Cracks, blisters and delamination usually appear during debinding, not during printing. The green part is fragile, the binder is leaving as vapour and gas pressure, and every thermal ramp is a trade-off between speed and safety.
The chemistry of binder removal
Debinding is a thermal and chemical event, not a mechanical one. Between roughly 100 °C and 600 °C, the organic binder chain breaks apart. Some fractions evaporate, some oxidise to carbon dioxide and water, and some leave behind a carbon residue that must be burned out later. If the temperature rises too quickly, gas pressure builds inside the part faster than it can escape through the pore network. The result is a blister, a crack or a complete fracture.
Our baseline ramp is 2 to 5 °C per minute through the critical binder-loss window. Thin-walled parts and open lattices can tolerate the faster end of the range. Thick sections, large solid blocks and parts with blind holes need the slower end.
Wall thickness and venting
Thick walls store more binder per unit volume and the diffusion path to the surface is longer. A 2 mm wall and a 10 mm wall cannot share the same schedule. For thick sections we extend hold steps and reduce ramp rates. We also recommend avoiding enclosed voids. A cavity with no vent turns into a pressure vessel during debind.
Channel design is equally important. Cooling channels, manifolds and hollow features need at least one opening to the outside. If the geometry demands a closed cavity, we can print separate halves and join them after sintering, or design the cavity as a leachable core that is removed later.
Atmosphere and contamination
Atmosphere controls whether binder decomposes cleanly or leaves carbon residue. In air, oxidation is faster and cleaner. Inert atmospheres may be needed for some materials to prevent unwanted reactions, but they can slow binder removal. We match the atmosphere to the material: alumina and zirconia typically run in controlled air, while our silica-based CoreCera SC grade uses a profile that preserves leachable chemistry.
Humidity and residual solvent from the wash step also affect debind. Parts are dried thoroughly before they enter the furnace. A wet green part can steam during the first ramp, which is a common cause of surface pitting.
How we verify a successful debind
We catch problems by weighing parts before and after debind. The mass loss curve should match the theoretical binder content. If a part loses mass too quickly, it is likely cracking internally. If it loses too little mass, carbon residue may remain and cause discoloration or reduced strength after sintering.
Visual inspection and low-pressure air testing round out the debind checks. Only parts that pass debind move to the sintering furnace. Catching a defect at the brown stage saves the cost of a wasted high-temperature cycle.