MIM debinding methods

MIM debinding is the process of removing binders such as paraffin wax and plastic, which are used to improve the injection molding process, from the metal powder to obtain a near-net-shape metal part. Depending on the binder system, debinding methods are mainly divided into two categories: two-step methods and one-step methods. Two-step methods include solvent debinding + thermal debinding, wicking debinding, etc. The one-step method is represented by the advanced Catamold catalytic debinding process.

The Wiech method, invented by Wiech in 1980, mainly includes three approaches: gaseous solvent debinding (Wiech (1) method) takes 3 days, is inefficient and prone to deformation; wicking debinding (Wiech (2) method) takes about 10 hours; and the evaporation method (Wiech (3) method) takes over a day. All three can serve as the first step in a two-step debinding process.

The Injectamax method (1988) is a two-step process. First, a trichloroethane solvent is used to selectively dissolve soluble components such as vegetable oil and paraffin wax. Then, thermal debinding removes the remaining binder. The entire process takes only 6 hours. This two-step method of solvent debinding + thermal debinding has become the mainstream production method in the MIM industry due to its simplicity, low investment, and high efficiency.

The water-soluble method uses water as the debinding solvent. It utilizes water-soluble binders (e.g., polyethylene glycol) that dissolve in water to remove most of the binder, followed by thermal debinding. This method is economical and environmentally friendly, but still faces challenges such as difficult mixing and the need for special storage and transportation equipment. It currently remains at the laboratory stage.

The Catamold catalytic debinding method is a one-step debinding technology developed by BASF in the early 1990s. It uses polyacetal resin as the binder, which is catalytically decomposed into formaldehyde in an acidic atmosphere. No liquid phase appears during debinding, effectively avoiding issues with deformation and dimensional accuracy control. The reaction interface advances at a rate of 1-4 mm/h, significantly shortening debinding time and reducing costs. When combined with CREMER's continuous debinding and sintering system, it enables continuous production and is currently the most advanced MIM debinding method. However, this method presents challenges such as equipment corrosion by the acidic atmosphere and exhaust gas treatment, and the equipment investment is relatively higher.