Polystyrene Injection Molding

Inox Cast is a leading polystyrene injection molding company dedicated to manufacture and supply quality moldings for more than 20 years. We are dedicated to providing polystyrene injection molding in all sizes and shapes. Let Inox find the perfect polystyrene injection molding solution for your business.

  • 20+ years of expertise in polystyrene injection molding production
  • Skilled and expert engineers and technical staff
  • Custom-built polystyrene injection molding
  • Provided excellent after-sales service

Why Inox Polystyrene Injection Molding is Your Best Supplier

Inox design and manufactured polystyrene injection molding for the past 20 years. We are supplying moldings to industries such as manufacturing plants, construction works, and related industries. During the years in the business, we gain rich expertise and the ability to provide excellent service. More and more customers trust Inox Cast. If you have polystyrene injection molding requirements, Inox will help you purchase the perfect product.

Polystyrene PS injection molding
Polystyrene PS injection molding

Inox supplies high-quality polystyrene PS injection molding at a very competitive price. We offer an OEM polystyrene injection molding service to be used in particular applications.

Polystyrene injection molding machine (1)
Polystyrene injection molding machine

This polystyrene injection molding machine is super-efficient. It will help your production increase productivity while reducing energy consumption. All machines are manufactured to meet all international norms.

HIPS injection molding
HIPS injection molding

Inox offers HIPS injection molding ideal for small plastic parts and products. This molding is FDA-compliant. Has the ability to maintain strength in high-impact applications. Ideal for the agricultural storage industry.

Custom polystyrene injection molding
Custom polystyrene injection molding

At Inox, we offer custom polystyrene injection molding to satisfy each customer’s requirement. You can send your own design, and further process to be followed. We also offer custom material selection and all technicalities.

Polystyrene mold maker plastic injection
Polystyrene mold maker plastic injection

This polystyrene mold maker plastic injection can be made of ABS/ PP/ PS/ PE/ PVC/ PA6/ PA66. Color can be customized as per request. The cavity range from 1-48.

Polystyrene cylinder nozzle injection molding machine (1)
Polystyrene cylinder nozzle injection molding machine

This type of machine is applicable to food&beverage factories, printing shops, and related industries. We can custom-built this machine according to your specifications.

High precision polystyrene injection molding (1)
High precision polystyrene injection molding

Inox manufacture and design high precision polystyrene injection molding to the latest technology. Inox set the bar for precision. This one is designed with up to 128 cavities.

CE-approved polystyrene injection molding
CE-approved polystyrene injection molding

Inox offers CE-approved polystyrene injection molding available at a competitive price. We offer a 1-year warranty on all parts and moldings. There is also online support for the product, if some issues may arrive, you can get in touch with us any time.

Polystyrene injection molding for car parts
Polystyrene injection molding for car parts

Inox polystyrene injection molding for car parts has more than 300000 mold life. The mold material can be 45#,50#, P20, H13, etc., The size and parts specifications are based on your requirement.

Injection molding of polystyrene cup
Injection molding of polystyrene cup

This injection molding of polystyrene cup is ISO9001 and QS certified. There is a range of surface finish options such as sandy, smooth, glossy, EDM finish… Two options for runner system – hot/ cold runner.

Injection stretch blow molding machine
Injection stretch blow molding machine

This injection stretch blow molding machine is applicable to the food& beverage industries. This is fully automatic machine energy-saving; provided with 1-year warranty service.

Polystyrene injection molding electronic case
Polystyrene injection molding electronic case

This polystyrene injection molding electronic case is made of plastic material. The case moulds life up to 500,000 shots. At Inox, we accept OEM orders. We can do production as your design.

Inox Polystyrene Injection Molding

Inox Cast – Your Expert Polystyrene Injection Molding Manufacturer

Inox Cast has the widest variety of polystyrene injection molding in China. We produce this equipment perfect for a number of different applications. In fact, Inox Cast developed and produced equipment and services for household products, automotive, appliances, and other commercial products.

Our polystyrene injection molding is designed to offer accurate results to any product. It is durable and ready for tough performance. This polystyrene injection molding also has moisture-resistant material to ensure that it is safe to use and hygiene requirements are met.

Inox Cast polystyrene injection molding is lightweight that gives you benefit by reducing the transportation cost. All the components of this equipment are CE-certified and approved by ISO9001.

Our polystyrene injection molding has reached different countries around the world and received good feedbacks from them. We also want you to have premium-quality equipment with good performance and outstanding services.

