Binder jetting is a powder-based additive manufacturing (AM) process that combines inkjet technology with a binding agent. Suited to higher-volume, lower-cost applications, binder jetting offers speed and cost advantages over some other powder-based AM processes. As with all AM processes, the quality of the final printed part is dependent to a large extent on a controlled atmosphere at many steps in the workflow.
The key steps involved in binder jetting are outlined below.
The liquid polymer binder is selectively deposited onto the powder bed to join the metal particles at room temperature. Even under these conditions, a controlled process gas atmosphere in the print chamber, using nitrogen for instance, offers major advantages relative to air:
The printed “green part” is heated to a temperature typically between 150°C and 250°C to crosslink and dry the binder in order to strengthen the sample. Curing in air can lead to severe oxygen pickup, depending on the alloy. Conducting this curing process under a controlled gas atmosphere will:
During de-powdering, inert environments are used to reduce the risk of reactive powders exploding in the dust clouds generated as part of this process. Furthermore, compressed gases are commonly used with a compressed air gun to de-powder channels and other intricate cavities.
Heating the printed component to approx. 450°C will evaporate and decompose the binder. Here also, replacing air in the furnace with a controlled atmosphere presents a number of advantages:
In this last step, the part is heated up to high temperatures to bond the metal particles, thus densifying the component to levels as high as 99%. But the high temperatures in the furnace - which typically exceed 1000°C for many alloys - present a high risk of reactivity between the metal surface and the furnace atmosphere. A controlled, high-quality gas atmosphere, tailored to the alloy metallurgy, is key to obtain the desired material properties in the finished part. Benefits of a controlled atmosphere here include:
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