Tesla Model Y May Have Bigger Cast Parts Than Expected

In a recent earnings report, Tesla published some information about Model Y production and photo, which made it possible to reflect on the technologies that the company uses and how they are implemented in production.

We know that Tesla improved the car battery. Due to continued engineering progress of the Model Y AWD, they have been able to increase its maximum EPA range to 315 miles, compared to it previous estimate of 280 miles. This extends Model Y's lead as the most energyefficient electric SUV in the world.

Also, on the earnings call Q4 2019, Tesla CEO Elon Musk said that they are moving to an aluminum casting instead of a series of stamped pieces. And in the future they want to go from 70 parts to 4, then 1 with a reduction in weight, improvement in MBH, reduction in cost, and a significant drop in capital expenditure for all the robots that used to put 70 parts together.

The way Model Y is produced is of great interest. Insideevs said they were contacted by Holger Erker, an expert from IPE Engineering GMBH, claiming that the cast parts will be bigger and more than previously thought.

Based on photos and reports, Erker suggests that the body structure (BS) of the Model Y is build up as a multi-material mix unibody, similar to Model 3. The car body itself consists of four main components - rear cast, front cast, BS Asm LH (bodyside assembly left hand), and BS Asm RH (right) - and a few further skin panels and closure parts.

Picture #1

In his opinion, the body (BS) is built as a three-layer structure. BS internal and external construction made of HSS (high-strength steel) or UHSS (ultra-high-strength steel) custom-made stamped steel panels. Due to the high tensile strength, the formation of panels can only be carried out by hot pressing. Thus, we can find the thermal marks visible on the panel.

Erker writes that the interesting part on the BS is definitely the upper front pillar and the roof section. This section appears to be made up of individual presses, which are then welded to the door rim panels to form the final body structure.

Picture #2

Erker understands that for this, the casting process, of course, must be very advanced, because the dimensions and weight of the cast parts go beyond what is known from today's auto parts. The process can be performed using HPDC (High-Pressure Die Casting) on ​​a cold chamber pressure casting machine with vacuum support to avoid casting defects such as pores, bubbles, cracks, etc

He and his team suggest that the rear of the structure can weigh about 40–45 kg.

Picture #3

They suggest that for the rear body structure, the closing force required would be above 6.000 metric tons. Usually, the maximum shot weight for aluminum alloy parts is around 10 kg, due to machine limitation in closing force capacity. The standard closing force is around 1.500 to 2.000 metric tons.

Only very few machine suppliers worldwide have the experience to build cold chamber casting machines with 4.000 or a maximum of 5.500 metric tons of closing force. Therefore, the machine at Tesla must be a special custom-build and quite gigantic.

This machine must be fast enough to meet production requirements. He suggests that if a full casting cycle, including all processing and preparation, can be completed in less than two minutes, the maximum annual productivity of the casting machine will be in the range of 150,000 parts. This seems normal for mass production. Since the front structure will also be cast, at least two of these machines should be sufficient for production.

“The body assembly shop most probably consists of two frame lines, two body side subassembly welding cells and a BIW (body-in-white) closure mounting and finish line. That would be roughly only 60 percent of a conventional body shop.

The total production time of a Model Y body-in-white compared to a conventional stamped steel body will be substantially lower. Considering the net process time for the underbody section, only the casting would eliminate between 1.000 to 1.500 weld spots, at 5 to 7 seconds each. That would total at an approximately 120-minutes net process time-saving.

If Tesla is able to manage the production process with high quality, production costs will be definitely lower than Model 3’s. Guess what would happen if the full-body frame casting machine would work as shown in their patent application...”

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