• Sara Hagmann

Manufacturing Surgical Instruments with Electrochemical Machining

The small margin of error in surgical procedures requires instruments that are precise and delicate, whether they are hand-held or robotic in nature

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HAND-HELD SURGICAL TOOLS


Hand-operated surgical tools are often made with stamping or metal injection molding (MIM). However, there may be unique advantages and opportunities when using pulsed electrochemical machining (PECM) to produce these tools.

Progressive stamping (1)

In stamping, a flat sheet of metal is progressively cut and bent to create a 3D shape. Stamping is fast and the least expensive option by far. However, stamping presents limitations in size, aspect ratio, and hardness of material. Additionally, it rapidly wears out the die, especially when using more durable materials, and can create burrs. These burrs are of particular concern in surgical applications, given that the burrs may detach during use and introduce foreign bodies to the patient.

Metal injection molding (2)

MIM can also make complex parts cheaply, although not as cheaply as stamping. Like stamping, MIM has limited compatible materials (although it can shape stainless steel.) Parts produced with MIM must also meet specific design requirements. For example, rapid changes in section thickness can cause parts to fail, due to stresses and shrinkage during the sintering process.


PECM is slower and more expensive than these processes (with some important exceptions) but can often yield a superior product. Given that there is no contact with the material, pristine and burr-free surfaces are the norm for PECM. This improves the “feel” of the tool in a surgeon’s hand, allowing for greater precision in the medical procedure. Furthermore, the manufacturing tools used have near-infinite life, even when used on hardened materials, allowing for greater consistency across the same surgical instrument. PECM also creates an ultra-clean surface, eliminating microscopic pits and bumps where microbes might hide. (3) This makes the tool easier to sterilize – an especially appealing benefit in surgical applications.


That said, it may suit your application best to use PECM only as a secondary process, allowing for the cost and speed benefits of stamping or MIM while using PECM to add specific high-aspect ratio or detailed features. By engaging with Voxel early in the design and manufacturing process, we can pinpoint the most germane opportunities to improve your surgical instruments.


SURGICAL END EFFECTORS

Stapler anvil manufactured by Voxel using PECM

Surgical instruments, whether hand-held or robotic, share the need for the precision that enables smaller incisions and more accurate devices. Trends indicate a growing demand for thin, miniaturized instruments, which reduce invasiveness and improve the outcomes of endoscopic procedures. (4) To meet this demand, the tools must be created with more delicate, exact geometries which may be difficult or impossible with stamping or MIM. Stapler anvils, for example, are now required with only two rows of anvil pockets per-side to minimize the necessary incision slot.

Order of stapler anvils ready to ship

For example, Voxel has already created stapler anvils for use in robot-assisted surgery. The precise smoothness of these anvils pockets (<0.1 μm Ra) ensures stapling success rather than screwed, misdirected, or crumpled staples that do not actually close the wound. This equates to less trauma on the surgical site, improved healing, and lower risk of reoperation. Voxel has also demonstrated the ability to produce thin walls <100 μm in hardened stainless steel which could be useful for enabling smaller devices.

Moreover, the market shows a push for haptic feedback in robots used for surgery (for example, a tumor resection would require a haptic device for palpation.) (5) Haptic devices require an accurate surgical tool with low sliding frictions so that the feedback is primarily representative of the tissue interaction instead of the device friction. Smooth interfacing and sliding surfaces provided by PECM may be beneficial for this application.


Aside from meeting current demands, PECM’s compatibility with more detailed geometries may also enable new surgical procedures, as unique, complex end effectors are designed and manufactured.


CONCLUSION


In short, PECM’s specialized process allows for the precise, delicate tools required for surgery, whether performed by hand or robot-assisted – and whether PECM is used for the primary manufacturing technique or as secondary value-added operation. If you would like to discuss how PECM may be able to improve your product or shape its design, contact us! We are eager to help.


REFERENCES:


1. https://www.gestiondecompras.com/en/products/sheet-metal/progressive-die-stamping

2. https://www.pim-international.com/metal-injection-molding/an-overview-of-the-metal-injection-moulding-process/

3. https://www.marlinwire.com/blog/5-benefits-of-electropolishing-stainless-steel-for-pharma-applications

4. http://www.tmd.ac.jp/bd/english/surg_dev1.html

5. https://goldberg.berkeley.edu/pubs/case2016-interchangeable-instruments-submitted.pdf

This article is part of our ongoing “Applications of PECM” series that illustrates scenarios where PECM is an especially good fit. Find other articles in the series below:


Forming Heat Exchangers Using Electrochemical Machining

more articles coming soon!





© 2019 by Voxel Innovations Inc.

Raleigh, NC

info@voxelinnovations.com

984-464-0701

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