5 Things to Know Before Buying custom plastic molding

04, Aug. 2025

 

5 Hints You Have The Right Injection Molding Manufacturer - Cadrex

February 1,

When it comes to choosing the right plastic injection molding manufacturer, it can be hard to know what you don’t know. Who do you trust? How many questions should you ask? What questions, specifically, should you be asking? With so many variables at play, it’s a challenge to feel like you’re choosing the right manufacturer.

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However, based on our decades of experience, we’re able to confidently say the best manufacturers have five major characteristics in common:

  1. DF(x) Engineering
  2. Assembly, Painting, and Secondary Options
  3. Supply Chain
  4. Automation and Robotics
  5. Tooling Design and Maintenance

To make your choice a little easier (and ease some stress), let’s take a closer look at all five.

1. DF(X) Engineering

Short for “Design for Excellence,” DF(x) is a group of design principles that are key to design success. In our experience, the most important values for x include these four critical elements.

Cost

Some designs include cosmetic details that don’t add to functionality, but definitely increase cost. While some parts of a product are imperative for the part’s functionality, non-functional details can be costly. Just as one example, a simple lifter or slide will increase the cost and cycle time of your tool by increasing labor costs. As a whole, a simple design addition makes the entire part more expensive to manufacture. An experienced manufacturer should be pointing out design areas for cost savings, not building in cosmetic details that do little in the end.

Quality

Cosmetics, however, can add to quality as well. It’s important that your manufacturer is looking at the parts within the product that are critical to the tolerances and quality required to be a functioning product. If any of those fail, you’ll never hit your tolerances or functionality, making it impossible to hit your quality requirements.

Material

Experience with specific materials is important. Certain materials act differently inside different injection molding presses. Experienced plastic injection molding manufacturers not only know this, but they understand the nuances different materials bring to the table.

Additionally, your manufacturer should not just be designing for specific materials, but should be helping with material selection too. While a specific material might sound great to you, an experienced manufacturer will know that a less expensive option may still offer what you need.

Manufacturability

Ultimately, you have to make sure your product is actually manufacturable. The way you intend for a product to function has to be compatible with the way you want to manufacture it.

Some plastic injection molding manufacturers will simply build your product the way you designed it without pointing out potential issues. But once hot plastic is pushed into a steel tool, you’ll want someone with the kinds of experience to ensure you get the product you desire, without later issues that become costly to correct. Draft and radii are important elements to build into the design along with identifying possible sink areas.

To learn about injection molding design tips, check this out.

2. Assembly, Painting, and Secondary Operations

Many products will require secondary finishes after parts come off the line. It’s important to consider whether your manufacturer has the ability to assemble your product in-house or apply finishes right away.

Keep in mind, also, that manufacturers who outsource secondary operations will have to ship your products and manage those operations on your behalf. Multiple touchpoints can increase the risk of damage. It becomes much harder to expedite shipping. You open yourselves up to quality issues. And, in the end, you’ll need longer lead times

If your product will need to be painted, pad printed, silk-screened, hot stamped, coated, or plated, it’s good to know in advance whether your manufacturer will be handling those processes in-house or if you need to outsource those processes.

3. Supply Chain

It is critically important to have a plastic injection molding manufacturer with a well-rounded supply chain team, especially if you have a product that requires assembly. Look no further than the very long supply chain issues for the COVID vaccine for evidence of the impact of supply chain issues. The manufacturer should be well connected with resin suppliers and be able to manage purchasing and lead-times of components that are required to assemble your product.

Part of working with a manufacturer that has extensive supply experience is knowing where your end-ship location is. If the final destination of the product is going from the manufacturer to Atlanta, but you’re manufacturing in China, you could be facing a number of environmental, time, cost, and logistical impacts. If your product is being shipped throughout North America, you should definitely be considering a North American manufacturing partner.

4. Automation and Robotics

How advanced is your injection molding manufacturer? Does your injection molder have the capabilities you need to produce your product — the right size machines, enough capacity, ability to scale your program?

In the end, you’re trying to create high-quality molded parts with the most cost effective production processes. Automation and robotics can help speed up and simplify the plastic injection molding process, resulting in more efficient cycle times, reduced manual labor costs, decreased waste, and increased part precision.

It's important to ask your manufacturer if they have invested in automation and robotics, if they're looking for ways to improve their processes for their customers. Make sure to partner with a molder who is innovative and can keep you ahead of your competition.

To read more about the benefits of automation and robots, check this out.

5. Tooling Design and Maintenance

Domestic

If you need something fast, having a domestic manufacturer handle your tooling is the way to go. You might have to pay a little bit more in the long run, but it’s because everything would be manufactured state-side, you’re able to cut leads times, meaning you get to market faster. And if you’re a company who values U.S.-only solutions, this is really your only choice.

Are you interested in learning more about custom plastic molding? Contact us today to secure an expert consultation!

International

If you choose an international manufacturer for your tooling, cost savings is the most obvious advantage, here. It’s possible to achieve decent lead times as well. Don’t forget, though, that at the end of the day, whatever you build still has to be put on a boat and shipped. It will take time, often weeks. Weighing this against cost savings is often overlooked.

