Success Story

Creating a Composite Battery Insert-Stud Solution for EV Trucks

Bossard worked with an OEM and its tier supplier team to meet tight electrical insulation and packaging tolerances while reducing tooling, molding and assembly costs.

Hybrid electric truck charging at station. 3D rendering.

The Challenge: Creating a Composite Battery Insert Stud Solution for EV Trucks

EV OEMs face challenges due to fragmented production processes, where design and assembly are their responsibility, but manufacturing is handled by a tier supplier. This often results in costly trial and error approaches, leading to poor product quality and high maintenance costs for end-users.

It was a familiar situation for a leading truck manufacturer. Collaborating with the OEM designer and tier supplier manufacturer, we developed an insert stud solution for an EV battery application that addresses stakeholder requirements and ensures precise design fit, electrical performance, and assembly loadability.

Meeting the Challenge of Tight Clearance

When designing vehicle batteries and electrical systems, minimizing weight and space utilization leads to thin materials and tight spaces. Multiple components, wiring, connectors, and busbars must fit within geometries that push polymer molding design rules to the limit. However, maintaining intercomponent spacings and clearances is crucial for reliability in harsh operational conditions (e.g., avoiding short circuits). Molding these complex arrangements often requires complex tooling, making conventional fastening solutions impractical.

Against this backdrop, we designed an insert stud fastener for securing electrical components onto a polymer carrier, ensuring a fit within the myriad packaging and electrical isolation constraints, while respecting polymer molding design requirements, and thus facilitating a viable mold solution.

Understanding the Material and Processes

Polyamides like PA6 and PA6.6, reinforced with glass fibers, are versatile for crafting durable, electrically insulating components in EV battery systems. Bossard's grasp of design optimization rules allowed it to propose solutions for embedded fasteners without constant guidance from injection molders, streamlining communication between design and manufacturing stakeholders. Understanding how fasteners interact with these materials, including pull-out and over-torque resistance, ensured optimal performance in the proposed designs.

Standard stud retention vs. pin stud retention

Tailored Standard Insert Studs for Manufacturing

In traditional mold setups, external thread mechanisms secure insert studs. However, space limitations in this case ruled out such methods, risking unsecured inserts during molding. To counter this, we worked with tooling engineers to integrate a core pin retention geometry into the insert stud design, a solution, that is compatible with standard practices.

Images: Standard Stud Retention and Pin Stud Retention

Meeting Assembly Loadability Expectations

Ensuring assembly loadability is crucial for maintaining torque call outs, like those for PC8.8 or PC10.9 fasteners. Simply enlarging the fastener wasn’t feasible due to constraints. Adding thickness risked violating anti-arcing requirements (A), while increasing diameter could have compromised neighboring components (B).

We addressed this challenge by patenting knurling designs that optimize engagement with the polymer. Finite element techniques validated mechanical performance, while CAD data-sharing expedited clearance checks. Continuous communication with tooling engineers ensured the feasibility of pin geometry.

Customer Benefits at a Glance

Faster time to market: We were able to save time and resources by guiding the design process, avoiding trial and error.
Optimized manufacturing setup: Our technical solution helped to avoid costs related to tooling damage, scrapped molded parts and product recalls.
Single point of contact: Our design expertise aided in defining relevant requirements, then ensuring that the designs met these requirements.

Fastening Composites

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