Deep Drawing of Rechargeable Battery Cases — 18650, 21700 and 4680 Cells
Cylindrical battery cells power everything from portable electronics to electric vehicles, and the precision required to manufacture their housings has never been higher. The shift from the familiar 18650 format to 21700 and now toward the larger 4680 cell has placed new demands on metal forming technology, pushing manufacturers to rethink their deep drawing processes from the ground up. At the heart of every high-quality rechargeable battery case lies a forming process that must deliver consistent wall thickness, tight dimensional tolerances, and surface integrity at production volumes that leave little room for error.
Deep drawing battery cases is one of the most technically demanding applications in precision metal forming. The geometry of a cylindrical cell housing looks deceptively simple, yet achieving it repeatably across millions of parts requires a carefully engineered sequence of forming stages, the right material choices, and press technology that can handle both the mechanical demands and the quality requirements of battery-grade components. Understanding how this process works helps manufacturers make better decisions about equipment, tooling, and process design.
Why cylindrical cell geometry demands precision metal forming
The cylindrical format is not simply a legacy choice. It offers excellent structural rigidity, efficient heat dissipation, and a geometry that lends itself naturally to deep drawing. However, the dimensional requirements for cylindrical battery cell production are exceptionally tight. A cell housing must maintain a consistent outer diameter, a uniform wall thickness along its full length, and a base geometry that supports the electrochemical assembly inside without distortion.
For the 18650 cell, the outer diameter is 18 mm and the nominal length is 65 mm. The 21700 format steps up to 21 mm in diameter and 70 mm in length, while the 4680 cell reaches 46 mm in diameter and 80 mm in length. Each increase in diameter and length ratio changes the forming dynamics significantly. The draw ratio, defined as the relationship between the blank diameter and the cup diameter, directly influences how much material must flow during each forming stage and how stress is distributed through the can wall.
Any deviation in wall thickness or concentricity can affect both the structural integrity of the housing and the performance of the finished cell. This is why deep drawing applications for battery cases demand press systems with excellent repeatability, precise stroke control, and consistent blank holding force across every cycle.
Material considerations for deep-drawn battery cans
The material used for rechargeable battery cases is not chosen arbitrarily. Nickel-plated steel is the dominant choice for cylindrical lithium-ion and nickel-based chemistries because it combines good formability with the corrosion resistance and electrical conductivity that battery applications require. The nickel coating also protects the steel substrate from the electrolyte environment inside the cell.
The base steel must have a fine, uniform grain structure to support multi-stage deep drawing without cracking or surface defects. Anisotropy, the directional variation in material properties caused by rolling, plays an important role. High normal anisotropy values indicate better resistance to thinning during drawing, which translates directly into more uniform wall thickness in the finished can. Material suppliers for battery-grade strip typically work to tight tolerances on thickness, surface roughness, and mechanical properties.
Lubrication is another critical factor. The forming process generates significant contact pressure between the strip and the tooling, and without effective lubrication, galling, scoring, and premature tool wear become serious problems. For battery can production, lubricants must also be compatible with downstream cleaning and assembly processes, since any residue that enters the cell can compromise electrochemical performance.
How multi-stage deep drawing shapes battery cell housings
Producing a finished battery can from flat strip material is not a single-step operation. The process follows a defined sequence that progressively transforms a flat blank into the final cylindrical housing, with each stage contributing a specific change in geometry.
From blank to cup
The first step is cupping, where a circular blank is cut from the strip and drawn into a shallow cup in a single stroke. This initial cup establishes the base diameter and the starting wall height. Specialized cupping presses are designed to perform this operation efficiently, converting wide coil strip into multiple cups per stroke and eliminating the need for complex intermediate material handling. The cup geometry at this stage is intentionally wider and shorter than the final housing.
Redrawing and wall ironing
From the initial cup, the part moves through a series of redrawing stages. In each stage, the cup diameter is reduced while the wall height increases, progressively approaching the target dimensions. For a typical battery can, this involves around four drawing steps to achieve the required length. The forming dies and punches must be precisely matched at each stage to control material flow and prevent wrinkling or cracking.
In some production approaches, wall ironing is combined with redrawing to achieve tighter wall thickness tolerances and improved surface finish. Ironing forces the material between the punch and a die ring with a clearance smaller than the incoming wall thickness, thinning and elongating the wall in a controlled way. This technique is widely used in high-volume can production and is directly relevant to the deep drawing process for battery cell housings.
