Precision Metal Stamping for EV Components: Materials, Tolerances & Quality Requirements

Electric vehicles are composed of hundreds of tiny metal components that facilitate power transfer, make the electronic connections, and withstand extreme temperature and mechanical stress for years. Most of these are precision metal stamping parts, such as terminals and charging connectors, manufactured in large volumes that easily go into millions of units a year. A single misaligned tolerance of a small power transmission bar or contact point may lead to voltage drop, local or general heat dissipation, or a failed internal connection in a battery pack. Automotive-grade stamping nowadays complies with ISO/IATF 16949 requirements.

Many EV suppliers hold tolerances as strict as ±0.001 inch on major contact surfaces. This article describes the selection of appropriate materials, the setting of tolerance targets, quality checks, and other key elements that need to be paid attention to when stamped parts are procured for EV projects.

Battery Components and Electrical Contacts

Battery packs, perhaps, constitute one of the hardest parts to get right in electric cars. Cell connectors, terminal tabs, contact springs, all are inside a sealed battery case where both the temperature and the mechanical stress continue to rise throughout the vehicle's life. A loose or oxidized part inside a battery can cause local heating or a failure of the vehicle, so tolerance and material choice matter more here than almost anywhere else in the ‌vehicle.

Copper Terminals and Their Role

Copper terminals act as pathways for electricity from one component to another, like cells, modules, and even down to the vehicle harness.

With pure copper and copper alloys such as C1100,C5191,C7025,C18160,C18150, there isn't much loss of energy. Their conductivity ratings can even approach 100% IACS, which allows low heat generation under the stress of heavy electrical loads. The thickness of terminals usually starts from 0.2mm to 1.5mm while the stamped edges are supposed to be kept free from burrs, so a rough edge will only increase the current's resistance and thus increase its temperature at the interface with a material.

Plating brings along a protective coating:

• Tin-plating helps a lot when it comes to regular corrosion, as a layer of corrosion prevents further corrosion besides allowing a very smooth soldering.
• Silver-plated surfaces give rise to super low-resistance contacts, which is exactly why they're used in high-powered terminals like this one.
• Nickel-plated parts are resistant to corrosion in places where the temperature is relatively high inside a pack, which makes them good for long-term outdoor exposure.

Electrical Contacts and Spring Design

The electrical connection held by spring contacts is an important aspect for a successful and durable device. Stamped spring contacts are called so because of their resemblance to the shrapnel of bullets, and bullets themselves are known to remain in shape after a countless number of insertion and removal cycles. That is why beryllium copper and phosphor bronze are considered the best materials for this application, as they can retain their spring qualities after continuous bending operations.

A spring contact that fails at its job results in an intermittent connection. So, that in real life terms means that dashboard indicators will turn off/on intermittently, or there will not be proper charging, which will be noticed later and will cause a lot of ‍‌trouble.

Busbars and Charging Connectors

The use of busbars to transport large quantities of current among battery pack units, the inverter, and the motor is quite common. Stamped busbar, as opposed to a wire harness, provides a fixed, very low-resistance path that can carry higher currents in a much smaller area.

Most EV busbars are made of either copper or aluminum sheet that is 1mm to 4mm in thickness. After being stamped, they are reshaped to perfectly align with the layout of the pack.

A charging connector carries different requirements for its wiring.

At times, a DC fast-charging connector might be transferring over 350kW via pins that are the size of a pencil tip; only then can you see that it is necessary to have a terminal made out of copper or stamped metal material, which will be used at the connector, having a clean surface finish and a very precise fit inside in order to avoid any arcing or overheating during that charging session.

Among the parts that Fortuna Metals produces for charging guns are the copper terminals made for new energy vehicle programs, which the company has to endure tight tolerances as our plug-and-unplug cycles keep going on.

Key Specs to Check on Busbars

When you want to go ahead with the approval of the busbar design, you should not forget to request the following specifications from the supplier:

Check that the current capacity is not based just on the average usage; the actual running conditions should also be considered.

• Plating thickness of contact surfaces, typically measured in microns
• Evenness over the length of the busbar, as a bent piece will result in different contact pressures
• Insulation coating when a piece of the busbar comes close to other conductive parts

Material Selection for Conductivity and Corrosion Resistance

You may have heard that materials used for various EV components are exposed to battery chemicals, road salt, and coolant, not to mention the constant movement due to vibration that accompanies driving these cars.