Since 1997, Inox Cast has been the most reliable provider of polystyrene injection molding and services in this field. For 20 years, we keep on expanding our knowledge in creating the best solutions at affordable prices. You can also help us create better polystyrene injection molding by giving your ideas.

Our engineers, professional personnel, and skilled workers focused on improving their jobs in order to produce more innovative polystyrene injection molding. Inox Cast also upgrades our manufacturing system by using advanced technology machines.

Inox Cast has the latest automated CMM machines and CNC machines. We are using the Gibbs CAM to assist our CNC machines to produce top-grade equipment like polystyrene injection molding.

Allow us to help you find your ideal polystyrene injection molding. We are aiming to gain your trust and be your best provider of all the solutions you need in this industry.

Contact us anytime you want!

Polystyrene Injection Molding: The Ultimate Guide

In this guide, you will find all information you are looking for about polystyrene injection molding.

From benefits, injection molding process, properties to common defects – everything you need to know about polystyrene injection molding is right here.

Let’s dive right in.

1.  What Is Polystyrene Injection Molding?

It’s a process that involve heating of polystyrene into fluid state and injecting molten polystyrene into mold to form plastic products.

polystyrene injection molding

polystyrene injection molding

2.  Advantages Of Polystyrene Injection Molding

Elevated Efficiency Production

The process of itself is actually very fast unlike the other method which helps to give you a high output production.

And this gives advantage of more efficiency and cost effective cause of high production speed depending with size of, old and complexity.

With this advantage of fast production means that it also has short period cycles to produce a great quantity of parts.

And this leads to increase revenue and profit margins because of increase of quantity of parts faster production thus meeting market demands.

Complex Part Design

The process actually handles very extremely complex components and with uniformity and make identical components at a short period of time.

After taking into account key design elements, you optimize the effectiveness of high production value of injection mold to give accurate quality parts.

Enhanced Strength

Because polystyrene s the material used in the polystyrene injection molding process there is enhanced strength to parts being produced.

The product you produced is usually strong and durable that can withstand the harshest environment without breaking or wearing out easily.


For the parts with complex design, the adjustability or flexibility of the polystyrene enables accuracy of measurements from polystyrene injection molding.

Short Period Of Production

It is fast and this helps to achieve shorter product fabrication and this enables you to meet the market demand faster.

Color Control

You can decide to change color of polystyrene because it’s usually clear fluid by adding additives with use of polystyrene injection molding.


It’s flexible to make custom color choices to even meet specific requirement of complex project there is freedom in design choices.

Lower Labor Costs

Most of the process is utilized by gadget and controlled by an operator, this helps to actually reduce labor costs.

And this leads to the decrease of risk of rework because of defects of parts that are caused by humor error.

Produces Lightweight Products

Because of polystyrene material, the products that come out in the end is usually light in weight with high strength and durability.

3.  Properties Of Polystyrene For Injection Molding


Consistent Fluid State

In its molten form, polystyrene is actually consistent, the products outcome all have the same best feature for the market sales.

Low Energy Consumption For Melting

Polystyrene melts at temperature that doesn’t need excessive energy that’s why it’s good to ensure you avoid excess heat with polystyrene.


The viscous molten polystyrene easily flows into the injection mold where it is shaped according to how you want it.

The melt flow index of polystyrene is very impressive and its easiest polymers to work with in industry; it’s less dense.

Because Of the Character of low density this enables polystyrene to make different plastic products without problem, it’s suitable to use.

Polystyrene has less weight and this is the reason you utilize it to pack food orders.

Low Shrinkage Rate

Unlike other polymers which shrink during injection molding and end up causing distortion in shape of product, polystyrene ha low shrinkage.

The final product of polystyrene has enough plastic surface space where you paste logos, design, posters depending on the business type.

4.  Injection Molding Of Polystyrene Defects

Flow Lines

These appear as wavy pattern often in slightly different color compared to surrounding place and the slender parts of molded parts of molded component.

They re as result of variation in cooing velocity of the matter as it flows in different directions throughout the mold.

When you have differences in wall thickness it causes the material to actually cool at different speeds thus leaving flow lines behind.

You can correct this by increasing velocity of injection, pressure and temperature of material to ensure mold is full before cooling.

You can also round edges of mold where thickness of wall elevates to keep consistent flow rate preventing flow lines.

You can also elevate or increase the diameter of the nozzle to help increase flow speed and prevent cooling early.

