Plastic Molding Ultimate Guide

Plastic Molding is a group of techniques used to form raw plastic materials to plastic parts using plastic molding machine and plastic moulds. Today, they are used for a wide range of applications.

Plastic products are widely used in today’s world. Plastic products such as household plastic components, plastic parts of the vehicle, plastic toys are our daily necessities. Thus, the plastic design came across the world to make our daily life easier. Therefore, Plastic manufacturers brought up with different plastic manufacturing processes. Plastic manufacturers invented how manufacturing companies can make plastic products with a profitable cost and ease of access. Plastic molding is rapidly used by most of the Plastics manufacturing companies. Mold (US Spelling) or mould (UK spelling) is the process of reshaping the plastic or metal from the melted stage to a final object by cooling process inside the moulding tools. Plastic molding is one of the easiest and profitable processes in the plastic market. In this article, we will discuss different mold-making processes and their pros and cons, mold maker machines, and plastic molding manufacturers across the world. Besides, we will explain the plastic mold techniques, CNC processes, and their categories. The following are some of the widely used plastic molding processes by different plastic molding companies.

Type 1: Injection Plastic Molding

what is injection moulding

Injection plastic molding is a molding process where the melted hot plastics are injected into an injection moulding tool to make different shapes and sizes by cooling inside. Injection plastic molding is used to produce solid shapes such as bottle caps, toys, musical instrument parts, combs, containers, plastic gears, plastic chairs, mini tables, etc.

The structure of an injection plastic molding machine is normally divided into two parts:

  1. Injection Unit: The injection molding Unit is structured with a motor and gear which generally provide the rotational speed of the screw ram in the barrel. The feed hopper is used to contain the plastics and make ready to go inside the barrel. There’s a heater connected to the barrel, makes the plastic into melted form. The temperature inside the barrel is generally from 180˚c to 200˚c. Then the screw rotates and lets the melted plastic to go inside the nozzle. So, the main task for the injection unit is to keep the plastic, melt, and pass it to the clamping unit.

2. Clamping Unit: The injection mold plastic will now enter the mold. The mold or mould can be in different shapes. It depends on the product of the factory. By the cooling process, the injected molded plastic will form a solid shape. There’s a movable plate that will let the final object pass away from the machine.

That is how a plastic product is made inside the injection plastic mold machine. There are many different types of injection plastic mold machine. General types include the manually operated and computer-operated mold machine. But in today’s world, most of the moulding companies prefer the Computer operated mold machine because it can produce a masse of production in a day. Ningbo Bole 280EKS plastic injection molding machine, PLASTIC INJECTION MOULDING MACHINE SERVO PLASTER, PSJ-150 Professional Plastic Injection Molding Machine2020, Haitian /CH/ JM /JSW Used Plastic Injection Machine can be the best example of injection molding companies produced machinery.

Advantage:

  1. Ability to produce a huge quantity of plastic product.
  2. Except for the entry cost, this injection plastic molding machine costs comparatively very low.
  3. Low scrap rates.
  4. Repeatable.

Disadvantage:

  1. High tooling cost
  2. Large lead times.
  3. Difficult to make changes.

Type 2: Blow Molding

what is Blow molding

Blow molding is generally used to manufacture hollow plastic products. Blow plastic molding is a process similar to injection moulding but the only difference is blow molding does not make solid shapes from the injected melted plastic, rather it makes hollow tube shape, and then the blower machine blows air inside it to make hollow shaped products. Because of this characteristic, this process is named as blow plastic molding. It is used for manufacturing blow molding products such as bottles, tubes, etc.

In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and injection stretch blow molding.

All of them have similar activities of plastic blow moulding process rather than the structure and nature of their specifications. Normally a blow molding starts from the hooper where the plastic materials are contained. Due to the rotation of the screw ram, the plastic materials will charge inside the barrel. The barrel has 3 heating chambers where the plastics are made in melted form. Now this melted plastic will enter inside the nozzle and this blow molds will make some tube shapes.

