What is the difference between metal 3D printing and traditional CNC machining in mold manufacturing?

一, Technical principle: a paradigm shift in additive and subtractive manufacturing
Metal 3D printing uses the "layer by layer stacking" method of additive manufacturing. It melts metal powder, like titanium alloy or cast steel, using a laser or electron beam and then builds complicated geometric shapes directly from three-dimensional digital models. Its main benefit is that it gets over the problems with traditional machining that make it hard to get to tools and use clamps. It can also do topology optimization design, including hollowing down the inside, filling in the lattice, and making cooling water channels that fit. For example, Zhongrui Technology made custom injection mold inserts for the car industry. These inserts increased the adhesion between the cooling water circuit and the product surface to 95% through 3D printing, cut the injection molding cycle by 42%, and cut the product warpage rate by 67%.
In subtractive manufacturing, traditional CNC machining works by "removing material." It uses linked cutting tools on many axes to cut, mill, drill, and do other things to metal billets. Its technological maturity is shown by its ability to manage precision at the micrometer level (± 0.005mm) and smoothness of the surface (Ra0.8 μ m). This makes it perfect for machining high-strength products with regular forms. For example, the ceramic carving and milling machine from Xintenghui CNC can keep the edge breakage rate of ceramic molds below 0.3% by using a special protection system and precision grinding technology. This meets the strict requirements of semiconductor packaging for mold wear resistance.
二, Application scenario: The line between complicated constructions and mass production
Breakthrough uses in making complicated structures
Metal 3D printing has a big impact on mold making in three main areas:
Shape following cooling system: Traditional mold cooling water channels are limited by drilling procedures, which makes it hard to get a perfect fit with the product contour. By mimicking fluid dynamics, 3D printing technology improves the uniformity of the mold temperature field by more than 50%. A certain company that makes home appliances used this technique, and the yield rate for injection molding air conditioning shells went from 89% to 98%. The annual savings on power for a single set of molds was more than 120000 yuan.
Lightweight construction: By optimizing the topology, 30% to 60% of non-load-bearing materials are removed, and the weight of 3D-printed molds is decreased by 45% compared to traditional designs, while keeping the strength of the structure. A new energy vehicle battery pack bracket made of a 3D-printed aluminum alloy framework has survived a 150% overload test, lost 38% of its weight, and gained 8% of its range.
Integrated molding of complicated parts: In traditional methods, including rubber tire mold pattern blocks and shoe sole pattern molds, parts need to be processed and put together separately. 3D printing can make a whole mold and get rid of mistakes in assembly. This technology was used in a tire company, and the time it took to make molds went from 45 days to 12 days, with a pattern accuracy of 0.02mm.
三, The main advantage of mass production
The fact that CNC machining can't be replaced in mold making is shown by:
Material adaptability: It can work with materials that are quite hard, such quenched steel and hard alloys (HRC55 or above), which is what die-casting molds need to be able to do. A specific die-casting facility employs CNC-processed magnesium alloy die-casting molds that last for 200,000 times, which is three times longer than 3D-printed molds.
Quality of the surface: A mirror-level surface (Ra0.2 μ m) can be achieved using post-processing techniques including precision milling and polishing. This meets the hygiene standards for optical molds and food packaging molds. A cosmetics packaging company used CNC-processed PET bottle preform molds, which made the product more transparent (92%) and cut down on waste (0.5%).
Batch economy: For molds that make more than 5000 pieces a year, CNC machining costs 60% to 70% less per piece than 3D printing. A certain automotive parts supplier uses CNC mass manufacturing for their bumper mold. The cost of a single mold is kept to 800,000 yuan, whereas the cost of 3D printing is 1.2 million yuan.
四, Structure of Costs: A game of balance between speed and accuracy
1. Costs of equipment and supplies
3D printing with metal: Industrial-grade tools usually cost between 2 and 8 million yuan, and titanium alloy powder costs between 800 and 1200 yuan per kilogram. The material utilization rate, on the other hand, is as high as 90%, which is 40 percentage points greater than CNC machining. A particular aviation company has used 3D printing to make engine blades, which has cut material prices by 35% compared to traditional casting.
CNC machining: Five-axis linkage machining centers cost between 1.5 and 5 million yuan, and roughly 15% to 20% of that cost is for tools. One mold factory decreased the cost of a single set of molds from 120,000 yuan to 70,000 yuan by optimizing the cutting path and employing reversible blades.
2. Time cost 3D printing: The time it takes to make molds with complex structures is cut in half to 70% compared to traditional methods. A medical company can make a custom orthopedic implant mold in just 72 hours, which is 80% faster than the 15-day cycle of CNC machining.
CNC machining: Mold processing time can be cut down by 30% to 40% by employing high-speed cutting (HSC) technology. An 8000rpm spindle machining center helped one 3C product mold business cut the time it took to make a phone frame mold from 18 hours to 11 hours.