Material options must, therefore, include considerations of conductivity in addition to being strong and corrosion resistant over a long period. Any component failing before its time is a huge expense in terms of warranty replacement and even, if it involves components related to safety, a life-threatening ‌situation.

Copper conductor has the best electrical conductivity, but it has to be plated or coated in order to protect it against moisture inside a battery pack. Aluminum is less conductive but much lighter - a feature appreciated in electric vehicles where battery weight directly impacts driving range. Structural brackets made of stainless steel that contain battery modules can often be seen because mechanical strength and rust resistance are the key factors and not electrical conductivity.

Consistency of Dimensions in Manufacturing

Ride-sharing vehicles have to last quite a lot while, of course, battery production is also going on simultaneously, so there is a need for consistency in terms of parts produced. In other words, a vendor has to make sure that the tolerance for part number one and part number one million remains the same. Consistency in dimensions is based on controlling wear of dies, maintenance of presses, and inspection during the process. When checking the supplier, one should keep in mind those activities.

• Use process control charts for critical dimensions only
• Use a coordinate measuring machine for quality checks on each produced batch
• Die maintenance should be done according to stroke counts rather than visual inspection alone
• Battery module suppliers should provide first article inspection reports of all newly developed tools after the sampling phase and prior to volume production

A supplier lacking such checks could deliver parts that meet specifications on day one but gradually deviate out of spec by month six, resulting in assembly line problems that surface far from the stamping press.

Brackets and Structural Support Parts

Not all stamped parts in an EV carry current. Brackets are used mainly to support the battery modules, wiring harnesses, and cooling lines inside the vehicle throughout its complete use. These parts undergo continuous vibrations from the road and temperature changes from the proximity of the battery packs. Therefore, material fatigue resistance is as important as the raw strength. Both stainless steel and coated carbon steel appear quite frequently in bracket applications; their choice is usually based on weight limitations and the mounting location’s potential for corrosion ‍‌exposure.

Quality Requirements That Matter Most

IATF 16949 is a set of quality standards used specifically by suppliers in an automotive or parts supply chain. Suppliers who are accredited for the IATF 16949, ISO 9001, and ISO 14001 environmental management systems have passed several audits that included process control, traceability, and continuous improvement. Fortuna Metals is certified for IATF 16949: 2016, ISO 9001: 2015, and ISO 14001: 2015. It is a certified stamping company that relies on 80+ stamping presses for stamping operations ranging from 25 to 300 tons and over 40 CNC machines for other jobs.

In addition to certification, here's a list of supplier-related things worth finding out:

• Material traceability from the mill certificate for each reel or coil
• Environmental compliance and reporting, including CBAM for parts shipped into the EU
• You might not need to wait as long if a die requires adjustment; therefore, a capability to perform onsite tooling design and repair work may be essential.
• If an EV component is exported from several countries and then put together in final assembly, it would probably need a company with international export experience.

Final Thoughts

Parts of an EV typically require the use of a metal stamping method that is highly accurate in order to manufacture such sensitive products. It is a very difficult but also very necessary task for any metal stamping factory to maintain the consistency of conductivity, corrosion resistance, and dimensional properties across a huge number of components over a long period of time. Cooperating with a supplier who actually holds relevant automotive certifications, in-house tooling capabilities, and has a solid history with products such as copper terminals, busbars, and charging connectors will surely give your project development program a more solid basis from the prototype phase up to full production scale.

Want your car stamped parts to be able to withstand EV applications? Visit dgmetalstamping.com to see what we can offer with battery cells, charging ports, and interconnect components, or call our engineers for a custom quote ‍‌today.

FAQs

1.What tolerance do EV stamped parts usually need?

The most important parts, like contacts, are held to much tighter tolerances of ±0.001 to ±0.003 inches. General industry parts are not usually that tight!

2.Why is copper used for EV terminals and busbars?

To maintain a very low resistance during high current loads, copper with 100% conductivity is the way to go.

3.What certification should an EV parts supplier hold?

IATF 16949:2016 certification, as well as ISO 9001:2015 and ISO 14001:2015 certifications for both quality management and environmental management systems

4.How thick are typical busbars used in EV battery packs?

The majority of those are from 1mm up to 4mm thick and vary according to how much space you are able to give and also how much current load the component will have.

5.Why does dimensional consistency matter more in EV production?

Since EV production runs are very long and parts are needed in very large volumes, even slight variations that accumulate over time might lead to assembly problems and serious safety issues in the long ‍‌run.