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GeneralChoosing the Correct Machine for Turned and Milled Medical Parts

For manufacturers in the medical industry, the choice of machine used for turned and milled medical parts is critical. The parts must meet strict safety and quality standards while being produced efficiently and cost-effectively.

In this comprehensive guide, we will delve into the various types of machines used in the manufacturing of medical parts specific to their shapes and complex geometries. This guide further distinguishes CNC milling machines based on the shape of the medical part required. For example, a 5-axis CNC milling can be used for complex shapes, while a Turn Mill is majorly capable of producing circular-shaped parts.

Common Materials Used for Medical Implants

Medical implants must be made from biocompatible materials to ensure safety and effectiveness for human use. Titanium, cobalt-chromium, and stainless steel are some of the most commonly used materials for medical implants due to their excellent mechanical properties and resistance to corrosion. All these high-performance polymers offer similar characteristics with superior mechanical, thermal, and chemical properties compared to traditional plastics.

Metals are known for their high strength and durability, making them ideal for use in medical implants and devices that need to withstand a lot of stress and strain over time. Additionally, high-performance polymers can withstand higher temperatures, making them ideal for use in applications where temperatures are critical. Since all of titanium, cobalt-chromium, and stainless steel are strong, to begin with, they generate more heat when drilled and deformed during the chip formation process.

Turning Machines: For Round or Cylindrical Implants

Turning machines are the ideal choice for creating round or cylindrical medical parts like trocars, forceps, cylindrical components for catheters, and round components for vascular access devices.

Swiss-type lathes and sliding headstock lathes are the two types of turning machines commonly used in medical manufacturing:

Swiss-Type Lathe: Swiss-type lathes are perfect for creating dental implants, bone screws, and other small parts with intricate geometries and slender shapes. Swiss-type lathes come with a guide bushing and specialised tooling to stabilise the workpiece as it is being machined.

Sliding Headstock Lathe: A sliding headstock lathe has a fixed headstock that houses the main spindle rotating the workpiece during the machining process. The machine is ideal for producing orthopaedic implants and prosthetics due to their larger diameter and length. Sliding headstock lathes use a tool turret to hold multiple cutting tools that can be quickly changed during the machining process. This allows for faster machining times and reduces the need for manual tool changes.

Milling Machines: For More Complex Parts

Milling machines are the go-to option for creating more complex medical parts that require a high degree of accuracy and precision. The two main types of milling machines used in medical manufacturing are turn mills and vertical machining centres.

Turn Mill: Turn mills come with a counter spindle to efficiently machine the interior and exterior components of a part to create a round/curved feature. Turn milling can be used to produce prosthetics such as artificial hips with complex shapes and tight tolerances. The technique allows for customized curving of prosthetics that fit the patient’s unique anatomy. The spindle comes with a 360-degree B axis to enhance efficiency and part application. The three tool carriers come with Y axis configuration for better removal rates.

5-axis Machining Centres: 5-axis CNC machining centres offer the ideal solution for creating highly complex medical parts including cranial plates, spinal implants, and joint replacements. These machines can move the part in five different directions simultaneously, enabling the creation of complex geometries that would be impossible to produce using traditional milling machines.

Vertical Machining Centres: Vertical machining centres are ideal for producing knee implants and hip cups. Hip cups are integrated within artificial hips, which are them implanted within the pelvis. The cups resemble a half-sphere and require high accuracy and exterior surface finishing. These implants usually require a series of milling and drilling operations that are better performed on a vertical machining centre. Vertical machining centres come with appropriate fixturing to hold the workpiece in place during the machining process. Vertical machining centres may also be equipped with a rotary table to enable 4-axis or 5-axis machining.

Advantages and Disadvantages of Different Machines

Each machine has its own advantages and disadvantages, and choosing the right one for the job is essential. The table below runs a comparison of the advantages and disadvantages you can expect from each machine:

Type of Machine Advantages Disadvantages
Swiss-Type Lathe – Suitable for small parts

– Ability to machine parts with high length-to-diameter ratios

– Tooling design allows for the simultaneous machining of multiple features

– Limited versatility in terms of workpiece shape and size
Sliding Headstock Lathe – Suitable for complex parts and implants

– Tooling design allows for the simultaneous machining of multiple features

– Limited cutting force and power due to small spindle size and low torque
Turn Mill -Higher productivity due to reduced setup time

– Suitable for small to medium-sized parts like hip cups.

– Limited workpiece size

– Expensive to purchase and maintain

5-axis CNC Machining Centre – Ability to machine complex shapes and contours like knee and hip replacements through 5-axis CNC

– Ability to machine multiple surfaces in a single setup

– High setup time and cost

– – Limited accessibility to all sides of the workpiece

Vertical Machining Centre – High precision, cutting force, and accuracy

– Suitable for large parts

– Automated tool changing

– Limited workpiece size

– – Requires skilled operators to program and operate

Price of Error: The High Cost of Choosing the Wrong Machine

Choosing the wrong machine can result in costly errors and delays that can have serious financial implications for manufacturers. While cost is an important factor to consider when choosing a machine, it is crucial to prioritise quality, accuracy, and efficiency. While CNC multi-spindles can cost almost 4-times more than a sliding headstock lathe upfront, the cost/piece after a year of usage is significantly lower than what you get from the latter.

In the medical industry, the cost of error can be particularly high. The cost of reworking or scrapping parts due to errors can quickly add up and result in missed deadlines and dissatisfied customers. Optimising your CNC or lathe machine and outsourcing your production can significantly help reduce costs associated with the machining of medical components.

Medical devices must meet strict safety and quality standards, and any defects can have serious consequences for patients. Choosing the right machine can help manufacturers ensure that their products meet these standards and avoid costly mistakes.

Conclusion

Choosing the correct machine for turned and milled medical parts is essential for manufacturers in the medical industry. Swiss-type lathes and sliding headstock lathes are ideal for creating round or cylindrical parts, while turn mills and vertical machining centres are suitable for more complex parts. 5-axis CNC machining centres offer unparalleled precision and flexibility and are ideal for creating highly complex parts.

While cost is an important consideration, manufacturers must prioritise quality, accuracy, and efficiency when choosing a machine. The cost of errors can quickly add up and result in missed deadlines and dissatisfied customers, particularly in the medical industry. By choosing the right machine, manufacturers can ensure that their products meet safety and quality standards and avoid costly mistakes.

This post has been sponsored by WayKen Rapid Manufacturing

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