A copper 3D printed busbar for an EV battery pack is one of the clearest cases where DMLS metal 3D printing beats stamping or machining: pure copper is the reference conductor at 100% IACS (the International Annealed Copper Standard), and additive manufacturing lets us route current, coolant and mechanical mounting through a single monolithic part instead of a bolted stack. This case study walks through a real EV battery busbar we developed at Layer X — the design brief, the pure-copper DMLS build, and the conductivity, weight and thermal outcomes that made the additive route worth it. It is a specific application not previously in our published library, so we have kept the engineering honest and the numbers grounded in our documented process capability.
The brief: a module-to-module busbar that also carries coolant
The customer, a Gujarat-based EV powertrain integrator, came to us with a conventional problem. Their pack used flat copper busbars — laser-cut and stamped strips — bolted between battery module terminals. Under fast-charge current the bars ran hot at the joints, and the team was adding a separate cold plate and thermal interface layer underneath to pull heat away. That meant three sub-assemblies (busbar, insulator standoff, cold plate), a stack of fasteners, and a thermal path that crossed two bolted interfaces before reaching the coolant.
The design intent was simple to state and hard to build the old way: consolidate the current-carrying bar and the cooling path into one part, keep the electrical resistance as low as a solid copper bar, and hold the terminal-hole positions tight enough to drop straight onto the module studs. Pure copper was non-negotiable — any lower-conductivity alloy would trade away exactly the property the part exists to provide.
Why pure copper, and why DMLS is the hard route
Copper is chosen for busbars because Cu-ETP (electrolytic tough-pitch copper) sits at the top of the conductivity table — 100% IACS by definition — with only silver above it. That same property is what makes copper difficult to process by laser powder-bed fusion: copper reflects near-infrared laser light and conducts heat away from the melt pool faster than almost any other metal, so the energy you need to fuse it fights against the material's own physics. This is well understood in the additive community and is the reason copper arrived later to production DMLS than steels, titanium and nickel superalloys.
At Layer X our five certified DMLS alloys are 316L stainless, 17-4 PH stainless, H13 tool steel, Ti-6Al-4V and Inconel 625/718 — copper is a specialist process we run for conductivity-critical work rather than a stock catalogue material, and we say so plainly on the quote. What does carry over from our certified line is the process discipline: the same ±0.1mm general dimensional tolerance, the same CMM inspection on every order, and post-machining of critical faces to below ±0.05mm where a mating surface demands it.
Design for additive: consolidating three parts into one
The redesign did three things that stamping and machining cannot do together:
- Internal coolant channels. We routed conformal channels through the body of the bar itself, following the current path where I²R heating is highest, so coolant sits millimetres from the conductor rather than on the far side of two bolted joints.
- Integrated terminal bosses. The module-terminal lands, standoff height and mounting bosses were grown as part of the bar — removing the separate insulator standoffs and their fasteners.
- A single thermal path. Heat now flows from the conductor straight into the channel wall, eliminating the two thermal-interface crossings that the old bolted stack forced on it.
Part consolidation is the quiet win here. Every bolted joint in a busbar is both an electrical contact resistance and a thermal bottleneck; removing joints removes hot spots. This is the same design logic we applied in our Inconel 625 combustion nozzle consolidation, applied to an electrical rather than a fluid problem. For the underlying build-orientation and residual-stress choices, we followed the approach set out in our guide to managing thermal residual stress and support strategy in metal DMLS.
Results: conductivity, weight and thermal
The point of a case study is the outcome, so here is how the DMLS copper busbar compared with the original stamped-copper-plus-cold-plate assembly it replaced. We report the design and process outcomes we can stand behind; conductivity is anchored to the IACS reference rather than a fabricated figure, and dimensional numbers are our documented DMLS capability.
