171 Parts, One Shot: Inside the Gigacasting Press That Swallowed an Entire Underbody

A modern car body starts as flat coils of steel and aluminum sheet. Stamping presses cut and form those sheets into individual panels: floor sections, shock tower mounts, rail reinforcements, cross members, brackets. A typical rear underbody comprises 70 to 171 of these parts, depending on the vehicle architecture and how aggressively the manufacturer consolidates subassemblies. Each part requires its own stamping die. Each die requires its own press cycle. After stamping, robots pick up the parts, position them in fixtures, and join them with spot welds, self-piercing rivets, and structural adhesive. A single body-in-white passes through 200 to 400 robots in the body shop before it reaches paint.

Gigacasting replaces that entire sequence with one step. Molten aluminum, heated to roughly 700 degrees Celsius, is injected into a steel die cavity under pressures exceeding 1,000 bar. Clamping force holds the two die halves together against the injection pressure. Solidification takes seconds. A robot extracts the finished casting, trims flash from the parting line, and the die is ready for another shot. Cycle time: 80 to 120 seconds per part, 40 to 45 parts per hour. No welding. No riveting. No adhesive cure time. No 300-robot body shop for that section of the car.

What sounds simple in outline is ferociously difficult in execution. Filling a cavity the size of a bathtub with liquid metal in under 100 milliseconds, then cooling it uniformly enough to avoid warping, porosity, and residual stress in a structural automotive part, requires simultaneous mastery of fluid dynamics, metallurgy, die thermal management, and vacuum engineering. Every automaker that has attempted gigacasting has discovered that the press is the easy part. Everything else is hard.

Why Scale Changes Everything

High-pressure die casting has existed since the 1800s. Automotive manufacturers have used it for decades to produce engine blocks, transmission housings, and structural nodes. What changed with gigacasting is not the fundamental process but the part size, and size changes the physics in ways that are not merely proportional.

A conventional die-cast structural node might weigh 2 to 5 kilograms. A gigacast rear underbody weighs 40 to 70 kilograms. Filling a larger cavity means more molten metal must travel farther before solidification begins. Aluminum solidifies rapidly on contact with the cooler die surface, forming a solid skin within milliseconds. If the fill front slows or hesitates, partially solidified material can block flow channels, creating cold shuts where two advancing metal fronts meet but fail to fuse. Cold shuts are invisible from the outside but act as pre-existing cracks under load.

Injection velocity must be high enough to fill the cavity before premature solidification blocks flow, but not so high that turbulent metal traps air pockets within the casting. Gate velocities in gigacasting typically range from 30 to 60 meters per second. At those speeds, the metal front moves faster than sound through air at atmospheric pressure. Vacuum-assisted die casting addresses the trapped air problem by evacuating the cavity to below 50 millibar before injection, reducing gas porosity from roughly 5 percent to below 1 percent in the finished part. Porosity matters because each void is a stress concentrator. In a structural underbody that must absorb crash energy, even small voids can initiate fracture under impact loading.

Alloys Without Ovens

Conventional high-strength aluminum alloys like 6061 or 7075 achieve their mechanical properties through heat treatment: solution treatment at 480 to 530 degrees Celsius, rapid quenching in water, then artificial aging at 120 to 175 degrees for several hours. Heat treatment works beautifully for parts that fit inside an oven. A gigacast rear underbody does not fit inside a conventional oven, and even if it did, quenching a part that large in water would introduce thermal gradients severe enough to warp the casting out of tolerance.

Gigacasting therefore requires heat-treat-free alloys that develop adequate strength in the as-cast condition. These alloys achieve their properties through careful control of solidification microstructure rather than post-casting thermal processing. Silicon content typically ranges from 7 to 11 percent by weight, forming a eutectic microstructure that fills thin sections and resists hot tearing during solidification. Manganese at 0.4 to 0.8 percent replaces iron-bearing intermetallics that would otherwise form brittle needle-shaped phases. Magnesium at 0.1 to 0.5 percent provides solid solution strengthening and enables some natural aging at room temperature over weeks and months after casting.

Alcoa's C611 EZCast alloy, recognized by the North American Die Casting Association in 2024, exemplifies this approach. Designed specifically for megacasting applications, C611 achieves yield strengths above 120 MPa and ultimate tensile strengths exceeding 250 MPa without any post-cast heat treatment. For context, mild steel used in conventional stamped body panels typically has a yield strength of 200 to 300 MPa. Gigacast aluminum compensates for lower per-unit strength by using thicker wall sections, typically 2.5 to 4.5 millimeters, and by optimizing rib geometry to carry loads through geometric stiffness rather than material strength alone.

