Plastic Injection Mold

Inox Cast Plastic Injection Mold

Inox Cast is a professional plastic injection mold manufacturer and supplier for more than 20 years. We have been trusted by thousands of customers from around the world. We offer one-stop solution and services to customers from different countries.

Our one-stop solution and mold services includes plastic injection molding, custom plastic injection mold, and mold design. Here in Inox Cast, we are committed to bringing the best services at a competitive price.

At Inox Cast, we are equipped with advanced manufacturing technology. We have more than 1000 employees and personnel including our engineers, designers, etc. Our factory covers around 32,000 square meters. Thus, we can produce large amount of plastic injection molds per month.

We specifically designed plastic injection mold for making home appliance or office device part/components. It is also widely used for making stationary, food containers, gadgets, device, automotive parts, electronic parts, and more.

We craft different types of mold design through our advanced software. We use SolidWorks, UG, Gibs CAM software, and more. It comes with different surface treatment for enhancing details like multi-gloss finish, matte finish, layered textures, and more.

Our plastic injection mold is made from high-quality steel. Thus, it can withstand high impacts and rigors especially in mass production. It features enough space and right transitions for preventing different defects.

Inox Cast also offer OEM services. We can custom-made your orders based on your specification. Just send us your details, drawings, or ideas. Inox Cast is surely your one-stop plastic injection mold services and solution provider.

Here in Inox Cast, we used advanced management system and top level management. We aim to produce only the best and highest quality products. Through continuous improvement and innovation, Inox Cast is recognized as the leading plastic injection mold manufacturer and supplier.

Request a quote for your next plastic injection mold order!

Plastic Injection Mold: The Ultimate FAQ Guide

I know choosing plastic injection mold can be an overwhelming task.

A reason this guide will answer all your questions on plastic injection mold.

So, keep reading to learn more.

1.  What Is Plastic Injection Mold?

A plastic injection mold is a tool for molding plastic parts. The process of plastic injection molding involves injecting molten plastic material into a mold.

2.  What Are The Parts Of Plastic Injection Mold?

A plastic injection mold consists of a series of parts. Every component is crucial to the molding process.

A Diagram Showing Parts Of A Plastic injection Mold

Parts of a plastic injection mold are as follows:

• Clamp plates
• Sprue bushing
• Feed system
• Cavities
• Cooling system
• Guide pillars
• Ejector system

3.  Which Is The Best Plastic Injection Mold Material?

The best mold materials for a plastic injection mold are steel and aluminium.

Pre-hardened and hardened steel are great options. Steel is a high quality and strong material which has a long lifespan.

The only downside of steel as a mold material is that it is costly.

A Steel Mold Material For Plastic Injection

Aluminium is a strong material as well. It can be able to withstand both clamping and injection forces. It lasts for long and is not prone to wear.

4.  What Are The Main Plastic Injection Mold Design Considerations?

The main design consideration of a plastic injection mold are:

• Shrinkage allowance- this is dependent on the shrinkage properties of the material core and the cavity size.
• Cooling circuit- water circulates through the core and cavity so as to minimize cycle time.
• Ejection gap- this must allow for all components to be fully ejected from the mold.
• Mold polishing- the parts of the mold should have a nice surface finish and be polished in the direction which the material flows.
• Mold filling- the process of component filling should be from the thicker to the thinner section.
• Draft- this is needed in the core and cavity for easy removal of finished parts.

5.  When Should You Choose Multi Cavity Plastic Injection Mold?

It is important to have an extensive knowledge on your market as well as the demand before choosing a plastic injection mold.

When producing parts at high volumes, you should choose a multi cavity plastic injection mold. Multi cavity plastic injection molds enable creation of more parts, faster and more efficiently.

Multi Cavity Plastic Injection Mold

Another time to choose a multi cavity plastic injection mold is when you do not have tight deadlines. This is because they need more lead time as they take relatively longer to create to create parts.

6.  What Are The Common Plastic Parts Defects Caused By Plastic Injection Mold?

The most common defects caused by plastic injection mold include the following:

• Sink mark

This is a depression that appears on the surface of the molded area. A sink mark is usually found where they are bosses or ribs on the underside of the molding.

They are caused by uneven cooling of the outer and inner surface.

Sink Marks

• Void

Voids are also referred to as air pockets. They occur as a result of the surface cooling and solidifying quicker than the inner material. Voids usually occur in the thicker parts of the molded part.

• Weld lines

This defect tends to occur when two melt fronts join but don’t but refuse to bond since they are only partially solidified.

A  Weld Line Defect

• Burn marks

These can be as a result of excessive heat or speedy injection. They usually appear as dark discoloration or charred patches on the finished parts.

