Bound Metal Deposition Uses MIM to Create New Metal 3D Printing Process

by Dave Macfie and Shawn Spinneweber, Cimquest

The advent of metal 3D printing, also known as additive manufacturing, has promised to dramatically change the way products are made. The benefits are: the reduction or elimination of up-front tooling and increased complexity due to the removal of conventional manufacturing constraints which lead to shorter lead times, part consolidation, and weight reduction. Today, metals represent one of the fastest growing segments in 3D printing globally. Shipments of metal 3D printers increased by 51% in 2015, compared to 2014, and they continued to climb in 2016. Various research firms project additive manufacturing will be a $20B industry by 2020. (Source: Wohler’s Report 2016). While global metal manufacturing is estimated to be a $1 trillion industry.

In spite of this growth, metal 3D printing options have not been accessible for the majority of manufacturers due to their cost and operational complexity. In addition, most technologies have relied on slow, laser-based processes that demand high levels of manual labor such as removal of metal supports with CNC. Handling the metal powder also poses health and safety issues which require a larger investment in equipment and facilities. For these reasons, metal 3D printing has been used almost exclusively for “high-value” applications such as body implants, aerospace applications and other products that are highly complex and produced in low quantities or require a high degree of customization such as patient specific devices in the medical industry.

So how might metal 3D printing become more accessible for engineering teams? When will it be fast enough and cost-effective enough for mass production? A company in Massachusetts, Desktop Metal, might have the answer. They recently introduced a technology called Bound Metal Deposition (BMD) which leverages the metal injection molding (MIM) process.

Bound Metal Deposition

MIM is a proven manufacturing technology that has been used for 40 years to create complex metal parts much like plastic injection molding. The process consists of mixing metal powder with a plastic binder that is shot into a precision mold creating a “green” part. The green parts are made larger to compensate for shrinkage and final part geometry and density are achieved by binder removal and sintering. MIM requires up-front Close up of metal hinges printed as an assembly tooling which adds from Desktop Metal Studio printer to the lead-time and part costs. Larger quantities of parts are generally required to amortize tooling costs, as such; the process is not great for low-volume production or prototyping.

BMD is similar to the safest and most widely used 3D printing technology; Fused Deposition Modeling. With this process, the metal powder and binder are pre-mixed and formed into rod stock. When combined with MIM, BMD is used to shape (3D print) the “green” parts thus eliminating the need for tooling. Metal parts can be printed one at a time for prototypes or up to hundreds for low-volume production. For mass production, another technology; Single Pass Jetting (SPJ) will be introduced next year. SPJ will build metal parts up to 100x the speed of today’s metal 3D printers and also leverages the MIM process. These technologies are the beginning wave of how metal parts will be prototyped and manufactured in the near future.