Injection Molding Plastic Parts for any Project

Injection molding is a manufacturing process for the mass production of simple or complex plastic parts in huge quantities. The primary advantage of injection molding for a project is its ability to scale production. In the case of injection molding, the production costs tend to dramatically decrease as more plastic parts are produced.   

Injection molding can often be perceived as daunting if correct guidance or right information isn’t available. In this article, we have enlisted injection molding details for any project.

Table of Contents

Injection Molding - What you need to know

Sets and Components

An injection molding process for any project consists of 3 components and 2 sets. 

The 3 components are as follows: plastic resins, an injection molding machine, and a mold. 
The 2 sets are as follows: Injection and Clamping 

  • Injection: The injection set includes the hopper for the plastic resins and the barrel which melts the plastic.
  • Clamping: The clamping set includes the mold for solidifying the liquefied plastic resins into finished plastic parts. 
setting up an injection machine

The Molding Machine

Injection molding machines are usually laid out horizontally. The following image illustrates the sets and components of an injection molding machine:

injection molding machine
  • An Injection molding machine includes a barrel which is a cylindrical pipe. 
  • The hopper is located at one barrel end. 
  • The heater is located on the barrel. This heater melts the plastic resins that are released from the hopper.
  • The mold consists out of a fixed half and a moving half. The moving half is attached to the clamping unit.
  • The mold cavity is located inside the mold. 
  • For most molding materials you want to achieve shorter cycle times by cooling the mold cavity sufficiently. The cooling tubes are connected to an external water supply.

How is it done?

Injection molding is carried out by first melting the plastic resins in the injection unit. The melted plastic is then injected into a high-quality steel mold. The plastic cools here which is then solidified into the final plastic part. The following entails injection molding steps that ensure that the process is smooth and seamless: 

  • First step would be to review the injection molding quote. 
  • A thorough consultation should be carried out upon various parameters to ensure that all the specifications of the project are met. These include, but are not limited to the project requirements, preferred lead time and budget. 
  • The manufacturing starts only when various details such as materials, components, an approved design etc. are established. 
  • Upon finalizing details about the project, a high-quality injection mold is built. 
  • Once the mold is built, a first part samples (T1) report is sent for approval. This also generally includes a First Article Inspection Report (FAIR) according to the required dimensions of the project.
  • Once the mold is refined as per suggestions, approved, and the part is within all critical tolerances, injection molding process for the production of plastic parts can be commenced.

Design Guidelines Checklist for Plastic Part Injection Molding

There are certain guidelines that should be adhered to in order to ensure that the plastic parts manufactured are of the required quality. 

The following list includes a checklist of such parameters: 

  1. Material Selection: Material selection is an important aspect as it helps to produce parts that are not only functionally operative but also durable enough to withstand environmental conditions. It should always be carried out keeping in mind the extent of the application. 
  2. Maintain a Uniform Wall Thickness: The next critical factor to ensure smooth and successful manufacturing is maintaining a uniform wall thickness so that there are no weakened spots.
  3. Rib Design: The next factor contributing to the plastic part’s stability in injection molding is rib design. It increases stiffness and durability in the plastic part without increasing the wall thickness.  
  4. Design Elements: In order to ensure that the product manufactured through injection molding is further durable and can withstand endurance, various design elements such as bosses, weld lines, vent placements and gate placements should be considered. 

A Molding Approach for any Project

Here are some basic inquiries that must be made while approaching any injection molding project: 

  • Open and Clear Communication –  One of the first and primary qualities to look for is the ability to communicate effectively and transparently with the project team. 

The following queries can help you understand the reliability of the injection molding company: 

  • Understand if the series of events are detailed enough or if they are simply an overview.  
  • Are they open enough to receive feedback upon the design or does it stop right, after the first round of drafts? 
  • Are they willing to send prototype samples? 
  • Does the team at your end have a way to contact and connect with the engineer/manufacturer to communicate? 
  • Are they willing to update upon the progress of the project/mold making at regular intervals? 
    • In-house Mold Making Services – The next aspect to look for is to understand whether they have their own in-house mold-making services. This aspect helps to manufacture optimum quality molds which ensure better lead time on a project. 
  • Certifications: Certifications such as ISO 9001 ensure that standard regulations are being adhered to for producing plastic parts for any project. They are often an indicator that the products manufactured will be consistent with high quality. 

 

Injection Molding Materials

Imidized Materials

Imidized materials are high-performance plastics with high resistance to steam, chemicals, and temperature. The most notable feature of imidized plastic materials is that it has a high resistance to temperature. Imidized materials are usually considered for high-temperature applications of 500℉. We have listed below imidized materials: 

  • PBI, abbreviated for polybenzimidazole, is a thermoplastic injection molding polymer and it offers the best wear resistance of any other thermoplastic.
  • PI, abbreviated for polyimide, is a polymer of imide monomers. It is great for insulation as it has excellent dielectric properties. In addition, it also has excellent wear resistance and stable chemical properties. 
  • PAI, abbreviated for polyamide-imide, is an amorphous, thermoplastic. It has a high creep resistance and extremely low coefficient of friction. This property provides excellent dimensional stability. 

