As with any manufacturing process, there are advantages and disadvantages to using plastic injection moulding to make required products. Advantages include the capability for large-scale production in a relatively short period of time, as well as the possibility of creating one-off prototypes using the same technique.

2. In direct compression type clamping mechanism, mold section oil passage and injection section oil passage are separated.

3. Pressure, flow, temperature, metering can be controlled to precise accuracy. Multi-stage injection can be used to ensure reproducibility of molding process and repeatability of product.

Examples of medical and healthcare products include syringes, vials, petri dishes, diagnostic devices and medication bottles. Also PPE, surgical equipment, implantable devices and stents.

Use of plastic injection moulding products is commonplace in automotive manufacturing. Components are widely used in cars, vans and lorries, as well as other modes of transport such as boats and aeroplanes.

Plastic injection moulded products can be made in a huge array of colours, finishes and polymers. The two main types of plastic materials used are polypropylene homopolymer and polypropylene copolymer. Each has different properties and benefits, including chemical and impact resistance, strength and stress crack resistance, high processability and durability. More information can be found here.

(1) Due to high injection pressure of precision injection molding machines. This requires a high stiffness of clamping system. Parallelism of moving and fixed templates is controlled in the range of 0.08 to 0.10 mm.

Accuracy of displacement sensor is required to be at least 0.1 mm, so that metering stroke, injection stroke and thickness of residual mat (injection monitoring point) can be strictly controlled to ensure accuracy of each injection and improve molding accuracy of product.

For variable pump injection molding machine, since pressure and flow output of oil pump are adjusted by swashplate angle of oil pump, it has high responsiveness and high responsiveness, repeatability of oil pump can reach 0.2% or less.

In order to achieve rated injection rate, there are two ways: one is to increase maximum injection pressure of system; the other is to modify parameters of injection device or injection system, including screw parameters;

Plastics are also useful for heavy-duty packaging to protect construction materials or industrial equipment before it is put into use. Warning and other signage is also often made using plastic injection moulding techniques for maximum impact.

Most of precision injection molding is done under high injection pressure and high rate of injection (connector or mobile phone button). Filling time is very short, generally only a few tenths of a second. This requires system to have high response performance, otherwise response will be delayed, eventually leading to a large deviation between output signal of system and input signal. Molding process is difficult to debug, which will directly affect size or weight stability of workpiece during production.

Uses for plastic injection moulding products across the medical and healthcare sectors is vast. Here, the materials are prized for their hygienic surfaces and ease of cleaning, their versatility and their resistance to bacteria and germs.

High responsiveness of injection molding machine depends on scan time of controller, response time of oil pump and oil valve. For hydraulic systems with servo valves, there are considerable advantages in terms of response and repeatability.

Generally, weight error of ordinary injection molding machines is about 1%, and better machine can reach 0.8%. Below 0.5% is a precision machine, less than 0.3% is an ultra-precision machine. As mentioned above, precision injection molding machines require product dimensional accuracy to be generally within 0.01 to 0.001 mm.

Plastic injection moulding products in the fast-moving textiles industry include tape strapping, plastics ropes and twines, sports clothing shoes and bags, sunglasses, watch straps, tote bags and beach shoes. The plastics offer good colour fastness, waterproofing and resistance to fading from UV rays from the sun or damage from bacteria mould and heavy usage when being worn, carried or used.

Hydraulic system of injection molding machine needs to use proportional pressure valve, proportional flow valve to achieve different working pressure and flow of system. Whether it is fixed pump hydraulic system or variable pump hydraulic system, there are proportional valves to control working pressure and working flow of oil pump output, achieve proportional linear adjustment.

Mold temperature has a considerable influence on later heat shrinkage of part, affects apparent quality and crystallinity of part, and also affects mechanical properties of part. If cooling time is same, thickness of product having a low mold cavity temperature is greater than thickness of product having a higher temperature.

Ideal state of injection molding machine for product control is to directly control size, quality, apparent quality and mechanical properties of product to feedback control feedback signal. However, for the moment, direct measurement and conversion of these non-electrical quantities into electrical signals has not been solved, so it can only be solved by controlling controllable variables of injection molding machine that affect quality of above products, mainly including:

Injection pressure has the most obvious effect on mold shrinkage of product. When injection pressure reaches 392 MPa, mold shrinkage rate of product is almost zero. At this time, accuracy of product is only affected by mold control or environment. Experiment proves that injection pressure is from 98 to 392 MPa, and mechanical strength of workpiece can be increased by 3 to 33%.

When temperature control system is heated, overshoot amount is small, temperature fluctuation is small. Precision injection molding uses PID proportional, integral, and differential temperature control to achieve a temperature accuracy of ±1℃. Temperature control accuracy of ultra-precision injection molding machine is ±0.1℃, and temperature deviation can be stably controlled between ±0.2℃.

At present, injection molding machine generally adopts full computer control, and functions are gradually improved. It has intelligent functions such as “human-machine dialogue”, fault self-diagnosis, molding status monitoring, and SPC quality monitoring. Hydraulic system of injection molding machine is power component of each action of injection molding machine. Controller is hydraulic system control center, and all kinds of instruments are auxiliary monitoring part of running state of machine. Injection molding machine is actually an intelligent combination of machine, electricity, liquid and instrument.

