The business pioneered the use of massive presses with clamping pressures ranging from 6,000 to 9,000 tons to mold the front and back structures of its Model Y in a “gigacasting” method that reduced production costs and left competitors scurrying to catch up.
According to the sources, Tesla is nearing a breakthrough that would allow it to die cast nearly all of the intricate underbody of an EV in one piece, rather than the approximately 400 pieces in a normal car.
The know-how is crucial to Tesla’s “unboxed” production strategy, which CEO Elon Musk outlined in March as a key component of his aim to produce tens of millions of cheaper EVs over the next decade while still turning a profit, according to the sources.
While Tesla has stated that their unboxed model entails building big subassemblies of a car at the same time and then snapping them together, the size and composition of the modular blocks remain unknown.
According to Terry Woychowski, head of the engineering firm Caresoft Global in the United States, if Tesla is able to gigacast most of the underbody of an EV, it would further change the way cars are built and manufactured.
While Tesla has stated that their unboxed model entails building big subassemblies of a car at the same time and then snapping them together, the size and composition of the modular blocks remain unknown.
According to two of the insiders, Tesla’s previously unknown revolutionary design and production procedures imply the business could construct a car from the ground up in 18 to 24 months, whereas most competitors presently take three to four years.
According to the five sources, a single huge frame integrating the front and back parts with the central underbody where the battery is located might be utilized in Tesla’s tiny EV, which the company hopes to debut with a $25,000 price tag by the middle of the decade.
Three sources said Tesla was expecting to make a decision on whether to die cast the platform in one piece as soon as this month, but even if they do, the ultimate product could alter during the design validation process.
Neither Tesla nor Musk responded to Reuters’ questions for this report.
SANDING AND 3D PRINTING
Tesla’s discovery is centered on how massive molds for such a large part are produced and tested for mass production, as well as how casts might integrate hollow subframes with internal ribs to reduce weight and improve crashworthiness.
The breakthroughs in both cases, created by design and casting specialists in the United Kingdom, Germany, Japan, and the United States, involve 3D printing and industrial sand, according to the five persons. They all spoke to Reuters anonymously because they are not authorized to speak to the media.
Until far, automakers have avoided casting ever-larger structures because to the “gigacast dilemma”: developing molds to manufacture sections 1.5 metres squared or larger increases efficiency but is costly and fraught with danger.
According to one casting specialist, once a huge metal test mold has been formed, machining modifications during the design phase may cost $100,000 every go, or rebuilding the mold entirely could cost $1.5 million. Another estimated that the entire design process for a huge metal mold would cost around $4 million.
That has been judged prohibitive by automakers, especially since a design may require a half-dozen or more adjustments to get a flawless die in terms of noise and vibration, fit and finish, ergonomics, and crashworthiness, according to the sources.
Despite the concerns, Musk’s ambition from the start was to discover a way to cast the underbody in one piece, according to the sources.
To address the challenges, Tesla turned to companies that use 3D printers to create test molds out of industrial sand. Binder jet printers use a computerized design file to drop a liquid binding agent onto a thin layer of sand and progressively produce a mold that can die cast molten alloys, layer by layer.
According to one source, the cost of design validation using sand casting is cheap, even with many iterations – only 3% of the cost of doing the same with a metal prototype.
That means Tesla may iterate on prototypes as many times as necessary before reprinting a new one in a matter of hours utilizing machinery from businesses like Desktop Metal (DM.N) and its subsidiary ExOne.
According to two of the sources, the design validation cycle for sand casting takes two to three months, compared to anything from six months to a year for metal mold prototypes.
ALLOYS MADE TO ORDER
To conserve weight and increase crashworthiness, the subframes in a car’s underbody are typically hollow. They are currently created by stamping and fusing numerous components together, leaving a void in the center.
Tesla intends to incorporate solid sand cores printed by binder jets within the overall mold to cast subframes with hollows as part of one gigacasting. After the part is cast, the sand is removed to reveal the voids.
Despite the increased flexibility in the design process and the intricacy of the big frames, there was still one key challenge to overcome.
The aluminum alloys used to make the castings performed differently in sand and metal molds and frequently failed to meet Tesla’s crashworthiness and other criteria.
Three of the individuals indicated that the casting professionals addressed this by developing unique alloys, fine-tuning the molten alloy cooling process, and developing an after-production heat treatment. When Tesla is satisfied with the prototype mold, it can invest in a final metal mold for mass manufacturing.
According to the insiders, Tesla’s future tiny car provides an ideal opportunity to cast an EV platform in one piece, owing to its simpler underbody.
Because there isn’t much of a hood or rear trunk, the little cars Tesla is creating – one for personal use and the other a robotaxi – don’t have a large “overhang” at the front and back.
“It’s like a boat in a way, a battery tray with small wings attached to both ends. That would make sense to do in one piece,” one individual suggested.
According to the sources, Tesla still needs to select what type of gigapress to employ if it decides to cast the underbody in one piece – and that decision will also determine how intricate the car frame would be.
People suggested Tesla would need new bigger gigapresses with a tremendous clamping force of 16,000 tons or more to punch out such large body parts quickly, which would come at a high cost and might necessitate larger production structures.
Three of the five sources stated that one issue with high clamping power presses is that they cannot accommodate the 3D printed sand cores required to build hollow subframes.
According to the sources, Tesla may overcome these challenges by utilizing a new sort of press into which molten alloy can be slowly pumped – a procedure that produces higher quality castings and can fit the sand cores.
However, the process takes longer.
“Tesla could still choose high-pressure for productivity, or they could choose slow alloy injection for quality and versatility,” one of the people said. “It’s still a coin toss at this point.”