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Plastic Mold Packaging

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What is Plastic Mold Packaging?

 

Plastic mold packaging is a process that uses heat and pressure to fill a mold with liquid plastic, which then hardens into a custom shape. This process is called plastic molding, and it's used to create a wide variety of products, including containers, bottles, vehicle parts, and syringes. The most popular types of plastic molding are extrusion, compression, blow, injection, and rotational molding.

 

7 Common Types of Plastic Molding

 

 

Different types of plastic molding suit diverse industry needs, each with unique features and benefits. By understanding the different molding processes and their common uses, you'll be better positioned to choose a type that provides optimal performance for your product.

Here are seven of the most common and effective plastic molding types you'll want to consider.

 

Injection Molding
Injection molding is one of the most versatile and popular molding processes due to its capability to create parts with varying shapes and sizes. The injection molding process involves injecting molten plastic material into a metal mold at high pressure.

Injection molding is commonly used for everything from large plastic car parts to small plastic bottle caps. This type of molding is especially ideal for creating high volumes of precise and high-quality parts at an affordable cost.

 

Blow Molding
Blow molding is the process of making hollow, thin-walled plastic parts. This molding approach is often beneficial when the shape of your product is important and you need uniform wall thickness.

Similar to glass blowing, the blow molding process involves heating plastic and injecting air into the hot plastic until it expands to fill the mold and create the required shape. The mold then cools and hardens, and the machine ejects the part.

 

3D Printing/Additive Manufacturing
The 3D printing process involves having a printer lay sequential layers of a material such as polylactic acid, nylon, or polycarbonate to create a product. One of the main benefits of 3D printing is that it allows engineers to design plastic parts from their desks and make them a reality in hours.

Given 3D printing's flexibility, it's a top choice for manufacturers in rapid prototyping, customization, and low-volume production scenarios. 3D printing also allows manufacturers to customize each item individually without incurring additional expenses, making it a cost-effective option for one-off or small-batch production needs.

 

Extrusion Molding
Extrusion molding forms long, cylindrical plastic objects. This plastic molding process also differs from other molding types in that it uses a die instead of a mold to shape the product. The process involves squeezing hot, raw plastic through a custom-shaped die to get the desired shape. The extrusion machine includes a screw that feeds the plastic resin to the feeder. As it passes through the die, it creates a long, consistent shape, which is often tubular.

Products formed with extrusion molding typically need to be the same shape along the length of the item. For this reason, companies mainly use it to create long and hollow products like straws, hoses, plastic decking, PVC piping, and plastic gutters. Some manufacturers may even create varying continuous shapes like U-sections, L-sections, T-sections, and circular sections.

 

Thermoforming
Thermoforming is a type of molding process that involves heating a plastic sheet of thermoplastic to a pliable forming temperature. A mold will then help the sheet form a particular shape, and a molding expert will trim it as necessary. This method also uses low pressures and can create 3D products from a 3D mold made from aluminum.

Depending on the product, the thermoplastic used in thermoforming will have varying thicknesses, materials, colors, and finishes. Professionals use thin-gauge thermoforming to manufacture containers, trays, lids, disposable cups, and similar products. Thick-gauge thermoforming is suitable for products like refrigerator liners and vehicle beds.

 

Compression Molding
Compression molding involves placing a heated plastic material into a heated mold and pressing it into a particular shape. This heating process, known as curing, allows the plastic to retain its strength. It is then followed by the cooling and trimming of the plastic before removal from the mold.

Compression molding is mainly useful for companies requiring strong, highly durable products. This process is ideal for automotive parts. Other valuable uses include creating sturdy plastic parts for household appliances, body armor, and clothing fasteners.

 

Rotational Molding
Rotational molding, or rotomolding, is ideal for producing larger hollow products or parts. The manufacturing process begins with placing liquid or powder resin into a metal mold and rotating it at high temperatures until the entire mold is coated with the resin. This constant rotation allows the resin to coat the mold evenly and create equal thickness throughout the product walls.

Rotomolding is one of the more economical molding options because you can reuse leftover plastic, reducing waste. You may use rotational molds for bulk containers, kayak hulls, recycling bins, storage tanks, and dog houses, among other products.

 

The Structure of An Plastic Mold Packaging

 

 

Injection molds come in all sorts of structures, from 2-plater to hot runner molds depending on application and design requirements, but most typically consist of these elements::

Mold bases Mold bases offer secure and accurate foundations for molds. The mold rests upon this rigid structure typically constructed out of soft steel such as S50C, P20 or, more expensively, 718, 1.2344 steel.

