Can a complicated engineering drawing be converted into 3D model?
Are Designers capable of modeling 3D models out of complex engineering drawing, such as engine block, clutch assembly, wheel hub etc. or is it the other way around?
Take a look at a lot of old engineering drawings of more complex components like automotive exhaust manifolds. They were designed to be built by pattern makers and thus contain a rather dense succession of 'section' views. The pattern maker would built the sections and the sections between were simply a best effort, hand worked to form nice continuous sections. Basically... a had built 'loft'. Block cooling passages and other complicated 'flow' sections were drawn the same way.
Those types of drawings are detailed enough to build models from; I've built a number of them over the years.
As for basic mechanical devices; if the drawings are detailed enough with all the pertinent dimensions, then yes, they can be modeled rather easily.
My first engineering job was to take old drawings of flight simulator instruments--many on vellum--and build the 3d components, assemblies and exploded views. I thought it was 'grunt' work but it taught me a a lot about good working designs in a very short amount of time.
In the engineering manufacturing industry creating a model from old existing 2D CAD and old manually drawn engineering is not uncommon. Having started my engineering career back in the 1970's all the engineering drawings then where 2D pieces of paper, then when 2D cad became the normal for engineering and other drawings often when producing drawings for updated machines and new machines you will start with a pile of old paper drawings and convert them to CAD versions, the same has happened with the transition from 2D CAD to 3D model based engineering drawings. A common task for a new employee in the engineering CAD department is to get them to model parts and assembles from old drawings that are to be used in a new project. This is a good way to test their ability to work efficiently and accurately and how well they understand how to read engineering drawings.
In my semi-retirement being involved with an organization that restores vintage trams. All projects start from a mix of old paper drawings, accurate measurement of existing parts and many years of engineering experience. I use these things to produce CAD models and finished drawings. The models are used by a pattern-maker with CNC machines to produce new patterns to cast bits that are missing or not usable anymore, also to have work done outside of our organization we can't do ourselves.
As well as converting old drawings to 3D models to make use of the technology possible with 3D models, CNC manufacturing, analysis and other useful things, taking old drawings and using them to make models is great practice for developing the skills required for a career in this industry.
I think you are really asking if there is an automated way to do it. That answer is no. Getting a 3D model requires modeling the part based on the instructions in the drawing. You need to do in computer software what the old-time pattern makes did in wood.