Recycled Plastic Injection Molding

Inox Cast Recycled Plastic Injection Molding

Searching for durable and perfect customizations of recycled plastic injection molding in China? Inox cast is one of the trusted recycled plastic injection molding and another related molding for different production industries.

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Recycled Plastic Injection Molding: The Ultimate Guide

Adopting recycled plastic injection molding help reduce waste.

In fact, it is an eco-friendly process most plastic injection molding companies have adopted.

The best part – this guide explores everything you need to know about recycled plastic injection molding process.

Let’s dive right in.

1. What Are Recycled Plastics For Injection Molding?

Recycled plastics refers to the plastic materials or wastes that are reprocessed into a new and useful product.

Mostly during the plastic injection molding process, a waste material called the sprues are formed which is basically pieces of plastic left over after the injection process.

Therefore it is some of these sprues that are used to make the recycled plastics or they can as well result from other plastic products.

recycled plastic injection molding

These recycled plastics does not lose their quality during the manufacturing process via injection molding process.

They can come in various configurations such as various types, sizes, colors and even with different usage.

With the advancement in the injection molding process, various types of plastic materials can be  recycled.

Such plastic materials may include; high density polyethylene, polypropylene, polyvinyl chloride, low density polyethylene among others.

Recycled plastics reduces the dependence on the landfill, conserve resources and protect the environment from greenhouse gas emissions and plastic pollution.

2. Benefits Of Injection Molding Recycled Plastics

Injection molding recycled plastics accrues a lot of benefits to the user, the manufacturing company as well as the environment.

Advancement in technology is one of the major ways that has played a major role in recycled plastic injection molding process.

Some of the advantages of injection molding recycled plastic include;

Faster And Saves Time

The plastic injection molding process is faster and therefore saves on time.

The higher speed is also as a result of the advancement in technology and also it depends on the complexity of the mold itself.

Suitable For Creating High Strength Component

This involves addition of fillers to component during injection molding.

The fillers reduces the density of the liquid plastics while enhancing the strength of the finished part.

Helps In Reducing Waste Material

Reduced waste since most of the waste plastic materials are reprocessed and repurposed into a new and useful products.

This makes the process of injection molding to have positive impacts to the environment by reducing the level of plastic being disposed to the environment.

Hence, may have negative impacts to the soil.

recycled plastics

Low labor cost during plastic injection molding as compared to other types of molding.

The process of injection molding is run using a self-gate equipment, automatic tools to keep the production ongoing and streamline the operation.

It Is A Flexible Manufacturing Technique

The type of plastic material, the size, the color of the recycled plastic can be easily changed.

This results into many type of recycled plastic products being produced.

Cost Effective Compared To Plastic Machining

Creation of mold may be costly but once the mold has been created, large volume of plastic components can be created at a lower cost.

However, in plastic machining, large production can cost up to 25 times more than recycled plastic injection molding.

3. Challenges Of Injection Molding Recycled Plastics

Even with the advancement in technology, there are still technological limitations that prevent them from attaining higher recycling rate and injection molding.

Some of the common challenges include;

A lot of capital and technological capability is required in putting up the recycling and the injection molding facility.

Co- injection molding can result into cross- contamination, procedural complications and variations affecting various parts.

Especially when the recycled plastics has differing properties and melting points.

Another challenge is reduced variability in that, often as the recycled content increases, the quality of the injection molded part decreases due to material variation.

4. Controlling Quality Of Recycled Plastic Injection Molded Parts

This is a crucial step in the production process.

It involves the detection and identification of the impurities in recycled plastic material in a fast, cost-effective and reliable manner.

It also involve the verification of the polymer type of granule.

Inspections are normally done after production is done to ensure the quality of the final product meet the application requirements.

5. Recycled Plastics Injection Molding Process

Injection molding process enables the manufacturer to create all their products over and over again with just one mold.

Besides, the process of recycled plastic injection involve six steps but before injection molding is done, first you have to ensure the plastic is recycled.

The process of plastic recycling involve three stages such as;

• Collecting
• Sorting
• Reprocessing the plastic ready to be used in new products.

In collection stage, plastic material is deposited into a recycling container.

Sorting is done at a material recovery facility but further sorting into different types of plastics is done at plastic recovery facility.

Reprocessing, the last stage of recycling, involves transferring of the sorted plastics to the plastic processor.

Once recycling is done, the process of plastic injection molding begins which involves the following steps;

First step of injection molding involves clamping.

plastic injection molding

In this step, the two halves of the mold are placed into the clamping unit and then the machine pushes the two halves together to prepare for the injection process.

The second step involve injection which starts once the clamping phase is complete and the two halves of the mold are put together.

