 2007 Smithers Rapra Limited

instrument-making, machine-building, packaging, and building industries took part in the seminar. As always, teachers, postgraduates, and students of the MITKhT, the D. I. Mendeleev Russian ChemicoTechnological University (RKhTU), and the K. E. Tsiolkovskii Russian State Technological University (MATI) were present at the seminar, as well as representatives of specialised journals and other publications and marketing organisations. Professor V. V. Abramov spoke about the creation in Russia of the Plastics Processors Association (ROPP). He presented the immediate and future tasks of the Association.

IMMEDIATE TASKS OF THE ROPP 1. To supply member enterprises of the ROPP with specific technical, economic, and legal information in response to inquiries, and, where necessary, to offer consultation services concerning the use of this information in the production, control, or other avenues of activity of an enterprise. 2. The organisation of a single stand for the member enterprises of the ROPP (primarily for small and mediumsized enterprises) at specialised exhibitions conducted in Russia (mainly in Moscow and St Petersburg), which will make it possible to lower considerably the cost of taking part in exhibitions for enterprises. The organisation of the participation of representatives of the Council of the ROPP in organising competent specialised exhibitions and conferences, and the invitation to exhibitors and speakers on interesting questions of the engineering and technology of plastics processing according to preliminary applications T/9

of member enterprises of the ROPP. The offer of organisational and information back-up to those taking part in exhibitions and conferences. 3. The enlisting of member enterprises of the ROPP, and also other organisations, including foreign ones, for work on inquiries of enterprises concerning different lines of scientific research, development, exploratory, and technical and economic work, and also market research. 4. Participation in the creation of innovative specialpurpose programmes for member organisations of the ROPP with respect to different, most in-demand technical problems for plastics processing enterprises. 5. Discussion of base information and explanations connected with Russia joining the WTO, with the aim of preparing plastics processing enterprises for work under these conditions. Organisation of a seminar on the above questions, with the involvement of specialists of the Chamber of Trade and Industry of Russia. 6. Examination of the readiness of plastics processing works for the switch to operation using new technological regulations, the introduction of which is being prepared for the entire industry. Have features of plastics production been taken into account in the 66 newly developed reguations for the chemical industry? Examination of the possibility of preparing a seminar (or conference) on these questions with the invitation of specialists of services for the technical regulation of Russian industry.

FUTURE TASKS OF THE ROPP 1. Development of a programme for saving energy resources at plastics processing enterprises, including the recycling of low-temperature heat sources formed in the run-off of cooling water after cooling of equipment for the production of plastic products. 2. Organisation of a system for protecting the interests of Russian manufacturers of plastic products in the ministries and departments of the Russian Federation (the Federal Agency for Technical Regulation, Standardisation, and Metrology, the Federal Agency for Labour and Employent, the Ministry of Health and Social Development, The Federal Office of Technical and Export Control, the Ministry of Defence, the Federal Customs Office, the Ministry of Economic Development and Trade) in accordance with obtained inquiries from participating enterprises of the ROPP. 3. Examination of proposals and observations on tax checks, unjustified impositions of fines and sanctions on enterprises of the ROPP, and protection of their interests in the Department of Tax and Customs Policy of the Ministry of Finances. Obtainment of the T/10

necessary explanations and recommendations on the current tax legislation. The holding of seminars for accounting and financial services of enterprises, with the involvement as speakers and consultants of specialists of the Ministry of Finances, the Federal Tax Office, and so on. 4. Practical help in protecting the interests of Russian manufacturers of plastic products from inferior lowquality products of foreign companies finding their way on to the Russian market, by the specification of customs codes. 5. The introduction of a common register of specifications, and help in their development and registration. Where necessary, registration in the “Standartinform” Federal State Unitary Enterprise. An as always interesting and extremely topical paper was presented by the manager of the seminar, Professor E. L. Kalinchev, on “Intensification of injection moulding processes”, which in summary form is given in the present review. At present the method of manufacturing products by injection moulding is being rapidly developed both in terms of the volume of production and in terms of creating different modifications of this method for different specialisations of application. The plastics injection moulding process has had a considerable influence on the development of the analogous method of metals die casting. The complexity of the injection moulding method, both in the technological and in the organisational regard, lies in its multifactorial nature. The aim of the paper was, on the basis of the collective experience of specialists and practitioners, and also available information in the scientific literature, to attempt to examine the most important questions associated with raising the effectiveness of the given method for producing plastic products. This is particularly important in the period of preparation for joining the WHO. Increase in throughput has been the most significant problem of the injection moulding of plastics in the past decade. The need to increase the throughput of the main equipment has resulted in the intensification of all stages of injection moulding. In turn, intensification of all stages (mechanisation, automation, control) is largely due to, and at the same time promotes, a reduction in the labour requirement of processing. The possibility of intensification is ensured by improvement in the quality of polymeric materials in terms of processability, improvement in the processing technology, and also improvement in the technological parameters of the processing equipment and the emergence of standard associated equipment. The effectiveness of production is dependent on the infrastructure of production, transportation of feedstock to the injection moulding machines, mechanisation of

