Post processing 3D-printed parts has challenges

The post process for a 3D printed part from left to right, a raw 3D printed part, a water blasted part, low energy finished and dyed part, high energy finished and dyed part. (Courtesy: Bel Air Finishing)

Additive manufacturing, or 3D printing, is becoming a widely popular form of production. Although it comes with its own set of challenges, the adoption of the process is accelerating. However, the finishing process (otherwise known as post processing) for 3D printed parts remains a challenging and arduous task for most producers of 3D parts. The medical, automotive, aerospace, and fire arms industries are having difficulty developing finishing processes for their parts. Bel Air has created a series of steps to help manufacturers create or improve the finishing of 3D parts.

In most cases, working with an experienced company such as Bel Air is the best way to design a finishing process for a part. In order to get the most out of the experience, it is best to understand how the process works.

First, a 3D model of the part should be made available to provide valuable information on how the part’s structure and size will affect the post process. A 3D model will help narrow down the machines, compounds, and media that can be used on the part. The 3D model, the size, and the geometry of the part will all affect the finishing process. For example, consider a large part with a complex geometry sent to Bel Air Finishing; since there are many aspects associated with this geometry, it is best to have a conference with the customer to discuss background information related to the part and its function. This will help decide which specific technologies to consider it can also provide vital information for creating a feedback loop that will 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 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/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.

The purpose of the parts is an important thing to consider and it directly affects the details of the finishing process. Deciding whether or not a part’s finish should be for cosmetic and/or functional purposes is important. Parts can be made to be shiny, matte, or coarse along with 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 parts they want to process a day and how consistent they want the process to be. In the mass finishing world, no two parts have the same exact finish, there are always slight variations. There are bound to be a small number of defects in the processing of parts whether they come from printing or accidental wear and tear in post processing. Consider the margin for error, what are the acceptable values for this number? Furthermore, additional processes can be considered. Dyeing, coating, and electroplating can be done to improve the look and feel of finished parts. After all the criteria have been set, the parts are ready to be processed.

Sending a sample of acceptably finished parts can 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 ZYGOT metrology data. This means that the surface data is recorded using a contactless method and a 3D image of the surface is created as well. These provide an in-depth look into how surfaces can be improved.

After the part has been analyzed thoroughly, 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, and/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 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.