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Plastic Clip and Fastener Designs

Lightweighting continues to remain a top priority for automotive manufacturers in order to help them meet strict fuel-efficiency requirements or to help get them one step closer towards getting the most mileage out EVs battery.  One way tiered suppliers are going about this is by redesigning traditional metal clamps with well designed injection-molded clips and fasteners.

Design engineering a plastic part to replace without compromising performance equires expertise in design, material, tooling, injection molding, and validation testing.  In this post, we’re going to explore some of the designs that have become the go-to for tier-1s and OEMs over the years.

Designs to Choose From

There is a vast library of different fastening clip designs automotive manufacturers can implement and optimize. Many of these designs include small, intricate features (such as the tree, hand-grip, and rib-cage designs) that are all subject to flashing and packing issues.  Without proper setup and precision tooling, these issues can lead to performance failures

Ultimately, it comes down to design.  Improper spacing between features, not enough material, too much material in some spots, etc. … all lead to parts that down operate or cannot be manufactured.

Below we’ve listed out some of the most common designs and what they’re typically used for. Each one has its pros and cons.

Tree Insertion Design

Tree insertion designs on fasteners and clips have long been used for body panel attachments of all kinds. It is well-known to be a strong design, capable of higher removal forces. An injection molder needs to work diligently to minimize insertion forces without compromising on retention capability.

The intricate features of the tree design require special attention to the spacing between features and areas where there may not be enough material vs. areas with too much material.


Butterfly Tab Design

Typically installed into panel holes, the ‘Butterfly Tab’ design is an Echo favorite.

This design is perfect for hard-to-reach places and areas requiring minimal insertion forces during the final installation. We don’t recommend this design for fasteners holding multiple, large lines. A tree design has higher retention.


Latch Design

A clip with the lid/latch and living hinge design is a very common method of retaining lines.  Latch designs make insertion easy, yet provides a reliable, strong hold. Adding multiple latches to a fastener is recommended when a fastener holds multiple lines.


Hand-Grip Design

This style of fastener installs onto a stud (screw). The design features great reliability ensuring low installation forces., but it’s a less attractive option for tight space though due to its larger profile.

Automotive clip design

Rib Cage Grip Design

Rib cage-style fasteners install onto a stud (screw). This design sometimes has larger insertion forces than the hand-grips design (above) but has a smaller profile than the hand-grips, making it a better option for tight areas.

Automotive fastener molder

Rabbit Ear Design

Lines install into this. Best for small diameter lines. Great for small areas.

When a fluid routing line is inserted into this type of fastening device, the rabbit ear flap area flexes down, allowing for easier insertion, and then spring back into place in order to retain the line.

bunny ear clip design

Wedge Clip Design

Fluid routing lines install into this design. It’s best for packaging small diameter lines together in bundles. Not as good for retention at the vehicle-level.


Wedge Clip with TPE Insert Design

This design includes an over-molded TPE material that helps with reducing NVH, and limits both rotation and translation of the lines. The wedge type design makes this clip a simple assembly, yet it also provides reliable retention once the line is inserted.


wedge clip with tpe for metal lines

TPE Grip

Commonly used in a lid-latch configuration. The TPE grip is great for reducing NVH, and limiting both rotation and translation. This design has higher retention forces than the Rabbit Ears w/ Grip, but it’s a little more complicated to assemble.

TPE Grip on clip



Overall, while these are some of the most popular and effective fastening designs being used in automotive applications, the rise of EVs and Hydrogen Fuel Cell vehicles continue to disrupt the industry.  We’re far from over with optimizing and rethinking the way plastic is used throughout a vehicle.

To see Echo & Ammex’s Design Innovations for yourself, head over to our Contact Us form to schedule time with our team.

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Automotive trends with plastics

Automotive Trends: Converting Metal Brackets to Plastic Clips

With the rise of Electric Vehicles and more demanding fuel efficiency regulation being mandated, is metal becoming a thing of the past?

