Additive Manufacturing Q&A


 

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Additive Manufacturing Q&A

By: Caitlin Oswald

Friday, August 11, 2017
 

Question:

What are important considerations for ensuring the quality of 3D-printed metal parts when working with a supplier?

Answer:

Here are the top-five steps for ensuring the purchase of high-quality metal additive-manufactured (AM) parts:

1) Consider your metal print as a raw material.

When purchasing metal 3D-printed parts, think about what your expectations would be from suppliers of forged or cast components. Are you putting as much thought and consideration into those expectations for your supplier of metal-AM parts? When the supplier employs powder-bed metal machines and uses powder from a raw-material supplier, several steps occur from when the powder ships from the atomizer to when it melts in the powder-bed machine. Confirm that your metal-AM part supplier has the best process controls and checks in place at every step. This will ensure that the material in your part meets all of your requirements.

2) Require your suppliers to meet industry standards.

Industry standards exist to provide a baseline of quality expectations and to ensure compliance. While the material and process specs from SAE, ASTM, AWS and NIST continue to evolve, consider using as many of the specs as possible. In addition, if your industry normally requires accreditations such as ISO9001, ISO13485 or AS9100, continue to enforce those when selecting a metal-AM part supplier. Moreover, start looking for a NADCAP AC7110/14-accredited facility that is specific to AM. The checklist is new this year; however, the list of accredited suppliers will continue to grow and give a baseline confidence that the facility employs a controlled process.

3) Provide detailed requirements.

As an AM supplier, too often we receive requests to print parts with “best effort” attached to the request. Unfortunately, we may not know the part’s fit, form and function as designed, and “best effort” for us may not align with “best effort” for you. While this is more easily said than done, especially when the purchasing company is new to AM, it is important to provide requirements and expectations to your supplier to help ensure that the parts meet requirements. Discuss with the printing experts their plans to meet your supplier’s expectations.

For example, if the part already exists as a casting or forging, start by providing a redlined drawing in order to alter the part into an AM candidate. This will get the conversation started. Suppliers that dig into this level of detail will automatically bring up difficulties and deal-breakers when reviewing the prints and comparing them to their inhouse process capabilities. Details of the conversation should include material specs, tolerances, surface-finish callouts and inspection specs. Since it can be difficult to completely redline a print to meet the AM version, seek to develop a clean statement of work type—a contract that spells out, in detail, the expectations of both parties.

With the expectations outlined, the price of your once “best effort” parts most likely will increase. This should not come as a surprise since good quality comes at a price, and it’s important for metal-AM suppliers to consider all of the true requirements when delivering conforming parts.

4) Require quality analysis.

Initiate a relationship with your supplier’s quality engineer(s). Does your supplier have a quality department? Does its AM parts flow through the same rigorous quality analyses as its machined components? AM-component quality analysis can look different from a dimensional first-article report, but the idea behind it is the same.

Consider these elements of metal-AM quality analysis:

  • Digital: One benefit to AM is the huge amount of data that can be extracted during the build process. Although the amount of data can be overwhelming, engineers must review and analyze the data during and after the build. Significant process variables should be monitored, measured, controlled and constrained. A good-quality metal-printing supplier will be open to share how it measures its process statistics.
  • Visual: There are visual specs that exist for machined parts, so treat as-built additive parts similarly. Inconsistencies in surface finish, color, layering, etc. can signify more than just visual artifacts, and may indicate underlying material concerns. Suppliers of metal-AM parts should employ a visual-inspection checklist in their process standards to fully analyze all parts.
  • Physical: Physical quality analysis includes measuring surface finish and dimensions, verifying proper powder removal, and inspecting for internal material characteristics using nondestructive-testing (NDT) techniques and material cut-ups, as well as evaluating chemistry, density and other material properties. Note that many go-to NDT techniques can become difficult to employ, due to the geometries and surface finishes of AM parts, so your supplier may need to use different inspection processes to verify build results.

Remember that when calling out a material specification that includes physical requirements (chemical composition, density, strength, etc.), the supplier is responsible for performing the necessary testing to prove conformance.

5) Ask for certificates of conformance.

After the supplier has completed all of the post-processing steps and has delivered the parts, ensure that it has met all of your requirements by asking for certificates of conformance from the quality department. This should require the supplier to ensure that it has met all requirements per the statement of work, including completion of reports related to quality analysis, the build process, thermal cycling and final dimensional checks (when performing post-machining or -processing).

Ensuring and documenting quality can be complex and intimidating for those new to 3D-metal printing. The best way to approach the task: Lean on the experts and define supplier expectations. Use every part order and delivery as an opportunity to learn, and apply those lessons learned to subsequent orders. 3DMP

 


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