In this blog, we would like to share some ideas on the plastic molding. It is onto considered when integrating a new mold in your production plant. It is essential that the operator analyze the project to understand the construction of the acquired equipment. And follow some basic guidelines for connecting the mold systems.

Once the mold is in the machine and all the connections and movements have been checked, we proceed to adjust the homogeneous temperatures. In addition, to obtain a process suitable injection, we must adjust different temperatures: Temp the cylinder, Tª of the mold, and Tª of the melt.

Plastic molding temperature-based division

The plastic molding temperature in the plasticizing cylinder is divided into zones. It is where we must be guided by the indications of the polymer manufacturer. The temperatures of the first and last zone cannot differ more than 30 ° C (5-10 ° C between each of the zones). The injection nozzle must be at the same temperature as the front part of the cylinder.

How to correctly define these temperatures, always within the allowed limits? We must know the product: its geometry, thickness, etc. The temperatures that we configure in the mold will be responsible for the quality of the injected product. The cycle time and the dimensional result of the pieces become accurate.

What is the cooling mechanism of plastic molding?

The plastic molding has a cooling system that allows the melt to solidify and control the temperatures from outside the mold. Controlling the result on the piece in injection process optimization is a significant part of injection molding and has its pre-defined.

If work with temperatures lower mold, will obtain cycles shorter, but this leads to work with more powerful machines’ injectors (higher injection pressure and greater closure force). And consider possible defects in the product (greater fragility of the product, hollow parts, dull product surfaces, etc.)

What to do if the work has hot molding?

If work with a hotter mold, we reduce the required clamping force of the plastic molding. It is improving the visual appearance of the product and filling easier. Sounds perfect?! Well, there are drawbacks: the contraction of the material under these conditions is increased, as well as the cycle time.

In addition, due to the greater adherence of the pieces to the surface of the mold, more visible ejector marks can be observed. Moreover, each operator, depending on the product, must adjust the process temperatures to find a compromise between different aspects of the product and the production process.

What is plastic molding?

Plastic molding is a transformation tool common to shape the raw material introduced under pressure and high temperatures for its interior with the use of specific injection machines, guaranteeing its solidification and cooling until the moment of the possibility of ejection of the final piece.

In this way, the mold receives the raw material in its liquid state from the injection machine. Gives it the previously defined shape (in the form of a negative in the cavity and male/punch), rapidly cools the molded part. And carries out the expulsion of the same. Example_mold_3plates

Types of plastic molding

There are 3 basic types of conventional molds:

1. 2-Plate molds
2. 3-Plate molds
3. Hot Runner molds

The fixation of the plastic molding in the injection machine (in its fixed and mobile plates) is carried out by means of mechanical fixation (screws). The clamping plates/clamping flanges move except for some exceptions. The entire mold has centering elements in its design to guarantee the perfect centering of the two main parts of the mold (cavity/punch or fixed / mobile part).

Precautions for plastic molding

During all operations, thus being able to avoid:

1. Dimensional problems in injected parts
2. Risk of damaging internal components, such as inserts and/or molding surfaces
3. Displacement of the two halves of the mold under high pressures of the injection machine

Examples of plastic molding

Some examples of centering elements for plastic molding are:

 →First, guide columns

→ Second, inclined guides

→ Moreover, interlocks / Side centering devices

→In addition, conical centering devices

→ Additionally, bushings

What is an ejection system?

The set of components that guarantee the ejection of the injected and solidified part is called the expulsion system. This system can be mechanical, hydraulic, or pneumatic, depending on the mold and type of product.

Ejectors of plastic molding

Some types of ejectors for plastic molding:

1. Firstly, Cylindrical head ejectors
2. Secondly, tubular Ejectors
3. Moreover, foil ejectors (common for thin gauge parts)
4. Lastly, ejector plate (which can even be part of the molding surface)

One of the important aspects that must be considered when designing a mold is the cooling system and its circuits. It consists of a set of channels in the mold plates for the passage of a cooling liquid. With a good cooling system correctly designed according to the type of product. It allows us to obtain a stable and sufficiently low temperature of the molding elements to cool the injected plastic and solidify it.

Factors of plastic molding

This factor has a direct impact on the quality of plastic parts (aesthetics and mechanics). To guarantee the same plastic molding results at different times / in different production plants, we must always maintain the 2 parameters: compaction and the temperature of the part when demolding/ejection.

As the last point to be discussed in this blog, we are going to talk about the feeding system of a mold. All the molds are divided into 2 large groups: cold runner and hot chamber. Within each group, there are numerous types of solutions, but we will see them in detail in one of the following blogs.

Conventional solution role in plastic molding

A cold runner or conventional solution is the cheapest that exists in the sector, but it presents several limitations. Which are solved with the hot runner solution? Hot runner injection allows the plasticized raw material to be carried to the molding areas.

The main advantages of this system are the significant reduction of material waste by eliminating the casting, the much shorter injection cycles. The product quality is significantly improved, given the large number of solutions provided by the manufacturers of hot runner systems.

