Archive: Feb 2021

5 Benefits of Working with a Full-Service Injection Molder

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5 Benefits of Working with a Full-Service Injection Molder 

Benefits of working with a full-service plastic injection molder

If you’re looking to produce a new plastic part, you might think you need to find one vendor for each phase of the project. However, choosing a full-service plastic injection molder that can do everything under one roof has many benefits.  

In-House Expertise

A full-service manufacturer has access to specialists that can assist with everything from design to production troubleshooting. These specialists are dedicated to their craft and can provide highly-focused solutions. This means you’ll be working with a team experienced with handling various design and production situations with clients across many industries.

Time Savings

Time management is an important part of every project. Much time can be wasted when you use several different suppliers to bring together your project. When it’s all under one roof, the project moves seamlessly from one step to the next. 

Hiring a full-service plastic injection molder can also help your team allocate enough time to their primary functions. Having everything you’ll need from idea to production and delivery in one place will help you meet deadlines and keep your project on track. 

Consistent Quality

When you have several “irons in the fire,” sometimes it’s hard to communicate exactly what you want to achieve through each stage of the project. A full-service molder can ensure that the design is manufacturable and that the final part is consistently within all visual and functional parameters needed. 

Long-Term Strategic Partnership

Full-service manufacturers provide more than just mass manufacturing capabilities. They strive to gain a better understanding of your products, your company, strategies, and preferences. Where single-service suppliers offer a transactional experience, full-service manufacturers are problem solvers dedicated to helping your project succeed over time. 


Having everything in one place is convenient, eliminates paperwork and recordkeeping requirements. This is especially important if you run into production issues in the future. Your full-service plastic injection molder will be able to easily access your original design files, collaborate with their expert team, and solve the problem quickly without waiting days or weeks for another supplier to send files or consult on design issues. 

Selmax Corporation is a Full-Service Plastic Injection Molder 

Selmax offers services through all stages of product development including: Design, Rapid Prototyping / 3D Printing , Mold Development, Production, Assembly and Distribution. 


Selmax takes great pride in meeting the most stringent design, material, color, and delivery requirements for our customers and providing solutions through each stage of the product development process. We have been serving customers in the construction, home consumer product, industrial/tool, outdoor sports, and toy markets since 1971. 


If you’re ready to bring a new product to market, call us at 1-800-860-3205 or request a quote

Plastic Part Design: 6 Considerations

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Plastic part design for injection molding requires several considerations to ensure that the part is moldable while reducing the risk of costly mistakes.

Plastic Part Design

Part of the appeal of plastic injection molding is the ability to produce thousands to millions of uniform, high quality parts at low cost so you can optimize project profit margins. At the beginning of any plastic part design project, it’s important to review all design considerations to avoid problems and reduce the cost of parts. Even the smallest mistakes can affect tooling costs, increase part costs, and cause problems with molding performance. 

Moldability guidelines for plastic parts recommend looking at the big picture of the plastic part design. It’s important to consider everything from materials that will be used to size to surface finishes to custom color matching needs.

6 important considerations when designing plastic parts

1. Wall thickness

One of the most fundamental rules of plastic injection molding is that parts need to have uniform wall thickness to avoid sink, warp, or even parts that are non-functional. Designing proper wall thickness into the part will reduce the risk of cosmetic defects in the finished part. Walls should be within the recommended thickness ranges for the material that will be used. Walls that are too thick are susceptible to sink. If extra strength is needed, supporting ribs should be added instead. 

2. Ribs

When a part needs to be more rigid or stiff, adding ribs into the design can increase strength and load bearing capabilities. It’s important to keep in mind that rib thickness should be less than the wall thickness, typically 40% to 60% of the adjacent wall. If a thick rib is needed, the center of the rib should be cored to allow for uniform wall thickness. 

3. Draft

Applying draft to the faces of the plastic part is essential for ensuring the part is moldable. Technically speaking, draft is the angle in which the part is tapered to allow it to release from the mold. Draft is designed into every plastic injection molded part in the direction of mold movement. It allows the parts to eject from the mold properly and prevents bending, breaking, and warping due to mold stress.

4. Bosses

 A boss is a raised circular rib that is typically designed into the part to help with assembly, as a receptacle for a screw or a pin from another part. While bosses need to be thick enough to perform at the strength needed, they usually shouldn’t exceed 40-60% of the thickness of the wall from which they protrude. If your part requires more strength than that would provide, it’s better to surround the boss with gussets to strengthen its walls.

If the boss is placed close to a vertical wall, it should be anchored with one or two ribs to prevent unnecessary thickness that can result in sink. It’s also important to design draft into each boss to facilitate ejection. Sometimes, shorts or burns may form on the rim of the boss if vent pins aren’t added to allow for trapped gasses to escape during the mold filling process. 

5. Radius

Sharp corners don’t typically mesh well with plastic injection molding. A radius can prevent a sharp corner that would otherwise cause unneeded stresses, inhibit material flow, and reduce part strength. Radii should be designed with material selection and end part use in mind.  

6. Gate location

The gate is the opening where the molten plastic flows through into the mold cavity. This area can leave behind a remnant that may need to be trimmed by hand after it ejects from the mold. Depending on the style of gate, the plastic used, and the part geometry, the gate should usually be designed into a non-cosmetic area of the part. It is critical to consider gate location in the design phase because it can ultimately make or break the project. Choosing the right type of gate and location can also affect many other areas of the project. 



Part Design For Plastic Injection Molding

Other Considerations for Plastic Part Design

It’s always best to work with a seasoned injection molder when designing your plastic parts, especially when they are complex or need to pass specific performance tests. 

Some common questions a design engineer will ask:

  • How will the part be used? Is it a single product or a component of a bigger assembly?
  • What are the dimensional and tensile requirements?
  • Does the part need to withstand certain elements, pressure, or chemicals?

Spending time and effort on designing the perfect part now can save substantial time and money over the long term. 


Selmax offers technical consultation at the earliest stages of product design. We have quite literally started several customer projects from designs scribbled on napkins. 

We work closely with our customers to define the requirements of the finished product – physical dimensions, structural supports, custom engraving, color, texture and finishing.

Since 1971, we’ve been providing our customers turnkey solutions from design to delivery. Ready to discover the low-stress experience of working with a full-service manufacturer?


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Plastic Part Design