Over the past 30 years, parts produced by Metal Injection Molding (MIM) technology have become increasingly complex and its application areas have covered a wide range of different industries. With the growing market demand for high-quality parts with small geometric deformation and strong material properties, MIM technology and processes have spread and integrated into production lines in various industries, such as automotive, medical device and mobile phone manufacturing. High-power density fields (such as modern car engines, powertrains and mechanical manufacturing) require small and compact mechanical systems because it can provide greater innovation potential and higher production efficiency. In addition, complex MIM technology parts have also brought many advantages, such as it can effectively reduce the assembly time of mass-produced products such as laptops and mobile phones.
To meet the industry’s evolving needs for technical requirements and related specifications, we must explore the growth space of MIM technology and process equipment in terms of accuracy and efficiency. Currently, limitations on mechanical and chemical properties and optical appearance of parts are mainly caused by the following aspects: uneven shrinkage (geometric deformation, uneven mixing of powder and raw materials; density fluctuations caused by injection and/or first debinding stage; uneven temperature in the sintering furnace. Chemical decomposition and discoloration, inaccurate process gas management; binder redeposition in the second debinding stage; residual sintering furnace contaminants. In addition to these technical limitations, the fiercely competitive market environment transfers cost pressure to part manufacturers. Therefore, in order to move the industry forward, more profitable and technologically sophisticated production equipment and materials are crucial.
In addition to the high raw material procurement costs (such as: fine-grained metal powders, polymer binders and ready-made injection raw materials) , high temperature sintering is one of the main cost drivers in the MIM process. The investment and operating costs of the debinding sintering furnace are key to the competitiveness of MIM parts manufacturers. In addition, choosing the most suitable furnace type according to the specific production situation is a prerequisite for success in the MIM industry.
Without considering tailor-made, highly specialized systems, most sintering furnaces on the market can be divided into periodic vacuum furnaces and continuous atmosphere furnaces. Brown parts after injection molding and catalytic/debinding contain residual polymers, and both furnace types provide solutions for thermal removal of polymers. On the one hand, if relatively large parts with exactly the same or similar shapes are mass-produced, it is more appropriate to make full use of continuous atmosphere furnaces. In this case, short cycles and high sintering capacity can achieve a favorable cost-benefit ratio. However, on small and medium-sized production lines, this minimum annual output of 150 ~ 200t, high investment cost, and large volume of continuous atmosphere furnace are not economical. Moreover, continuous atmosphere furnace requires longer downtime for maintenance, which reduces production flexibility.
If you want to keep production uninterrupted and maintain low maintenance costs, you must consider protecting key structural components through effective binder collection systems of MIM technology. The separation of airflow and binder is achieved in modern vacuum sintering furnaces. A vacuum pump realizes efficient hot zone vacuuming, which consists of a Roots pump supported by a mechanical pump. The high-temperature and high-speed process gas carries the saturated evaporated polymer material and is extracted through the exhaust pipe at the bottom of the vacuum furnace shell. When the MIM technology airflow is affected by the cold pipe wall and turns, it suddenly slows down and cools down, causing part of the gaseous binder to condense again instantly; in this way, up to 20% to 25% of the binder material has been deposited in the pipeline, which will eventually lead to pipeline blockage.