Bespoke Injection Molded Parts for Your Unique Needs

Table of Contents

custom injection molded parts machine
Custom injection molded parts machine

1. Introduction

For big manufacturing companies, the request for custom injection molded parts may not come often. But for DIY and low-volume injection molding companies, the crux of what they do is custom-made parts. However, both of these categories of manufacturers need to understand the creativity, artistry, and engineering brilliance required for making such parts.

Custom injection molded parts bear the uniqueness of brands while promoting quality service with innovative products. These parts are created to serve the needs of end users and industries according to specified designs and project requirements.

In this piece, we delve into the techniques and considerations that result in excellent and functional custom parts production. So, without further ado, let’s go.

2. Understanding the Plastic Injection Molding Process

To begin with, when it comes to custom parts and designs, there isn’t a better method to adopt for this purpose than plastic injection molding.

How so you may wonder?

Well, plastic injection molding comfortably and efficiently produces parts that suit different objectives and applications. The versatility of this marvelous engineering technique works in combination with its precision abilities. Also, the carefulness invested in fashioning the molds in the high-quality mold manufacturing industry accounts for the much-celebrated precision it offers.

Furthermore, adept technicians and designers have a massive influence on the handling of injection molding machines, further contributing to the remarkable results of the plastic injection process.

3. Types of Plastics for Injection Molded Parts

Having taken some notes from understanding the process of injection molding, the types of plastic materials used in the process become our next concern.

It’s interesting to find that plastic injection molding benefits from an array of plastic materials available for use. Frankly, plastic materials such as thermoplastics and thermosetting plastics are the best choice of materials to employ in this process.

With their ability to create various custom components, the reaction of plastic materials under injection molding differs as well. On top of that, considerations such as impact resistance, tensile strength, and excellent aesthetics must be factored in before making a material choice. These are the critical considerations that can make a significant difference in the success of your custom injection molding projects.

4. Temperature and Pressure in Molding

After high-quality mold manufacturing, injecting molten plastic into the mold is another core activity of the injection molding process. Its impact on quality cannot be overstated. Hence, the need to carefully monitor critical parameters like temperature and pressure at the point of molten plastic injection.

Temperature regulation ensures the plastic is melted at the appropriate melting point specified by the designer. Also, controlling the injection pressure maintains the even distribution of the molten plastic as it is injected into the mold.

The proper regulation of these factors culminates in a smooth, consistent, and functional component. What’s more, it creates a product with immense durability and superb structural integrity.

Let’s take it up a notch and examine how to achieve high-quality custom parts.

Quality injection molded parts
Quality injection molded parts

5. Achieving High-Quality Custom Injection Molded Parts

A non-negotiable part of custom parts is quality. However, the level of quality of these parts is often determined by the steps taken before, during, and after the plastic injection molding process. For a high-quality custom part, certain factors are necessary. And they are not limited to but include

  • Precision: Precision is at its best when the margin of error in manufactured parts is little or non-existent. This is a result of a fusion of professionalism and engineering artistry, especially when constructing a custom part. That being so, the use of sophisticated design tools to design custom molds is a prerequisite to achieving the desired quality. Moreover, the mold is the decisive element in injection molding. Consequently, precision is one step that should be considered at the beginning of the process.
  • Design Considerations: In a bid to achieve high quality in injection molding, designers work closely with customers to get a full understanding of their design needs. The design considerations are necessary to determine other factors including material selection. Moreover, other factors such as wall thickness and surface finish directly affect the outcome of the part produced.
  • Quality Assurance:  A functioning and management-supported quality management system must be in place as part of the whole injection molding process. This often includes quality assurance deliverables like quality plans and inspection test plans and quality control activities like visual inspection. Quality assurance guarantees that errors are quickly highlighted and fixed during and after the production run.

6. Managing Lead Times

The idea of lead times in manufacturing, especially with precision-based methods like high-quality CNC machining and custom injection molding is quite essential. It helps manufacturers monitor the beginning of a production run up to the delivery of the products manufactured.

When dealing with custom injection molded parts, the lead time commences from the customer’s order to the delivery of the parts ordered.

Several strategies are useful to manage this production parameter. And first of all, is understanding the complexity of the part to be produced. The more complex the design, the more time of completion is likely to increase. Once the complexity of the project is duly understood, then proper planning can commence.

Planning in managing lead times includes identifying and selecting material, part requirements, and mold design. Concluding on all these factors then leads to scheduling a production time.

Ultimately, a manufacturer with a simplified production run might be the best choice for managing lead time. Also, ensuring that there is accurate communication between manufacturer and customer encourages completing projects within the estimated time frame. With the necessary progress report constantly relayed in an effective and efficient communication line.

Compliance with these strategies helps to deliver your custom injection molded part within a specified duration.

7. Injection Molded Parts’ Design Considerations

Frankly, manufacturing custom injection molded parts can be seamless. It’s only a matter of aligning your project requirements with the objective of the part to be molded. One such project requirement is the design considerations necessary to aid the seamless production of your custom injection molded part. They include

  • Mold Design: Mold design kick starts the process of achieving excellence in custom injection molding. Most benefits if not all benefits are hinged on a carefully crafted mold. Mold design accurately crafted reduces production time, saves the cost of post-production, and eliminates chances of flaws.
  • Wall thickness: Just imagine creating a custom part with a thick wall, yes, that will strengthen the part produced but it may consume more material while cost is increased and vice versa. Nonetheless, balancing strength, durability, and material cost can still be realized, and that’s the reason for a proper wall thickness.  
  • Surface finish: How well your parts fit into each other is a function of the surface finish. Beyond that, functionality and aesthetics are likewise affected by the surface finish. Notwithstanding, with custom injection molding surface finishes are attainable according to requirements.
3D Printer Printing Head
3D Printing for custom mold

8. Customization with 3D Printing

3D printing is often at the core of getting the precision right when producing bespoke parts. In fact, 3D printing technology doesn’t just elevate your customization prowess, it redefines it as some designs often appear as nearly impossible. This is where custom injection molding thrives.

