At what stage of jewelry manufacturing is 3D printing used?

This is an excellent question. The answer to this is going to be pretty long. So kindly bear with me.

The thing you have to know about conventional jewelry manufacturing is most often, the jewelry is made by using a process called investment casting or lost-wax casting. Recommend reading this article for a background: Investment hd casting

Once you have read that, I am sure you would have understood that there are several properties you need from the pattern you will make a mold from. Ideally you would want a material with the following qualities :
You need to have a good surface finish of the jewelry so that it shines better and is aesthetically more pleasing. Therefore it is of paramount importance that your pattern has a good surface finish. You need to use a substance which burns off quickly without much residue. It is durable in variable conditions of temperature. You don’t want your pattern to be made of a material which distorts easily. Should be easy to transport.
The material which most often meets these requirements is wax. Although, it sometimes has issues on the 3rd parameter.

The usual manufacturing process (I am not sure if the OP knows how the jewelry manufacturing process works, but for the ones who might now know, here is how it goes. Bold indicates the stage in the manufacturing process):3d printing prototyping service tamilnadu, andhra pradesh - sla technology

  1. Design of the part in a CAD/CAM software.
  2. Prototyping by use of a CNC machine to cut a block of wax in the shape desired from the CAD file.
  3. Urethane casting [Optional only if multiple copies are needed] : Making urethane molds to make multiple wax model copies.
  4. Casting: Setting up of a “Christmas tree” where these models are attached to a runner and then dipped in a ceramic slurry.
  5. Pouring of the liquid metal into the runner. The metal burns and evaporates the wax and solidifies in the desired shape.
  6. Surface Finish: Minor finishing required.