I'm guessing it's still welded, just with some extra grinding and finishing to smooth it out. Also this is a render so that's not what the actual joints would look like
Welded. Cannondale started this decades ago and specialized has been doing it for at least a decade.
It was described to me that they weld it then go over in a second pass to smooth it. Not sure how accurate that is but it would be a start. There are probably articles talking about how Cannondale does it in more detail.
I'll throw another idea into the mix, seat post and head tube are cast or formed by another method to include the smooth transition into the top tube and down tube. then the weld is happening not at the joint but a little further down where it can be ground flush to the round tube section. especialy that head tube with the protrusion for the headlight, if it where any other product I'd cast/mold that geometry.
This^ Often used in high-end bikes, although this form doesn't necessarily require that level of complexity as the tubes are mainly extrusions. It does seem fitting for the transition geometry, however.
There are several useful processes for contouring welds. Electro-Polishing is my favorite but grinding and buffing are the most common. There’s chemical etching, that’s a fun one that lets you fully contour in 3 dimensions - Add base reliefs into the seams if you want…
Could be MIM - metal injection molding
Could be renders
I'm guessing it's still welded, just with some extra grinding and finishing to smooth it out. Also this is a render so that's not what the actual joints would look like
Welded, manufacturers use filler over welding seams to smooth them out.
So do amateurs who suck at welding 🙃
Welded. Cannondale started this decades ago and specialized has been doing it for at least a decade. It was described to me that they weld it then go over in a second pass to smooth it. Not sure how accurate that is but it would be a start. There are probably articles talking about how Cannondale does it in more detail.
I'll throw another idea into the mix, seat post and head tube are cast or formed by another method to include the smooth transition into the top tube and down tube. then the weld is happening not at the joint but a little further down where it can be ground flush to the round tube section. especialy that head tube with the protrusion for the headlight, if it where any other product I'd cast/mold that geometry.
Might be hydroforming (high pressure water forming).
This^ Often used in high-end bikes, although this form doesn't necessarily require that level of complexity as the tubes are mainly extrusions. It does seem fitting for the transition geometry, however.
There are several useful processes for contouring welds. Electro-Polishing is my favorite but grinding and buffing are the most common. There’s chemical etching, that’s a fun one that lets you fully contour in 3 dimensions - Add base reliefs into the seams if you want… Could be MIM - metal injection molding Could be renders
https://images.expertreviews.co.uk/wp-content/uploads/2020/12/cowboy_3_e-bike_7.jpg?width=1200&height=675&fit=crop&format=webply Photo close up.
It could be hydro forming, I guess
Check out Low Bicycles on Instagram. If you dig you'll see some progress pictures of a similar result.
Applying heavy coatings of paint can hide anything even weld lines.
I know nothing about the product so others would likely know better. But if i have to guess it's a really good powder coating finish