Metal 3D printing, a subset of additive manufacturing is a dynamic process used to make fully-finished, machine-grade metal parts. There are many types of metal 3D printing methods in use today. However, two-methods stand out for their speed, ease of use and cost-effectiveness.
Binder Jetting and Feedstock Extrusion both create parts either by building or extruding a combination of finely powdered metals and wax or plastic binders along a precise path, layer-by-layer directly onto a build plate. The binders serve a critical purpose to form the metal powder into a specific shape. However, the binders must be removed before the green parts can be exposed to the high heat required for the next step of sintering.
Used either in the liquid or vapor phase in a vapor degreaser, the debinder fluid selectively dissolves up to 4% of the binders and transports them out of the metal parts, creating pores and voids in the parts in preparation for sintering. The binders are progressively removed to avoid deformation and cracking during sintering, while also allowing the parts to maintain their dimensional accuracy, compress uniformly and sinter evenly.
This is where the physical properties of the debinding fluid become important and should be chosen carefully.
- Good materials compatibility: The debinding fluid should be safe to use on delicate uncured substrates. Use a fluid that is compatible with both the metal powders and the binders to safeguard the integrity of the formed parts.
- Right solvency or strength: Fluid strengths are typically indicated by Kb values. The debinding fluid should be aggressive enough to selectively remove the right amount of binders yet still maintain the integrity of the parts. Too much binder left behind could result in cracking, deformation or part expansion during the sintering process.
- Low toxicity: To protect workers and the environment, choose a fluid without n-propyl bromide, methyl pyrrolidone, heptane or trichloroethene which all carry health and or environmental baggage.
- Low boiling: Low boiling fluids still melt the wax and additives but allow the vapor degreaser to run more efficiently, saving energy costs. The low boiling point also prevents damage to the non-soluble binder components.
- Fast evaporating: Fluids with low latent heat of evaporation dry more quickly, translating into greater product throughput.
- Low surface tension: Low surface tension allows the fluid to work its way into the parts structure to penetrate the pores and internal channels to remove the binders more easily.
- Low viscosity: Fluids with low viscosity flow around the parts more easily for more complete debinding and cleaning.
- Nonflammability: Nonflammable fluids are safer for workers and do not require specialty fire or explosion-proof equipment.
- Maintenance-free: Debinding fluids should be stable and not require acid acceptance testing or stabilizer maintenance.