International Polymer Science and Technology, Vol. 34, No. 2, 2007

labour-intensive operations, and the composition of the injection moulding equipment. Increase in the overall effectiveness of this sector of production requires its enlargment and its closer organisational interaction between individual enterprises. Analysis of the throughput of the injection moulding machine according to the operating schedule indicates that the schedule can be divided into two parts: machine time and technological time. Machine time is a registration certificate quantity. This time is determined by the speed of the machine. New machines with high speed are effective with efficient processing technology. The technological time is made up of the time of injection of the material into the mould and the cooling time of the material in the mould. An efficient technological regime is developed in such a way that there are no pauses between the individual operations and cycles. Reduction in the power requirement of the injection moulding equipment is achieved by using new machines equipped with accumulators having a hydraulic system with separate drives of the moulding part and the injection part, and also a screw rotation drive. The quality of the products is the main purpose behind raising the throughput and making advances in the intensification and effectiveness of production. Product quality is determined by the combined influence of the product design, the design of the injection mould, the injection moulding schedules, and the regimes for preparing material for injection moulding. So it is that product quality is created at the stage of product and injection mould design, the choice of the type of injection moulding machine, and the development of the production schedules. This is why it is very important that there is collaboration between the designer and the production engineer at the stage of product and mould design. This is the essence of injection moulding technology. The creation of modern moulding compositions based on thermosetting plastics and the evaluation of their properties was spoken about by Professor I. D. Simonov-Emel’yanov. He noted that, in the area of the injection moulding of thermosetting plastics into thinwalled electrical engineering casing parts of complex configuration, an urgent problem was to increase the melt flow of home-produced phenolic plastics. The low melt flow of injection-moulded phenolic plastics of grades O250 and O251, governed by the high melt viscosity and the inadequate time of the viscoplastic state, leads to the impossibility of ensuring the production of highquality products on account of incomplete moulding. Comparative tests of the viscoplastic properties of injection-moulded phenolic plastics of grades O250 and O251 and imported phenolic plastic from Germany © 2007 Smithers Rapra Limited

were conducted by standard procedures on a “Polimer R-1” plastometer at a temperature of 120ºC with a shear rate gradient of 15 s–1. The obtained data showed that home-produced grades are inferior to the imported material in terms of their viscosity coefficient and time of the viscoplastic state. The greatest difference in properties is observed in phenolic plastic of grade O251, which possesses increased tropical resistance, and the use of which for the indicated parts is very important. Analysis of patent materials concerning the compositions and methods for producing injectionmoulded phenolic plastics and subsequent investigations showed that the most effective means of improving the flow of injection-moulded phenolic plastics is to use complex additives containing in their composition a mixture of plasticisers of different compatibility in a quantity of 1–5 wt.%. The introduction of additives made it possible to lower the melt viscosity coefficient of phenolic plastics by a factor of 2–3 and in this case to increase the time of the viscoplastic state by a factor of 1.5–2.2. Investigations at the Lomonosov Institute of Fine Chemical Technology in Moscow into the processing and mechanical properties of new formulations for injection-moulded phenolic plastics, based on industrial home-produced grades O250 and O251 with the use of home-produced modifying additives, made it possible to produce new high-flow materials differing favourably in their combination of properties from known and imported material. In spite of a certain reduction in mechanical properties by comparison with the initial values, all the materials produced meet the TU specifications. To assess the melt flow of injection moulding grades of phenolic plastics directly under conditions of injection moulding, use was made of the procedure for moulding a spiral, which makes it possible to determine the length of the spiral and the value of the limiting shear stress on the wall of the spiral injection moulding machine with cessation of melt flow in the mould at prescribed (constant) values of injection pressure, mould temperature, and melt material. The advantage of this procedure is that it makes it possible to obtain reliable data on the melt flow of injection-moulded thermosetting plastics directly on any injection moulding machine under actual injection moulding conditions with a spiral mould, in contrast to the use of different instruments, where it is not possible fully to model the behaviour of the thermosetting plastic melt during flow in the mould. The comparatively high consumptions of materials for conducting the experiments can be considered to be a shortcoming of the procedure. To investigate the effect of different modifying additives on the melt flow of thermosetting plastic and operational comparison of the properties of different grades and batches of injection-moulded thermosetting plastics, a procedure T/11

