By Sean Fenske, Editor-in-Chief
 
The world of medicine is getting smaller and smaller, and the devices, instruments, and technologies critical to its delivery must continue to shrink in a similar manner. As such, device makers are seeking supply partners who can provide components that are extremely small, but must still offer certain physical characteristics. The challenge is not for every supplier, so it’s important to know what’s involved in the effort.
 
One such option for micro-sized components that still offer strength and durability is micro metal injection molding (micro-MIM). Device parts made with this fabrication method can provide cost advantages over the long term when volumes are high. Details can also be incorporated that may not be able to be machined efficiently.
 
Sharing insight and expertise on this less commonly used component fabrication method is Donatelle’s Chief Research and Technology Director, Raghu Vadlamudi. In this Q&A, he discusses the applications where micro-MIM can be ideal, differences compared to other options, and considerations to keep in mind when specifying parts for this process.
 
Sean Fenske: Before we get into micro-MIM, can you first provide an overview of what is involved with metal injection molding (MIM)?
 
Raghu Vadlamudi: Metal injection molding involves molding, de-binding, and sintering to manufacture metal parts economically as compared to traditional metal machining. The metal powders are blended with proprietary binders (polymers and waxes) to enable injection molding into the desired part shapes at high production rates. These molded parts are then de-bound in solvent or water to remove the binders, and then sintered at high temperatures to fuse the metal particles. Metal machining is a subtractive process whereas metal injection molding is a forming process.
 
Fenske: How does micro-MIM differ from other metal fabrication process, such as micro-machining?
 
Vadlamudi: Micro-MIM excels where micro-machining is cost prohibitive. As feature sizes get smaller, they become difficult to machine with the current equipment technology and cutting tools. Some parts have wall sections down to 150 microns. Micro-MIM needs capital investment in building the molds during the initial stages of the project, but is better in cost performance during scale-up when compared to machining.
 
Fenske: What applications are ideal for micro-MIM for medtech? Where is it being used?
 
Vadlamudi: With miniaturization currently a big trend in the medtech industry, micro-MIM will become the manufacturing process of choice as metal-cutting processes are limited in producing micro features and meeting tight tolerances. If a part is high volume with tight tolerances or micro features, micro-MIM may be a solution. Even though the initial investment cost may be high, micro-MIM offers better accuracy, consistency, and cost advantages for high-volume manufacturing.
 
Micro-MIM is a viable alternative for many parts currently being machined, including metal connectors in implantable pulse generators, gear pump components, and pacemaker components for cardiac rhythm management. Other applications include dental, ophthalmic, drug delivery, and surgical ablation components.
 
Fenske: What material considerations and/or limitations are there when using micro-MIM?
 
Vadlamudi: The hardness of micro-MIM parts is inferior compared to machined parts due to porosity of the material. However, micro-MIM parts can meet the performance requirements of medical devices. And, depending on the application, one can employ secondary operations such as HIP, H900, and electropolishing to improve the properties to fit their needs.
 
Fenske: What are common misconceptions regarding micro-MIM and what do you say to dispel them?
 
Vadlamudi: Many are concerned about the strength and stability of a micro-MIM part. We assure them metal injection molded parts can be manufactured with porosities less than two percent. The porous structure is also not interconnected, as most believe. Metal parts molded with cobalt-chromium and titanium alloys can find their applications expanded to implantable devices.
 
Fenske: What considerations should a medtech OEM take into account when selecting a micro-MIM supplier?
 
Vadlamudi: They need to be aware of critical capabilities required to produce quality parts. Through our experiences in working with medtech OEMs, Donatelle has identified four areas where micro-MIM suppliers can fail—causing delays, added costs, and often the need for a new supplier. Here’s what they should asking:
 

1. Is the supplier using scientific principles to develop manufacturing processes?
2. How vast is the supplier’s knowledge of materials?
3. Does the supplier possess the equipment and technology expertise required?
4. Does the supplier understand the product requirements?