I don't think they'll ship around stamped panels: to store them safely against damage is both a significant expense and decreases transportation density, which increases logistics costs.
Here's what Elon said about what will be made in the Shanghai Gigafactory, on the Q4 conference call 2 months ago:
Elon Musk:
"And earlier this month, we saw the construction of our Gigafactory in Shanghai, and by the end of this year, we expect to be producing Model 3s using a complete vehicle production line. That's body paint, final assembly, general assembly and module production."
"So it basically would be - this will be extremely fast. I get like daily updates of progress of the Shanghai Gigafactory, and those factories are going to go up like lightning."
Note that while he didn't mention press/stamp lines, he didn't mention injection molding lines either - those are
naturally placed close to the body and final assembly lines. Completely-knocked-down-kits (CDK's) sometimes get shipped around the globe but are a major complication on the Fremont Model 3 production side which Tesla doesn't need.
Nor are stamps really expensive at the 3k/week rate they are targeting: I believe the main expense are the paint shop baths and booths, the robots of the chassis/body lines and the robots/stations of the general and final assembly line. I suspect they'll do a plastics shop too, with a lot of molding machines. Plus a new Grohmann Machine to make SR packs.
Big stamping machines may have long lead times - but that simply means that they have to sequence their orders properly for it all to arrive at the intended date. The dimensions and capacity should already be well specified at this stage, as the Model 3 and Model Y dimensions are already pinned down.
Do dies have long lead times, or is Tesla making those themselves?
Have I forgotten anything else?
Cell supply is the big question, IMHO.
Edit, Tesla mentioned stamp lines in the Q4 update letter:
"In the initial phase of Gigafactory Shanghai, we expect to have stamping, paint shop, body joining, and general assembly shops in operation by the end of 2019. This accelerated timeframe should be possible due to the radical simplification of our manufacturing layout and processes compared to our first-generation production line in Fremont. Higher-spec models such as our long-range all-wheel drive (AWD) and Performance versions will continue to be shipped to China from the US."
I believe "general assembly shops" includes the plastic molding shop.
The only things missing from the China plan is:
- Cell factory: This is probably still being negotiated, but I'd expect cells to be made at the Shanghai Gigafactory, in a similar construct to GF1.
- Power-train factory: these are high density, low volume, small size components which are easy to export from the Gigafactory and might help them protect their EV IP.
- Seat factory: which they have in Fremont and which is relatively easy to export as well, although it might make sense to move this to China next, as they are low density components which makes transportation more expensive, plus seats could probably be further simplified for the Chinese market to reduce ASP.
- Glass factory: I think it's made in GF2 right now, and that's not necessarily easy to export. They might be outsourcing window production, and they might opt for a metal roof instead of the glass roof. This would also differentiate the Chinese versions from the import versions very clearly.
- HW3 board factory: this too is probably better done in the U.S., although they might eventually bring this to China too.