has been developed at the MITKhT that uses an IIRT capillary viscometer.

• Automation of Krauss-Maffai linear robots (LRs) with an integrated control system.

D. V. Kobylichenko, on behalf of the authors A. A. Mavrin and B. E. Vostorgov (“Poliplastik-Tekhnopol” Joint Company) presented a paper entitled “The influence of equipment design features and injection moulding schedules on the degree of moulding shrinkage of thermoplastics”. It was pointed out that the magnitude of shrinkage depends on the following factors:

• New technologies. DEKOFORM technology – injection moulding on a film or textile base (moulding and backing within a single production process). SkinForm technology – a new generation of surfaces of parts owing to symbiosis of thermoplastics and polyurethanes. Production technology in an absolutely clean room: “a clean room zone”. Injection moulding compounder (IMC) technology – the symbiosis of injection moulding and compounding in a single unit. Multicomponent moulding, barrier moulding, and in-mould labelling (IML) technology.

• the type of polymeric material, and the type and concentration of filler in the material; • the shape of the article and its geometric dimensions; • the position and size of the sprue channels; • the parameters of moulding; • the technical state of the injection moulding machine. In the paper, an examination was made of the influence of the above factors on the degree of shrinkage. In summary, the following conclusions were drawn: 1. Data obtained in determining shrinkage on standard specimens of different shape and size, recommended in the GOST 18616–80 standard, are not comparable and cannot directly be used in mould design. These data make it possible only to compare the degree of shrinkage of different thermoplastics, and also to predict the nature of change in shrinkage with control of the injection moulding parameters? 2. To obtain initial data for mould design, it is necessary to study the shrinkage on model moulds whose configuration and size approximate the designed product. 3. To obtain more reliable values of the shrinkage produced on a standard specimen, and the possibility of comparing the obtained shrinkage values with data from the catalogues of foreign companies, we developed, and had approved by the Interstate Council on Standardisation, Metrology, and Certification, the Amendment No. 2 to GOST 18616–80. This amendment calls for the use, as the standard specimen, of a 60 × 60 × 2 mm sheet (on which shrinkage measurements are carried out according to ISO 294-4). In amendment No. 2, the parameters of the injection moulding machine, the size of the sprues, and also certain moulding parameters are regulated for the first time. A block of papers – modern injection moulding equipment of the leading companies figuring on the Russian market – was opened by a representative of the Krauss–Maffei company, V. R. Modlinskii. He presented the principal Krauss-Maffei equipment and technologies for injection moulding. In particular, the following were illustrated: • New series of automatic thermoplastics injection moulding machines: CX, MX, EX. T/12