The food and drinks industry uses plastic injection moulded products for packaging such as trays, boxes, shrink wrap, bags and protective layers. They are lightweight, hygienic and can be hermetically sealed to keep the contents contamination-free. The versatility of the end products also make the plastics useful for rigid packaging, point of sale and advertising materials. Other things that can be packaged in this way include tobacco, electrical appliances, toys, clothing and electronic devices.

(3) Pre-plastic displacement of screw, and periodic signal is detected by displacement electronic ruler, thereby extracting speed signal;

1. Requirements for repeatability (reproducibility) of injection molding parameters are high, and multi-stage injection feedback control should be adopted.

Usually precision injection molding machines have two indicators: one is repeated size deviation of product; the other is repeated weight deviation of product. The former is difficult to compare due to size and thickness of product; the latter represents comprehensive level of injection molding machine.

Disadvantages include the fact that some polymers may be more difficult to recycle, making them a less environmentally-friendly option. There can be a higher initial cost setting up the machinery and designing bespoke moulds, plus the lead time can also be affected if the project is complex or intricate. Anything that introduces an undercut or locks the mould must be designed with extreme care.

The construction industry uses plastic injection moulded products for both large and small applications. So, they can be found inside heavy-duty machinery and furniture, as well as in decorative fixtures, fittings and tools.

This requirement is for a direct pressure injection molding machine because direct pressure injection molding machine starts to inject melt and fill mold cavity immediately after high pressure is applied. At the same time, oil must be filled with clamping cylinder to form a high clamping pressure. Otherwise, middle plate will retreat due to filling pressure and mold expansion force, which is not allowed. This requires that mold clamping oil line and injection oil circuit are separated. Otherwise, oil pump overload problem occurs due to oil filling clamping cylinder and injection cylinder at the same time, injection speed and system stability are affected.

Plastic injection moulding products are used all over the world across multiple sectors. This is because they are versatile, hard-wearing and easy to design to highly accurate specifications. The plastic injection moulding process itself is efficient and effective, offering the capacity for large-scale production, as well as bespoke, one-off projects.

Change of oil temperature of injection molding machine leads to fluctuation of injection pressure. It is necessary to use a cooling device for hydraulic oil to stabilize oil temperature at 50 to 55℃.

As already mentioned, plastic injection moulding products can be found all over the world being used by most, if not all industries. Some examples of industries and how they use this type of products include:

(4) Plasticized parts: screw, screw head, check ring, barrel should be designed into a structural form with strong plasticizing ability, good degree of homogenization and high injection efficiency; screw drive torque is large and can be continuously variable.

Taking PC as an example, ordinary machine has a injection pressure of 177 Mpa, which can form a product with a thickness of 0.8 mm, and a precision machine with a injection pressure of 392 MPa can form a product with a thickness of 0.45 mm or more. Ultra high pressure injection molding machines can obtain products with a larger flow length ratio.

(4) Injection system pressure, installed on injection cylinder with a strain sensor, detecting periodic signals, measuring injection pressure, holding pressure and back pressure signal;

There are various methods of plastic processing available, including injection moulding, extrusion and blow moulding. The plastic injection moulding technique involves pouring melted plastics into a rigid mould, which is shaped to form the required part or component. Polymer pellets are fed into a hopper before being melted so that they can fit the mould. The mould is secured and the plastic left to cool and harden. The final product is then released and quality tested.

(1) Temperature of each section of screw melting cylinder, non-periodic signal, generally at least 4 sections of heating;

Multiple parts can also be created to accurate specifications and with precise uniformity. There is a vast choice of colours, designs and finishes available for excellent versatility. Materials used are readily available and offer good durability, strength and resistance to damage from UV rays, chemicals and general wear and tear.

2. Clamping system has sufficient rigidity and clamping precision. So-called clamping precision refers to uniformity, adjustable, stable and repeatable of clamping force, position accuracy of opening and closing mold is high;

4. Hydraulic system of precision injection molding machine should fully embody machine-electric-liquid-integration project.

The electronics sector uses plastic injection moulding products for several different applications This is because the finished products can be designed to highly bespoke specifications, with a huge choice of finishes, textures, shapes and colours. They offer good insulating properties too. Some uses for plastic injection moulding products in the electronics sector include smartphone and tablet components, battery casings, printed circuit boards and charging devices.

(8) Injection speed is at least 4 levels of setting curve and feedback signal detection, displacement variable is converted to speed feedback, and feedback control is performed.

Precision injection molding machines require high injection speeds. Injection speed of precision hydraulic injection molding machines is required to reach 200mm/s or more, and injection speed of all-electric injection molding machines can reach 300mm/above.

As already mentioned, injection molded products have been applied to various fields and are widely used to replace high-precision metal parts, thereby placing strict requirements on dimensional accuracy, quality accuracy, apparent quality and mechanical properties of injection molded parts. At the same time, higher requirements have been placed on process factors affecting quality of injection molded products.

(2) It is required to protect low-pressure mold and control accuracy of clamping force. Because size of clamping force affects degree of mold deformation, it will ultimately affect dimensional tolerance of part.

Ordinary injection molding machine: 147 ~ 177Mpa; precision injection molding machine: 216 ~ 243 Mpa; ultra high pressure injection molding machine: 243MPa or more, usually between 243 ~ 392 MPa.

Precision injection molding machines refer to molding machinery suitable for forming precision plastic products. How to measure or judge a precision injection molding machine?

1. Oil system requires use of proportional pressure valves, proportional flow valves or closed-loop variable pump systems.