Technology Guide for molding machine operators
(Reference prepared by the example of casting materials of Bayer AG)

Table of contents

1. Products Overview
2. Getting Started
2.1 Drying
2.2 Cleaning machines; changing the starting material for engineering thermoplastics

3. Selection of machinery and equipment
3.1 Determination of the diameter of the screw, the injection dose and dosing way
3.2 Suitable for use, and the possible ways of dosing
3.3 Determination of effort form circuit
3.4 The geometry of the screw
3.5 nozzles
3.6 Wear protection

4. Terms of recycling
4.1 and a melt temperature of the mold
4.2 Tempering form
4.3 Melt temperature sensor
4.4 injection pressure and holding pressure; injection speed
4.5 Rotational speed of the screw; reaction pressure
4.6 Cooling Time
4.7 Optimization of the set parameters of the machine; production control
4.8 Ratio of flow path length and detail of the wall thickness
4.9 Injection molding vented from the cylinder
5. Recycling regenerate; recycling of waste

6. Defects in injection molding and measures to address them

Injection molding – a process in which the starting material is injected into a special mold, and then linearly solidifies, ie at the cold walls of the mold solidification is faster than in the center.
For plastic injection molding pellets are commonly used thermoplastics, thermoplastic elastomers or termoreaktivov. This kind of products made of plastmassyavlyaetsya one of the most common, which is due. Its simplicity and low cost for mass production.
Injection molding is carried out using special equipment – injection molding machines, which are controlled by electronics and automation. Injection molding of rubber or other material is carried out in termoreativnogo reaktoplastavtomatah.
Injection molding is used mainly for the manufacture of thermoplastics. Carried out under the pressure of 80-140 MPa on injection molding machines of the piston or screw type, having a high degree of mechanization and avtomatizatsii.Litevye machine is dispensing pelletized. material transfer it into a plastic condition, the injection (injection) dose melt into a mold, in the form of an extract pressurized before its hardening or curing and ejection opening shape of the finished product.
During the processing of thermoplastics by injection molding a mold thermostated (the temperature should not exceed the glass transition temperature and crystallization temperature), while processing thermosets heated to curing temperature. Pressure casting material depends on the viscosity of the melt, the mold design, the size of the runner system and molded articles. Casting at high pressures (up to 500 MPa) reduces the residual stresses in the material increases the orientation of crystallizable polymer that promotes hardening of the material and provides a more accurate reproduction of part dimensions.

Fig. 1. Injection molding machine: 1 -materialny cylinder; 2 – heating elements; 3-screw (auger); 4 cooling channels; 5-bin for the material; 6 hydraulic motor; 7-reducer; 8-cylinder injection unit; 9-gauge; 10, 17 fixed plate; 11 – guide column; 12 injection mold; 13 movable plate; 14-wheel-linkage; 15 hydro-cylinder clamping unit; 16 nuts; 18-fence; 19-nozzle.
The pressure in the injection mold while filling the molten resin increases gradually (at the end of holding pressure reaches 30-50% of the molding pressure) and distributed along the length of the cavity is unevenly due to high melt viscosity and its increase with rapid cooling forms. Injection molding of rubber and thermosets takes place, on the contrary, by heating the casting mold.
Injection molding allows to produce parts weighing from a fraction of a gram to several kilograms. When choosing a machine for molding products take into account the volume of melt required for its production, and the clamping force required to hold the mold in the closed position during filling of the mold cavity melt.
To equalize the pressure, and improve the conditions of filling in the form apply injection molding to be preceded. compression of the melt, injection molding, injection molding, with the imposition of mechanical vibrations and others. method.
Injection molding with the preliminary compression is performed at a melt molding machine, which is provided with a nozzle unit crane. When the valve is closed compress the polymer melt in the material cylinder machine to pressure casting. After opening the tap melt under high pressure at high speed fills the mold cavity and is further heated by operating friction. To prevent mechanical degradation of plastics melt flow rate of the runner is sometimes limited. Pre-melt compression allows 1.5-2 times reduce the time of filling forms and increase the melt flow path until its solidification, which allows long-length molded thin-walled parts.