ELEKTRA series injection moulding machines of the company Ferromatik Milacron and peripheral equipment of the company Wittmann were presented by A. A. Chernyshev (“Engineering Company AB Universal” LLL). Ferromatik Milacron was the first to propose machines with a full electric drive on the European market. At present the most ideal development is the Elektra Evolution machine, which has been in production since 2001. In 2003 the company was again the first to propose multicomponent machines with a full electric drive. Since 2004, a new MOSAIC controller sensor screen has been used on the machines, noted for its intuitive userfriendliness. Assimilation of the machine now requires minimum effort on the part of the operator, in spite of the fair amount of complexity of the modern equipment. So why did the company go to such great lengths to develop machines with a full electric drive? Above all, to increase the efficiency of the machines. The electrical energy consumption is halved by comparison with similar modern hydraulic injection moulding machines. Besides net energy costs on operation of the closure and injection assemblies, there are losses associated with the transfer and conversion of energy. The losses on the transfer of energy of electrical machines can be ignored since they are near-zero, while the costs on converting the energy in these machines are lower. In fact, in electrical machines the moment is transferred from the drive (servomotor) directly to the actuator, while in hydraulic systems the number of driving units increases. It must be pointed out that, as the hydraulic system assemblies wear, the losses on transfer and conversion of energy will increase. Reduction in the number of driving units leads to an increase in machine reliability and in the stability of indices. This is also connected with the capacity of liquid to change volume with change in pressure and temperature. Increase in machine reliability leads to a shorter machine maintenance time. Maintenance involves not only repair of the assemblies of the equipment but also the scheduled replacement of oil, filters, gaskets, and other types of work connected with operation of hydraulic systems. There is no need to reuse spent oil. Electrical machines undoubtedly have a number of

International Polymer Science and Technology, Vol. 34, No. 2, 2007

shortcomings, which limit their wide use in the market, but nevertheless the areas of application of machines of the given class in plastics processing are constantly expanding. A reliable partner of the company Ferromatik Milacron is the Austrian company Wittmann – a producer of rotameters for cooling systems in injection moulding equipment. Besides rotameters, the company is currently producing thermostats, material distribution systems and chargers, batch feeders, material drying systems, crushers, and moulding automation complexes. The product range of the company was presented in detail in the paper. Babyplast equipment for the production of small articles from polymeric materials was reported upon by V. A. Kazantsev (“TESIS” LLL). On the market of equipment for the processing of thermoplastic materials, the company “TESIS” offers the smallest, entirely hydraulic Babyplast automatic thermoplastic injection moulding machines (ATIMMs) with a closure force of 6.2 t and an injection volume of 4–15 cm3, designed for the production of small products weighing 0.02–15 g. The guide of the Babyplast equipment is a horizontal and vertical Babyplast 6/10 guide, and also a UAI Babyplast independent injection assembly making it possible to carry out multicomponent injection moulding on an originally single-component injection moulding machine. The use of Babyplast equipment makes it possible to reduce one of the main cost elements of product manufacture – the cost of the mould. A feature of the Babyplast ATIMM is a simplified mould design in which there are no fastening plates. Their role is taken by plates of the injection moulding machine. In comparison with an analogous mould (in terms of the number of points in the moulding) for a “traditional” ATIMM, the mould for the Babyplastic ATIMM is 20–40% cheaper to produce. Babyplast equipment also helps to save money on variable elements of manufacturing cost, which is promoted by low service costs (power requirement 2.9 kW, water consumption ~120 L/h) and economic consumption of material. Babyplast moulds possess a minimum ratio of moulding mass to part mass. The nozzle of the Babyplast 6/10, developed by the company Ewikon, makes it possible for certain parts to abandon the sprue system altogether, injecting the material directly into the part. However, this does not rule out operation with hot-channel moulds on the Babyplast ATIMM. Specially for this, a hot-channel-system (HCS) single-zone temperature regulator is incorporated, while the companies HASCO and Ewikon have developed various hot-channel nozzles for moulds. The Babyplast ATIMM can also be used for the production of multicomponent parts. The independent Babyplast UAI injection assembly, developed on the basis © 2007 Smithers Rapra Limited