• Flow lines

Flow lines are streaks in the surface caused by the molten plastic travelling at different speeds throughout the cavity.

Flow Line Defect

7.  Is Plastic Injection Mold Suitable For All Materials?

Plastic injection mold is suitable for a variety of materials. The most common are as follows:

• PMMA/Acrylic

This is a clear and strong thermoplastic. It is light weight and shatter proof which makes it a great alternative to glass.

Acrylics have high tensile strength which allows it to withhold loads, they also have a high tolerance during injection molding.

Furthermore this material is UV light and weather resistant making it perfect for outdoor use.

An Acrylic Molded Material

• Nylon/ Polyamide

Plastic injection mold is suitable for this synthetic material because of its high heat resistance and toughness.

This material has a good fatigue resistance, it is heat resistant and possesses noise dampening properties.

Injected molded nylon has a low coefficient of friction making it suitable for applications with high friction, wear and tear.

• Polycarbonate (PC)

Polycarbonate is one of the toughest strongest and naturally transparent plastic.

As an injection mold material, polycarbonate has a uniform and consistent mold shrinkage thus offering accurate dimension control.

However, polycarbonate is not BPA free so injected molded polycarbonate should not be used for food grade.

A Polycarbonate Molded Material

• Polyoxymethylene (POM)

Also known as acetal, this material is an engineering plastic. It can be inject molded into parts need properties such as minimal friction, high dimension stability and stiffness.

Note that this plastic is opaque or white in color due to its high crystalline structure.

• Polypropylene (PP)

PP is one of the most commonly used plastics in the world. It is highly resistant to chemicals and retains its shape after bending. This material has a high melting point and is not affected by moisture or water.

Injected molded polypropylene can be recycled up to four times. You can combine it with other plastic materials as well.

Polypropylene

Note that injected molded PP is highly flammable and is not UV resistant.

• Other materials suitable for plastic injection mold are: acrylonitrile butadiene styrene (ABS), polyethylene (PE), thermoplastic elastomer (TPE), polystyrene (PS), thermoplastic polyurethane (TPU), etc.

8.  What Should You Consider When Choosing Plastic Injection Molding Machine?

Important factors to consider when selecting a plastic injection molding are as follows:

• Production capabilities

When choosing a plastic injection machine ensure that it aligns with your capability requirements. Make sure that it is in your desired size, and is suitable for your preferred materials and colors.

It is also important to consider the latest technologies. Plastic injection molds have undergone through multiple technological advancements over time.

• Quality standards

When choosing a machine make sure that are ISO certified. It is also important to ensure that they pass the required inspections and meet the safety standards. Additionally, ensure that the machine produces high quality parts.

• Price

This is one of the top factors to consider when choosing a plastic injection molding machine. Ensure to settle for a machine that bests suits your budget.

While at it, make sure that the machine has a proper design and in good condition. Sometimes settling for a cheap bargain can cost you more in repairs and part replacements in the long run.

A Plastic Injection Molding Machine

9.  Which Parts Can You Make With Plastic Injection Mold?

Plastic injection molding is extremely versatile and can be used to create many different parts for a variety of applications.

Examples of parts you can make with plastic injection molds are:

• Toys
• Plastic bottles
• Flower pots
• Roofing vents
• Vending machine components
• Trash and recycling bins
• Mop heads

Mop  Heads

• Electrical boxes
• Syringes
• Household containers
• Car cup holders
• Trays
• Training tools, etc.

10.  What Are The Benefits Of Plastic Injection Mold Prototype?

A plastic injection mold prototype is a mold that facilitates the production of parts for functional testing. Benefits of using this prototype are:

• It has no size limitation.
• Low cost- the cost of producing plastic injection mold prototypes are significantly low.
• It produces good quality parts.
• It has relatively low lead times.

11.  What Are The Advantages Of Plastic Injection Molding?

Plastic injection molding is an efficient and extremely versatile method of creating parts. It is simple and more reliable compared to other plastic molding methods.

Other advantages of plastic injection molding are:

• Efficiency

Plastic injection molding is considered one of the most highly efficient method of molding. The molding process is very fast and has a higher production output rate compared to other methods.

• Complex part design

Plastic injection molding is very precise and is able to handle very complicated designs. With this method of molding, it is possible to produce very high quality as well multiple identical parts.

• Strength

Parts produced by plastic injection mold have enhanced strength as well as stability. The mold consists of integrating ribs or gussets which can be used to make a part as rigid as desired. Strength is among the top factors to consider when creating a plastic injection molded part.

• Flexibility

Plastic injection molding is suitable for a variety of plastic materials. This provides you with multiple options to choose from depending on your needs.

Furthermore this molding method is able to produce parts of whatever color you need.

