What are the advantages of martensitic stainless steel in mold 3D printing?

一, Technical feasibility: Moving from the lab to the manufacturing line
1. Complete coverage of the material system
Metal 3D printing can now work with all the materials that are typically used to make molds. For example, laser powder bed melting (LPBF) technology may print classic mold materials including H13 tool steel, P20 mold steel, and 1.2709 martensitic steel. By fine-tuning the process settings, important measures like hardness, toughness, and wear resistance of printed parts have matched or exceeded the specifications for forging materials. For instance, one company used LPBF technology to make mold holes out of H13 steel. The hardness went up to 52HRC after heat treatment, and the thermal fatigue life was 40% longer than with typical processing. It can handle more than 500,000 cycles of injection molding.
Metal 3D printing has shown to have particular benefits in the area of specific materials. Because people wanted materials that were both highly conductive and resistant to corrosion, the company created a copper-based alloy printing process. This process has a thermal conductivity coefficient of up to 380W/(m · K), which is 25% higher than traditional beryllium copper molds. Because people wanted materials that were lightweight, aluminum alloy and titanium alloy printing technology can reduce mold weight by 30% to 50% while keeping the strength of the structure.
2. Unrestricted progress in structural complexity
Traditional mold making is limited by the geometric limits of subtractive processing. To make complex structures, methods like splitting, splicing, and welding must be used, which makes the molds less accurate and shortens their lifespan. Metal 3D printing can make any complicated shape right away, especially new ones like conformal cooling channels, breathable steel, and dot matrix filling.
For example, traditional drilling methods can only make straight or simple line-shaped water channels. In contrast, 3D printing can make irregular water channels like spiral, tree branch, and biomimetic leaf vein shapes, which can improve cooling efficiency by more than 40%. After using topology optimized canal design for a mold for a decorative strip for a car door frame, the time it took to make one piece went from 120 seconds to 75 seconds, and the yield rate went from 89% to 98%. Companies who make breathable steel have been able to precisely manage the 0.04mm aperture using porous layer printing technology. This has tripled the exhaust efficiency of molds and fixed problems like weld lines and bubbles that happen when gas gets trapped.
3. Constantly improving the quality of the surface and the accuracy
Early metal 3D printing had a hard time meeting the high-precision needs of mold making because the interlayer bonding force wasn't strong enough and the surface was too rough. But this problem has been fixed thanks to technical progress. At the moment, high-end metal 3D printing machines can make parts with a dimensional precision of ± 0.05mm and a surface roughness of Ra ≤ 1.6 μ m. When used with polishing, sandblasting, and other steps, it can make the surface as smooth as a mirror.
For example, Mantle's TrueShape technology uses a combination of "3-axis CNC machining+drawing and printing+software design" to make mold cavities very accurately. This process prints an H13 steel mold cavity with a surface roughness Ra of only 0.8 μ m, which means it can be utilized for high gloss injection molding right away without needing to be polished first. This technology also allows for multi-material composite printing, which can put wear-resistant coatings on the mold's surface. This can make the mold last more than three times longer than traditional methods.
二, Industrial Practice: From Testing Ideas to Using Them on a Large Scale
1. Automotive molds: a double revolution in cost and efficiency
Metal 3D printing has moved beyond the idea verification stage to large-scale use in the realm of automobile molds. One company that makes cars employs LPBF technology to make molds for engine cylinder heads. The injection molding cycle is 37.2% shorter and the cost of each item is 22% lower when the design of the conformal cooling water channel is improved. What is even more impressive is that this technology can "one-time mold" molds without having to wait for the mold to open. This cuts the time it takes to develop new products from 6 months to 2 months and speeds up the reaction time in the market by a lot.
Metal 3D printing also works great for making lightweight molds. A certain new energy vehicle company makes battery tray molds using aluminum alloy printing technology. The mold's weight is cut by 45%, and the energy used for injection molding is cut by 18%, all while keeping the mold's strength. The mold has gone through 200,000 injection molding cycles, and it works well and is dependable.
2. Medical molds: the best way to make things exactly how you want them
The medical profession needs molds that are very specific and individualized, and metal 3D printing is the best way to do that. A company that makes molds for orthopedic implants uses cobalt chromium alloy printing technology to make molds that are "patient specific." A digital model of the mold is made right away by getting bone data from the patient through a CT scan. The mold can be accurate to within 0.02mm after 3D printing, which means it fits the patient's body exactly. This technique has been used in more than 5000 procedures, and it has cut the time it takes for patients to recuperate after surgery by 30% and the number of complications to less than 1%.
Metal 3D printing also has distinct benefits in the area of medical device molds. A certain company makes heart stent molds using titanium alloy printing technology. The risk of thrombosis is greatly lowered by making the mold cavity's surface as smooth as possible, which lowers the stent's surface roughness Ra to ≤ 0.2 μm. This mold has been certified by the FDA and is the first 3D-printed heart stent mold in the world.
3. Aerospace molds: the best use of high-performance materials
The aircraft industry needs molds that can handle high temperatures, are very strong, and are very light. Metal 3D printing is a new way to do this. A certain company makes molds for aircraft engine blades using nickel-based alloy printing technology. The mold's weight is cut by 35% by optimizing the lattice filling structure, and it stays stable at a high temperature of 1200 °C. The mold has gone through 2000 thermal cycle testing, and its performance is far better than that of typical casting molds.
Metal 3D printing also works very well for making molds for satellite parts. One company makes satellite bracket molds using aluminum alloy printing technology. By using topology optimization design, the molds' weight is cut by 60% while still being able to hold their weight, which lowers the cost of launching rockets. This mold has been used to make more than 10 satellites, and it works well and consistently.