of Babyplast 6/10 ATIMM assemblies, is fastened directly on the mould installed in a single-component injection moulding machine and carries out the injection into the mould of an additional component. The Babyplast UAI is completely autonomous equipment which enables it to be used not only with Babyplast 6/10 but also together with the ATIMMs of any other manufacturing companies. Three Babyplast UAIs can be fitted simultaneously on a single mould, both on a mobile and on a stationary plate. For operation of the entire complex, it is necessary only to combine in the automation system of the ATIMM the production cycle of two machines. The vertical Babyplast 6/10V was developed for the convenience of manufacturing articles with riveted elements. The Babyplast 6/10V can be furnished with a turntable to increase throughput. The turntable makes it possible to shorten the production cycle by combining the main technological time (moulding and cooling) and auxiliary time (riveting of fittings). While the part is being moulded in one half, the fitting is being riveted in the other. Babyplast injection moulding machines make it possible to process any thermoplastic materials, including filled materials, occupy less than 1 m2 of production area, create no noise, and are capable of independently monitoring the quantity and quality of the parts being produced. The automatic thermoplastic injection moulding machines of the company Dr Boy and technology for the production of microparts by injection moulding were presented by M. Zaitsev, representing Dr Boy. A. A. Vasil’eva (the “Atlant” Closed Joint Stock Company) presented a report on automatic thermoplastic injection moulding machines produced by the “Atlant” CJSC (Belarus’). She presented: • an equipment complex for plastics processing; • an ATIMM of the BZST series: hydraulic system, control system, features of the BZST-series ATIMM, variants of injection assembly designation, a model line, a modular system, and add-ons. Breakers of the shredding type and cutter type and special breakers were presented in the paper given by Yu. R. Belyaev (“Atlant” CJSC, Belarus’). Below are given the main features of the paper presented by E. Yu. Lobachev (the journal Mezhdunarodnye Novosti Mira Plastmass) on “The Automatic Thermoplastics Injection Moulding Machine Market”. Worldwide there are of the order of 115 000 enterprises that are producing plastic articles by injection moulding. Over 120 engineering companies worldwide are producing automatic thermoplastics injection moulding machines (ATIMM). The world ATIMM market in 2003 was estimated to number 70 600 (according to Demag Plastics Group data). T/13

The largest user of ATIMMs in the world is China, which “eats up” 30 000–37 000 machines per annum. In 2003, China accounted for 37 200 machines, Europe for 10 300, the United States for 4700, other countries of Asia for 17 800, and other countries of the world for 600. In the regional structure of the use of ATIMMs, the proportion belonging to Europe has decreased: 10 500 in 2002, 10 300 in 2003. However, on the Russian market for automatic thermoplastics injection moulding machines, an increase is being observed, taking account of the fact that the market is filled almost entirely with imported equipment. The dynamics of the importation of injection moulding machines into Russia is presented in Figure 1.

Table 1. Importation of automatic thermoplastic injection moulding machines into Russia in 2004* European equipment

303

Demag (Germany)

100

BM Biraghi (Italy)

51

Husky (Canada)†

34

Battenfeld (Germany)

22

Arburg (Germany)

15

Netsal (Switzerland)

13

Engel (Austria)

13

Negri Bossi (Italy)

11

Krauss Maffei (Germany)

12

Sandretto (Italy)

8

Dr Boy (Germany)

4

Plastic Metal (Italy)

2

Ferromatik Milacron (Germany)

2

BMB (Italy)

2

Yelkenciler (Turkey)

1

Babyplast (Italy) Others Asian equipment

Figure 1. Dynamics of growth of ATIMM importation into Russia

The importation of ATIMMs into Russia in 2004 increased by almost 10% by comparison with 2003 and amounted to 1200 machines. The total number of new ATIMMs of European production increased to 303 in 2004, as against 220 in 2003, which amounts to 38%. In 2002, the Asian segment of new equipment in Russia was estimated at 300, and in 2003 it grew by 123, or 41%, and in 2004 the growth amounted to 30%, with an increase by 126 machines. Here, the volume of importation of second-hand and reconditioned equipment fell. Thus, whereas in 2003 this segment of imported equipment accounted for 426 machines, in 2004 it accounted for 329 machines, i.e. a fall of 23% was observed. Competition on the market is increasing on the whole. In 2004, over 70 companies were actively operating on the Russian market (Table 1). In the Asian segment the competition appears to be more dynamic. Thus, in 2004, new Asian equipment was supplied to the Russian market by over 30 ATIMM manufacturers. Finally, a third block of papers was opened by V. A. Braginskii (MOOIP – IP SPE) with a report on “The latest achievements in the production of injection-moulded T/14

1 12 549

LG Cable (South Korea)

87

Cosmos (China)

78

Haitian (China)

43

Dong Shin (South Korea)

41

Po Yuen (China)

34

Chen Hsong (China)

31

Huarong (Taiwan)

22

Taiwan Unio Machinery (Taiwan)

18

Elite (China) + Top Fine (China)

17

Year-Chance (Taiwan)

