Documenting 3D-Printed Production Parts

The beauty of additive manufacturing (AM) is the ability to go directly from a CAD model to a physical part. This is great for prototyping, especially when compared with traditional model making. When looking at the production of end-use parts, it is tempting to assume that this single step can be used as well. The reality is that production parts made under any proper design and manufacturing process require information beyond the CAD model.

The documentation effort for AM is less than most traditional manufacturing processes, but drawings and specifications are still necessary. Manufacturing needs to know what processes to use, acceptable tolerances, post processing and how to mark and store the part. The purpose of part documentation, usually in the form of a drawing, is to tell manufacturing and quality what the correct part is. The CAD geometry usually only contains the geometry so non-graphical attributes need to be placed on the drawing, in notes or in specifications.

A Standard Approach

The easiest way to efficiently make this type of documentation is to use standards. Engineering should develop drawing standards for parts made using additive manufacturing that define what information needs to be included on any drawings. These standards should be reviewed with manufacturing and quality control to make sure they contain all of the information that both departments need.

As with any engineering document, the key to making a good package is to assume that it will be used by someone who knows absolutely nothing about the part. Everything they need to make, post process and inspect needs to be included in the documentation package. For additive manufacturing, this should include things like which process to use, which machine type to use and possibly the required machine parameters. Support removal, surface finish and especially build orientation are also critical requirements that must be specified.

If a significant number of parts will be made using additive manufacturing, it is a good idea to invest in creating standard notes and specifications to put on drawings. As an example, instead of spelling out a given post-processing regimen on every drawing, create a standard and controlled process and simply refer to it on the drawing. This also allows manufacturing to develop process plans that fulfill the standard requirements, saving everyone time and money while delivering a consistent end-use part.

Building Documentation

An important related documentation requirement is to keep the build file used by the 3D printer. Every 3D printing method involves taking a solid model and turning it into a set of instructions that specify the layer-by-layer building process; in essence, the toolpath for the machine. This file should be stored and controlled like any set of machine instructions to ensure repeatability.

The form that this documentation takes should be determined by what is most efficient and fits in with existing company practice. The least common denominator is a detailed paper drawing with notes and dimensions, but it is also the most cumbersome. A more efficient solution would be a controlled file, mostly text with a few key figures and probably a PDF that refers to the 3D STL file, which should also be controlled. Just like notes on a drawing, it contains all of the information needed but in a concise and standard format that all potential users can easily reference. If key tolerances need to be defined and inspected, those can be on a related electronic detail drawing or included as figures in a simpler document. The key is that needed specifications are captured in a consistent and easily accessible way.

In the end, creating a document package for a 3D-printed part should be approached in the same way as any manufacture component. The distinction is the type of information required on the drawing because the process is so different, as is the post processing. But once established—along with a set of standards—3D-printed production parts will become just as simple as traditional methods.

Eric Miller is a principal at PADT Inc. Send email about this commentary to [email protected].