What is the basic principle of metal 3D printing in mold manufacturing?

1. Technical principle: Changing digital models into metal objects
The main idea behind metal 3D printing is "digitally driven layered melting and stacking." The main processes in the process include model processing, powder spreading, energy melting, and interlayer bonding. For example, the popular laser selective melting (SLM) technology:
Cutting apart 3D models and designing paths
After using CAD software to make a 3D model of the mold, it needs to be transferred into slicing software for layering processing to make 2D cross-sectional data that is 20 to 50 microns thick. The route planning algorithm uses the cross-sectional profile to make laser scanning paths and adjusts the overlap rate of the melt pool to avoid stress accumulation between layers. For instance, while making injection molds with conformal cooling channels, the algorithm would carefully manage the order in which the spiral channel is scanned to make sure the coolant flows smoothly.
Melting of the powder bed and buildup of layers
The device puts a coating of metal powder (such titanium alloy, aluminum alloy, or mold steel) inside the molding chamber. The laser beam then melts the powder along a set path to make a pool of molten metal. After the melt pool cools and solidifies quickly, the forming platform is lowered by one layer thickness. The cycle of distributing powder, melting it, and solidifying it is continued until a metal mold with a density of 99.9% is made. This method doesn't need molds or fixtures, and it may make complicated internal cavity structures directly, like die-casting molds with honeycomb reinforcing ribs.
Collaborative control in the realm of multi-physics
During the printing process, characteristics including the temperature of the melt pool, the amount of oxygen in the air, and the flowability of the powder must be monitored in real time. For instance, Yunyao Shenwei's closed-loop control system uses an infrared thermal imager to capture the shape of the molten pool, dynamically changes the laser power (200–1000W) and scanning speed (500–2000mm/s), and prevents warping deformation induced by thermal stress. Some firms employ green laser technology to improve energy coupling efficiency and fix partial fusion flaws in materials that reflect a lot of light, like copper.
2. Technological edge: Solving the three biggest problems with traditional mold making
By changing the way things are made, metal 3D printing adds three new values to the mold industry:
A huge improvement in design freedom
The "linear processing" nature of drilling, milling, and other procedures makes it hard to make molds in the traditional way. Cooling channels are often made as straight lines or simple polylines. This means that injection molded parts don't cool evenly (the temperature differential might be more than 30 °C). 3D printing can make conformal cooling channels that can be designed like spiral, dendritic, or biomimetic leaf veins to fit the geometry of the mold chamber. Audi has used this technique to make die-casting molds cool 40% faster, shorten the injection molding cycle by 35%, and lower the scrap rate from 8% to 1.2%.
Twice as fast and twice as cheap to make
For example, an automobile bumper injection mold: It takes 6 weeks for traditional CNC machining to make an electrode, do electrical discharge machining, and other steps. It only takes 72 hours for 3D printing, and the material utilization rate has gone up from 25% to 95%. For small batch custom molds, such cases for medical equipment, 3D printing costs 60% less per piece than traditional methods. This makes it ideal for the prototype validation and trial production stages.
Optimizing the performance of materials and structures
3D printing's quick solidification (cooling rate up to 10 ^ 6 ℃/s) can create a fine grain structure that makes the mold much harder and more resistant to wear. For instance, H13 mold steel made with SLM technology has a thermal fatigue life that is 2.3 times longer than that of forged parts. This makes it good for die-casting situations with heavy loads. Also, gradient material printing technique may put high-hardness coatings (such WC Co) on the mold's surface while keeping the core tough, which means "one material for multiple uses."
3. Common use cases include conformal cooling and functional integration.
Metal 3D printing has made a big impact on many areas of mold making, creating unique solutions:
Injection mold: a big use of a conformal cooling water channel
In big home appliance shell molds, 3D-printed waterways can cut the cooling time from 45 seconds to 28 seconds and get rid of weld flaws. A company produced a biomimetic canal for air conditioning panel molds that has a surface flatness of 0.02mm, which is the same level as a mirror.
Die casting mold: a design with a complicated chamber and light weight
To make complicated internal cavities using traditional die-casting molds, you have to put together several sections. using 3D printing, you can make molds with holes that cross each other and thin-walled ribs all at once. For instance, the new energy vehicle battery box die-casting mold uses topology optimization design to cut weight by 42%. The mold life is also extended from 50,000 times to 120,000 times with 3D printed canals.
Rubber tire mold: making pattern blocks with great accuracy
In the past, it was hard to make tire patterns with micrometer-level accuracy, like a rain tire drainage channel that was only 1.5mm wide. Using high-precision laser control, 3D printing can make pattern block molds directly, which avoids the pattern deformation that can happen with electrical discharge machining. The repeated pattern positioning precision of the F1 racing tire mold made by a certain company is ± 0.01mm, which is what the International Automobile Federation requires.
4. Industry Trends: From Breakthroughs in Technology to Changes in the Environment
Metal 3D printing is changing in the mold industry from "single point substitution" to "system innovation":
A big step forward in multi-material printing technology
Right now, printing composite materials like copper aluminum and steel ceramic is still a problem in the business. However, new technologies like green laser and multi beam collaboration have made some materials compatible with one other. For instance, a company came up with a copper steel bimetallic printing technique that uses interface metallurgical bonding to find a compromise between heat conductivity and strength. This approach is good for molds for liquid-cooled radiators.
Mode of additive composite manufacturing
The hybrid manufacturing method that combines CNC precision machining is already common. For instance, the conformal waterway is made first using 3D printing, and then the cavity is improved using a five-axis machining center. This takes advantage of the design benefits of 3D printing and makes sure that the mold's surface quality is good (Ra ≤ 0.8 μm).
Building an intelligent and uniform system
Companies in the US are working to create standards for metal 3D printing molds. These standards include the qualities of the powder (sphericity ≥ 90%, oxygen content < 0.05%), the ability to find defects (CT scan porosity ≤ 0.5%), and the criteria for post-treatment (heat treatment hardness deviation ± 1HRC). AI algorithms have also been used to improve printing pathways at the same time. Through machine intelligence, one platform has made supporting structures 30% lighter and printing 25% more efficient.