Precision Acme Screws Drive Medical Device Advancement

Christopher Nook by Christopher Nook

The medical field is one that's advancing at an unprecedented rate. One of the keys to this rapid advancement is the medical industry's increasing use of technology. One of the unheralded components doing the most to propel the medical industry forward is the precision acme screw.


The medical field is one that's advancing at an unprecedented rate. One of the keys to this rapid advancement is the medical industry's increasing use of technology. One of the unheralded components doing the most to propel the medical industry forward is the precision acme screw.

Acme screws work with an acme nut to convert rotary motion into linear motion by turning either the screw or nut. There are a lot of reasons why these intricate components are driving innovation in many industries; not just medical. Some of the reasons are their affordability, quiet operation, design flexibility and their precision. Product developers are increasingly coming to realize the many benefits of precision rolled acme screws and we are seeing their inclusion in many new medical applications.

When it comes to the medical industry, there are two very different, yet critical, pieces of equipment that Helix acme screws are helping to advance -- the automated syringe pump and the automated hospital bed.

Here's a closer look at each application:

Automated Syringe Pumps

Why they're important: These small infusion pumps serve a primary purpose of injecting patients with very precise amounts of medication (i.e. pain-killers, antibiotics, etc.). They're also used in medical research settings.

Challenges: Automated syringe pumps need to administer exact amounts of medication or deliver a precise amount of fluid in a research project. Failure to do so could be detrimental to a patient’s treatment or to a research project. Of course there is always pressure to combat rising medical costs and the development of automated syringe pumps is no different. Their increased proliferation drives the need to use low cost, quality components.  They need to be easily produced and have low maintenance costs.

Syringe pumps have historically incorporated ball screws and, although the provide good precision, they can be problematic. Ball screw assemblies are noisy, bulky, high maintenance, and otherwise costly to manufacture. Ball nuts incorporate precision balls that need to re-circulate through tubes. The rolling balls create noise and the precision fit is not very tolerant of contaminants. All of the components that comprise a ball screw assembly require considerably more space than a simple precision lead screw and nut.
Fewer parts translate into lower cost and lower maintenance because acme screw assemblies are also more tolerant of contaminants. Acme screws cost less because they are produced efficiently by the process of roll forming rather than more costly machining or grinding. Rolling is much faster than other methods but still maintains the precision accuracy needed for the application and Helix lead screws have a standard lead tolerance of 0.0003"/in. Acme screws reduce cost in other ways as well. The screw ends and nut bodies of Helix lead screw assemblies can easily be customized for the application to reduce assembly part counts, complexity, and overall footprint. Today’s acme lead screw is designed for precision, accuracy and low cost and Helix precision screws are ideal for syringe pump and many other demanding applications.


Hospital Beds

Why they're important: Hospital beds are intended to keep patients safe, as well as comfortable, while they are being treated.

Challenges: Since there are many more hospital beds than there are medical professionals in most hospitals, there is a need for increased automation and ease of automation. Hospital beds present a few notable design challenges. They have little space for linear actuators but also require high power, high efficiency, and clean operation.

Acme lead screws play a big role in helping to automate these beds. Bed parts are moved by electric linear actuators which combine an acme screw and nut with an electric motor. Linear actuators have high load capacity in a small package, with clean, quiet operation. Probably the most important benefit is that they have infinite positioning. When combined with a smart controller, many combinations of movement and position can be programmed. In this way, the bed can automatically be moved to different positions. This shifts the patient weight, for example, to prevent bed sores that happen when a patient stays in one position for too long. Ball screws and other technologies, on the other hand are complicated, noisy, and their added accuracy is simply overkill for this type of application.

Proprietary materials used in Helix lead nuts reduce friction and therefore increase design life, especially in a low duty cycle application such as a hospital bed. Helix proprietary nut material can even be run without lubrication, which means lower maintenance and the elimination of messy lubricants such as grease. Acme lead screws run much quieter without the circulating balls required for ball screw assemblies and Helix lead nuts can easily be modified to facilitate their direct integration with the bed assembly.

The medical industry is developing at a rapid rate -- and it will likely continue to do so. Helix is doing its part to provide the precision components that help make equipment like automated syringe pumps and hospital beds perform at their best while lowering their cost to manufacture and maintain.


Download this informative Case Study: Maintaining Syringe Pump Precision at Lower Cost with Helix Solutions


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