Get in touch with us for plastic molding

We hope that this information on plastic molding will serve to improve your production processes and reinforce your improvements on the road to success. Lastly, welcome to contact us; We will accompany you towards the success of your project.

Injection molding helps in making toys to car body parts, phone cases, water bottles, and containers. Lastly, many of the plastic products we use in our daily lives are molded under pressure. This is a quick process of creating identical plastic parts.

Ability to perform different shapes and sizes, achieved by using injection molding. The boundaries of design are consistently expanding, which allows the use of significant alternatives to traditional materials due to the large variety of products and their lightweight.

What is the function of an automatic injection molding machine?

The automatic injection molding machine produces polymeric products by injection molding and consists of three main components – the loading bunker, the screw, and the cylinder.

The plastic that is placed in the hopper usually has a powder or granular shape. Then the material melts due to the frictional action of the piston auger and the operation of the ring or semi-ring electric heaters.

Molten plastic vs Injection molding

Molten plastic may seem like a fairly simple process, but injection molding is a very complex type of production. While for injection molding in the cavity of the mold, the material is cooled and solidifies to the configuration of the cavity. When the part hardens, the movable half on which the form is established opens.

The dimensions of the injection molding machine can vary from 5 tons of clamping force to more than 6000. The larger the tonnage, the larger the molding machine.

Classification of injection molding

Injection molding machines are classified based on tonnage, or, more precisely, clamping force or pressure. The automatic molding machine is easy to equip with a hot runner system.

The most complex and high-quality products for injection molding are easy to make using hot-runner systems. Let’s talk about the nuances of working with them. The temperature at which the processing of polymers in the gutters affects the quality of the final product.

Thermal component role in injection molding

Also, the thermal component in the molds during molding will affect the temperature of the molten polymer raw material in the cavity of the mold. This subsequently at the time of curing and the appearance of the finished product.

If the temperature regime of injection molding is violated, a plug of hardened material may form in the intake manifold. Which will stop production. It is important to consider the thermal regime. Heat distribution on the pouring channels, the method of temperature control and regulation when choosing the design of GCS parts, and the temperature control system.

Thermoplastics role in injection molding

Thermoplastics are thermally unstable materials, so increasing the thermal values ​​during production, is necessary to reduce the residence time of the melt in such conditions. But here there can be a second problem in the form of a decrease in stability of process and quality of finished goods.

The uneven effect of the temperature of injection molding is on the molten polymer increases the risk of destruction of the material. Especially often such problem arises in the conditions of a long cast cycle which is characteristic of the production of details with thick walls.

Drawbacks of injection molding

Some of the problems of injection molding and temperature control of pouring channels of TEN 24 is the subject matter ahead. Overheating of the molten polymer, which occurs due to too high a temperature effect.

Or increased residence time in the heating zones leads to changes in the characteristics of the polymer product. Overheating may be accompanied by an unpleasant odor, and the product will show dark spots, strokes. For injection molding, you can also see the destruction and inconsistency with the stated size.

Drawbacks for injection holding

Considerable problems can arise when changing the color of polymer raw materials. On the walls of the channels of the spout can form fixed layers of polymer of another color. The polymer is easy to deposit on some types of nozzles.

What affects the temperature of the polymer in the gutters?

The most important source of heat in the processing of polymers is the dissipation of temperature in the melt. This heat arises from two mechanisms: flow shifts and compression of the material. The rate at which heat q is released in the molten polymer mass in shear flow per unit volume is:

   1-q = η ŷ²  

For injection molding, first, η effective viscosity (depending on the shear rate, temperature, and pressure)

   2- ŷ – shear rate.  

The temperature rise ∆T of the polymer mass under adiabatic compression of indeterminate volume with a simultaneous increase in pressure by the value of P is easy to calculate by the following formula:

   3-∆ T = ∆ P / (Cp)

P is the average density of the molten polymer; Cp is the average specific heat of the molten polymer under constant pressure. Dissipation in the polymer comes by shear flow is a major contribution to the overall heat balance during casting.

The greatest amount of heat for injection molding is released during plasticization and injection because the shear rate is very high. The dissipation that comes by compression will differ in different areas of the ACS. Due to changes in the pressure of the polymer mass during the casting cycle, dissipation will change over time.

How does injection molding work?

Through the channels of the spout and in the cavity of the mold, the melt at the loading stage proceeds due to the increase in pressure drops throughout the system. The dissipation that comes by compression at these stages has almost no effect on the temperature of the polymer.

In injection molding because of the pressure in the flow areas close to atmospheric values. Moving away from the flow front, the effect of dissipation increases. The temperature of the polymer in the ACS affects by the temperatures of the material.

An overview of heat balance

The total heat balance includes the heat produced by the heating elements placed in the GCS and the collector. Electric heaters are common for hot-channel casting in modern equipment. Heat losses in the forms of hot-channel casting can occur for various reasons.

• Firstly, thermal conductivity
• Secondly, convection
• Thirdly, heat radiation

 Cooling of the molten mass can occur due to its expansion due to reduced pressure.

