Automatic injection moulding

The Automatic processes are those such as pultrusion, filament winding, centrifugal casting and injection moulding. 

The application of instrumentation to the automatic control of a sequence of operations, e.g., injection moulding processes. Once the mould has been loaded with inserts (assuming a rubber to metal bonded part) into the press, the operation of a push-button starts the controller which closes the press, injects the rubber, controls the cure cycle, recharges the injection unit, opens the press, operates the ejectors and presents the mould for cleaning and loading of inserts. 

The form of or act of laying strip material taken off a mill or extruder into a basket in an oscillating manner. Such material is then suitable for subsequent automatic feeding of production equipment such as injection moulding machines. Wild Rubber... 

It should be emphasized that in the case of thermoplastics, injection moulding will be referred to as low-pressure moulding for pressures not exceeding 5 MPa. This limitation provides a possibility to distinct confine the scope of our review and disregarding the processing by conventional automatic moulding machines. 

Developments in micro-processing have made it much easier to monitor and to control conditions in the course of manufacture, and to prepare and maintain written records. Injection moulding may be supervised with the help of melt thermocouples fitted in the nozzle, pressure transducers in the hydraulic line and in the mould, and a transducer to monitor linear movement of the screw. Information from these sensors may be displayed and depicted in relation to the control limits (upper and lower) and the operator thus made aware immediately of variations that could be significant. Conditions can be corrected more rapidly and if need be any mouldings that might not be satisfactory diverted for examination. Should the number of suspect products exceed a limit set in advance, a line can be shut down automatically. 

Compounds are short (/w 0.3 mm) or long (> 0.6 mm) fibre reinforced thermoplastic or thermoset polymeric materials, which are processed automatically (injection or compression moulding), have good (mechanical) properties (for automotive, electric and electronic applications) and are relatively cheap. Composites contain continuous fibres (rovings, fabrics or mats), usually combined with thermosets, have excellent mechanical (structural) properties, but are very expensive because lack of an industrial process (mainly used in aerospace and aircraft industry). 

Securing tabs of the TV surround, when compact injection moulded in HIPS, are normally made 2 mm thick for stapling purposes, so this thickness was retained for the present SM model since the tabs will automatically be produced in solid plastic. 

Pigmented pellets from a twin-screw extrusion compounding line are diverted to an adjacent injection moulding machine to prepare test plaques. These are transported automatically by robot to a spectral photometer, where colour intensity is measured and, if necessary, to maintain consistent quality, subsequent automatic adjustments are made to the rate of colourant addition at the compounder. The whole system is centrally computer controlled. 

Automatic and waste-free operation of HR moulds enables production to be continuous, even during holidays. In this respect the set comprising injection moulding machine, mould with HR and peripheral equipment may become a Flexible Work Centre (FWC). 

All injection moulding machines capable of operating in an automatic cycle are suitable... 

Note. Full thermal balance and correct functioning of the HR system may only be achieved through automatic operation of mould and injection moulding machine, thermostatic control of the mould and the use of plastic material with no mechanical impurities. 

The thermal equilibrium of any HR system is governed by variable and fixed values of all components of the thermal balance of the mould/injection moulding machine/ambient conditions system. The fact that variable factors are always present means that automatic temperature control and regulation of the HR system must be used to keep deviations from the required temperature to a minimum. The following initial conditions must be fulfilled ... 

Since most injection moulding machines can be run automatically, the process is suited to the making of large quantities of similar shapings at low cost. Complex mouldings may need retractable mould parts. 

Most injection moulding machines currently available can be operated either manually, semi-automatically or automatically. The source of power is invariably electricity, but drives are based on mechanical, hydraulic or even compressed air modes of operation. 

Injection moulding is an economical method of processing ceramics. The material is plasticised by a screw. Dosage and plasticising take place simultaneously, while the previously moulded part still cools inside the mould. With automatic removal devices the entire process can run automatically. 

The Semi-Automatic processes include processes such as cold pressing, hot pressing, compression moulding of SMC and DMC, resin injection. 

In commercial use are a wide variety of machines which transfer fixed volumes of compound to clamped moulds, by the operation of a ram in a cylinder fed with pre-heated slugs. These machines are capable of high speed semi-automatic cycling and are a great advance over the use of loose transfer moulds in conventional presses. The components which are produced are to a large degree flash-free, it only being necessary, in the majority of cases, to remove the injection feed and runner system. 

A further condition for proper operation of an HR system is reproducibility of injection parameters, attainable in principle only with an automatic mould operating cycle. To achieve the desired profitability of prodnction, it is essential to employ skilled technical staff, since proper handling has a very considerable impact on the functioning of an HR mould. A lack of skill may be the weakest link in the production process. 

One condition of proper functioning of an HR system is the automatic operation of mould and injection machine, as far as possible without between-shifts or maintenance stoppages. 

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