Researchers at Nature's npj Computational Materials published a multi-objective alloy screening method in 2024 that developed a non-heat-treatable die casting alloy achieving 290 MPa ultimate tensile strength and 145 MPa yield strength in five months of development. Traditional alloy development cycles measure in years. Computational screening narrows the composition space before any metal is melted, testing thousands of alloy variants through thermodynamic simulation before committing to physical casting trials.

Nine Thousand Tonnes of Clamping Force

IDRA Group, based in Brescia, Italy, built the first presses specifically for automotive gigacasting. Tesla's initial deployment used IDRA's OL 6100 CS, a machine generating 6,100 metric tonnes of clamping force (61,000 kilonewtons). Clamping force must exceed the injection pressure multiplied by the projected area of the casting. For a rear underbody with a projected area of roughly 2 square meters, injection pressure of 800 bar would require 16,000 tonnes of clamping force just to keep the die closed. Actual clamping requirements are lower because not all of the cavity area is subject to full injection pressure simultaneously, but the numbers illustrate why these machines are measured in thousands of tonnes rather than hundreds.

Bühler Group entered the market with its Carat series, scaling to the Carat 920 with 92,000 kilonewtons (9,200 metric tonnes) of locking force. At that clamping capacity, the machine can inject over 200 kilograms of liquid aluminum into a single cavity within milliseconds. Over 50 Carat machines have been sold to OEMs and Tier 1 suppliers worldwide since Bühler began production in 2020. LK Machinery, based in Hong Kong, supplies competing equipment to Chinese manufacturers including NIO and Li Auto.

Machine footprint constrains adoption as much as purchase price. An IDRA 9,000-ton press occupies roughly 20 meters in length, 8 meters in width, and 7 meters in height. Installation requires foundations capable of absorbing the vibration from thousands of tonnes of clamping force cycling every 90 seconds. Bühler's machines arrive in modular sections transported on multiple flatbed trucks. IDRA shipped its 9,000-tonne Cybertruck press to Giga Texas in two semi-trailer loads, each carrying die platens and toggle mechanisms that individually weigh more than most finished cars.

Dies That Cost More Than Houses

If the press provides force, the die provides geometry. Gigacasting dies are machined from H13 hot-work tool steel, a chromium-molybdenum-vanadium alloy developed for resistance to thermal fatigue, erosion, and heat checking. A complete die set for a rear underbody weighs 80 to 120 tonnes and costs between $1.5 million and $4 million depending on complexity. Die fabrication takes 12 to 20 weeks from design release to first trial shot.

Thermal management within the die determines both part quality and die life. Molten aluminum enters at roughly 680 degrees Celsius and must solidify uniformly across the entire cavity. Conformal cooling channels, drilled or sometimes additively manufactured into the die blocks, circulate oil or water at controlled temperatures to extract heat at rates matched to local wall thickness. Thicker sections solidify more slowly and require more aggressive cooling to prevent shrinkage porosity. Thinner sections solidify too quickly and may not fill completely if cooling extracts heat before metal reaches the extremities.

Die inserts address the most brutal thermal cycling. Certain zones within the cavity, particularly around gates where molten metal enters at peak velocity and temperature, experience thermal gradients exceeding 300 degrees Celsius per cycle. H13 tool steel resists heat checking through its combination of hot hardness (maintaining 45 to 48 HRC at 500 degrees Celsius) and thermal fatigue resistance. Even so, inserts in high-heat zones last only 30,000 to 80,000 shots before requiring replacement. Tesla runs two complete die sets per machine, rotating one into production while the other undergoes maintenance. This rotation strategy keeps the press producing at 40-plus shots per hour without scheduled downtime for die service.

In 2023, Tesla began experimenting with 3D-printed sand molds for prototype casting development, using binder jetting technology adopted from BMW and Cadillac. Sand mold prototyping reduces development cost by up to 90 percent and compresses timelines from a year to two or three months, allowing engineers to validate fill patterns and solidification behavior before committing to a $3 million production die.

