The perception and promise of 3D printing are that it offers a digital workflow that is simple, fast, and automated — a process that is complexity-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, pushbutton process becomes a manual operation that impacts time, cost, and quality.
The uninitiated — those who 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-value-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 who 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.
Secondary post-processing includes optional part finishing that improves the aesthetics or function of the part. Secondary post-process commonly 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.
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)
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)
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.
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.
For this article, six companies contributed their post-processing experiences. These companies represent the automotive, consumer products, 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 who do the post-processing — ranges from 1:1 to 1:3. For smaller labs, an operator may split his/her time among file preparation, machine operation, and post-processing, which means that there is a labor cost but the budget has no added wage expense. 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 floor-plans that use one-half to one square foot for post-processing for each square foot of 3D printer space.
Impact: Primary Issues
It comes as no surprise that the biggest issues with post-processing are the added cost and the added time, which can be quite significant. Both time and money were noted by the six contributing companies as their primary concerns; however, the ranked priority for each varied and were driven by the current climate within the businesses. Cost was secondary for those who urgently need to accelerate delivery of 3D-printed models and prototypes.
The business climate and corporate goals also influenced the perceived impact of post-processing; for example, the wages paid for post-processing labor were viewed as a barrier to advancement and innovation, a throttle on total production, or a drain on financial resources.
While the negative effects of post-processing are universal, the implications of this required step are interpreted through the lens of the organization's current challenges and goals.
Cost. Post-processing adds cost to 3D printing operations in a number of ways, but the most-cited aspect is labor cost. Using a fully burdened labor rate, the companies reported an hourly cost of $30.00 to $100.00. With four to ten 3D printers, the annual labor cost, fully burdened, ranged from $100,000 to $500,000. This equates to a direct labor cost for post-processing of roughly $25,000 to $50,000 per year for each 3D printer. If the machine operator, or another higher-wage employee, performs post-processing, the annual cost can rise significantly.
When adding a 3D printer, this burdened labor cost must be included in annual operating budgets. The additive manufacturing technology leader at a medical device company said that when budgets are taken into consideration, “adding one more parts finisher means that there is one less machine that I can purchase.”
For those who are already saddled with post-processing labor, the benefit of eliminating this task may not be cost reduction — instead, it could be capability expansion. Considering budgetary limits that preclude hiring, the contributors indicated that they would reallocate the post-processing staff to value-added activities; for example, the medical device company stated that it would redeploy its personnel to activities that either improve its 3D printing operations by advancing the technology or redirect the staff to secondary post-processing activities that improve the quality and appearance of 3D-printed parts.
Michael Zerbe, RP technologies supervisor at Newell Rubbermaid, noted that staffing limitations impact part quality and 3D printer utilization. He said that without primary post-processing, the staff could invest time to improve the 3D-printed models with additional finishing and painting. But more importantly, he could increase his 3D printing output. He said, “With my post-processing resources, I can only run my 3D printers at a 60% utilization rate. Eliminate post-processing and I would have the capacity to run them around the clock. This would mean more throughput, which would allow us to do more iterations for each project.”
Another expense element related to labor is the increased cost for models and prototypes when demand exceeds the capacity of the post-processing team. An engineering manager at a consumer products company noted that during peak periods, he may have the needed 3D printer capacity but lack the required post-processing resources. In these situations, he either has to pay for overtime or subcontract the work to a service bureau. He noted, “Outsourcing increases the part cost by three or four times, and we can't deliver as fast as if we kept the work in-house.”
Time. A key benefit of 3D printing is speed, so anything that slows the process is undesirable. Although a single part may be post-processed quickly, the aggregate effect can extend lead times by days or weeks.
As the contributors shared, post-processing adds 17% to 100% to 3D printing time on a batch-by-batch basis. What those numbers do not reflect is the full impact of this manual, bottleneck operation on schedules. A few hours of post-processing can translate to a 24-hour delay, even with a well-staffed operation. When compounded across multiple design iterations, the delay can be measured in weeks.