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FEATURE MATERIALS IN DESIGN & PROTOTYPING


DebinDing: Releasing the holD on aDDitive ManufactuReD PaRts


With Additive Manufacturing (AM), or 3D printing as it’s also known, parts design possibilities are nearly limitless. Not only can engineers rapidly iterate designs, make changes to custom-made prototypes and test them, but AM


is a quick and practical way to make detailed, precise and often customised designs. With AM, the parts are constructed in progressive layers by depositing or extruding construction materials. But, building the parts is


just the beginning, using the right debinding and cleaning fluid is also key, as Elizabeth Norwood, senior chemist at MicroCare, LLC, explains


A


lthough plastic is still widely used for most AM, the use of metals, ceramics and composite materials is rapidly gaining


momentum. Metal additive manufacturing employs the same layered-build process as plastic, but uses fine metal powders and a binding agent, typically wax, to create green-state parts. After layering, the green parts are sintered in an oven to render fully dense metal parts. The binding agents help form the green


parts, but they must be partially removed before the parts are exposed to the high-heat sintering. Too much binder left inside the parts could result in part cracking or deformation while sintering; too little could cause the parts to lose their dimensional integrity. In many cases, the binders are extracted using


a specialty fluid inside a vapour degreaser. The fluid is engineered for selectivity so the right amount of binder is removed, preventing damage to the part structure. Some of the binder is taken out, but not so much that it impacts the part’s stability during sintering. Once the select amount of binder is removed,


the parts are thermally sintered under high heat to bond the metal powder into its finished, solid, mass state. After sintering, the parts can be post-processed using standard metal finishing techniques like grinding, cutting or coating.


chooSing the Right DebinDing FluiD


Although parts debinding is a straightforward process, it is important to get the fluid details right for the best possible outcome. The physical properties of the debinding fluid are important. Here are the chief factors to consider. Materials Compatibility: The debinding fluid


should be safe to use both with the metal powders and the binders to safeguard the green parts. The debinding fluid should be aggressive enough to selectively remove the right amount of binders yet still maintain the parts’ integrity. Also, it helps if the debinding fluid is low-


boiling. Low boiling debinding fluids still melt the wax binders but do not damage the non- soluble fragile parts. Plus, it allows the vapour degreaser to run more efficiently. A lower boiling point reduces the vapour degreaser start-up time, energy consumption and cost, and requires less heat input to operate. Low Surface Tension and Viscosity: Low surface tension and low viscosity debinding fluids work their way into, and more importantly out of, blind holes, end holes and tight, internal geometries, for more complete debinding. This prevents parts from expanding and cracking during sintering should any of the gasified binders get trapped inside. Sustainability:


Debinding fluids must meet strict global regulatory requirements and environmental


5 DESIGN SOLUTIONS OCTOBER 2022 4 Metal additive manufacturing


sustainability standards. Most have a very low GWP (Global Warming Potential) under 10 to help reduce greenhouse gas effects. They also have zero ODP (Ozone Depleting Potential) and low VOC formula content. This


allows them to meet strict regional air quality regulations. Many are not considered a HAP (Hazardous Air Pollutant) and do not require National Emission Standards for Hazardous Air Pollutants (NESHAP) permits. They also follow global environmental directives including the European F-Gas and REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) legislation. In addition, when used in a vapour degreaser, modern debinding fluids are distilled, recycled and reused, limiting environmental waste.


DebinDing FluiD Selection


Additive manufacturing offers greater flexibility for designers to create devices that would have been too costly, too time-consuming or too complicated to make using more traditional subtractive manufacturing methods like cutting, boring, drilling or grinding. With the right tools, including effective debinding fluids and a vapour degreaser, manufacturers can gain operating efficiency, lower their additive manufacturing costs and improve their overall production timelines. To learn more about fluid debinding using


vapour degreasing, partner with a fluid supplier that specialises in vapour degreaser debinding. They can help conduct on-site audits, perform in-lab tests with sample green parts and make environmentally sound recommendations on which debinding fluids will work best.


MicroCare www.microcare.com


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