Advanced Engineering Materials

Advanced engineering materials are plastics that are specifically engineered to exhibit enhanced properties. They are manufactured to include superior performance over other plastics. Some examples of advanced engineering materials are as follows: 

  • PEI, abbreviated for polyetherimide, is a high-performance thermoplastic. It is used in various applications and has various advantages such as heat resistance, stiffness and stability. 
  • PEEK, abbreviated for polyether ether ketone, is one of the most versatile, and popular injection molding materials. It is a high-performance thermoplastic. It is ideal for medical applications as it is tolerant to sterilization processes and gamma exposure.
  • PTFE, abbreviated for polytetrafluoroethylene, is corrosion resistant. Due to its excellent chemical properties, it is widely used in the medical and electrical industries.
  • PSU, abbreviated for polysulfone, is an amber-colored amorphous plastic. Polysulfone is also often used in the medical and food industry as it exhibits excellent resistance to steam.  

Engineering Plastics

Engineering plastics are designed to withstand extreme environmental conditions and thus, have better mechanical and thermal properties than other commodity plastics. Some examples of engineering plastics are listed below: 

  • Acrylic is a popular injection molding material that has excellent optical clarity. It is a clear thermoplastic homopolymer that has outstanding strength. It is also scratch-resistant which is why it is very popularly used for the application of various consumer goods.
  • PC, abbreviated for Polycarbonate is a polyester of the carbonates. It is an amorphous engineering material that has exceptionally high resistance to impact and heat. 
  • PPO, abbreviated for polyphenylene oxide, is a type of thermoplastic. It is suitable for a variety of applications as it has a great balance of thermal, mechanical and electrical properties. 
  • POM, abbreviated for Polyoxymethylene is produced by the polymerization of formaldehyde. It is also referred to as acetal and is a semi-crystalline thermoplastic. It has excellent rigidity and a low coefficient of friction which gives it great dimensional stability. 

Standard Plastics

 Standard plastics are general-purpose plastics. They have good bonding and great formability but they have a low-stress resistance as compared to the other plastics. Some examples of standard plastics are listed below: 

  • PP, abbreviated for polypropylene, is known for its tough and flexible properties. It exhibits excellent resistance to chemicals and electricity which is why it is widely used for medical and food industry applications. 
  • ABS, abbreviated for Acrylonitrile Butadiene Styrene, is a polymer made up of three monomers: acrylonitrile, butadiene, and styrene. It is a type of thermoplastic polymer that is recyclable and ensures the reproducibility of results. 
  • PVC, abbreviated for polyvinyl chloride, is a common thermoplastic material. It exhibits excellent dimensional stability and has great dielectric properties. 
  • HDPE, abbreviated for high-density polyethylene, is resistant to impact and has strong durability. It is a versatile plastic that can be used to manufacture a variety of consumer goods. 
  • LDPE, abbreviated for low-density polyethylene, is a type of plastic that’s lightweight, soft and flexible. LDPE should only be used in low-temperature applications as it is prone to degradation at high-temperature. 

Products made by Injection Molding

Today, injection molding is one of the most preferred processes for mass-producing plastic parts due to its high output rate and consistency of quality. It can be applied to a multitude of daily use products such as:  

  • Automotive Parts: Dashboards, bumpers, grilles.
  • Electronic Components: Electrical connectors, enclosures.
  • Furniture parts – Sofa, Dining table accents, Chairs.
  • Medical Devices – Petri-dishes, syringes and valves.
  • Consumer Goods – Mobile phone cases, bottle caps, toys.

The above list is only inclusive and not limited. Injection molding can be used to make a wide array of products across various industries.

Advantages and Disadvantages of Injection Molding

Advantages

  • It’s highly efficient in terms of production. Molds can be set to have numerous cavities so that quality plastic parts can be produced in quantity.
  • It’s a repeatable process, which leads to a consistent quality of products.
  • The output rate is high due to fast production. 
  • It can be a completely automated process. The entire process is performed and completed in an injection molding machine thus, the process is easy to automate for any project.
  • Manufacturing complex plastic parts that require high-precision is possible through Injection molding as it applies high pressure. 
  • Injection Molding can be modified for any project to include more than one type of material through co-injection.

Disadvantages

  • It’s not cost-effective for small batches.
  • Each and every technical aspect needs to be ensured as the quality of the plastic parts can be affected by various factors.
  • It is imperative to design the molds to a high standard, which takes skilled workers.
Contact VEM for any Queries

VEM Tooling encompasses an extensive experience in injection molding plastic parts. If you have a query regarding a project about injection molding, please feel free to reach out to us. We would like to understand the task at hand and provide you with any guidance.