And relocate the gates of mold to help fabricate more distance between them and coolant thus preventing material from early cooling.

Burn Marks

This burnt marks are black in color or rust colored discoloration that is on the edge of a plastic molded component.

These burnt marks don’t really affect the component integrity generally unless the component is burned to an extent of degradation.

It’s caused by trapped air, or resin itself overheating in mold cavity during injection, increases injection speed leads to this too.

You correct this by lowering melt and mold temperature to help prevent overheating, reduce speed of injection to limit trapping air.

Enlarge gas vents and gates this enables trapped air to escape mold and shorten cycle time of mold to prevent trapped air from overheat.


This is a deformation that comes about or occur in injection molded products when different parts of component unevenly shrinks.

It is mainly caused when cooling happens too fast and mostly excessive temperature or low conductivity in term worsens the problem.

Sometime design of mold contribute to warping when mold walls are not even, the increase in shrinkage elevates with wall thickness.

You prevent this by making sure that process of cooling is gradual and longer to prevent uneven stresses on matter.

You can try lowering temperature of mold or matter and then try to use a material that has less shrinkage during cooling.

Then remodel mold to give it very even wall thickness and symmetry part to enable stability in part when cooling.

Vacuum Voids/ Air Pockets

These are actually trapped air bubbles that tend to appear in finished molded part, they are minor defects according to quality control.

But when you have larger amount of voids they weaken molded component because of air occupying where material should be molded.

Its cause by less molding pressure force trapped air out of the mold cavity or wall of mold closes fast.

The material you use itself can be vulnerable to voids when the density of material changes from the hardened molten state.

You can actually correct this by elevating or increasing the injection pressure to help force out the trapped air pockets.

Or you can choose a type of material that has lower viscosity to help reduce risk of air bubbles from forming.

You can place the gates close to thickets edges of mold to help in preventing premature cooling where matter is most vulnerable.

Sink Marks

These are small depression that are flat and consistent surface on molded part they occur when inner part of component shrinks.

Caused by the material cooing very slowly, the resulting shrinkage pulls the outside material inward before cooling leading to depressions.

Prevent this by raising the holding time and pressure to enable the material near the parts surface to cool.

Then elevate time of cooling to help reduce shrinkage and then redesign your mold with thin component wall to enable rapid cool near surface.

Weld Lines

This is result of weak material bonding which reduces strength of component, two polymer need to maintain certain temperature when colliding.

Or they end up being partly solidified and this will not bond sufficiently when melting thus results in the weld lines.

You can avoid this by raising the temperature of material to prevent partial solidification and increase the speed and pressure too.

Remodel mold to ensure you eliminate the partitions and then switch to or material that has decreased melting temperature to enable faster flow.


Its deformation in molded part occurring when an initial jet of molten matter injected into mold cavity then starts solidifying before cavity is filled.

Is caused by excessive injection pressure, squats faster through the gate other than fill up in old cavity gradually.

You prevent this by reducing the injection pressure to help prevent the fast squirting of matter into mold cavity.

When you elevate the temperature of material mold, you keep the initial jet of matter cooling to solidify early.

You can also design the mold with injection gated location to be, that the material is directed across mold rather than lengthwise.


Another name is color streaking, it occurs when molded components of a different color than the actual intended color.

Its usual limited to colored area and the defect then affect the appearance of the component without actually decreasing the strength.

The common cause of this is leftover pellets inside hopper or residual resin in nozzle or mold that’s from previous production run.

When there is poor thermal stability of the coloring agent or improper mixing up the master batch causes the discoloration too.

You prevent this by cleaning properly the hopper nozzle and mold between productions.

This is to help rescue the residual pellet.


These are thin layers on the exterior surface of molded component that easily separates or peels off the underlying material.

Cause of this, there is usually contamination of resin pellets with foreign material, flaky separation is because of improper bond between two materials.

You can prevent this by increasing the mold temperature or pre-dry the material properly if excess moisture is an issue.

5.  PS Injection Molding Parts And Components.

Optical Industry

Because of the feature of good light transmission it is utilized to fabricate optical glass and optical instruments, transparent ones and brightly colored.

Electronic Appliance

Connector, switch parts, household appliance accessories parts, small electric cover or heat resistance, flame retarded, electrical insulated molding process ability.

Automotive Electrical Parts

Automotive ignition coil stranded tube and variety electrical connectors.

Machining And Equipment

Electronic computer cover, mercury lamp cover, iron cover, backing machine pats and a large number of gears, cams, and buttons, electronic watch housing.

