一、电动注塑机的优点：
全电动注塑机具有节能低噪、高重复精度维修方便、可靠性高等优点，符合近年来国际注塑机发展的趋势。其中：
1、精确度高：伺服电机作为动力源，由滚珠丝杠和同步皮带等组成结构简单而效率很高的传动机构。它的重复精度误差是0.01%。
2、节省能源：可将工作循环中的减速阶段释放的能量转换为电能再次利用，从而减低了运行成本，比相应的液压驱动注塑机能量降低50%以上，连接的电力设备仅是液压驱动注塑机所需电力设备的25%。
3、精密注射控制：使制品接近需要注入原料的极限，熔胶螺杆位置由数字精密控制，减少了背压，大大降低了模腔内张力，特别适合光学元件、医疗器具、食品行业等对精度和洁净度要求高的塑料产品。
4、改善环保水平：由于使用能源品种的减少及其优化的性能，污染源减少了，噪音降低了，为工厂的环保工作，提供了更良好的保证。
5、降低噪音：其运行噪音值低于70分贝，大约是液压驱动注塑机噪音值的2/3。
6、节约成本：此机去除了液压油的成本和引起的麻烦，没有硬管或软喉，无须对液压油冷却，大幅度降低了冷却水成本等。
7、生产周期短，例如：在2002年上海国际塑料机械展览会上，日本NISSEI公司展出一台ES200全电动注塑机，其速度快得使人难以致信，一个产品生产周期只须0.63S(秒)，合模时间0.1秒，开模0.13秒，注射0.05秒，加料时间0.25秒，整个周期全自动连续进行，这预示着注塑将向电动，高速方向发展。
NETSTAL 全电动注塑机
二、NETSTAL 全电动注塑机
Development of technology for moulding new types of disc originates in the laboratories of the major materials suppliers and is eve- ntually directed by them to replicators, or to replicators via integrators and mak- ers of injection moulding machines. A set of machine control parameters for the pro- duction of a particular type of disc does not, how- ever, apply universally to all makes and types of ma- chine because there are design differences between models, for example in the location of thermal and pressure sensors and the response times of control systems. It is therefore necessary for machine manufacturers to augment thedevelopment work of materials suppliers to be able to provide users with advice specific to their products.
Machine manufacturers also tend to become involved in specific projects which might result in profitable sales for them but not the consumption of large tonnages of material. Materials manufacturers may understandably be reluctant to participate heavily in such ventures, but the overall picture is that the R&D efforts of materials and machinery manufacturers complement each other for the replicator抯 benefit.
A replicator seeking novel technology for the production of 22 or 100 gigabyte pre-recorded, recordable or rewritable discs, for example, has therefore to seek it from a materials manufacturer or the integrator from whom he obtains his lines. However, the production of future advanced formats will not depend entirely upon the availability of materials with suitably refined properties butalso the development of appropriate moulding techniques. These will necessarily be more complex owing to the highly critical configurations of the discs concerned. It is also desirable that a reasonable processing window be available for replicators working in an indu- strial, as distinct from a laboratory, environme- nt. This is a further incentive for machine ma- nufacturers to undertake R&D in relation to advanced formats. They simply will not be able to sell their machines unless they can also supply the know how that replicators will need.
It is not possible at the present time to describe in any detail what these new techniques might be, if only because the necessary development work is still going on and under wraps to a large extent, but a study of Michigan to assist R&D into DVD and recordable format production.
Moulding trials conducted by Dow in cooperation with UK replicator Plasmon have proved that data densities of 15 to 18 GB per layer can be obtained using Dow PCHE (polycycloexylethylene) material. The discs were metallised, bonded and tested on blue laser players. Nanophotography of a disc with 15 GB density showed features 65 nm deep, 175 nm wide, 0.27 microns wide, 0.27 microns long and 0.4 microns track pitch.
PCHE is stated to have an inherent moisture content of less than 0.01 per cent, conferring good dimensional stability. No drying is required before processing, says Dow. The special characteristics of PCHE material can be employed to identify legitimate disc production, the company adds.
