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Remanufacturing by 3D Printing of Metals? A Great Potential but Big Challenge

Hongtao Ding

 

 

 

 

 

 

 

  By  Hongtao Ding, PhD
Assistant Professor
University of Iowa
2015 SME Outstanding Young Manufacturing Engineer
 SME Member Since 2013

 

 Do you have expensive equipment that needs to be fixed? Are you looking for a cost-saving repair method? Remanufacturing offers great potential for restoring nonfunctional, discarded or traded-in products to like-new condition.

The key idea in remanufacturing is “like-new,” and reconditioning is the most important step when it comes to ensuring like-new condition. Welding has traditionally been used to restore the shape and functionality of damaged engineering components. However, since the welding process cannot rebuild three-dimensional (3D) features, it is not ideal for damaged 3D structures. In addition, it usually creates a nonuniform subsurface microstructure from the filler materials and base material. These undesired microstructures cause poor bonding between the filler material and the damaged part, leading to the loss of original product identity.

After the geometric features of a damaged part are rebuilt, post-processes are often required to achieve desirable dimensional tolerances, hardness and surface roughness, and to ensure like-new performance. Heat treatment is normally used in industry to increase hardness and wear resistance by introducing solid-state phase transformation in the material. However, there are major problems with these bulk-material hardening methods: (1) the severe thermal distortion induced to the whole structure; (2) the lack of versatility for parts to be rebuilt with complex and delicate geometric features; and (3) poor energy efficiency. Heat treatment is usually followed by hard machining to semifinish the hardened part to desirable dimensional tolerances and to eliminate distortions. Grinding is then applied to achieve the required surface roughness as the last step. However, the equipment used for these post-processes, such as CNC machining centers and grinders, is the same as that used in the production of new parts in manufacturing plants. This poses a serious challenge for remanufacturing a small batch of parts because setting up machining centers and grinders for damaged parts with complex geometric features and toolpaths can be very costly. Even if geometrical reconditioning is achieved, surface integrity and material properties are difficult to restore to original standards with processes from new parts production.

 

Remanufacturing Using a 3D Printer?

Recent progress in life-cycle engineering has shown that accurate 3D printing/additive manufacturing technologies have made 3D feature rebuilding economically viable. Furthermore, it has been demonstrated that remanufacturing cuts down the cost of waste disposal because it builds on the nondamaged portion, which is close to its final form, and thus requires only a fraction of the material processing. Consequently, remanufacturing by accurate additive processes will enable industries to save energy and material. Laser metal deposition (LMD) is one of the most promising 3D printing technologies for creating 3D solid forms from damaged parts. During the LMD process, metal parts are fabricated directly from a computer-aided design solid model by using a metal powder injected into a molten pool created by a focused, high-powered laser beam. This technique is equivalent to several trademarked techniques such as laser direct deposition and direct metal deposition.

Post-processes are still required after 3D printing the damaged part to achieve the desirable dimensional tolerances, hardness and surface roughness and to ensure like-new performance. The dimensional accuracy and porosity of parts made by LMD have been studied extensively. However, data on their metallurgical and mechanical properties are very sparse and disorganized, as these coupled attributes are highly process and material dependent. The essential feature of the LMD technique is that, as a result of layer overlap during the build-up of a part, the deposited material undergoes consecutive thermal cycles leading to progressive modification of its microstructure and properties. As a result, the microstructure evolution during the LMD process is very complicated, and the solidified microstructure and mechanical properties are highly nonuniform within different layers and different zones, which prevents the use of these repaired components in high-strength applications.

Very few have discussed systemic methods to innovate the post-processes and modify/control the microstructure properties of the repair for desirable surface integrity, mechanical property, microstructure, residual stress, etc. One reason is the lack of standardization of the LMD process. Inadequate knowledge of how to modify/control the surface and microstructural properties are significant technical barriers to and/or limitations for widespread implementation of LMD processes for remanufacturing of engineering components. The good news is that some large US companies in the aerospace, defense and biomedical fields have adopted LMD technology for high-value, complex part remanufacturing. For instance, GE has spent significant resources on learning how to use LMD technology for remanufacturing oil and gas components and how to post-process them to meet their own production and legal requirements.

 

Scholarship Applicants Needed
 SME Education Foundation

The SME Education Foundation is now accepting scholarship applications for the 2016–17 school year. These scholarships offer students a powerful reason to choose a manufacturing-focused education. With the generosity of its many corporate partners, the Foundation is able to provide millions in scholarships to attract thousands of new students into manufacturing every year. Scholarships range from $1000 to $6000, and can be used for tuition, books or lab/course fees related to attaining a technical or engineering education. In addition, the SME Education Foundation annually offers substantial scholarships to students with at least one parent or grandparent who has been an SME member in good standing for the last two years. The Family Scholarships include one award in an amount up to $70,000 payable over four years and two, one-year scholarships of $10,000 each. To apply, students must first register at smeef.org/scholarships. Submission Deadline: Feb. 1, 2016

 

2016 Design Competition

For SME’s 2016 Design for Direct Digital Manufacturing Competition, designers and engineers are challenged to take a base, unmanned aerial vehicle (UAV) design and apply additive manufacturing to improve it. Contestants may choose from two different “stock” designs available in the public domain. Improvements in performance are to be quantified at the part and systems level. Contestants are encouraged to employ more than one additive process and material. However, they do not need to build the item(s), but must analyze and justify the processes and materials selected by providing supporting data and/or evidence.

The top designs will be recognized during SME’s RAPID 2016 event, May 15–19, 2016, in Orlando, FL. All entries must be submitted by March 21, 2016. Visit sme.org/ddm-competition for complete details and submission guidelines.

 

 

This article was first published in he November 2015 edition of Manufacturing Engineering Magazine. Click here for PDF.

 


Published Date : 11/1/2015

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