The medical manufacturing field has grown exponentially in recent years as medical technology advances and evolves. The development and introduction of innovative devices and medical instruments, including diagnostic devices, surgical instruments and implantable medical devices, has driven medical manufacturing companies to advance in turn to keep up with the field. Demand for extremely precise and sometimes incredibly small devices has prompted medical manufacturers to develop new methods to handle the needs of these products with incredible care and detail, for both the safety of the patient and the integrity of the application.
In order to ensure maximum precision, medical manufacturers have needed to employ highly controlled production methods when working with biocompatible metals. The most common of these methods are machining, hot forging and cold forming. While machining is often appropriate for larger devices, it is a much more wasteful process than forging, often resulting in burrs and sharp edges. It also tends to be extremely difficult with small products or soft meals. For this reason, forging metal is generally a more desirable method for medical manufacturing.
When most people think of forging metal, they assume that it requires intense heat to melt the metal and cast it. This method, known as hot forming, is neither required nor even ideal for all applications, as it can reduce the tensile strength and hardness of the metal product. It is also not ideal for softer metals, resulting in defects and imperfections in the finished product. The alternative to this method is known as cold forming.
Alternatively known as cold heading or cold forging, cold forming is the process of forming a metal at or slightly above room temperature through the application of pressure. Whereas traditional hot forging involves heating a metal to a liquid state before forming or casting, cold forging gently heats the metal, making it more malleable and an ideal forming process for soft metals like gold and silver. In addition to this ability to work with soft metals, cold forming comes with numerous benefits, including a more efficient, more versatile forming process and a stronger end product.
At STS Intelli, we are proud of our cold forming processes and the multitude of benefits it can lend to our clients in medical manufacturing. We encourage our clients to learn more about the process, its benefits and what cold formed metal can do for the medical industry. If you or your company are looking to produce medical devices with biocompatible metals, read on to learn how cold forming may benefit your project.
Cold Forging with Biocompatible Materials
Biocompatible materials, also known as biomaterials, are artificial or natural materials used in biological systems. These materials include anything from ceramics and natural and artificial polymers to metals. Because of their relative longevity, and often their electrical properties, biocompatible metals are commonly used in numerous medical devices and implants.
Some common biocompatible metals include stainless steel, cobalt alloys, titanium alloys, gold, silver, nickel, platinum and tantalum. Some of these metals, like titanium and steel, are capable of undergoing traditional hot forming in a foundry. However, other metals, such as gold, silver, nickel, platinum and tantalum, are too soft to use with a hot forming method and too “gummy” to be machined. This is especially true when producing smaller forms, which can often emerge deformed when hot forged or machined. Instead, manufacturers make medical devices using these materials using a cold forming process.
The Cold Forming Process
Biocompatible alloys typically come in wire, strip or slug form before undergoing the cold forming process. Wire is the most common, as it’s easy to feed into a machine to cut it into appropriate portions for mass production. Regardless of the form, these “blanks” are measured carefully to ensure that the volume of the blank is the exact volume of the die. Too much material and the die will crack open when pressure is applied. Too little material and the part won’t fill every bit of the die. Both options result in a deformed part, which is why blanks are carefully measured before continuing with the cold forming process.
The process of cold forming with biocompatible alloys generally works like this:
- The slug is cut and closely measured to be the exact volume of the finished part.
- The prepared slug is placed in a die, or mold, of the finished form.
- A hydraulic or mechanical press punches the material into the mold. This may happen repeatedly in order to make sure that the volume of the slug fills the die completely, or in a sequence of actions to elicit different effects.
- The manufacture removes the shaped product from the die and takes it to the next stage of the production process, where it may receive further shaping to produce more complex forms and textures.
This process can involve one or more different techniques in order to form the shape of the end product. The most common techniques include the following:
- Heading: The slug is slid into a slot, leaving one end exposed on all sides. This side is then pressed, causing the material to mushroom, creating a “head.” This is one of the oldest forms of cold forming.
- Forward Extrusion: Also called impact extrusion, this involves punching metal through a hole in the die, producing a smaller cross section than the original wire or slug.
- Backward Extrusion: This process is similar to forward extrusion, except instead of punching the metal through a small hole, the metal is pushed backward and around the press’ punching mechanism, causing the metal to form a cup shape.
- Combined Extrusion: This is the simultaneous combination of forward extrusion and backward extrusion to create a unique shape.
- Upsetting: Similar to heading, this process is used to create diameters larger than the diameter of the starting blank by forcing the metal outward from the die.
These processes in combination create many common parts in the medical industry and beyond. This popular process is obviously very different from other processes like machining and hot forming. These differences in process also lend to different attributes of the final product, many of which are highly beneficial for medical applications.
Advantages of Cold Headed Medical Parts
Cold forming offers numerous benefits that make it an ideal forming process for biomaterials. These benefits include, but are not limited to:
- Size Variety: Cold forming is capable of forming extremely small parts with greater efficiency and effectiveness than other methods. This production of small parts using this technique is micro cold forming, and is a specialization in itself. While hot forming and machining are capable of producing smaller parts, these methods are much more likely to produce defects as the product gets smaller.