15

articles and moulds for their manufacture according to the results of the “Euromould-2005” exhibition. In his contribution, the following points were made: 1. This was the 12th International Euromould exhibition. The constant motto of the exhibition has been “from design – via prototype – to series’. 2. The scale and the exhibitors of the 2005 exhibition were convincing proof that in practice an independent sector of industry has taken shape – modern instrument production for the plastics industry, with all the necessary elements and attributes necessary for its future development; guarantee of the production of highly competitive plastic products has been possible only on the basis of advances in this industry which have essentially eliminated limitations in relation to the achievable degree of complexity and in many ways the accuracy of plastic products. One of the

International Polymer Science and Technology, Vol. 34, No. 2, 2007

Huasu (China)

11

Jon Wai (Taiwan)

11

Hwa Chin (Taiwan)

10

TMC (Taiwan)

9

Liguang (China)

9

Steady Stream Business (Taiwan)

8

Chuan Lih Fa (Taiwan)

8

Enaviv (Taiwan)

7

Fu Chun Shin (Taiwan)

6

Jinhwa (South Korea)

3

Nan Rong (Taiwan)

3

Asian Pacific Machinery (Taiwan)

3

Haitai (China)

2

Creator (Taiwan)

2

Maurgan (Taiwan)

2

Hengrun (China)

1

Juda Mechanics (China)

1

Blue Ocean (China)

1

Ekou (China)

1

Lien Yu (Taiwan)

1

Nissei (Japan)

1

Others

63

CIS equipment

19

Termoplastavtomat (Ukraine)

10

Atlant (Belarus)

8

TZLM im. Kirova (Moldova)

1

Second-hand Total

329 1200

* Data based on sources considered reliable, but the author cannot guarantee their absolute accuracy. † ‘Husky’ (Canada) is provisionally grouped with the European segment

intensively developing directions in this sector is the practice of virtual control of production (as a whole, and all stages of its set-up), which was discussed in detail at the forum on “Virtual technologies + modelling”. At another forum – “Materials” – new developments were presented, for example, ceramic screws (for extrusion and injection moulding), ceramic components for rapid prototyping, optical quartz glass for microlithography, steels and aluminium alloys with considerably improved service properties, etc. Seminars and an exhibitions were held on “Hot channels”, “The manufacture of small series”, “Rotary moulds”, “The future of industrial application of rapid prototyping and production”, and “Future technologies lie in nature”. All the papers were oriented towards visiting the corresponding stands. © 2007 Smithers Rapra Limited

3. Problems of producing injection-moulded articles and moulds for their manufacture were dealt with by exhibitors from over 250 companies (105 dealt with moulds, 76 with technology and products, and so on). Several examples will be given. The paper of I. E. Gold’berg was called “The creative component – one of the most important factors for developing modern, competitive equipment”. In it the author presented the results of much experience in design development over the course of many years of work in this area. The speaker pointed out that companies engaged in the manufacture of such equipment have invested great effort in producing injection moulds of high quality that correspond as far as possible to their functional tasks. The injection moulds must ensure the necessary number of articles in the shortest possible time by using the minimum number of units of equipment. To ensure profitability of production, the manufacturing cost of injection-moulded articles must be as low as possible. This occurs in the case of a reduction in equipment manufacturing and injection moulding costs, and with a reduction in the consumption of initial polymeric materials. To achieve these targets, companies do not spare resources in the development of brain centres working in this direction. The unification and normalisation of assemblies and different parts of equipment, including its plates, have been widely developed. This has made it possible to shorten considerably the times of manufacture of injection moulds, their cost has decreased, and the reliability of their operation has increased. However, the range of injection-moulded articles and conditions for their production is so wide and diverse that, for the injection mould design engineer, a broad field of activity opens up. He has to coordinate in one compact assembly the design features of the article, the requirements laid down for it, the financial possibilities and the wishes of the employer, the potentialities of available injection moulding equipment, the technological effectiveness of the article, features of the thermoplastic used, and so on. Where necessary, the design of the article must be optimised to improve its technological effectiveness during moulding. When developing a mould design, to solve the problems set, the designer must use all his or her experience and all known new progressive design solutions from various sources. In individual cases, when he or she understands that the resources available do not ensure the desired results, the designer must try to develop entirely new design variants hitherto unused by anyone. However, only those who, with particular experience, are inclined towards inventive activity should tackle this greatest of problems. These, as shown by experience, are very few. Since the experiment set-up has, as a rule, not been specified by anybody, T/15