What Tesla Proved at Scale

Tesla's Model Y was the first high-volume vehicle to use a gigacast structural component. Beginning at Giga Shanghai, the rear underbody consolidated 70 individual stamped and cast parts into a single aluminum piece. Cost reduction for that section reached 40 percent. Weight decreased by over 10 percent compared to the multi-piece assembly. More significantly, the body shop for that portion of the vehicle shrank from roughly 300 robots performing spot welding and riveting to zero.

For the Model 3 Highland refresh, Tesla extended gigacasting to both front and rear underbodies. Combined, the two castings eliminated approximately 600 robots from the assembly process. Production throughput increased because the bottleneck shifted from body shop cycle time (limited by robot travel paths and weld schedules) to press cycle time (limited by solidification physics and die thermal recovery).

Cybertruck production at Giga Texas uses IDRA's 9,000-tonne press, the largest gigacasting machine deployed for serial production. Cybertruck's exoskeleton architecture, where the outer body panels serve as structural members, pairs with gigacast underbody sections that provide the floor structure, battery enclosure mounting, and suspension pickup points in a single casting per section.

Tesla now operates 14 gigacasting presses across its global factory network. Giga Press 4.0, reportedly under development, targets even larger castings that could consolidate the entire underbody into a single piece rather than separate front and rear castings. Reports suggest clamping forces approaching 16,000 tonnes for full-underbody casting, though no production deployment has been confirmed.

Crash Energy and Continuous Load Paths

Safety engineers initially questioned whether a single brittle aluminum casting could absorb crash energy as effectively as a spot-welded steel assembly. Stamped steel underbodies manage crash energy through controlled deformation: engineered crush zones fold progressively, converting kinetic energy into plastic work. Aluminum castings cannot fold in the same way. Cast aluminum fractures rather than yielding, and fractured structural members provide no residual load-carrying capacity.

Gigacast underbodies address this through rib topology optimization rather than material ductility. Finite element models optimize rib patterns to direct crash loads through defined paths that lead to sacrificial crush structures still made from extruded or stamped aluminum or high-strength steel. Crush cans, subframe mounting brackets, and bumper beams remain separate components designed to deform progressively. Gigacast sections serve as the stiff central structure that distributes crash loads to those sacrificial elements without deforming themselves.

Results speak through certification data. Tesla Model Y earned IIHS Top Safety Pick+ and NHTSA five-star ratings with gigacast rear underbodies. In 2026, the refreshed Model Y became the first vehicle to meet NHTSA's updated NCAP standards for advanced driver assistance, though those standards evaluate sensor and software performance rather than structural crashworthiness. Continuous cast load paths arguably improve crash consistency because there are no spot weld failures or rivet pullouts to introduce variability. Every casting exits the die with identical geometry, whereas spot-welded assemblies vary with electrode wear, shim gaps, and fixture drift across thousands of production cycles.

Repair Economics

Insurance companies noticed gigacasting before most consumers did. A minor rear-end collision that would require replacing three or four stamped panels in a conventional car could, in theory, total a gigacast vehicle if the single underbody casting sustained structural damage. Early Model Y repair costs alarmed the insurance industry.

Tesla responded with sectional repair procedures. Rather than replacing the entire rear casting, approved body shops can section the casting at designated cut lines using structural adhesive and high-strength rivets to attach replacement panels. Tesla's service documentation specifies 21 high-strength structural rivets, 12 standard rivets, and structural adhesive for a one-piece rear underbody repair. A two-piece repair variant uses fewer fasteners by cutting at a different location, allowing partial replacement of the damaged section while leaving undamaged portions intact.

Repair techniques have matured significantly since initial deployment. InsideEVs documented that Model Y gigacast repairs "have improved greatly," with shops increasingly able to repair rather than replace damaged castings. Aluminum welding, previously considered impractical on die-cast structural parts due to porosity and heat-affected zone embrittlement, has become viable for localized repairs when performed by certified technicians using pulse MIG equipment and appropriate filler alloys.

Beyond Tesla: Who Follows and Who Waits

Volvo committed to megacasting for its EX60 electric SUV, producing a 43-kilogram single-piece aluminum rear floor at a dedicated casting facility. Volvo's implementation eliminated 1,600 welds from the rear body structure. Toyota has ordered gigacasting equipment and demonstrated prototype castings for future EV platforms. Ford and General Motors have sourced presses but remain in early deployment phases, with neither announcing a production vehicle using gigacast structural components.