An important part of a mold is the mold cavity, Mold cavities play an essential part of molding; they determine both shape and size of molded parts. Hardened steel such as 718, 1.2738, NAK 80, 2344 or S136 is commonly used, often precision machined using high speed CNC or mirror EDM for flawlessness and defect-free results.

An injection mold's core determines the internal shape and features of its finished part. A mold cavity, the outer portion that defines its external form, usually features more durable material for external shape creation. As another part of its mold half structure, core inserts may also be attached to something called core half which moves into position when closing up and forms its shape as you close down your mold half. As with all injection mold components, cores play an integral part in molding finished parts based on internal dimensions as well as any external features required by final product manufacturers.

Molten material enters a mold cavity via its sprue and runners. A gating system directs this flow with multiple gates such as side gates, pin point gates, direct gates, submarrine gates and channels; runners act as passageways from sprue to mold cavity via gates.

Molten material enters a mold cavity via its sprue and runners. A gating system directs this flow with multiple gates such as side gates, pin point gates, direct gates, submarrine gates and channels; runners act as passageways from sprue to mold cavity via gates. Plastic melt is injected through gates into an injection mold to start flowing outward, and its size and shape has an immediate impact on its final quality. Mold gates typically reside at the surface of mold cavities to evenly disburse molten plastic before molding begins; several varieties will likely be employed depending on material, size and shape requirements of part being produced.

Cooling systems help material solidify in molded parts while decreasing mold heat production, with cooling time typically accounting for 70 percent of every cycle. Therefore, their presence is absolutely key to effective injection molding processes.
Ejection systems are used to remove cool and solidified parts from mold cavities. Components in an ejection system include ejector pins, ejection bars, air ejectors, plates and more.

For complex movements or shapes in their parts, injection molds might also include slides or lifters in addition to these core components.

 

Selecting the Right In-Mold Labeling Process for Your Packaging
 

In-mold labeling is a process in which manufacturers place a pre-printed polypropylene label in the mold of the packaging during the manufacturing process. Hence, when the mold gives shape to the plastic packaging, it also adds the labeling to the packaging. The mold gives the shape to the end product as well as performs the labeling. After the curing time, the packaging and the labeling becomes a single piece. There are three methods of in-mold label printing processes. These include the injection molding, the blow molding and the thermoforming.

 

Injection Molding
Injection molding is the most common form of molding thermoplastics or thermosetting polymers. During this process, manufacturers inject heated and liquefied plastics or polymers in a mold. The mold generally has a small hole or opening through which the injection takes place. After the injection is done, the mold is allowed to cool where the plastic takes its shape. This is the way a lot of plastic containers a made. Butter or ice-cream tubs are very common examples of products that use injection molding as well as in-mold labeling.

For example, the Amul Lite butter tubs, and a lot of skin cream packaging is made using this process. Smaller plastic paint buckets also use the same manufacturing process. Computer keyboards and cell phone keypads also use this manufacturing technology.
In case of injection method of in-mold label printing, the printed label is first placed into the mold and during the injection process, the printed polypropylene film fuses with the thermoplastic. So, in one step, we get the labelled plastic packaging.

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Injection Moulding Tool Makers

Blow Molding
Blow molding is used for hollow plastic parts. This is a process in which manufactures stretch or extrude a heated plastic mass to take the shape of a mold. Blow molding is a very old process. Glass bottles used this manufacturing process and hence, even today, plastic bottles use the same principles of glass blowing. In blow molding, the extruded plastic is first put into a hollow tube. The hollow tube is captured in the mold and air is blown into the hollow tube so that it captures the shape of the mold. The inner wall of the mold contains the polypropylene sheet that has the labeling printed on it. As the plastic cools down, the labeling infuses into the mold.

Manufacturers use this process to produce liquid containers, such as containers for liquid soaps, shampoos, dishwashing detergents, ketchup, and sauces. Most shampoo bottles on the market use this form of labeling as it is waterproof.

 

Thermoforming
Thermoforming is slightly different than the previous two processes as in this case, the plastic is not completely melted. Manufacturers use heated plastic sheets for the process. They use a forming tool that gives the plastic sheets the form of containers. Here, during the forming process, the preprinted labels accompany the plastic sheets. The heated sheets are stamped onto a mold and during this stage, the printed label and the plastic sheet binds together.

Manufacturers use thermoforming for making plastic cups. Ice cream cups, as well as plastic coffee cups, are made using this process. Also, plastic tubs used for packaging ice cream use this manufacturing process.

