To answer this frequently asked question properly, one needs to take a few things into consideration first. The files you may need to send can vary from one shop to another based on their software, equipment, capabilities, and type of fabrication. The files needed for a laser cut part will be different than the file needed if it is being 3D printed. Each phase of a project often requires files specific to that particular stage.
The best method is to contact each potential vendor and find out what they require. This gets you to the quoting stage faster, and generally a more accurate quote and timeline. If this isn’t possible, then the following process can get the job to the quotation stage for most applications.
1. Provide a 3D .pdf or a .stp file because anyone can open it and view the part without specialized software. Free .stp file viewers are available for those who don’t have CAD software, and shops can open these files directly within their CAD system. Also send a 2D drawing in the .pdf format for the same reason. This will provide general dimensions or notes that are necessary for quoting. This gives the shop a good general overview of what needs to be done.
2. After the shop reviews these items, there are usually some additional questions or comments that require more details. Revisions can be made to the existing documents, or additional files may be necessary at this stage. Item specifics such as material, plating, GD&T, heat treating, or special processing may need to be discussed. Surface finishes, custom materials, flatness, and dimensioning standards all affect the quotation cost, as well as establishing what tooling, fixtures, and processes will be required to make and inspect the part.
3. At this point the specific files that are required can be generated, based on what the shop determines is the best fabrication process. Some shops prefer 2D dwg or dxf files, some need .iges or .stp files, others might need native CAD files, or even 3D models with embedded PMI information. Some CAM programs can create CNC files directly from mesh polygon files.
The shop will then generate all needed programming and tooling based on their equipment. Each shop will want to make the part their way, based on their experience and equipment needs or limitations. The machinist often has a specific approach that may not have been considered during the design process, or a more efficient way to complete fabrication.
If the CAM programming and tooling is a significant portion of the quote, you may want to consider dividing the quote into a non-recurring engineering fee, and a cost per part. The shop would charge one fee to program and create tooling, and charge a separate amount per part. Future orders will only incur the per part charge. Maintain ownership of the fixtures/tooling in case you want to have a different shop make parts in the future. Announcing that you intend to send the work to a different shop, and requesting the tooling used to make the part (if you don’t own it) rarely has a pleasant outcome.