The MIM Process
Metal Injection Molding (MIM) can create components for a wide variety of industrial applications. The MIM process combines injection molding technology with powder metallurgy to achieve near-net shape, high volume production of complex mechanical components.
One Step at a Time
Parmatech works closely with customers to ensure the best production at the minimum cost. While MIM generally consists of a few main steps, we will optimize the material, binder system, and processing path for your application.
MIM tooling is similar to tooling used in plastic injection molding. These tools can range from simple prototype tools to high volume multi-cavity production tools.
We start with a fine metal powder (particle size approximately 10-20 microns) and mix this with a proprietary blend of plastics that we call “binders”. The powders are incorporated, or compounded, into the fluid binder and granulated to form a feedstock for an injection molding machine.
After compounding, the feedstock is injected into a mold to form a “green” part. The injection molding machine, similar to that used in the plastic injection molding industry, heats the feedstock and injects the viscous fluid into the mold. The MIM part in this molded state is often referred to as a ‘green’ part.
The binders are removed through solvent and thermal processing. The step is called debinding, and helps separate the binder materials from the powder metal. Debinding can be done in two or three process steps, depending on the equipment capability.
Finally, the parts are put through a high-temperature sintering furnace where the remaining binders are removed. The powder particles fuse together to reach 98%+ of theoretical density. During this critical step, the parts shrink approximately 20%. We utilize special techniques that result in exceptional metallurgical and dimensional controls, resulting in very repeatable and stable parts.
After sintering, the parts are inspected against high quality standards. At this point, additional operations – such as machining, heat
treating or plating – may be undertaken to achieve tighter tolerances or enhanced properties.
Part design greatly impacts process capability. From uneven wall sections to features that need support through sintering, there are specific factors that determine the tolerances possible on a part. By working with you as early as possible in the MIM process, our sales and engineering staff can help you to match the process’ capability to the tolerances needed to achieve required design function. Without secondary operations, the MIM process is capable of ± 0.3% to ± 0.5% of a given dimension; for example, 1.000 ± 0.003 inches or 25 ± 0.075mm.