Plastic injection unit

What is a plastic injection machine?

The process of producing plastic injectable products based on thermoplastics and thermosets is called injection molding. In this method, after the material enters the hot soldering, the materials are mixed and sent to the mold quetta by a spiral. Inside Quetta, the mold of the mold is cold and firm. The template is designed to fit the design of a piece by an engineer or industrial designer. Injection molds are usually made of steel or aluminum. The steps are very precise. These injection molds are used to produce a great deal of equipment.
How did the world of injectables come from?

In 1868, John Wesley Heath, producer of Phelan and Colander billiard balls, devised a method for making ballistic balls of celluloid injection into a mold. By upgrading cellulose, he prepared it for processing and making the final shape. In 1872, John and his brother unveiled the first injection machine, which was less expensive than modern machines. This device was injected into the mold through a cylinder through a piston. With the slow progress of the industry over the years, other products such as shirt jackets, buttons and pocket shoulders were produced. In the 1940s, due to the massive demand for cheap and massive products during the Second World War, the concept of injection molds became remarkable.
In 1946, James Hendry, with the invention of the first spiral injection machine, changed the plastic industry. The re-designed drill is designed to replace the piston. This drill material was inserted into the cylinder before the injection, and then it was molded into the mold. In this way, before the injection operation, it was possible to combine colored plastic or recycled materials. Today, these mache machines account for 95 percent of the company’s production.

What are the injection molds?
Nowadays, plastics injection molding is the best way to make plastic products. Using injection molds, you can create a huge collection of products, such as household electrical appliances, dishes, bottle caps, internal components of cars and more of the existing plastic products. Having the ability to fabricate multi-chip components and, in fact, simultaneous production of several products over a cycle of work, has made injection molding an ideal choice for producing a high volume of products. High accuracy, repeatability, wide range of consumables, low labor costs, low dispersion and low requirements for finalizing post-molding products are all among the benefits of plastic injection molding. Its disadvantages include the cost of a machine tool and the need for a prototype (since some complicated parts may experience problems such as flaking or leakage during the injection process). Consequently, the design of plastic injection parts should include precision molding tips.

Examples of best polymers for injection molding
Most polymers, including all thermoplastics, some thermosets, as well as a number of elastomers, can be used in injection molding. In fact, there are tens of thousands of different substances for this purpose, and each year their numbers increase. Materials can also be mixed with pre-made alloys or compounds. This feature enables designers to combine materials to the exact specifications of the final product. Consumables are selected depending on the strength and application, and therefore their intrinsic properties should be evaluated to achieve the target. Common polymers like epoxy and phenol are two examples of thermosets and nylon, polyester and polyethylene samples of thermoplastics.
Injection machinery

Plastic injection machines are made up of a feeding hopper, an injection spiral drill and a thermal unit. The plates are locked on the clamping plates, and then the plastic is inserted from the sprocket into the mold and into the injection mold.
Depending on the amount of force applied to the clamping plates, the injection devices are divided into various tanks. This force retains the die during stationary and immersion injection process. The tonnage of the machine can range from 5 to 6,000 tons, and, of course, the high tonnage is relatively less useable. The required clamping force is determined by the image area of ​​the piece. Then, for each square inch of this area, the coefficient between 2 and 8 tons is multiplied and the required clamping force is obtained. As a general rule, 4 or 5 tons per square inch is acceptable for most injectable parts. If the plastic used is very dry, we will need more injection pressure to fill the mold and, consequently, a higher clamping force will also be required to keep the mold. Also, the required clamping force may be determined by the type of material and dimension of the piece: larger plastic parts will require more clamping force.
At present, the presence of all-electric machines in the field is becoming more common in conventional hydraulic injection machines. Corporations prefer these machines to a prevailing hydraulic model for 80 percent energy savings, as well as a repeatability of almost 100 percent thanks to the presence of a servo motor. While the price of an electric injection machine is about 30% higher than the typical hydraulic device, the widespread demand for plastic products is struggling to overcome this financial barrier.

Production process cycle

The production cycle in the plastic injection process is very short and usually takes about 2 seconds to 2 minutes. This process includes the following steps:
Before inserting the material into the mold, first two halves of the mold should be locked together by the clamp unit. Both sides of the die are attached to the machine, but only one of them can be movable. The clamping unit, based on hydraulic force, compresses the two halves of the mold and keeps them under constant pressure during the continuous injection process. The time required to close and squeeze the two halves of the mold varies depending on the device used: large devices (those with higher clamping force) will require more time. This time can be evaluated according to the cycle time of the device.

1 – Injection

Raw plastic materials are usually inserted in the form of plastic pieces and driven by the injection unit towards the mold. During this process, the material is introduced by applying heat and melting pressure and immediately into the injection molding. The accumulation of pressure on the back of the material will result in more compression in the interior of the mold. The amount of material required to complete the mold space is called a shot. Due to the complex and variable flow of materials in the form, it is generally difficult to calculate and estimate the injection time. However, this time can be evaluated by considering the required amount of shot, pressure and injection strength.

2 – Cooling

The molten material in the mold will gradually lose its heat as soon as it contacts the inner surface. At the same time as cooling, the material will take shape and mode of the desired piece. However, during this period, the phenomenon of fragmentation may also be mixed. The accumulation and flow of more material into the mold at the injection stage can reduce the amount of visible shrinkage. The mold will remain locked and immobilized until the end of the cooling period. Also, the cooling time will be estimated by considering the thermodynamic properties of the plastic and the maximum thickness of the piece.

3 – Exit the piece

After a sufficient amount of time, the cooled piece can be removed from the inside of the mold using a probe system embedded in the back of the mold. When the mold returns, a specific mechanism is activated by pressing to expel the piece. The need for these pressures is due to the fact that the piece is absorbed into the core of the mold while cooling down and smaller. To facilitate the ejection of the piece, sometimes before the injection operation, the spray is an auxiliary element to Quietie interior mold. The time required to open the mold, as well as to completely exhaust the piece, can be estimated from the time of the bicycle cycle. After removing the piece, the mold is again locked and prepared for the next shot.