Can medical device molds also be manufactured using metal 3D printing?

一, Looking at the main benefits of metal 3D printing technology
1. Geometric degrees of freedom and design for conformal cooling
Drilling procedures limit the cooling channels in traditional moulds, thus they normally use linear or simple cross architectures. This makes the cooling less efficient and the temperature uneven. Selective Laser Melting (SLM) and Electron Beam Melting (EBM) are two technologies that make it possible to design conformal cooling channels freely using metal 3D printing. For instance, in orthopaedic implant moulds, using simulation software to optimise the water path so that the distance between the cooling water channel and the mould cavity surface stays within 2mm can save the injection moulding cycle by 35% and cut product warpage by 60%. This design is very important for making heart stent moulds because micro-level precision cooling channels make sure that the stent materials shrink evenly during the moulding process, which prevents cracks from forming due to stress concentration.
2. Guarantee of biocompatibility and material performance
Moulds for medical devices must meet very high biocompatibility criteria. Metal 3D printing allows for direct moulding of materials including titanium alloy (Ti6Al4V), cobalt chromium alloy (CoCrMo), and medical stainless steel (316L), all of which have been certified as biocompatible by ISO 10993. For instance, Ti6Al4V titanium alloy is commonly used to make moulds for joint replacement implants since it doesn't corrode easily and is safe for use with human bones. You may regulate the grain size of the material between 10 and 50 μm by changing the printing settings, like laser power and scanning speed. This strikes a balance between mechanical qualities and biological activity.
3. A design that is both lightweight and functional
Metal 3D printing allows for lightweight designs like lattice structures and lattice structures. This cuts down on material use while still making sure the mould is strong. For instance, Platinum's hollow lattice cooling channel for aircraft engine blade moulds cuts weight by 40% and increases cooling efficiency to 2.3 times that of standard designs. This design is used in the medical profession for the end effector moulds of surgical robots. It reduces the number of steps needed to put the equipment together and makes it more reliable by adding functional elements like thermocouple mounting holes and fluid channels.
二, Common use cases and case studies
1. Making moulds for orthopaedic implants
Case: Mould for a 3D-printed hip implant
Aikang Medical's 3D ACT artificial hip joint system uses bimetallic 3D printing technology to make the femoral stem mould. The bone bonding layer is made of Ti6Al4V titanium alloy, which has a microporous structure that encourages bone cell growth; the wear-resistant layer is made of CoCrMo cobalt chromium alloy, which has a surface roughness of Ra<0.2 μ m, which reduces friction and wear with the polyethylene lining. The transition layer is formed of Ti Co gradient alloy, and powder mixing technology is used to make the composition gradient so that stress doesn't build up. This mould makes the product last for more than 15 years, which is three times longer than usual methods.
2. Making moulds for cardiovascular stents
Case: A mould for a micro size vascular stent
To make vascular stents, the accuracy of the manufacturing process needs to be between 10 and 50 μm. This is hard to do with typical machining. The Huazhong University of Science and Technology team employed SLM technology to make Nitinol stent moulds. The stent wire diameter inaccuracy was less than 2 μm by controlling factors such layer thickness (20 μm) and laser power (150W). In a pig coronary artery model, the stent made with this mould shows great support and flexibility, with a 40% lower thrombosis rate than typical devices.
3. Making moulds for parts of medical equipment
Case: Wire grid mould for CT scanner anti-scattering filter
Dunlee's pure tungsten 3D printed filter grid mould uses EBM technology to make intricate conical shapes in one go. Compared to standard milling methods, this mold's filter grid may boost the signal-to-noise ratio of cone beam CT by 1.7 times and cut down on material waste by 85%. Also, pure tungsten's high density (19.3 g/cm ³) protects against X-rays, which keeps the image quality good.
三, Problems and solutions in technology
1. Quality of the surface and the process after treatment
The surface roughness of metal 3D printing moulds is normally between Ra6 and Ra10 μm. After treatment, including electrolytic polishing and sandblasting, it needs to be brought down to Ra0.8 μm or lower. The Beijing Institute of Aeronautical Manufacturing's chemical mechanical polishing (CMP) method can make the surface of Ti6Al4V moulds smoother, bringing them down to Ra0.2 μ m, which is the standard for medical equipment.
2. Control of residual stress
During the printing process, quickly heating and cooling can easily cause residual stress to build up and mould to change shape. The answer is:
Optimising processes: Using an island scanning method, the single layer is split into several separate sections that may be printed on one at a time. This helps to spread out the thermal stress evenly.
Heat treatment: To get rid of more than 80% of residual tension, heat the mould to 650 degrees Celsius and let it cool down.
Online monitoring: Using an infrared thermal imager to watch the temperature field in real time and changing the power of the laser as needed.
3. The cost and value of materials
Medical-grade titanium alloy powder costs 2000–5000 yuan per kilogramme, which is 5–10 times more than regular mould steel. The answer is:
Powder recycling: By screening and oxidation treatment, the rate of recovering unmelted powder goes up to 95%.
Topology optimization design: Lower the cost per unit and cut down on material use by 30% to 50%.
Large-scale production: The cost per piece has come closer to that of traditional methods thanks to better equipment efficiency (for example, Huashu High tech FS1211M equipment can print at a speed of 50cm ³/h).