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3D Printing: The Impact of Post-Processing – Part 1 of 3-Part Series

Excerpt from White Paper by Todd Grimm

The perception and promise of 3D printing are that it offers a digital workflow that is simple, fast and automated; a process where complexity is free. That perception is generally correct up to the moment that parts are removed from the 3D printer. As soon as parts enter the post-processing phase, the automated, push-button process becomes a manual operation that impacts time, cost and quality.

The uninitiated, those that are new 3D printing users, are often shocked to discover what is really required to prepare parts for delivery. Longtime users, on the other hand, tend to accept post-processing as a “necessary evil.” Since all 3D printing technologies to date require post-processing, the experienced users accommodate the added burden and make operational adjustments.

Post-processing is a non-valued-added operation that increases overhead and imposes limits. It complicates the 3D printing workflow, adds expense and extends delivery time. For the 3D printing lab where operations are centralized and run by a dedicated staff, this is undesirable. For office-environment operations, it is unacceptable, making it a technology that is best suited for the lab rather than being a hands-on convenience for engineers and designers.

Independent of the operating mode, the burdens of post-processing are an impediment to expansion by current users and an obstacle to broader adoption by those that have yet to establish in-house operations. This non-value-added process limits the frequency of 3D printing use, the viable applications and the markets that are served.

Post-processing encompasses all of the actions that are performed after parts are removed from a 3D printer. There are two categories of post-processing, primary and secondary.

Primary post-processing includes the mandatory steps that must be performed on all parts to make them suitable for use in any application. The steps vary by technology but generally include cleaning and support structure removal. Experienced users often refer to this basic finishing level as “strip and ship” because the resulting parts lack any embellishment that enhances quality. This paper focuses solely on primary post-processing.

Secondary post-processing includes optional part finishing that improves the aesthetics or function of the part. Most commonly, secondary post process includes sanding, filling, priming and painting. However, it can also include machining or plating, for example.

Post-processing operations may be automated, semi-automated or manual, and they can be either serial or batch processes. For example:

Fused Deposition Modeling (FDM):

  • Remove support structures. (manual, serial)
  • Light sanding to remove support structure remnants. (manual, serial)

or

  • Gross support removal. (manual, serial)
  • Soak to dissolve supports. (automated, batch)
  • Pick out/cut off any undissolved remnants. (manual, serial)
  • Rinse and dry. (manual, serial)


FDM: soak to dissolve supports.

Stereolithography (SLA):

  • Gross removal of supports. (manual, serial)
  • Soak to remove residual resin. (automated, batch)
  • Cure in an ultraviolet (UV) oven. (automated, batch)
  • Remove remaining support structures. (manual, serial)
  • Light sanding to remove surface imperfections. (manual, serial)

2D ANALOGY

In the context of 2D printing, post-processing is analogous to the steps needed to prepare multiple copies of a report when printed on a basic desktop printer. The job isn’t finished when printing is complete. Prior to distribution, the pages are collated, three-hole punched and inserted into a binder. This manual operation adds time and cost.

However, a better analogy is to photography. The perception and promise of 3D printing is a process similar to digital photography: the moment after taking a picture, the images are ready for distribution.

The reality is that 3D printing is more like film-based photography where the photographer develops the images in a darkroom that houses equipment and chemical solutions. During development, the resulting photo quality and image effects are controlled by the photographer. Contrary to the 2D printing analogy, which adds only time and cost, film photography also requires floor space, equipment and skills.

Time, cost, equipment, floor space and skill are the hallmarks of 3D printing’s post-processing phase.

Six companies contributed their post-processing experiences. These companies represent the automotive, consumer product, medical device, sporting goods and architecture industries. Each noted that the post-processing time and required resources vary by technology and by part. Yet, they kindly reported their typical demands.

Time

According to these companies, prospective users should plan for one hour of post-processing for every one to six hours of 3D printing. This translates to a 17% to 100% increase in the total process time. However, the total elapsed time will often have a much larger increase, as discussed later.

All of the companies noted that time is dependent on the intricacy, or complexity, of the part. For example, small, intricate parts take longer to post process than large, simple parts.

Staff

Staffing is another consideration for prospective users. The companies reported that the ratio of machine operators to part finishers, the employees that do the post-processing, ranges from 1:1 to 1:3.

For smaller labs, an operator may split his/her time between file preparation, machine operation and post-processing, which means that there is a labor cost, but the budget has no added wage expense. However, once total throughput reaches a level where a single individual cannot perform both functions, additional staff will be required.

Facilities

Facilities must also be considered. When providing ample room for the required equipment and workspace to conduct post-processing, these companies report that they have floorplans that use one-half to one square foot for post-processing for each square foot of 3D printer space.

In next Monday’s blog, part 2 of this 3-part series, Todd closely examines the primary impact of, and issues associated with, post-processing experienced by the six companies interviewed.