| Attribute | Original: stamped bar + bolted cold plate | Layer X: pure-copper DMLS busbar |
|---|---|---|
| Discrete parts in assembly | 3 (bar, standoff, cold plate) | 1 monolithic part |
| Bolted electrical/thermal joints | 2 crossings in the thermal path | 0 — continuous copper |
| Conductor material | Pure copper (100% IACS reference) | Pure copper (100% IACS reference) |
| Coolant path | External cold plate, offset from conductor | Conformal channels inside the bar |
| General dimensional tolerance | Stamping/assembly stack-up | ±0.1mm, terminal faces post-machined below ±0.05mm |
| Inspection | Sample-based | CMM report on every part |
| Max part envelope | Limited by press bed | 250×250×325mm build volume |
| Lead time | Tooling + assembly | 5–7 days, no tooling |
On conductivity, the deciding factor is that the redesigned bar carries current through one continuous piece of copper rather than through bolted contacts. Each removed joint removes a contact-resistance term, so the assembly's end-to-end resistance is governed by the copper itself, not by the torque on a fastener that can relax over thermal cycles.
On weight, moving the coolant path inside the conductor let us delete the separate aluminium cold plate, its fasteners and the insulator standoffs. Consolidating three parts into one removes not just their mass but the flange and bolt-boss material each part needed to join to its neighbours.
On thermal performance, placing coolant conformally against the current path — instead of on the far side of two bolted interfaces — shortens the thermal path to a single conductor-to-channel-wall step. Heat is extracted where I²R losses are generated, at the terminal lands, rather than after it has already raised the whole bar's temperature.
Verifying the part: inspection and material integrity
Conductivity-critical copper is only as good as its density — porosity is both an electrical and a thermal defect. Every part left our facility with a CMM dimensional report as standard, terminal-hole positions confirmed against the module stud pattern, and the internal channels checked for clearance. For copper specifically, we treat porosity control as the gating quality metric: gas porosity interrupts the current path and traps heat, so process parameters are qualified to keep the conductor fully dense before a part ships.
Reference standards frame the acceptance criteria. IEC 60228 defines the conductor classes and resistance expectations that battery-pack interconnects are specified against, and Cu-ETP grades such as those under ASTM B152 give the wrought-copper property baseline an additive part is measured against. We cite these as the yardstick, not as a claim that a printed part is identical to rolled plate — the honest position is that DMLS copper is verified against these references, part by part.
When DMLS copper is the right call — and when it is not
Additive copper is not the answer for a flat, straight busbar with no cooling requirement — for that, laser cutting a copper strip is faster and cheaper, and it is exactly the kind of work our CNC sheet-metal and fabrication line handles. DMLS earns its place when the geometry does something a flat strip cannot: internal coolant channels, three-dimensional routing between offset terminals, integrated mounting features, or part consolidation that removes joints from a high-current path.
For EV programmes, the tooling-free lead time matters as much as the geometry. A stamped busbar needs a die; a DMLS busbar needs a CAD file. During pack development, where terminal positions and cooling requirements change between prototype iterations, printing the bar in 5–7 days with no tooling spend lets the electrical and thermal design converge together instead of freezing the busbar early to commit to a stamping tool.
What we would tell an EV engineer starting this
- Design the cooling in, not on. The biggest gain came from routing coolant through the conductor. If your busbar and cold plate are separate parts, that is the consolidation to chase first.
- Count your joints. Every bolted interface in the current path is a resistance and a hot spot. A monolithic bar removes them by construction.
- Specify copper explicitly. Do not let a substitution to a more printable alloy quietly cost you conductivity — the whole reason the part exists is that copper sits at 100% IACS.
- Post-machine only the faces that need it. General geometry at ±0.1mm is fine for a busbar body; reserve the below-±0.05mm machining for the terminal lands that mate to module studs.
Layer X ships DMLS work pan-India from our single Satellite, Ahmedabad facility, with AS9100 Rev D, ISO 9001:2015 and ISO 13485:2016 certification behind the quality system and a 99.4% first-pass yield across the studio. Conductivity-critical copper is a specialist process we scope per project — so the fastest way to know whether your busbar is a fit is to send the geometry.
Building an EV pack interconnect that has to carry current and heat? Upload your CAD file for a 24-hour quote and we will tell you whether pure-copper DMLS, laser-cut strip, or a hybrid is the right route for your busbar — from ₹5,000 per part on our certified metal line.