The debinding step in a powder metallurgy process is designed to remove binding agents in the part prior to the sintering process. Depending on the specific binder being used, this is done via degradation and/or evaporation or with a solvent. The “binder” is necessary in order to shape the part in the printing process and create a way in which the powdered metal can be extruded in a controlled manner.
- Degradation: A chemical reaction between the gas used in the furnace and the binder that degrades the binder into new components that can then be evaporated.
- Evaporation: The binder is brought to an elevated temperature where it becomes vapor. Many times, the binder will break into small molecules before evaporating. The vapors can then leave the part through surface-connected pores that will later be removed during sintering. Gas flow helps to sweep the binder away from the part and out of the furnace chamber.
- External Solvent Debind (What DM Uses) – The Studio System debinder immerses green parts in proprietary debind fluid, that uses heat and agitation to dissolve primary binder and creating open-pore channels throughout the part in preparation for sintering.
The temperature at which thermal debinding occurs depends on both the binder material and metal being used, but generally happens between 200C and 550C. Furnaces typically ramp up slowly to ensure the binder isn’t converted to gas too quickly, potentially damaging parts. During the furnace cycle, gas constantly flows through the furnace to remove binder and ensure the atmosphere prevents oxidation of the metal. The gas will either be inert or reducing to ensure minimal oxidation occurs. The original Desktop Metal Studio system and some of the materials used on the Studio 2 system use the external solvent debind process with the debinding system. The Studio System 2 removes the need for the debinding system by utilizing the evaporation method.