Later on, the blower will blow air inside to make them hollow shaped. The cutting tools reshape the size of the bottle. The vacuum checking tool will check if there has any lick inside the bottle if so that will be rejected from the production line. Later the bottle will be ready for the discharge and move out of the factory. Automatic PET Bottle Blow Moulding Machine, MG-S250L extrusion blow molding machine with an accumulator’s head, MG-D Series Extrusion Blow Molding Machine (Double stage) are the significant plastic blow moulding machines from the different blow molding companies.

Advantage:

  1. Large production quantities.
  2. The array of different products.
  3. Automation
  4. Blow moulding machine price is comparatively lower than other machines.  

Disadvantage:

  1. Waste of requirement precision.
  2. Petroleum Usage.
  3. Affects the environment.

Type 3: Compression Molding

what is Compression Molding

Buttons, cups, bowls, switches, handles, etc are the few example of the compression moulding products. Compression molding is one of the fabrication processes. Fabrication means giving the desired shape of plastic from different molding processes. Compression molding can also be used for rubber compression molding. Compression molding involves the molding of molten plastic through the compression process. It is normally used for thermoplastic or thermosetting polymers. The compression molding machine consists of two parts, the Upper compression part, and the Lower compression. The lower part is fixed with the ground where the upper part can be moved upside down by the guide pins. The lower part of the system has a heating and cooling system.

The plastics be contained at the mold cavity in the lower part of the machine. Then the Upper cavity will pressurize the plastics at the mold cavity. The pressure measured from 100-500 kg/cm² and the heating scale measured at 130˚C-180˚C. After the heating and pressure are given the mold will form into a final shape. The cooling system will let the plastic compression molding to make a usable and solid-state product. With the help of the extraction pin, the upper part of the system will go upward and the product is ready to be discharged.

Ever fine compression molding models, Chongqing Qibiao Technology Co., Ltd, Yihui Compression molding machines, Dongguang Tian cheng machinery, Dongguan jieyang machinery are the top compression molding machine factory in the recent market.

Advantage:

  1. Low capital and tooling cost.
  2. Low mold maintenance.
  3. Low residual stress.
  4. Retains mechanical and electrical properties.

Disadvantage:

  1. Not economical making a small quantity of the products.
  2. Sometimes secondary machining (trimming, machining) of product is required after compression molding.
  3. Sometimes odd parting lines are observed.
  4. Limitation on molding depth.

Type 4: Rotomolding / Rotational Moulding

what is rotational moulding

Rotational moulding is also be called roto moulding is a moulding technology for making hollow plastics. Comparing with the other technique rotational moulding process doesn’t need any pressure. With a rotational movement by the rotomolding machine, the plastic powder will fabricate into the hollow plastic. This process can offer any sized or shaped plastic products. There are no limited measurements or sizes for this process. There are many rotational moulding products, as we said using this process any hollow shape can be formed. Among the products, watercraft, automotive, agricultural products, kayaks, waste containers, roadway safety, lighting, toys are industrial products. The rotational molding process is generally divided into 4 parts.

  1. Inserting.
  2. Heating
  3. Cooling
  4. Demolding

The rotational plastic molding is very simple. The raw material plastics are inserted as a powder form into the container. The container then is closed, the machine starts to rotate. While rotating the machine provides 130˚C- 180˚C to melt down the powder. The rotomolded plastic will now reshape into the container size. If we want to add other layers, we can give other raw materials into the container manually. In the same way, the different layers will be shaped inside the container. After the shaping is done, the cooling system works here for making the molten state to solid-state. After that, the product is ready to demolding. Wenling Rising sun roto-molding company Ltd, Shanghai yunyan Prototype and mould manufacture factory, Shandong jinxiu shanhe environmental Engineering company Ltd. are the noteworthy rotational molding machine companies in the recent markets.