Here, the plastic material is pumped into a container in which it is melted into a complete liquid.

Once the melting is done, the liquid is then injected into the mold.

Subsequently, the next step is the dwelling phase which involved the plastic being filled to the entirety of the mold and this is done through pressure.

When pressure is applied on the plastic material, it covers all the mold cavities and this help in ensuring the product comes out correct.

The forth step is the cooling phase in which mold is left alone so that the plastic inside can cool and form solid inside the mold.

It is then followed by, mold opening and then the final step of injection which reveal the final plastic product from the mold.

6. Types Of Injection Molding Techniques To Use On Recycled Plastics

There are a variety of injection molding techniques that are considered to be most effective and most popular.

Examples of injection molding techniques are;

• Cube molding
• Reaction injection molding
• Micro injection molding
• Gas assisted injection molding
• Thin walled injection molding

Cube molding – molding process for manufacturing plastic components and it allows for the manufacture of circular parts

Reaction injection molding – this process involve mixing highly reactive plastic liquids under high pressure and then injected into a mold to react, polymerize and turn into foamed plastics.

reaction injection molding

Micro injection molding – this process involves the manufacturing of plastic components having small weights of 1 to 0.1 grams.

Gas assisted injection molding – inert gas is introduced at a pressure, this pushes the plastic melts into the mold extremities.

Thin walled injection molding– this is a specialized form of injection molding that focuses on the mass production of plastic components that are light and thin.

7. Choosing Mold For Recycled Plastics Injection Molding

Mold is a tooling system we use to make parts via injection molding process.

It is a cavity where you pour molten plastic or material

The cavity takes the shape of material you intend to make

Most of these molds are made from aluminum or steel.

When choosing mold, there are factors that should be put into consideration such as;

Order quantity/ production volume, type of the material, quality requirement and assurance, speed, cost, project development stage, complexity among others.

recycled plastic injection mold

Complexity Or Part Geometry

Some parts geometry and features may involve different mold making approaches.

Steel molds has always been the better option in making designs that may change but is highly complex with fine features.

This type of mold is preferred since it allows the flexibility of change until you firm up your final design.

Cost Of The Initial Mold Build

Factors such as the specialty molding features, mold classification, complexity of the parts, mold cavitation has impact on the cost of your mold.

Mold Speed

This determines the production volume of the recycled plastics as well as the duration for the production.

Mold with higher speed has high chances of producing large volume of plastics within a given duration while molds having lower speed may produce less.

Type Of Material

The type of plastic material chosen and its application areas as well as the weight of the material will determine the type of mold to use.

Project Development Stage

For example in early stages of project development, multiple design changes and revisions are done.

Therefore during early stage, steel mold is the most preferred due to it hardness and its ability to allow flexibility of change until you firm up your final design.

8. Are Parts Made From Recycled Plastics Injection Molding Durable

Yes, the parts made from recycled plastic injection molding are durable, adaptable, economical and flexible to be used in various industrial applications.

However, the durability and the quality of the recycled plastic becomes lesser as compared to the original plastic product.

This is because as the plastic is being recycled and regrounded into new recycled material, it becomes weaker.

Some of the industrial applications include; textiles, in consumer products, medical device, transportation, electrical and electronics and industrial machinery.

9. Choosing Recycled Plastic Material For Injection Molding

There are wide range of plastic materials that can be used for injection molding.

Choosing the best plastic material to use will depend on the application area/the purpose of the recycled plastic among other factors.

Some of the examples of the recycled plastic material that can be used for injection molding include;

Acrylic- this is a hard transparent plastic material that is most commonly used in automotive parts and in electronics.

Other benefits of acrylic include; it offers resistance to weather especially moisture and ultraviolet discoloration.

It also has good impact strength and rigidity as well as dimensional stability.

Also, it provides resistance to chemicals hence cannot be easily affected water, weak acids and alkaline solutions.

High density polyethylene- it is always the best plastic material when in need of heat resistant and rigid material.

This plastic material is good for holding chemically based products such as laundry detergents, cleaning agents, bleach and shampoo.

Besides that, it is also safe to use around food that’s why is commonly manufactured around refrigerator shelving, storage containers and kitchenware.

Some of the other advantages of using high density polyethylene include;

• Can be mass produced at a lower price therefore inexpensive.
• Sustainable- it is 100% recyclable.
• Corrosion resistant, rust and resistance to chemicals.
• The material cannot easily melt and corrode at high temperature.

Polypropylene- useful for wide variety of food related applications such plastic kitchenware, storage containers, dishwasher safe plastics due to its chemical resistance and elastic properties.

Other advantages of polypropylene include; has strong insulation properties, has the ability to retain its shape after a lot of flexing and bending.

