Pre-planning for post-processing

Developing the right finishing process for 3-D printed parts

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Additive manufacturing, also known as AM or 3-D printing, is becoming a widely popular form of production. Although it comes with its own set of challenges, the adoption of 3-D printing

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The post-process for a 3-D printed part from left to right: a raw 3-D printed part, a water blasted part, a low energy finished and dyed part, and a high-energy finished and dyed part.

is accelerating based on a variety of factors, including the development of more affordable equipment, the emergence of new powdered metals and the increase in the speed of the overall process.

While the use of 3-D printing is increasing, the finishing process, otherwise known as post-processing, for 3-D printed parts remains a challenging and arduous task for most 3-D part manufacturers. Even those in the medical, automotive and aerospace industries experience their share of headaches when it comes to developing finishing processes for their 3-D printed parts. Fortunately, companies like Bel Air Finishing Supply Inc. are working diligently to overcome these shared issues. Bel Air has created a series of steps to help manufacturers create or improve the finishing of 3-D printed parts.

Plan ahead

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There are many ways to finish process 3-D printed parts, and working with a post-processing expert is the best way to narrow down the choices and improve efficiency and process time.

In most cases, working with an experienced, knowledgeable expert is the best way to develop the right finishing process for a 3-D printed part. But even after the process has been developed, it’s critical that the manufacturer understands how the process works and how to measure the results of the process.

First and foremost, a 3-D rendering or CAD/CAM file of a part should be made available to the expert that will be developing the finishing process. The rendering can provide valuable information on how the 3-D printed part’s structure and size will affect post-processing while also helping to narrow down the machines, compounds and media that can be used on the part.

Understandably, the size and geometry of a 3-D printed part ultimately determines the chosen finishing process. For example, consider a large part with a complex geometry that was recently sent to Bel Air. Because there were many aspects associated with its geometry, it was key to schedule a conference with the customer to discuss additional background information related to the part and its function. This helped decide which specific finishing processes to consider and also provided vital information for creating a feedback loop that would help improve post-processing.

A feedback loop is how Bel Air works with companies in order to produce a more effective post-processing operation. The 3-D printed part may not be fully optimized for post-processing and by suggesting alternative print layouts, post-processing can be more expedient and productive. This step also aims to preserve and improve the cosmetic and functional components of the part. Once the suggestions have been made and the design of the part has been decided, it is time to consider the finishing needs of the part.

Continued considerations

The intended purpose of a 3-D printed part is equally important when considering the method in which it will be finished. Whether or not a part’s finish is for cosmetic or functional

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Bel Air’s Water Jet is capable of removing build powder off of 3-D printed parts.

purposes is a determining factor when choosing the best finishing process for the application.

3-D printed parts can, of course, be made to be shiny, matte, coarse or have a number of other surface qualities. The part can be processed to a certain Ra value, too. (Ra is a measure of the surface’s roughness.)

Manufacturers also need to know how many 3-D printed parts they want to process a day and how consistent they want the finishing process to be. In the mass finishing world, no two parts have the same exact finish; there are always slight variations. Therefore, there are bound to be a small amount of defects in the processing of parts – whether they come from the 3-D printing part of the process or from accidental wear and tear during post-processing. To overcome these inconsistencies, manufacturers must consider the margin for error. What are the acceptable values for this number?

Furthermore, additional processes must be considered, such as whether dyeing, coating or electroplating can be done to improve the look and feel of a finished 3-D printed part. After all of the criteria have been set, the parts will be ready to be processed.

Sending a sample of acceptably finished 3-D printed parts can also help create a more effective post-process. Bel Air is able to take sample parts and analyze them to determine the exact cosmetic and metric details of the part using Zygo metrology data. This means that the surface data is recorded using a contactless method, and a 3-D image of the surface is created, as well. These provide an in-depth look into how surfaces can be improved.

Final finish

After the 3-D printed part has been thoroughly analyzed, it is time to decide what technologies to incorporate into the sample process. A sample process is determined based on the manufacturers’ needs whether they are finish quality, price or pure throughput. Machines, media and compounds are recommended and then selected for the sample processes. Then, the processes are done and metrology is taken to determine the exact effects of each one.

After all of this is completed, it is best for all parties to discuss the results and determine how to move forward. Additional equipment should also be considered in order to preserve the life of machinery and media in order to lower maintenance costs. More sample processes can be made and manufacturer specifications can be changed in order to further improve or create a more realistic finish.

Bel Air Finishing Supply has developed these steps in order to provide manufacturers with everything that they need to create a finishing process. The key is to remember that despite the challenges associated with 3-D printed part finishing, there are experts available that can help.

Bel Air Finishing Supply Inc. 

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