• Low labor costs

Because the plastic injection mold runs with an automatic tool, labor costs remain relatively low. This automated process ensures that production goes on and all operations are streamlined.

All this requires very minimal monitoring and supervision.

• Waste reduction

A significant amount of excess plastic is generated throughout the molding process. Most plastic injection molding companies have a recycling system to deal with this excess.

12.  How Do You Maintain Plastic Injection Mold?

Maintaining a plastic injection mold involves cleaning and repairing of parts to keep it in its best working state. You should perform routine preventative maintenance as well as repairs when problems arise.

Maintaining an injection mold can prolong its lifespan. It also improves the quality of the plastic components it produces.

When purchasing a plastic injection mold ensure it has clear and detailed instructions on maintenance. These should include:

• A detailed list of approved cleaning agents and solvents. These cleaners should not destroy or cause corrosion to the injection mold.
• A list of all suitable lubricants safe to use on the mold.
• What components to inspect and at what intervals. It is important to regularly check parts of injection mold to ensure they are in good condition.
• The right procedure of storing the plastic injection mold after use. This can differ for different types of molds. But basically, you should keep your injection mold in a cool dry place. Ensure you keep the components lubricated and spray it with an anti-corrosion to keep it from rusting.
• Lastly, the maintenance manual should include the criteria of inspection for all the components of the mold. These includes all fittings, moving parts and all surfaces.

Please note that failing to perform routine maintenance on your plastic injection mold can cause it problems. These include wear and tear, reduced efficiency, low quality molds and eventually total failure.

Routinely Cleaning And Repairing Your Machine Is The Best Way To Maintain It

13.  What Causes Wear In Plastic Injection Mold?

Contact or friction between parts of a plastic injection mold can cause wear. Additionally, it can be as a result of glass fibers found in the plastic resin.

If the degree of the wear surpasses the tolerable range, it could break down or cause quality problems. Plastic injection molds undergo two types of wears; normal and abnormal.

Normal wear is caused by friction resulting from parts touching and sliding against each other.

Abnormal wear on the other hand can be classified in different types. These are abrasive wear, adhesive wear, corrosion wear, fatigue wear and fretting wear.

Routine maintenance such as lubrication, cleaning, treating with anti-corrosion can minimize wear in a plastic injection mold.

14.  Are Plastic Injection Mold Suitable For Low And High Run Production?

Certainly, plastic injection molds are suitable for both low and high run production. This made possible by single cavity and multi cavity injection molds.

A single cavity injection mold is used for low run production of parts. It only creates a single part per cycle. As much as they are used for low volume production, single cavity injection molds have less lead time. They take a relatively shorter time to create parts.

Multi cavity molds on the other hand are suitable for high run production. They use multiple cavities at once which facilitate the production of parts in high volumes. Multi cavity molds produce many parts per cycle.

15.  How Much Do Plastic Injection Mold Cost?

The cost of plastic injection mold is relative and can be quite expensive. Factor that influence the cost of plastic injection molds are:

• Quality- plastic injection molds are made from high quality materials which can be expensive.
• Plastic injection molds are made and designed by highly skilled personnel who have quality training as well as lots of experience.
• Making plastic injection mold requires special tools such as CNC machinery, precision features, software which can all be very costly.

16.  Are There Specific Construction Requirements For Plastic Injection Mold?

Plastics injection molds should be made by high skilled personnel  using the correct machinery and tools. In addition, they should be precisely machined to tolerances of +/- 0.001*or 0.025mm.

17.  What Are The Main Steps In Plastic Injection Molding Process?

Plastic injection molding involves the following steps:

• Clamping

The plastic injection mold has a high strength clamp which holds its two halves together during the cooling and injection stages.

Clamping is achieved through either electric or hydraulic pressure.

• Injection

During this step, the plastic material in pellet form flows into a hopper which is on top of the injection unit. The pellets then feed into a cylinder where they are melted.

Then molten resin is mixed by a motorized screw and pushed towards the end of the cylinder.

The process of injection starts once enough material has gathered in front of the screw. The molten plastic material pushed into the mold. The screw is responsible for controlling the pressure and the speed.

Injection And Clamping Steps Illustrated

• Dwelling

This step is for providing increased pressure throughout the injection process.

Pressure is applied to ensure that the molten plastic fills all the mold cavities.

• Cooling

This step allows the molten material to cool down properly. Note that cooling periods differ depending on the thickness of the parts’ walls.

• Opening stage

The pressure of the clamping releases allowing the mold to separate. The mold is then separated into halves.

• Ejection

The finished part is ejected from the mold by the ejection rod and plate.

The excess plastic is collected for recycling.

Cooling And Ejection Stage Of Plastic Injection Molding Process

For all your plastic injection molding needs, contact us now.