 

Understanding Insert Molding vs. Overmolding

 

Injection molding involves injecting molten plastic into a mold, cooling it, and ejecting it. Manufacturers can repeat the process to quickly and cost-efficiently to create thousands of identical parts.

Several subprocesses fall under the general umbrella of injection molding, including insert molding and overmolding (a.k.a. multi-shot injection molding, two-shot injection molding, or double-injection molding). Keep reading to learn the differences and similarities between insert molding and overmolding, their applications, and how to figure out which type of multi-material molding is best suited for your project.

 

What is insert molding
The insert molding manufacturing process involves injecting molten plastic around pre-placed inserts (usually metal), forming a strong bond between the two materials and helping cut back on assembly operations and time. Common inserts include pins, blades, threaded nuts and knobs, sleeves, bushings, and the metal shanks of tools, such as screwdrivers.

 

What is overmolding?
Overmolding enables manufacturers to create parts from multiple materials using a manual two-stage process for small production runs or an automated two-stage process for large production runs. Regardless of production volume, the overmolding process works in the following way. First, a thermoplastic injection forms the rigid substrate. After the substrate forms, another shot (generally thinner and more pliable) is injected in, on, or around the substrate. As the materials cool, they bond together, creating a unified, strong, and durable part. Bonds can be chemical or mechanical, depending on the materials as well as the design of the part or product.

 

Comparing insert molding to overmolding
Overmolding and insert molding enable manufacturers to create multi-material products without using adhesives, help eliminate secondary assembly steps, and improve the final product. However, it's important to note the differences between insert molding and overmolding, including:

 

Process
Overmolding involves injecting two shots of materials to form the substrate and the overmold. Insert molding only involves injecting one shot of molten plastic, though the metal insert needs to be purchased or created separately.

 

Speed
Insert molding involves one shot while overmolding involves multiple, which means the insert molding cycle time is generally faster than the overmolding cycle time. However, that doesn't necessarily mean that insert molding is always the fastest option for production. In some cases, manufacturers may be unable to find pre-made metal inserts that meet their requirements, meaning they'll need to create a custom metal insert, which can lengthen production timelines.

 

Cost
Insert molding and overmolding can reduce assembly costs and accelerate production, helping companies simultaneously save on production costs and generate greater profits when producing large quantities of parts. However, overmolding is more expensive than insert molding, as it involves two steps. This is particularly true when it comes to prototype or small production runs, as overmolding requires manufacturing two tools — one for the substrate and one for the overmold.

 

Applications
Overmolding is often used to make toothbrushes, medical instruments, disposable razors, and phone cases, or to enclose electronic circuit boards (e.g. USB flash drives).

 

Consider using overmolding if
Your part's surface needs to have different electrical or thermal properties.
You want to increase your part's shock absorption or vibration damping.
You need a multi-colored plastic part.
Your part needs a comfortable and non-stick grip.
You need to embed soft seals into your part.
On the other hand, insert molding is a popular option for connectors, dash panels, electric sockets and wires, dials, remote control coverings, handles, scissor grips, and surgical implements.

 

Use insert molding if
Your part has a metal component.
Your substrate includes wires, electronic parts, or circuit boards.
You want to avoid incurring the cost of a complex two-shot mold.
You must incorporate threaded inserts into your part.
Insert molding and overmolding are both types of multi-material injection molding, but they each have their own benefits and drawbacks and can't be used interchangeably. To ensure you use the best process for your part, you'll need to be familiar with each method.

 

 
Our Factory
 

 

SJ Group was established in 1987, Hongkong. SJ Group starts from precision automotive mold building, and step into packaging mold building, medical mold building, liquid silicone rubber mold building, precision part injection. After 30 years of development, now we have 6 subsidiaries, several overseas after-sale offices. SJ Group is a group company integrating with part research, manufacturing, After Sales Service, and technical support. The major business of SJ Group: precision injection molds for automotive, packaging, medical and liquid silicone rubber.

 

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FAQ
 

 

Q: What is a plastic mold?

A: Mold, in manufacturing, a cavity or matrix in which a fluid or plastic substance is shaped into a desired finished product. A molten substance, such as metal, or a plastic substance is poured or forced into a mold and allowed to harden.

Q: What is molding in packaging?

A: In manufacturing, molding refers to the process of shaping a type of pliable material or liquid by using a rigid matrix or mold. In plastic injection molding, raw polymer resin granules are melted into a liquid and injected into a mold, where the plastic takes the desired shape.

Q: What are plastic molds made from?