and consequently is not financed, the designer should be extremely careful and incorporate fall-backs. If the maximum results are necessary, or when the production of the given product is generally in question, it is necessary to speak with the customer and to draw up appropriately, in the corresponding contract, the need to conduct and finance experimental work and the possibility of obtaining a negative result. Only after this can the designer begin subsequent work. The paper gives examples of mould designs in whose development the author, in the process of his working activity, has used the above recommendations in order to produce moulding equipment with maximum throughput and with a comparatively low cost of manufacture for the conditions available. Furthermore, an examination is made of examples of the production of articles under extreme conditions caused by features of their design, the properties of the initial material, and features of the injection moulding equipment. The importance of skilled mould development by the designer and its manufacturers is emphasised in the paper. “Thermoplay” hot-channel sprue systems for singlecavity moulds were spoken about by V. G. Duvidzon (“Engineering Company AB-Universal” LLL). The effectiveness of using a hot-channel system (HCS) in injection moulds is illustrated in the simplest and most graphic way by calculation of the minimum number of moulding cycles warranting expenditure on an HCS by their comparison with the cost benefit from reducing the consumption of plastic and the cycle time: N c = K : (M + T ) where Nc is the number of cycles warranting expenditure on an HCS, K represents the HCS costs ($), M is the saving of resources through reducing the consumption of material on the sprue ($), and T is the cost of saved time through reduction in the cycle time ($). The easiest to assimilate and the simplest to operate are HCSs for single-cavity injection moulds. The supply of melt to the cavity can be done in several ways: • from the side of the outer visible surface to the centre of the part; • from the inner invisible surface to the centre of the part; • to the side surface of the part; • at several points over the plane of the moulding. The feeding of melt from the outer visible surface to the centre of the part is realised by three main variants: “cosmetic injection”, “technical injection”, and “injection with smoothing”. All examples are illustrated on HCS elements according to the Thermoplay catalogue (Italy). Cosmetic injection. For this, the Thermoplay company proposes D6/1 and F6/1 series sharp-tipped nozzles. T/16

D6/1 series nozzles are simple to assemble and produce: 22, 30, and 44 mm, with lengths of 39–169 mm, of two designs: A – with two heaters for all types of plastic; B – with one heater for the moulding of polyethylene (PE), polypropylene (PP), and polystyrene (PS). To control the heaters of the nozzles, an electrical plug and socket unit is necessary, and a two-zone heat regulator for nozzles of type A and a single-zone heat regulator for nozzles of type B. The Thermoplay E05156 single-zone heat regulator costs 981, and the E05157 two-zone heat regulator costs 1501, including VAT. The prices of the D6/1 nozzles, depending on the diameter, length, and design, varies from 560 to 1610, including VAT. F6/1 series nozzles are produced in diameters of 11, 16, 24, 32, and 46 mm and lengths of 36–356 mm with two heaters. All nozzles, besides the 11 mm diameter nozzles, can be used for all types of plastic, while the 11 mm diameter nozzles can be used only for the moulding of PE, PP, and PS. The operation of the F6/1 series nozzles is controlled by a two-zone heat regulator. The price of the F6/1 nozzles, depending on their diameter and length, varies from 947 to 2387, including VAT. F series nozzles have a replaceable heater, a replaceable thermocouple, and a replaceable tip. The nozzle is chosen from the table in the catalogue according to the weight of the moulding and the type of polymer. Since, for each type and size of nozzle, its inlet diameter is regulated, later the nozzle size is corrected according to the dependence of the injection diameter on moulding weight and melt type. Later, an examination was made of features of the use of series F6/2 straight-flow nozzles and series F6/3 nozzles with a cut-off valve. The paper presented by M. S. Krainov was entitled “Standardisation of the consumption of feedstock in the production of injection-moulded articles from plastics” (MIPP – NPO “Plastik”). The speaker noted that, at present, there are two main procedural documents on the standardisation of the consumption of feedstock in plastics processing, including injection moulding: 1. “Procedural guidelines on the standardisation of the consumption of synthetic resins and plastics during their processing”, developed by the “Plastik” Research and Production Association (NPO “Plastik”) in 1984, first edition in 1991 and second edition in 1991 (referred to below as the “Procedural guidelines”). 2. OST 180550–85 “Standards of plastics consumption”, developed by the Saratov Scientific Research Technological Institute in 1985. On the whole, of all the authorised procedures, the most successful are the “Procedural guidelines” (two editions). However, from the viewpoint of practical problems of