Chinese manufacturers moved fastest after Tesla. BYD, Geely's Zeekr brand, Li Auto, NIO, and XPeng all produce vehicles with gigacast front or rear structural modules. Li Auto's implementation uses Alcoa's C611 EZCast alloy for its rear floor frame, reducing part count by 87 percent and assembly costs by 20 to 30 percent. Some Chinese OEMs are experimenting with casting nearly the entire underbody in a single shot, pushing beyond the front-plus-rear approach Tesla currently uses.

German manufacturers have been more cautious. Mercedes-Benz is running pilots but has not committed to serial production. BMW has not announced gigacasting plans for body structures, though the company uses large aluminum castings for other applications. Porsche has not adopted gigacasting for its vehicles, likely because the Taycan and Macan Electric platforms were designed before gigacasting equipment reached production readiness.

Prof. Wolfram Volk at the Technical University of Munich has publicly cautioned that gigacasting's technological challenges, including air entrainment, casting defects, and quality variability, hinder its economic viability for automakers who lack Tesla's vertically integrated manufacturing control. JFE Holdings, a major Japanese steelmaker, has expressed concerns about steel consumption displacement, a perspective colored by obvious competitive interest but grounded in legitimate questions about whether aluminum castings can match hot-stamped boron steel's energy absorption in crash structures.

What Gigacasting Cannot Replace

Not everything in a car body can be cast in aluminum. B-pillars, the vertical structures between front and rear doors, must absorb side-impact energy and support the roof during a rollover. Hot-stamped boron steel achieves ultimate tensile strengths exceeding 1,500 MPa for these applications. Cast aluminum at 250 MPa cannot approach those numbers, and the wall thicknesses required to compensate would negate any weight advantage.

A-pillars, roof rails, and door intrusion beams similarly rely on ultra-high-strength steel's combination of ductility and strength. Gigacasting is best suited for large, relatively flat structures that serve as platforms: floor panels, shock tower mounts, battery enclosure frames. Vertical structures that must absorb concentrated impact loads in very small cross-sections remain the domain of advanced high-strength steel and hot stamping.

Joining gigacast aluminum to steel structures introduces galvanic corrosion concerns. Aluminum and steel in contact create an electrochemical cell in the presence of moisture, accelerating corrosion of the aluminum. Isolation techniques including adhesive barriers, coated fasteners, and polymer washers prevent direct contact, but each joint adds complexity that gigacasting's part consolidation was meant to eliminate. Most current implementations minimize aluminum-to-steel transitions by confining gigacastings to the lower body, where they interface with extruded aluminum crash structures and stamped aluminum outer panels rather than steel.

What 40 Shots per Hour Means for Manufacturing

A gigacasting press producing 40 underbodies per hour can supply a final assembly line running at 60 jobs per hour if two presses operate in parallel. Two presses and two die sets represent a capital investment of roughly $20 to $30 million, including installation, foundations, melting furnaces, and trim tooling. A conventional stamping and body shop for the same section of the car costs $50 million or more in dies, presses, robots, fixtures, and floor space.

Labor requirements shrink proportionally. A body shop section that employed 50 operators across three shifts for robot maintenance, die changes, and quality inspection reduces to a handful of casting technicians monitoring press parameters and X-ray inspection results. Bühler's Carat machines incorporate integrated process monitoring that tracks injection velocity, cavity pressure, die temperature, and vacuum level on every shot. Statistical process control algorithms flag drift before it produces defective castings, enabling predictive die maintenance rather than reactive scrap-and-replace.

Sustainability metrics also favor consolidation. Fewer manufacturing steps mean less energy consumed per vehicle. Aluminum is infinitely recyclable, and casting scrap (gates, runners, flash) feeds directly back into the melting furnace with no degradation in properties, unlike steel scrap that accumulates tramp elements through repeated recycling. Springer's analysis of giga casting in body-in-white structures found lower material costs and lower emissions per vehicle compared to multi-material stamped-and-welded approaches, particularly when production occurs in regions with clean electricity grids.

Seventy parts, 1,000 welds, 300 robots, and a body shop the size of a football field, all replaced by a single machine that does its work in under two minutes. Gigacasting has not solved every problem in automotive manufacturing. It cannot match ultra-high-strength steel where concentrated energy absorption matters. It introduces repair complexity that the insurance industry is still learning to price. Its alloys trade peak strength for dimensional stability. But for the large, flat structural platforms that define modern electric vehicle architecture, the math is already settled. One cavity. One shot. One part. Move on.