Plastic is increasingly being used in place of metal for many different purposes. Specifically, plastic clips are replacing metal brackets used on automotive fluid routing assemblies as mounting supports for HVAC and brake lines. Plastic clips are perfect alternatives in these automotive applications and many more.

Why are manufacturers looking to convert more brackets to plastic?

  • Plastics cost less than metal and less costly to manufacture
  • Ability to manufacture more complex designs
  • Weight reduction

Plastic clips have multiple benefits. In the following, we discuss the top advantages of replacing metal brackets with plastic clips.

Plastic Clips Cost Less

There are a variety of reasons that factor into why plastic fastening devices cost less than their metal counterparts.  A few of the major factors include:


Because plastic is lighter weight compared to steel, injection molded clips will cost less as heavier weights typically equal greater costs.


Compared to most metal brackets, the process of injection molding clips is typically way less labor intensive.  Metal fabrication will most likely include a variety of additional steps, including: cutting, bending, welding, metal finishing prep, coating.  Each of those steps can add significant costs to the project.


Tooling for metal stamping and forming has a much higher cost than tooling for plastic. The tools needed for plastic can cost up to 50% less, a huge reduction in cost.

The tools for metal also wear more rapidly and need to be replaced more often than the tools for plastic, creating even more additional costs.


A commonly overlooked factor towards the overall cost of a metal bracket compared to its plastic counterpart is shipping & handling.

When transporting metals, protective shipping products must be used in order to prevent damage, unlike most plastic clips, which don’t need much protection during shipment.

A more important factor going towards shipping is that plastic weighs way less than steel brackets, which we’ll explore in this next section.


If you were to compare a part made of steel to the exact same part made from thermoplastic, the plastic version could be up to more than 6 times lighter! Design changes will most like need to be made in order to successfully replace a metal bracket with a plastic clip, but most likely, there will be a significant weight reduction.

For example, most automotive line clips you’ll find are made from Nylon 6/6.  Nylon 6/6 typically has a  density of 1.14g/cm3. Compare that to steel, which typically has a density of around 7.85g/cm3.

So, with lightweighting being an automotive megatrend that has become incredibly important for OEMs as new fuel efficiency regulations are mandated, it’s time to explore thermoplastic alternatives in order to improve a vehicle’s efficiency and performance.

Plastic Clips are Non-Corrosive

Another element that can easily get overlooked is that metal brackets are more at risk for corrosion issues.  This corrosion weakens the metals over time, causing them to be damaged, resulting in potential liability issues.  Plastics, on the other hand, won’t corrode and are less likely to suffer from a chemical exposure.

A common issue that has to be addressed with automotive HVAC lines is preventing galvanic corrosion. Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte.  In order to combat that with metal brackets, the tier-two bracket manufacturer or tier-one HVAC line manufacturer must also source a non-conductive EPDM grommet, which is an unwanted additional cost.

By converting to plastic, automotive manufacturers are able to avoid this issue completely with the correct clip.

Plastic’s Versatility

Plastic is an extremely versatile material, unlike metal. Plastic clips can be made into complex shapes and in a variety of different colors straight from the start. This makes them basically ready to go right out of the tool.

Unlike plastic, metal almost always has to go through several secondary processes before it is ready for installation. Metal brackets usually have to be cut or stamped, drilled, formed, pre-treated/cleaned, coated to prevent rust, packaged appropriately, etc.

Metal may also need multiple components added or installed such as a fastener or an isolator. With plastic, all of those can be built in, eliminating the need of multiple parts.

How to Make the Conversion from Metal Brackets to Plastic Clips

If you’re currently exploring the option of converting to plastic, you’ll want to make sure you work with  a partner that has experience across the product design, tool design, validation, fulfillment spectrum, and will:

  • Design from scratch to meet your needs or work with an existing design and suggest changes to ensure all specifications are met
  • Take the time to understand the assembly parameters and is able to design and perform comprehensive test plans to match real world applications
  • Use FEA software to optimize the clip’s mechanical properties and eliminate potential failure points
  • Use mold flow analysis and tool design improve product performance and meet tight tolerances

About Ammex Plastics and Echo Engineering

Ammex Plastics and Echo Engineering have been investing heavily with the automotive fastening market by developing a library of different designs, hiring plastics and process engineers, adding additional presses, and purchasing new testing and measuring devices.