Suppliers of PMMA (acrylic) materials emphasise the claimed better light transmission and lower birefringence of this material compared with PC and its resultant suitability for advanced formats. Both companies claim that birefringence achieved with their acrylic materials is less than 20 nm across the full radius of the disc compared with a range of from 50 to 100 nm in PC.
A transmission rate of 92 per cent with a laser wavelength of 630 nm is claimed both by Atoglas for its Oroglas VOD-100 material and Roehm for its Plexiglas DQ501 and ompared with 89 per cent for DVD grade PC. Better light transmission is not only advantageous in respect of disc performance, particularly with blue lasers, but also UV curing.
Roehm ran two Netstal Discjets on its stand at Replitech Europe 2001 to demonstrate DVD5 moulding in Plexiglas DQ501 material. Rudolf Blass, marketing director, said: "PMMA discs have a harder surface than PC and this is important for the video rental sector as they do not scratch so easily. We have installed ultra clean material production lines and are easily able to supply the DVD market.
"We claim a 15 per cent price advantage for PMMA over PC anywhere in the world. Pre drying is unnecessary in most territories except humid Asian countries." Atoglass has also established a Singulus Spaceline laboratory line equipped with two Netstal Discjet machines and Axxicon moulds in a Class 10000 clean room. Raphael Cherbonneau, Atoglas applications engineer, claimed: "VOD-100 is easy to process and offers potential to reduce cycle times."
三、KM 电动注塑机
The changes in moulding technology brought about by the introduction of the DVD following the CD gives some indication of the problems that the new formats may present.
When production of the thinner substrates for DVD began, typical interactions and sensitivities involved in making CDs were found not to apply. A number of fresh factors became critical. As well as the introduction of injection compression moulding, these included the use of higher melt and mould temperatures and dependency upon the accuracy and repeatability of clamping pressure and timing.
The number of processing factors that affect the physical properties of a DVD were found to be greater than for CD and the interactions between them more critical. If any one factor changed, others altered in a greater magnitude than occured in CD moulding.
GE Plastics Corporate R&D Optical Media Development Center in Massachusetts, USA, used a rigorous methodology to understand the interactions that influence DVD production. The chief lesson learned was that all attributes had a high dependence upon initial clamp tonnage and timing. The next step was to identify the critical interactions of the clamping and filling sequences and determine whether any other parameters could be eliminated or their effects minimised.
It was found from this that initial clamp tonnage, injection timing and the clamp tonnage profile all had considerable effects upon product quality, and a further experiment to define the interaction of clamping with other variables was undertaken. This revealed that control of clamp timing, clamp tonnage and the profile at which clamping pressure was applied during mould fill were highly critical.
Close control of the clamping profile was found to be the key to DVD moulding. Almost all other variables are highly sensitive to small changes in the clamping profile. For example, a change of only 0.05 second in clamp delay time had a significant effect upon peak injection pressure. Accurate control of the clamping speed profile was defined as essential to minimise cycle times while maintaining product quality. Six significant factors were chosen for further investigation - melt temperature, mould temperature, cooling time, first stage clamp tonnage, first stage clamp duration and second stage clamp tonnage.
Results showed that pit replication and HF signals improved as melt temperature, mould temperature and first and second stage clamp tonnages were increased. However, raising these tended to worsen tangential and radial tilt.
GE Plastics researchers concluded that factors that make for good optical properties and electrical performance are ‘at war’ with making good flat discs that bond easily and the replicator must walk a tightrope between the two. The company also established that less variation in birefringence occurs when material viscosity is controlled within close limits during production. The ability to mould flat discs is affected by viscosity variations. Better control of viscosity reduces variations in radial and tangential tilt. GE Plastic’s patented material production process enables the viscosity of the melt to be controlled within a melt flow range of 0.6, compared with a range of 1.4 typical of a process without this control. The technology constantly monitors and adjusts the viscosity of the Lexan material during the stage of its manufacture when it is converted from powder into pellet form. Response to the smallest fluctuation in molecular weight is immediate so that viscosity variations is greatly reduced.