Calibration and finishing steps
After the main drawing sequence, calibration steps refine the outer diameter and improve roundness. Additional operations such as embossing or beading may be added to create features required by the cell design, such as the groove that retains the positive cap or the base profile that supports the current collector. Each of these steps is performed within the same transfer system, keeping the part moving through a continuous sequence of stations without manual intervention.
Transfer presses, also known as multi-stage presses or strip-fed transfer presses, are well suited to this type of sequential forming. They move parts from station to station using an integrated transfer system, maintaining precise positioning and enabling high cycle rates across the full forming sequence.
Key quality challenges in high-volume cell case production
Producing battery cases at the volumes demanded by modern cell manufacturing introduces quality challenges that go beyond what is typical in general deep drawing applications. Every defect that reaches the cell assembly line has the potential to cause a reject, and at high production rates, even a small defect rate translates into significant material and cost losses.
Wall thickness variation is one of the most closely monitored quality parameters. Uneven thinning during drawing can create weak points that are vulnerable to deformation during cell assembly or in service. Maintaining consistent blank holding force and precise die alignment across every stroke is essential to controlling this variation. Press systems with good repeatability and integrated process monitoring are better placed to catch drift before it causes a quality problem.
Surface defects such as scratches, scoring, or material pickup on the tooling can compromise the nickel coating and create sites for corrosion or electrical contact issues inside the cell. Regular tool inspection and maintenance, combined with effective lubrication management, are the primary defenses against surface quality problems in high-volume production.
Dimensional consistency across the full production run is equally important. The 18650 and 21700 formats have well-established dimensional standards, and cell assembly equipment is designed to work within tight tolerances. Any drift in outer diameter or length will cause assembly problems downstream. Calibration steps within the forming sequence help maintain dimensional consistency, but the stability of the press system itself is the foundation on which everything else depends.
Scaling production for the 4680 format and beyond
The 4680 cell format represents a significant step change in cylindrical cell geometry. With a diameter of 46 mm, the draw ratio and the forces involved in forming are substantially higher than for the 18650 or 21700 formats. This has direct implications for press selection, tooling design, and process sequencing.
The larger blank required for the 4680 housing means more material must flow during each drawing stage, increasing the demands on blank holding force control and lubrication. The longer draw length also means that the number of redrawing stages may need to increase compared to smaller formats, and the calibration requirements become more demanding as the absolute dimensional tolerances remain tight even as the part size grows.
Press capacity must be matched to the increased forming forces. For high-volume 4680 production, mechanical press systems with sufficient tonnage and a transfer system capable of handling the larger part geometry are the natural starting point. Servo-driven press technology adds the ability to optimize the ram motion profile for each stage, which can be particularly valuable when forming the larger, more demanding 4680 geometry.
Looking beyond the 4680, the direction of travel in the industry is toward even larger cylindrical formats as manufacturers seek to increase energy density and reduce cell-to-pack complexity. Each step up in cell size will continue to push the boundaries of what deep drawing technology must deliver, reinforcing the importance of investing in press platforms that offer flexibility, scalability, and the process control needed to maintain quality at the next level of cell dimensions.
How H&T ProduktionsTechnologie supports battery can deep drawing
We have developed deep expertise in the deep drawing of rechargeable battery cases, and this application sits at the core of what our transfer press and cupping press platforms are designed to do. Our solutions address the full forming sequence from coil strip to finished housing, covering every stage from the initial cupping operation through multi-stage redrawing, calibration, and finishing.
- Cupping presses: Our specialized cupping presses convert wide nickel-plated steel strip directly into high-quality cups in a single, efficient operation, eliminating complex material transport and setting the foundation for consistent downstream forming.
- Multi-stage transfer presses: Our strip-fed transfer presses and multi-stage press systems guide parts through the full sequence of redrawing, calibration, embossing, and beading steps with precise transfer control and high cycle rates suited to volume battery can production.
- Servo technology: Our servo spindle press technology allows ram motion profiles to be optimized for each forming stage, supporting tighter process control and the flexibility to adapt to new cell formats including the 4680.
- Process reliability and lifecycle cost: Our machines are engineered for long service life, excellent energy efficiency, and high process stability, reducing the cost per part across demanding high-volume production environments.
- Tailored solutions: We provide individual consulting and comprehensive after-sales service, working with customers to configure the right press platform and tooling concept for their specific cell format and production volume requirements.
Whether a manufacturer is scaling up 18650 or 21700 production, transitioning to 4680 cell manufacturing, or planning for the next generation of cylindrical formats, we are ready to support the process from the first consultation through to full production. Contact H&T ProduktionsTechnologie today to discuss how our metal forming technology can strengthen your battery can production.