We are experienced in designing and manufacturing a variety of different automotive clips used on HVAC lines, brake lines, harnesses, etc.

Thinking of making the switch from metal to plastic? If you are or if you have any other questions, visit our Contact page and send us a message! We have a team of technical experts ready to find the best solution for you.


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The burden of hose connector part design and design for manufacturability has shifted from the OEM to the tier-1 supplier and their injection molding partner.  Throughout this post we’ll discuss the reasons behind this shift, what makes a fluid connector technically complex, and the expertise your molding partner needs to deliver a stable and repeatable part.

Design Responsibilities Shifts to the Tier-1 Suppliers

Engineering resources at automotive OEMs have shifted away from “classic” part design and toward strategic priorities, such as electrification.  As a result, the burden of part design and design for manufacturability is falling more and more to you—the tier 1 supplier—and your injection molding partner.  Since so much production has gone to low-cost countries it’s even harder to find a molding partner with local expertise in part design, tool design, and processing.

Automotive Barbed Hose Connector Specs Tighten

Fluid routing specs have really tightened over the past decade.  OEM teams tend to ratchet up roundness and concentricity specs every time an end-user failure occurs.  Now the specs on connectors are much higher than the hoses that they attach to!

It’s Challenging to Produce Round Plastic Parts To-Spec and On-Budget

Injection molding is a dance between quality, cycle time, and cost.  All three are tightly wound together.  Experienced tool designers and molding partners will tell you that it’s really tricky to produce round parts.  It looks easy but plays hard.  This is because residual stresses in the part can make it challenging to hit the specs, which can lead to longer cycle times to let the part cool, which can increase the cost.

Residual stresses can warp round parts (like fluid connectors) after they are released from the mold.  This can be offset by exotic materials and longer cooling cycles, but that also drives up cost.

Early Recognition of Complicated Fluid Connector Designs Is Crucial

Some design elements can make a fluid connector very tricky to produce on-time, on-budget, and to-spec. These include varying wall thicknesses, sharp transitions in geometry, small port sizes, and unreasonably tight tolerances/ GD&T specs.

The trick is to spot these very early in the quote process, and a top-notch molding partner will do just that. Catching it early is key because small changes to part design can avoid headaches down the road. These headaches can include very long PPAP time lines, high PPM rates, and having to ask the OEM for a deviation.

Injection Molding Tool Design Can Offset Complex Geometries

Hopefully most recommended design tweaks can be accommodated.  If not, an experienced injection molding partner can overcome many challenges through tool design.

Quality tool engineers can balance melt flow and reduce cycle times with hot runner systems, increase cooling capacity with copper cores and forced air flows, and produce precise round parts with out-of-round tools (what??).  Yes, you read that correctly.

Depending on the part design, material flow, and residual stresses, sometimes it takes an out-of-round tool to produce precision round parts like fluid connectors.  Molding partners that don’t know this can set themselves and their customers up for a very long and hard journey.

Finding the Right Injection Molding Partner

If getting the fluid connector done right is your primary driver, then make sure you choose the right molding supplier.  If they aren’t asking you lots of questions about wall thicknesses, sharp transitions, knife edges, tolerances & technical specs, gate locations, and materials, then they probably are not doing an in-depth part feasibility up front.  That should send off warning bells.

Ammex Plastics has been tooling up and supplying hose connectors for 20 years, has shipped millions of parts, and runs at a PPM rate of <2.  If you’re looking for a new or alternate molding partner, head over to our Contact Us page today, and we’ll get back with you ASAP.

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