Bayer, maker of Makrolon PC material, states that new advanced disc formats always set fresh requirements. Material specifications become more demanding because of the increasing data storage density. Material has to fulfil different standards but still offer a balanced product profile. The company’s criteria for substrate materials are set out in Table 1. Improving an existing material or developing a new one means taking all these into consideration.
TABLE 1 (SOURCE: BAYER)
STANDARDS TO BE MET BY SUBSTRATE MATERIAL
Optical properties
Transparency
Birefringence
Purity
Mechanical properties
Dimensional stability
Stiffness/toughness
Heat resistance
Processing factors
Flow characteristics
Thermal stability
Pit and groove replication
Release properties
Metal adhesion
Water uptake
Cycle time
Economical factors
Price
Processability
Recycling
Surface quality considerably determines disc quality and, in particular, replication is of great importance for a DVD-RAM structure which has information written and read on pits and wobbled grooves. Bayer initiated a replication program using special stampers with prismatic nanostructures even more finely configured than those for DVD. The replication of these was examined for different materials under various moulding conditions.
These tests showed that replication quality between different materials varied even when viscosity was constant and confirmed the importance of polymer composition. Indents comparable to the size of actual pits were made with an atomic force microscope, and the microhardness of the surface area of a disc was determined by analysing the geometries of a set of indents in relation to the force needed for their indentation. Materials can produce disc surface hardnesses which are different from their hardnesses in bulk form, that is before processing, and material development has to take this into account. The influence of material composition upon surface hardness must be distinguished from that of processing factors, Bayer emphasises. The more information that a disc carries, the smaller the tilt limit becomes and a disc has to be extremely flat and remain so under environmental changes. If the climate changes from dry to wet, the substrate material at the surface of the disc absorbs water and swells, causing tilt. After a time, the water concentration becomes more evenly distributed throughout the substrate and the disc relaxes, but the extent of water uptake and its kinetic function are determined by the polymer structure.
Optical properties are the key factors for future formats, Bayer states. The company employs a special optical test bed which can operate with different lasers including infra red, red, green and blue. In addition, the optical pick up is capable of being set to different numerical apertures and disc thicknesses over a wide range. This makes advanced testing of new formats possible. Copolycarbonates - polycarbonates with a modified chemical structure and having tailor made properties in respect of water absorption and rheological and optical characteristics - are believed by Bayer to be the key to further development. Increase in storage density also means that particular attention will have to be paid to dimensional stability.
The micro hardness of the surface of a moulded disc can differ from that of the bulk raw PC material because of variations in the stability of the polymer during processing. Taking a cross section through the thickness of a disc, birefringence is higher on the outer surfaces than in the middle. This is because the material at the surfaces is subject to greater shear (as it flows over the surfaces of the mould and the stamper) and the anisotropy and orientation of the polymer molecules - which determines birefringence - is different from that occurring in the centre. However, the degree of anisotropy can be reduced by modifying the chemical structure of the PC material, described technically as adding a further aromatic ring linked to the polymer
backbone.
Much of the work undertaken in the Bayer laboratory at Leverkusen, Germany, concerns the interdependence between process parameters. Suitable settings for general parameters such as melt and mould temperatures, clamping force and cooling time normally result in discs that pass quality control for electrical signals, but slight changes to parameters that seem less important, such as screw suckback, nozzle temperature and punch delay, can produce major faults during the injection moulding stage. These parameters have to be fine tuned for every machine/mould set up as they depend greatly upon specific conditions.
Teijin-Kasei claims that its Panlite AD-5503 PC material has capacity for 10 to 27 GB per side. The company is developing materials for the next generation of high density media. Teijin-Bayer Polytec, a joint venture between Teijin Chemicals and Bayer Japan, has introduced ST-3000 PC material which is claimed to reduce birefringence by 50 per cent and water absorption by 25 per cent compared with conventional materials. This grade is also being directed towards new high density discs.
Dow Plastics has installed a CD Associates DVD 1000P with Pulsetec drive DVD tester and a Dr Schenk Prometeus MT-136E instrument at its Optical Media Development Laboratory in
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