International Polymer Science and Technology, Vol. 34, No. 2, 2007

today, they possess a number of shortcomings, the most important of which are: 1. They specify the standardisation of the direct consumption of primary and secondary feedstock. Meanwhile in practice the need arises to standardise the amount of waste produced, including the waste accumulated for use in the production of other articles. 2. No provision is made for the possibility of taking into account off-grade articles arising in the production of high-tech products. 3. Lack of correspondence of the standardised level of losses in the processing of waste that is incorporated in the standardised consumption coefficients to the actual level of losses that is reached at enterprises. Many specialists in the field are aware of the given shortcomings. As an interesting example of how to overcome them it is possible to cite “A procedure for calculating the consumption of main feedstock” developed at the “INTEKO” CJSC, but in this procedure only the variant of using primary feedstock is examined. With account taken of the demands of practice, a supplement has been developed to the “Procedural guidelines”. In it, two additional initial positions are formulated that do not contradict the positions of the “Procedural guidelines”. If the feedstock losses at any stage of production differ significantly from the standardised values, then the corresponding standardised components are taken out of the standardised consumption coefficient and calculation of the feedstock losses at the given stage is additionally included in the calculation of the consumption standard. If in the production of any article, with adherence to the established technology, the systematic production of off-grade products occurs, then the calculation of feedstock losses is additionally included in the calculation of the consumption standard. In the supplement, for cases both of using primary feedstock and of using recycled waste, formulae are given for calculating the overall feedstock consumption standard and the consumption standards of primary feedstock, secondary feedstock, and superconcentrates of dyes, and also the amount of non-recycled losses and accumulated waste. On the whole, the supplement makes it possible on the one hand to eliminate largely the shortcomings of the “Procedural guidelines” and on the other hand to utilise more fully the scientific and information potential that is built into it. The use of the “Procedural guidelines” on the whole yields satisfactory results in the production of a fairly large set of articles of comparatively low quality, including with the use of injection moulding machines of 10–15 years age. © 2007 Smithers Rapra Limited

However, at individual enterprises, by virtue of certain technical and economic features of specific processes, such as: • narrow specialisation of production • high product quality requirements • a high-tech level of production • a small volume of manufactured batches the objective level of production losses of feedstock can be far removed from that laid down in the “Procedural guidelines”. Similar discrepancies may occur for individual groups of products. In these cases it is possible to propose a procedural approach based on the development of an analytical system of works technical and economic standards of feedstock and materials consumption that should include: • standards of losses for all process stages of production (from feedstock preparation to the treatment of articles and the processing of waste); • standards of losses with the appearance of process interruptions and their elimination; • standards of losses on transition from one type of product to another (from colour to colour, from one item to another); • standards of consumptions for the start-up of equipment after a downtime and for trial start-up after a repair; • standards of consumptions on the testing of products (acceptance, periodic, and certification tests). In the development of a system of standards, they must be differentiated as a function of a number of most significant factors, including: (a) internal factors: type of feedstock, size of injection moulding machine, type of sprue system, and so on; (b) external factors: the weight of the article, the colour of the article, and the volume of the batch of articles. Under conditions of a system of standards of this kind, the definition of a consumption standard for a specific article acquires a calculated-analytical nature: the final consumption standard is defined as the sum of useful consumption and standards of losses corresponding to a combination of values of different factors. In conclusion, an example of calculation of the consumption standards for the “inhaler parts” group of products is given. Participants of the seminar, entering into a discussion held after the papers had been heard, emphasised the topicality of the seminar programme. In conclusion, it can be noted that the scientific and practical seminars on the injection moulding of plastics, like those on extrusion, have become popular and carry authority among representatives of Russian and foreign industry, including small and medium-sized businesses. T/17

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International Polymer Science and Technology, Vol. 34, No. 2, 2007