- Unique Materials: Most medical products require precious alloys or biocompatible materials to produce. Many of these, like gold, silver and nickel, are considered to be “too gummy” for machining and hot forming, and can result in deformities. With cold forming, these materials are easily shaped into the end product while minimizing deformities and wasted material.
- Free of Burrs and Overflow: Machined parts run the risk of having surface imperfections, such as overly sharp edges and burrs, while hot forged parts can often have excess material from sprues and overflow. The manufacturer must carefully remove this excess material, or else run the risk of causing tissue damage. Cold forming, on the other hand, produces minimal excess material, and the edges and corners are naturally rounded, eliminating burrs.
- Minimal Scrap: Machining removes metal from a starting slug, while hot forged parts often produce overflow. Both of these methods produce substantial waste. Cold forming, however, uses precise measurements to ensure minimal excess material, cutting material costs. This is an especially significant benefit when working with more expensive materials like gold or platinum.
- Increased Strength: Cold-formed parts tend to exhibit excellent strength because the material flows into its final form. This is in direct opposition to machining, which involves cutting the material and can often result in a weaker product.
- Corrosion Resistance: Machining can result in microscopic surface abrasions, which make the surface of a metal more prone to corrosion. Cold forming eliminates the need for cutting into the metal, retaining the surface quality of the product and improving its resistance to corrosion.
- Precision Tolerances: Cold forming can produce parts with extremely close precision and minimal waste, maintaining that precision regardless of the size of the part. With hot-formed products, softer materials may be “too gummy” to guarantee precision at very small sizes.
- Mitigating Contamination: Hot formed metals are heated to high enough temperatures that they can interact with the air around them, in addition to any residual materials in their container. Because cold forming does not involve heating the material to that degree, the material retains much of its integrity.
- Product Consistency: Cold forming often uses the same die multiple times to produce the end product, resulting in impressive product consistency. With machining and hot forging, this consistency is somewhat reduced by the introduction of human error when handling subsequent parts.
Common Cold Formed Medical Device Components
Because of the unique and beneficial attributes of cold forming, it is commonly used to create a variety of medical devices components. A few of the more commonly cold formed medical devices include:
- Dental Implants: Artificial implants are used to secure dental prosthetics to the jaw. Most common of these, making up a total 98% of all dental implants, are screw implants, which are embedded directly into the bone. These implants are commonly made of cold formed titanium pressed into a helical shape so that they hold securely to the bone.
- Hearing Aid Devices: Hearing aids require tiny components so that the end product can fit comfortably into the ear of the patient. For this reason, housings and locking mechanism in hearing aids are commonly made of cold formed metal, as well as the small screws holding it all together.
- Sensor Components: Endoscopic devices, ultrasound and magnetic resonance instruments all involve miniscule parts in their designs, which are best produced using cold forming. This process more accurately and consistently produces high quality parts that usable in manufacturing sensors for both external and internal use.
- Pins and Miniature Fasteners: Cold forming has been used to create small pins and fasteners for years, as it is an easier process with less scrap than hot forging or machining. The parts are typically created by cold heading the material into a pin with a mushroom head. If forming a screw, the pin is then rolled to form the threads. This method continues to be used to produce miniature screws, bolts, contacts, studs and other fastening parts. These also feature within medical devices.
- Custom Devices: Cold forming is also used to form custom medical device components. These small quantities of device components require a process that is not only precise, but also cost-effective. While machining and hot forging are both valuable methods for creating custom parts, neither are as cost-effective as cold forming, nor do they support the same wide variety of materials.
Cold Headed Applications For Pharmaceuticals
Cold formed materials also feature heavily in the packaging of pharmaceuticals. Packaging is an important part of the pharmaceutical industry, as it protects the product from the environment, provides a vehicle for expressing information about the product, facilitates easy and accurate dosing and ensures the integrity of the product as it is transferred from production line to shelf.
One common packaging method is the blister pack, where pills are deposited into a plastic or PVC casing backed with cold formed aluminum. This thin aluminum coating is sandwiched between layers of print and protective lacquer. The aluminum provides protection from light and external contaminants, while simultaneously creating a non-resealable barrier. This inability for the blister pack to reseal is important for checking if a product has been damaged or tampered with, or for users to easily see how much of the product they have remaining.
Choose STS Intelli
If you are looking for a manufacturer to produce medical device components, STS Intelli has the experience to get it done. We have a fantastic reputation for making high quality biocompatible materials and implanted devices with the utmost efficiency. We are also renowned for accommodating the strict regulations set on medical equipment by worldwide governments, meaning that you can count on us to produce a product that keeps to the highest standards.
Our top-of-the-line equipment and professional staff work hard to meet all of your cold forming needs, regardless of your products’ size, quantity or stage of production. STS Intelli is a renowned micro cold forming company, providing micro cold forging services to a variety of companies across the United States. We also welcome low volume orders for prototypes and concept proofs.
Are you considering cold forming in your next medical manufacturing project? Contact STS Intelli today for more information, or get a free, no obligation quote!