Influence of characteristics and components of vacuum sintering furnace on high-performance MIMtime：2020-05-12Views：298 Author：Best Seiko
One. In the past two to three decades, the parts produced by metal injection molding (MIM) technology have become increasingly complex, and its application fields have covered a wide variety of different industries. With the increasing demand for high-quality parts with small geometric distortions and strong material properties, the MIM process has been expanded and integrated into production lines in various industries, such as automobile, medical device and mobile phone manufacturing. High power density areas (such as modern automobile engines, powertrains, and machinery manufacturing) require small and compact mechanical systems because they can provide greater innovation potential and higher production efficiency. In addition, complex MIM parts also play a role There are many advantages, such as it can also effectively reduce the assembly time of mass-produced products such as notebook computers and mobile phones. In order to meet the industry's continuous development of technical requirements and related specifications, we must explore the space for growth of MIM process equipment in terms of accuracy and efficiency. The current limitations such as the mechanical and chemical properties of the parts and the optical appearance are mainly caused by the following aspects: 1) uneven shrinkage (geometric deformation) uneven mixing of powder and raw materials; density caused by injection and/or the first degreasing stage Fluctuation; uneven temperature in sintering furnace. 2) Inaccurate process gas management for chemical decomposition and discoloration; binder is deposited again in the second degreasing link; residual sinter furnace contaminants. In addition to these technical limitations, the fiercely competitive market environment shifts cost pressures to parts manufacturers. Because of this, in order to move the MIM industry forward, production equipment and materials that are more profitable and sophisticated in technology are crucial. In addition to high raw material procurement costs (such as fine-grained metal powders, polymer binders, and ready-made injection materials), high-temperature sintering is one of the main cost drivers in the MIM process. The investment and operating costs of degreasing sintering furnaces are the key to the competitiveness of Mhu parts manufacturers. In addition, choosing the most suitable furnace type according to the specific production situation is the prerequisite for success in the MIM industry. two. The applicability of different furnace types does not consider tailor-made, highly specialized systems. Most of the sintering furnaces on the market can be divided into periodic vacuum furnaces and continuous atmosphere furnaces. The brown parts after injection molding and catalysis/degreasing contain residual polymer. Both types of furnaces provide a solution for thermal polymer removal. On the one hand, if it is a relatively large part with mass production that is completely consistent or similar in shape, it is more appropriate to make full use of the continuous atmosphere furnace. In this case, the short cycle and high sintering capacity can obtain favorable cost-benefit ratio. However, on small and medium-sized production lines, such a continuous atmosphere furnace with a very low annual output of 150-200t, high input cost, and large volume is not economical. Moreover, the continuous atmosphere furnace requires longer downtime for maintenance, reducing production flexibility. On the other hand, the periodic vacuum sintering furnace is equipped with outstanding degreasing and sintering process control technology. The previously mentioned limitations, including geometric deformation and chemical decomposition of the finished MIM parts, can be effectively resolved. One solution is to use a sophisticated gas control system to wash away the volatile bonding material with laminar flow of process gas. In addition, by reducing the capacity of the hot zone, the temperature uniformity of the vacuum furnace is very good, up to 1K. In general, the good atmosphere cleanliness of vacuum furnaces, the adjustability of process parameters and the small part vibration make it a technical choice for producing high-quality parts (such as medical devices). Many companies face fluctuating order conditions and need to produce parts of different shapes and materials. The low investment and high cycle flexibility of the vacuum sintering furnace will create favorable conditions for them. Running a group of vacuum furnaces can not only provide a surplus production line, but also run different process programs at the same time. However, some specialized vacuum sintering furnaces with the above technical advantages are limited by the small available capacity. Their disadvantages in input-to-output ratio and low energy utilization rate make the sintering cost of parts may offset the cost savings in other MIM process steps. three. An important factor in the MIM industry's requirement for vacuum furnaces to have cost-effective operation of vacuum sintering furnaces is economical process gas and power consumption. Depending on the type of gas, the two major cost elements of the sintering process can account for 50% of the total cost. In order to save gas consumption, an adjustable gas flow partial pressure mode must be implemented, while ensuring that the degreasing and sintering processes are protected from contamination. In order to reduce power consumption, heat zones are manufactured with optimized heating elements to reduce heat loss. In order to realize these design points and control R&D costs within a reasonable range, a modern resource-saving vacuum sinter furnace will use fluid dynamics calculation tools to find very optimized gas flow and heat flow patterns. Depending on the weight of the sintered parts and the residual polymer content, the binder will accumulate on the peripheral components to varying degrees (such as exhaust pipes, pumps, and hot spots), which will result in long downtime for manual cleaning and daily maintain. If the net weight of the material reaches 400 kg (furnace volume> 1000 L) and the binder content is 3% to 4%, then the polymer up to 15 kg will be removed in the degassing stage. Even so, most of the exhaust gas (>95%) should be collected at a specific condensation point (such as a binder collector or wax separator). Due to decontamination and manual cleaning, the door-to-door cycle time will increase by more than 2 hours. In this way, an inefficient and poorly designed vacuum sintering furnace will reduce the performance by 15%. MIM manufacturers will consider more advanced equipment with automatic cycle cleaning systems to reduce maintenance and keep unexpected failures at a very low level. Fast-growing MIM companies need to be able to flexibly plan their production capacity and respond quickly to changing market demands, but the long delivery time of production equipment will slow down the development of the company. Usually, equipment manufacturers start production after receiving orders, rather than pre-store key components and important raw materials in the warehouse. When the MIM enterprise receives a new emergency order, the 9-12 month delivery time of the new equipment will be the bottleneck of the MIM production line. Until very recently, the leading vacuum furnace manufacturers introduced the concepts of lean production and standardized production. For example, through the modular and standard component design, Ipsen reduced the delivery time of their newly introduced TITAN@DS vacuum sintering furnace to 3 months.
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