There are many materials on the internet for creating welded frames. I would like to ask about tutorials for creating a frame consisting of profiles and connectors, for example used in the air handling units.
I prefer Inventor or SolidWorks.
If you have SolidWorks, it has a built in tutorial on weldments. I have not made a weldment in years, but the tutorial got me started when I did have a bunch of weldments to make years ago.
These are the types of racks I later converted to weldments. Initially I had made them as assemblies, "Weldments" simply did not exist in the software when the frames were originally created.
Genetic Research Rack
This photo shows where to find the tutorial:
This is just a short video of one, but if you follow it, you'll get the basic ideas on how to make them.
I suggest that if you are using a lot of content center type parts like steel tubing that you save them as ipt files so you can make appropriate cuts before assembling them. Good luck!