Advantage:

  1. Low-cost tooling
  2. Consistent wall thickness
  3. Double-wall construction
  4. High Durability
  5. High stability
  6. High Strength
  7. Appearance

Disadvantage:

  1. High cycle times
  2. Limited material options
  3. The high cost of raw materials
  4. Low repeatability

High labor costs.

Type 5: Extrusion Molding

what is Extrusion Molding

The plastic extrusion molding process can also be called as plastification extruding. We have seen the electric wire on the wall in our room, we have seen the charger, electric cables, etc. These are the plastic extrusion products by this plastic extrusion technology. Extrusion molding is used for the thermoplastic polymers. It is used for manufacturing long articles. Extrusion molding is partially the same as the injection and blows molding machines except for the later parts of them. The melted plastic surrounds the metallic wire to provide resistance from the electricity. The plastic extrusion machine consists of a hooping container for inserting the plastic powders. The screw conveyor rotates the plastic powders move inside the barrel. The temperature is set as usual as the other molding machine. The heater keeps heating the plastic till the wire is successfully inserted into the plastic by the plastic extruder. Micro machinery manufacturers, Extrmac Engineers, Extrusion blow molding machine are some significant plastic extrusion companies in today’s market. There are a few types of extrusion molding machines such as PVC extrusion, pipe extrusion, polymer extrusion, polycarbonate extrusion, etc.

Advantages:

  1. The most efficient and rapid method for producing long articles.
  2. Low cost relative to other molding processes.
  3. Flexibility in manufacturing products.
  4. Plastic remains hot when it leaves the extruder, which allows for post-extrusion manipulation.

Disadvantages:

  1. It is used only for the linear polymers.
  2. When hot plastic exits the extruder, it frequently expands.
  3. The nature of the extrusion molding process places limits on the kinds of products it can manufacture.  

Type 5: Thermoforming

what is Thermoforming

Thermoforming plastic is a process where the molten plastics are formed into a pliable sheet to form a different shape by the vacuum molding process. Thermoforming is not similar to the injection, blow, or rotational moulding processes. The thermoforming products are container lids, blisters, trays, products for food, medicine and retail industries, disposable cups, etc.

The thermoforming process has normally two types, one is male form and another is the female vacuum form. When the thermoforming plastic sheets come across, the male shaping mold tool moves upward to make shapes where the female vacuum machine manufactures with the vacuum forming process. After that, with the trimming process, the plastic shapes separate from the production line. The male mold is a simple and solid structure, on the other side female mold consists of a plug, clamps, mold cavity. When the preheated thermoforming plastic mol sheets come inside the female mold, the plug comes down due to the attraction of the vacuum force. This is also known as vacuum forming plastics. It makes the plastic the same as the female mold structure. The thick thermoforming plastic preheated sheets are normally 3 mm in size, and the thin sheets are normally 1.5 mm in size. Ruian City Litai Machinery Company Ltd., Nanjing Biy science technology company Ltd, Taixing Automu automation equipment company Ltd. Ruian ming yuan machinery company Ltd, etc are the thermoforming machine companies from the molding manufacturers in the market.

Advantages:

  1. Allows large sizes from plastic sheets.
  2. The tool requires a low cost.
  3. Easy and simple.
  4. Superior quality products

Disadvantages:

  1.  Frequently feeding the machine.
  2. Break at a certain temperature.
  3. It needs more plastic than other processes.

Plastic molding or moulding process has several kinds because of the different nature of the product we use every day. The product designers made easy for the moulding industries to manufacture the different products easily, fast, and hugely in quantity. Injection molding, blow molding, rotational molding, extrusion molding, compression molding, thermoforming are the notable processes that are widely used in today’s factories. Besides this, there are other moulding processes such as gas assist molding, structure foam molding, etc. There are lots of industries that are producing these machines. In this article, we described the basic knowledge about these molding or molding processes. Later, we will review different molding machines based on customer reviews, specifications, and prices. We will always be with you with complete knowledge and will provide the best suggestions.   

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