List of factors to be considered for plastic injection molding

Following are some important factors to be considered for plastic injection molding:

1. High productivity/efficiency – fast production

There are several basic reasons why injection molding of plastic parts is considered the most acceptable and effective type of injection molding. The process itself is quite fast compared to other methods, and high productivity makes it even more efficient and cost-effective.

The speed of the process of course depends on the complexity and size of the mold, but the interval between each cycle is only about 15-120 seconds. By reducing the duration of the molding process cycles, this method allows the production of more molds in a short period of time, while increasing profits.

2. An integrated approach to the design of plastic parts

The method of plastic injection molding under pressure can be common to produce both complex parts and uniform. This method also allows you to make millions of identical parts. To optimize and increase the efficiency of high-quality injection molding and maximize the accuracy and quality of the parts themselves, it is necessary to consider the basic design elements and design requirements of the part.

3. Design element in injection molding

The design of the part must be as precise as possible to increase the efficiency of the process. The properly designed part allows you to make the element smoothly and with high accuracy. At the same time, without a detailed and calculated drawing of the part.

You may make big and expensive mistakes to the company regarding plastic injection molding. Industry experts unanimously believe that in any part drawing and mold making, there are basic design/drawing elements that must be considered for the injection molding process to take place correctly.

4. Elements of plastic injection molding

These elements include:

1. Wall thickness
2. Design of the sides of the mold
3. The structural round protrusion on the surface of the part
4. Corner transitions
5. Welding lines
6. Placement of entrances
7. Properly placed vents

5. Power in plastic injection molding

The increase in capacity is one of the important factors that must be considered when designing a mold for the manufacture of parts by injection molding. The designer needs to have information on whether the part should be flexible or rigid.

Power in plastic injection molding is to adjust the integrating fasteners/mold plugs or corner fasteners. Understanding the purpose of the part, as well as the environment in which it will be common is also an important nuance.

6. How to maintain balance for mold strength

Finding the balance between the elements of the drawing form will determine the required strength (load, endurance, resistance of the material) and stability (hardness, strength, margin of safety). Another important element is the choice of material.

7. The function of flexibility in injection molding Products

The choice of the appropriate material and color of the product are the two main factors in the manufacture of plastic parts. Given the great variety of both components of plastic injection molding. There are many variations of their combination. Advances in polymers have contributed to the development and invention of new polymers/resins.

8. Polymer selection and working

To ensure the correct choice of polymer, the following elements are important:

• impact strength (resistance)
• tensile strength (tensile load)
• modulus of elasticity/flexibility
• heat absorption and water absorption

Polymers are easy to obtain using a variety of coloring systems, each of which has its own characteristics, advantages, and disadvantages. It is important to use a molding machine that has already been common to produce plastic products from various polymers, especially those that meet FDA, RoHS, and REACH, and NSF standards.

9. How to reduce waste in plastic injection molding?

When choosing a partner for plastic injection molding, you should choose those companies that use green technology in their activities. The latter allows to obtain the highest quality, ensure sustainability, and optimal safety.

During the molding process, there will be excess plastic. When choosing partners, you should focus on those companies that use technologies for processing excess plastic. The most environmentally friendly manufacturers of plastic products use state-of-the-art machines and machines to reduce waste, reduce transportation and packaging costs.

10. Reducing labor costs

In the production of plastic products, labor costs are usually low compared to other ways. Foundry equipment usually works with a stand-alone, automatic tool that allows you to optimize processes and establish uninterrupted production.

In plastic injection molding which it requires minimal control. And the ability to produce parts at a fairly high level with a high volume of production contributes to the economy and efficiency of the process.

11. The Relationship of plastic injection molding with 3d printing

Injection molding and 3D printing are popular manufacturing processes for the manufacture of plastic parts of varying complexity. Although there is a large selection of plastics and thermoplastic materials on the market that are perfect for any part in any process.

There are situations of plastic injection molding where we choose either injection molding or 3D printing. This is what our article is about. To determine which technology to choose for your production, it is necessary to understand the advantages and disadvantages of both methods.

12. Molding of plastic parts under pressure

Injection molding is a rapid process that is based on the injection of molten plastic or other molding material into a prefabricated mold.

List of reasons to choose plastic injection molding

Following are some of the points regarding plastic injection molding based on which you can choose plastic injection molding

1. The Importance of cost in plastic injection molding

After the manufacturing of the mold, the production of the part is simple. The molten material comes into the mold under high pressure.

Injection molding of plastics allows the most efficient use of raw materials, so it leaves virtually no waste.

2. Production quality aspect in plastic injection molding

Every millimeter of the mold fills with material as much as possible to prevent air bubbles or other design defects.

Moreover, it does not require additional actions, e.g., suturing or assembly. The work quality is very high, and the result is durable.

So you can get more than one part in one press. This, in turn, speeds up the production of plastic injection molding. Thus, in a day you can make hundreds of thousands of parts and easily sort your products by batches.