3D printing is a crucial tool for mold design to achieve near-impossible geometries as it can handle the complexity of the custom mold with a charm. This is why it is commonly referred to as additive manufacturing. The speed and accuracy at which a 3D mold printer creates a mold design and makes necessary iterations can be mind-blowing.

Moreover, the seemingly unattainable heights of mold designs for conventional mold making are seamlessly conquered by employing 3D printing in custom injection molding. On top of that, it does not incur needless extra costs like the traditional mold-making. With the use of 3D printing, custom injection molding is faster and parts can be available pronto.

Finally, flexibility becomes a child’s play with 3D printing. For mold designers who appreciate innovation and experimentation with different design complexities, say no more.

9. The Role of Mold Cavity and Injection Machine

How can we fully grasp the idea of injection molding if we do not examine the roles the mold cavity and injection machines play? These are the harmonizing tools of injection molding. Consequently, this would be a good place to start if you want your custom injection molded part to come to fruition.

Let’s begin with the mold cavity. This is a crucial element in the injection molding process that possesses the intended design of the component. It is for that reason mold designers devote abundant time and resources to crafting it. Any mistake committed while crafting the mold renders it unusable, and that increases production time and cost. In addition, within the mold cavity proper cooling, undercuts, and ejection is fostered.

Now onto the injection machine. This machine is the heart of the process. Injection machines as their name implies inject the molten plastic with controlled pressure at a regulated temperature. As a result, specifications such as injection speed and clamping force are crucial to the process.

When the injection machine is carefully picked according to your project specifications, and the mold cavity design is accurate, then you can be assured of seamless teamwork between both elements. That partnership would be one made in heaven.

Manufacturing equipment for molded parts
Manufacturing equipment for molded parts Source:

10. The Manufacturing Process

Having come this far, we deem it necessary to take you through a few more critical points on your way to a successful custom-made injection molded part. But right now, it’s a step-by-step drive through the manufacturing process. Let’s go

  • Mold Preparation: The manufacturing process begins with the mold preparation. Keeping it clean and ready for use. Note, that it must be free of any residue from the preceding cycle.
  • Material Selection: The project specifications dictate the material to be used. Once this is decided, the selected material is prepped and transferred to the hopper. The hopper represents a bowl-shaped container where melting takes place. If you have been following us, you’ll remember melting must be regulated to its required temperature.
  • Injection: Injection follows next, as the injection machine injects the molten plastic into the mold cavity. Once again just like the material, the injection machine’s pressure is regulated. This is to avoid short shots or overfilling that may impair the custom molding.
  • Cooling: Cooling comes next after injection, and this is done within the mold. Cooling systems are adequately infused to ensure proper solidification. Lack of this can result in shrinkage or warping.
  • Ejection: Ejection is carefully done to avoid damaging both the component and mold cavity. Ejection is aided by the ejector pins that push out the parts. Additionally, undercuts and tolerances allow the smooth ejection of parts.
  • Quality: Quality control maintains industry standards by testing and checking for defects both internally and externally. Once it is certified for shipment, it becomes ready for use.

11. Material Selection and Properties

As different products serve different purposes, the same applies to the selection of materials even in custom injection molded parts. Some components can withstand harsh conditions, same goes for the materials. But for us to comprehend in totality the importance of choosing materials for specific projects we must first understand its characteristics. Here are some material properties in various applications for different industries.

  • Biocompatibility: This is a material property common with medical devices and tools. In creating custom molded parts that are biocompatible, they must be safe for use when they interact with the human body. The best biocompatible material remains Polyether Ether Ketone (PEEK).
  • Temperature Resistant: For temperature-resistant materials, exposure to high temperatures does not compromise the features of these materials. Only materials such as Polyphenylene Sulfide (PFS) and Polytetrafluoroethylene (PTFE) can offer such qualities.
  • Chemical Resistant: These kinds of plastic materials are usually applicable to an industrial environment that deals with chemical exposure. Polypropylene and PEEK are materials that will give you your money’s worth in these conditions.
  • Strength and Durability: You can surely bank on ABS (Acrylonitrile Butadiene styrene) or Polycarbonate (PC) materials to provide you with strong and durable properties.
  • Flexible and Cost efficient: When creating flexible components silicon (Thermoplastic Polyurethane) is your best bet for elasticity. But if you’re in the market for a cost-efficient plastic material Polyethylene and Polypropylene are affordable materials you can use.

12. Ejector Pins and Part Removal

Let’s take you back a little to the manufacturing process where we briefly pointed out the role of ejection in the manufacturing process.

Ejection of the part from the mold is helped by an essential tool called ejector pins. They are typically infused within the mold to safely push out the part produced after cooling and solidification. A crucial step that requires perfect timing.

Without proper timing, the part could be damaged or deformed. Nonetheless, the part removal process occurs immediately after the part solidifies. A delay could result in difficulty removing the part, while quality is compromised if done too early.


Although we’ve come to the end of the road, let’s take a quick recap. Custom injection molded parts as we’ve established have their unique purpose. However, creating the custom injection molded part comes with a bunch of considerations. Some of these are material selection, design considerations, and attaining high quality.

 In material selection, the types of materials must be well understood. In design considerations, your mold design plays a huge role. Speaking of mold design, let’s not forget that customization of molds employing 3D printing offers a wide range of benefits. To cap it all, the manufacturing process becomes a marvel when all these considerations are fused together to create magic. And voila, there’s your custom injection molded part. 


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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