A: Plastic injection molds are typically constructed from hardened or pre-hardened steel, aluminum, and/or beryllium-copper alloy. Steel molds cost more, but are often preferred because of their high durability.

Q: How do you make molded packaging?

A: First, the raw materials (cardboard / newspaper / natural fibers) are blended with water to make a pulp slurry. A mesh forming tool is lowered into the pulp slurry tank. A vacuum pulls the slurry through the mesh tool until the desired thickness is achieved. The wet parts are released from the mesh tools and dried.

Q: How does plastic moulding work?

A: The injection moulding process involves heating & injecting plastic material under pressure into a closed metal mould tool. The molten plastic cools & hardens into the shape inside the mould tool, which then opens to allow the mouldings to be ejected or removed for inspection, delivery or secondary operations.

Q: What is the process of plastic mold manufacturing?

A: The basic manufacturing process of injection molding: plastic is melted in the plastic injection moulding machine and then injected into a mold under high pressure. There, the material is cooled, solidified and afterwards released by opening the two halves of the mold.

Q: What is the difference between overmolding and insert molding?

A: Overmolding involves injecting two shots of materials to form the substrate and the overmold. Insert molding only involves injecting one shot of molten plastic, though the metal insert needs to be purchased or created separately.

Q: What are the applications of insert molding?

A: Applications of Insert Molding Parts
1. Automotive. Manufacturers in the automotive produce insert molding parts as an alternative to metal parts. ...
2. Consumer Electronics. Manufacturers in the consumer electronic industry often use insert molding to avoid using fasteners and solders during manufacturing. ...
3. Medical Devices.

Q: How do you use plastic molding?

A: Compression molding involves placing a heated plastic inside of a heated mold, then closing it to compress the plastic into the desired shape. Once cooled, the part is removed from the mold. The heating process, called curing, helps ensure that the final product will maintain its integrity and shape.

Q: What is the inside of a mold called?

A: Core. A portion of the mold that goes inside a cavity to form the interior of a hollow part. Cores are normally found on the B-side of a mold, thus, the B-side is sometimes called the core. Core-cavity.

Q: What is the process of film insert molding?

A: Film insert molding (FIM) enables one-step fabrication of plastic components with a decorated or functional surface. In this process, a plastic film, usually decorated by printing on the back, is shaped and trimmed before being placed in an injection mold and back-injected or over-molded with a thermoplastic resin.

Q: What temperature should plastic injection molding mold be?

A: The mold temperature should be set in a manner such that the surface temperature will be between 120 to 180°C. Also, ensure that the surface of the mold has a uniform temperature distribution. If the mold temperature is excessively low, moldings may warp or crack (rupture) due to residual stresses.

Q: How long does plastic molding take?

A: Generally, it can take anywhere from 2 to 18 weeks to complete a mold. Simple molds for small-scale production can be ready in as little as 2 to 3 weeks, while more complex molds for large-scale production or those requiring high precision might take 12 to 18 weeks or more.

Q: Who needs plastic injection molding?

A: Packaging industry
Plastic molding is commonly used to create items such as lids, jars, tubes, bottles, and other forms of packaging. This is the preferred packaging manufacturing technique because it provides a wide range of plastic resins and additives.

Q: How is silicone molding done?

A: The process involves compressing or injecting silicone rubber into a mold where it takes the shape and form of the mold cavity. The processes used to produce silicone rubber molded parts are injection, compression, and transfer molding each of which relies on a mold made of steel or cast iron.

Q: How thin can you injection mold plastic?

A: On average, the minimum wall thickness of an injection molded part ranges from 2mm to 4mm (. 080 inch to . 160 inch). Parts with uniform walls thickness allow the mold cavity to fill more precisely since the molten plastic does not have to be forced through varying restrictions as it fills.

Q: How accurate is plastic injection molding?

A: In general, a typical tolerance for injection molding is +/-0.1mm while a very tight tolerance is +/- 0.025mm.

Q: Which four processes are used to mold and shape plastics into packaging?

A: Injection moulding. Rotational moulding. Plastic extrusion & injection blow moulding. Vacuum casting.

Q: What are the methods to finish plastic?

A: As with wood and metal, plastics can undergo processes to achieve a desired finish. Abrasives such as emery cloth, silicon carbide paper, or steel wool are used to remove blemishes or marks before a polish is applied and the plastic is buffed to a good finish.

We're professional plastic mold packaging manufacturers and suppliers in China, specialized in providing high quality customized products. We warmly welcome you to buy high-grade plastic mold packaging made in China here from our factory.

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