That said, it is possible to find an inexpensive, but quality resource with decent lead times. However, they will require a lot more vetting than a domestic manufacturer will.

It's important your injection molding manufacturer can navigate this for you. They should have trusted domestic and international suppliers as well as experienced tooling design engineers on staff. Here at Cadrex, we’ve visited all of the facilities we use in North America and Asia. We can personally vouch for them and their quality.

In-House Maintenance

When it comes to taking care of your tool, it’s really important that you work with a manufacturer who can provide in-house tooling maintenance. There is never a “perfect tool.” Things will happen and tool maintenance will be required. In fact, preventative maintenance should be part of your manufacturers routine.

Because your manufacturer is deeply embedded in the process, they will be able to pay more attention to your project, ensuring the quality of the tool will work within your desired manufacturing environment.

To learn about injection molding tooling design tips, check this out.

5 Steps to Finding a Custom Plastic Injection Molding Partner | Thogus

Before you can begin to work on any custom plastic injection molding project, you need to find a manufacturing partner you can trust whose capabilities match your needs. Plastic injection molding is not a one-size-fits-all process, and your requirements may vary based on your industry, the design of your products, or your production schedule.

For example, medium- to high-volume projects require a partner that can handle fast production on a large scale. Specialized or custom parts require expertise and ingenuity to make sure that your parts are manufactured properly. All projects require access to the equipment, materials, and expertise necessary to create high-quality parts.

Custom molding is all about communication, and that requires buy-in and commitment from you and your manufacturing partner. Sometimes designs need to be adapted, or production changes occur at the last minute. That means that you have to focus on the people that you’ll be working with (not just the products you’ll be working on) to avoid the delays and headaches that come with a communication breakdown.

Here are five steps to finding a custom plastic injection molding partner that’s right for you.

Step 1: Plan for your product

Your manufacturing partner should provide the expertise you need to carry out your vision for your project. To begin building this relationship, you need a reasonable understanding of the function you want the part to fulfill, the circumstances in which it will have to operate (i.e., high heat, extreme cold, humidity or wet conditions), and an estimate of the number of custom parts you’ll require.

If you need 10,000 units or fewer — to fill a need in a low-volume market such as highly specialized medical equipment, for example, or to begin prototype testing prior to full market production — then you are looking for a low-volume molder. Larger-quantity jobs that require hundreds of thousands of units should be handled by a high-volume molder who is capable of producing many parts quickly and efficiently.

With your vision in mind, your manufacturing partner should provide services that can help you bring it to life. Look for a manufacturer who can begin providing feedback early and whose expertise aligns with your understanding of the function and volume of your project.


Step 2: Examine the company’s facilities and material availability

The complexity of your project will greatly impact your choice of manufacturing partner. The manufacturer you choose should have experience running the selected material and capabilities to satisfy all requirements. Consider the following when evaluating potential production partners:

  • Do they have the proper equipment to satisfy all program requirements (i.e. injection molding machines, material handling, automation, etc.)?
  • Do they have qualified team members with experience running similar projects?
  • Does their facility satisfy all regulatory requirements (i.e. ISO, FDA, clean room, etc.)?
  • Do they have experience running the selected resin and materials?
  • If your program requires value-added services like assembly, do they have experience with similar projects?
  • For larger volume programs, do they have systems and processes in place to successfully manage the flow of material

Step 3: Ask about ISO Certification

Whatever your production needs are, you want to make sure that you find a manufacturer who will create a reliable product for you. Consider finding a manufacturing partner who holds a certification from the International Organization for Standardization (ISO). Such certifications are both optional and difficult to obtain, so only manufacturers who are truly committed to product quality will hold one. This can be a quick and efficient way to identify a short list of high-quality companies.


Step 4: Look for experience

An experienced manufacturer can help you anticipate problems and offer solutions in advance. Look for a manufacturer who has experience running and launching programs similar to the one you are trying to launch. Not only will this experience bring expertise to your project, but it also ensures that the manufacturer you choose has the equipment and infrastructure necessary to do the kind of work you’re planning.

Personal experience is important as well, so look for a company with experienced professionals at all levels to make sure that you have access to the quality of work that you need.


Step 5: Decide on the kind of relationship you want to build

Commodity relationships are typically based on the lowest price due to little or no value-added requirements. Commodity relationships typically have reliable forecasts, objectives and quality requirements (and therefore are easily measured), which makes satisfying customer requirements relatively easy.

For projects that are not super simple and straightforward, you want to build a more complex relationship that allows flexibility to adjust to evolving project demands. In short, complex projects require a partnership built on successful, ongoing communication. These partnerships allow you and the manufacturer to work together to adjust the manufacturing process and determine appropriate quality standards for your unique project. When forming a partnership, look for an experienced manufacturer who communicates clearly and frankly, with minimal personnel shifts. Whenever possible, you want your contact person to stay the same throughout your working relationship.

It is important to choose a manufacturing partner who you can work with productively, and who can ensure the delivery of high-quality products. At Thogus, we pride ourselves on building client relationships and offering white glove service that keeps operations running smoothly. Download our free PDF to learn other considerations:

Contact us to discuss your requirements of structural foam molding. Our experienced sales team can help you identify the options that best suit your needs.