Food Packaging Industry

Beverage over-caps, conveyor system components, beverage filtering components, food and beverage containers,

PS injection molding components

PS injection molding components

6.  Injection Molding Of Polystyrene Conditions And Specifications.

It becomes a liquid a melting point of 410- 450 degree Celsius once cooled t can be reheated again with degradation.

Tensile strength is 700ps1 important to halt determine the breaking of material under tension.

Injection Molding Temperature 100-150 F degree

Impact strength-0.8 ft- notched 120d

Hardness level; R75

Flexural strength- 1200PSI

Shrinking Rate; 0.3-0.7%

7.  Injection Polystyrene Process

The main process here involve:

Step1; Closing The Mold After Fill Up

After filling the mold the cycle timer usually starts the process of heating the polymer matter that’s inside the mold.

Step2; Injection

Heated polystyrene is injected into mold cavity as it enters displaced air escapes through vents in injection pins and along parting line.

Runner gate and vent design are vital to make sure that the mold is filled up properly as needed for the process.

Step3; Cooling

Once mold cavity is filled, the component is then cooled to solidify into a tangible component each mold has cooling lines.

Step4; Plasticizing the polystyrene

While the part is cooling, the barrel screw retracts and draws the new polystyrene molten into barrel from the material hopper.

The heater bands then maintains the required barrel temperature for the bend of resins being utilized in the barrel.

Step5; Ejection

The molds opens and the ejector rod then moves the ejector pins forward and the part falls into bin below mold.

Step6; Removing Runner And Packaging

Then separate the good parts from the leftover runner, then they are weighed, counted and package for shipping or assembly.

polystyrene injection molding process

polystyrene injection molding process

Polystyrene Injection Molding Technologies

Some of the most common technologies include:

Structural Injection Molding

Suited for larger plastic parts, it’s of low pressure injection molding process where inert gas is brought into molten polystyrene.

The reason for doing this is to help decrease he density and weight of the finished product while elevating the strength.

structural injection molding

structural injection molding
The lower pressure enables more efficient molding equipment and tooling to be utilized resulting in the mass production in a single machine.

Gas-Assisted Injection Molding

Parts that actually have heavy walls for structure and durability has a risk of breaking and wrapping as the components cools.

Cooling doesn’t take place at same rate for wall thickness or uneven cooling leading to a part being messy after cooling.

Gas assisted injection molding
Gas-assisted injection prevents wrapping and distortion by injecting pressurized gas into plastic material-filled injection mold.

8.  Polystyrene Thermoforming Vs Polystyrene Injection Molding

Here is what you need to know between these two processes:

Polystyrene Thermoforming

This process involving large sheets of polystyrene heating and fitted over custom tool then utilize vacuumed forming or twin-sheet forming to achieve shape and design.



Vacuum Forming

Involves use of  vacuum  that is fitted between tool and plastic, suctioning out all air in between the melted plastics  while pulling thermoplastic filmy against tool thus giving a shape.

vaccum forming

vacuum forming

Pressure Forming

This is same method as vacuum forming but utilized with high pressurized air to achieve detailing on surfaces and corners.

pressure forming

pressure forming

Twin-sheet Forming

The most complex impact polystyrene thermoforming method where two sheets is heated simultaneously then fitted and fused together.

twin sheet forming

twin sheet forming

Polystyrene Injection Molding

Works by melting polystyrene into molten liquid then inject into double-sided mold with extremely high pressure once cooled product is labeled.

9.  PS Injection Molding Temperature

Ranges from 179-260 degree Celsius, injection temperature is not suppose to be too high.

10.  Choosing Polystyrene Injection Molding Machine

Look at the shot size

  • Tonnage
  • Platen size
  • Tie Bar Spacing
  • Ejector –Strike.

11.  High Impact Polystyrene Injection Molding Vs Expanded Polystyrene Injection Molding

Here is all you need to know:

High Impact Polystyrene Injection Molding

It’s ideal for small plastic parts and products especially those needed in large quantities.

Expanded Polystyrene Injection Molding

It’s light in weight 98 percent made up of air and used as packaging material to help reduce total product weight.

12.  Selecting Best Polystyrene Pellets For Injecting Molding

Depending on Some products, you require;

  • Material that can handle high heat, chemicals.
  • Some need FDA approval
  • Some need crystal clear.
  • Strong to hold weight
  • It should be of the best quality

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

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