Precision and efficiency

To create titanium medical implants more precisely and efficiently, manufacturers are turning to advanced techniques. Doing so allows production of customized implants more easily while wasting fewer materials. Different iterations can be made when designing a new unit, without the added expenses of tooling up, as is the case with traditional machining processes that use injection molding.

Companies designing and building medical devices prefer titanium because this biocompatible, nontoxic metal does not stimulate cancer growth or cause patients to develop thrombosis from the device’s contact with blood. What’s more, it does not provoke immunogenic responses, which may occur when other alloys encounter patients’ fluids.

For those reasons, manufacturers use additive manufacturing (AM) techniques to create surgical instruments and orthopedic and dental implants with titanium, especially when customized units are called for. A common use case is when orthopedic surgeons want to use titanium when patients need hip replacements.

Introduction to advanced manufacturing techniques for titanium medical devices
The healthcare industry is now increasingly relying on medical devices and implants made from titanium alloy, thanks to the material’s superior biocompatibility and mechanical properties that do well at integrating with patients’ bones.

For example, novel and advanced manufacturing techniques known as additive manufacturing — such as laser metal deposition (LMD), electron beam melting (EBM) and selective laser melting (SLM) — enable building devices with porous structures to promote osseointegration, as explained by a journal report.

With additive manufacturing for devices destined for use in clinical environments, manufacturing costs and waste are reduced while creating implants customized to individual patients, thanks to digital data from tomography scans. Titanium medical devices are prized for being strong, helping to reduce fractures after implantation. They also excel in resisting corrosion.

AM processes are an improvement over standard techniques developed decades ago, such as machining, hot rolling and forging. Titanium is added to the structure layer by layer as needed, rather than removing titanium from the desired final form during fabrication.

Three important methods of additive manufacturing to create medical devices with titanium
Laser metal deposition: In laser metal deposition, the equipment operator employs a laser to melt titanium powder and fuses the particles one layer at a time. Powder is injected into the laser beam to melt it, as a computerized drive system moves the work piece along the X-Y axis to create the desired geometry.

The minimum wall thickness for LMD is 0.9mm.

Electron beam melting: With the electron beam melting technique, heat from the electron beam melts titanium powder in a vacuum. Work occurs in a vacuum because titanium alloys are attracted to oxygen.

The minimum wall thickness in EBM is 0.6mm.

Selective laser melting: Typically done with an ytterbium fiber laser, selective laser melting harnesses the heat of the laser beam to manufacture metal parts by fusing titanium powder. After producing the initial layer of a two-dimensional cross-section, the platform lowers to add another layer, which is repeated until finishing the shape of the biocompatible component.

When using SLM, the minimum wall thickness is 0.3mm.

Benefits of these advanced techniques
Key benefits of these advanced manufacturing techniques include superior precision, efficiency and better product quality overall:

Superior precision: With additive manufacturing using titanium, the precision ranges from ±0.1% to ±0.2%, according to a technology report. The thickness of layers ranges from 20 micrometers to 100 micrometers. Features as small as 100 micrometers are possible.

Efficiency: AM processes for manufacturing titanium devices are more efficient than traditional machining techniques. The system’s flexibility allows for experimentation with different designs, achieving reduced lead times when running smaller batches (such as anywhere from 10 units to 10,000 units).

For companies that promise just-in-time manufacturing, AM is a useful way to make customized parts tailored for specific patients. Meanwhile, AM cuts down on waste, since products are built one layer at a time.

Product quality: t’s possible to create lightweight geometries at the level of complexity typically found in medical implants and other devices. AM allows printing of extremely complex shapes, while the molding injection technique only allows for simpler 2.5D geometries.

Readily achieve desired tensile properties, such as an elastic modulus of about 110GPa, for reduced stress shielding. Indeed, titanium units made with AM are able to meet or surpass the fatigue strength and tensile strength of units produced with casting.

When creating biomedical implants out of titanium, it’s possible to design parts according to pore size and shape, which is important when considering cell proliferation in the body. Cellular structures can be stochastic (random) or nonstochastic, exhibiting no variation in size and shape, which is preferred because unused powder is removed more easily and because nonstochastic structures have stronger mechanical properties when replacing human bones.

Finally, startup costs for titanium products will be lower as compared to traditional manufacturing processes, which require upfront tooling expenses.

Unique challenges associated with titanium material processing
With all the benefits of titanium material processing, there are some unique associated challenges to keep top of mind:

Developing medical devices from titanium with the additive manufacturing process typically costs more in small batches than when using standard high-volume manufacturing processes.

When an application calls for porosity to promote osseointegration, use hot, isostatic pressing.

Creating devices or implants with complicated channels inside them makes it challenging to get rid of excess titanium powder used in manufacturing.

The size of devices is limited by the size of the 3D printing equipment.

Build extra time into the production schedule to account for the post-processing work to ensure the devices have the required properties. For example, since traditional processes using molds result in smoother surfaces, post-processing might be necessary to achieve the desired level of smoothness.

Compared to traditional machining techniques, expect less dimensional accuracy during production runs. And while a better surface finish is achieved when using a molding process, in AM processes, the surfaces must be processed further after depositing all the layers of the unit.

Taking advantage of titanium additive manufacturing for better product development
It’s clear that there are many benefits to titanium additive manufacturing, such as the ability to quickly create multiple iterations of a design in a process that’s well-suited for producing small batches. Material isn’t wasted as it would in a traditional machining environment. Being able to quickly fabricate units, such as for just-in-time manufacturing, can alleviate worries about supply chain issues; additive manufacturing will help save time and money.

Rapid prototyping with multiple iterations is easier with AM processes. What’s more, production teams require less lead time to start new projects. Patients will have a better experience with customized implants based on their tomographic scans, instead of using generic parts.

Titanium additive manufacturing is an ideal solution when developing medical implants and other healthcare products out of titanium with complex shapes that are biocompatible.