Polystyrene- type of recycled plastic material commonly used in hinged applications such as disposable food containers and bottles.

It can as well be used to make rigid foam insulation and sheeting for laminate floor.

Apart from that, there are other benefits of using polystyrene recycled plastic material such as;

• Mass production at lower cost hence cost effective.
• Dimensionally stable- its rigidity makes it suitable for packaging purposes.
• FDA grade, meaning, it is safe to use when packaging food and consumable materials.

Polyetherimide- most commonly used in medical devices, electronics and industrial plastics parts due to its high heat performance and its rigidity.

It also has high tensile strength, meaning, it has the ability to resist breaking and cracking in hard environmental conditions.

Polycarbonate- suitable recyclable plastic material for applications that requires transparency or high impact resistance.

Due to its ability to resist impacts, polycarbonate material is most commonly used in eyewear applications, pipes for LED lights, sporting equipment and clear windows.

Other advantages of using polycarbonate material include;

• Does not corrode or discolor in ultraviolet light/ UV resistance
• Does not corrode from chemicals/ chemical resistant.

10. Examples Of Recycled Plastic Injection Molded Parts

Many variety of recycled plastic parts can be made from injection molding.

The molded parts can be categorized based on their application areas for example;

• Medical parts which include; syringes or surgical device.
• Automotive industry/components I.e. dashboard switches, intake manifolds and knobs.
• Others which include; electrical circuit board, bottle caps, toys, jewel boxes, component of portable pottyes.

recycled molded injection parts

11. Common Defects In Recycled Plastic Injection Molding

These are the normal defects during plastic injection molding process.

They may affect the normal functioning of the product or even result into unusable workpiece.

Therefore it is always important to find out some of the causes of these defects before the process of molding begins.

Common defects may include;

Shrinkage Defect

It is due to uniform thickness of the wall or uneven wall thickness of the product.

Also, short cooling time in injection mold, higher mold temperatures among others.

It can as well be due to thermal contraction which describes the extent in which material changes in volume as they change from liquid to solid state.

This defect can be avoided by the following ways;

• In parts with thick walls, the mold temperature should be lowered while those parts with thin wall the mold temperature should be increased to ensure the material is smooth.
• Normally crystallize plastics shrink more than non- crystallize recycled plastics therefore, during molding processing.

It is recommended to increase the amount of material or add a replacement agent that will reduce the shrinkage.

• Temperature of plastics with poor fluidity should be increased to ensure smoothness of the material.

Charring Defect

These are burn marks caused by internal combustion effects during injection molding process.

High temperatures above 600 degree Celsius and injection speed that are too fast can lead to the degradation of plastic material by causing burn marks.

Some of the possible ways to avoid burn marks/ charring include;

• Reduce the injection speed
• Reduce the temperature of the plastic during injection
• Reduce the injection pressure.
• Ensure there is adequate gas vents to allow gas build up to escape the cavity.

Weld Marks Defects

These are lines generated at the hole of the product

It is affected by the number of water entry points to the final product.

Some of the ways to avoid or to eliminate weld marks include;

• Water entry method should be changed
• Bone where the weld line appears
• Increase the exhaust equipment

Jet flow – it is another defect which forms earthworm like line in water inflow parts.

Improvement can be done through addition of obstruction needle to the area where the water flowing in.

Impurities – mixed impurities on the product may affect the intended purpose of the final products.

Impurities can be introduced to a mold if the mold plate of the machine is not properly cleaned in preparation to production.

Lack of glue is also a common defect.

For example, a multi-mode cavity may lack glue due to the different length of channel of each cavity or different size of the inlet point.

Sometimes lack of glue can be due to the bad exhaust of the die.

12. Estimating Cost Of Recycled Plastic Injection Molding

In estimation of the cost of the injection molding process, a number of factors needs to be considered such as;

• Complexity of the part design
• The size of the mold
• Mold material
• Process used to create mold.
• Production volume
• Labor cost or outsourcing cost

Online injection molding cost estimators from injection molding service provider can be used to estimate the cost of injection molding specific parts.

The online injection molding estimators options that can be used to aid the calculation process include;

• Protolabs
• Custompart
• ICOmold
• 3D Hubs

Alternatively, a molding cost comparison table can be used to provide a rough estimate of the injection process.

Usually, a small and simple single cavity plastic injection cost between $1000 and $5000 while the very large and complex mold normally cost as much as $80000 and more.

More Resources:

2K Injection Molding

Rubber Mould

Prototype Injection Molding

Plastic Extrusion Process

Plastic Thermoforming Process

For all your recycled plastic injection molding needs, contact INOX now.