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Reducing Hand Fatigue and Variability in Medical Device Assembly Processes
Last Updated: 12/01/2012
Reducing Hand Fatigue and Variability in Medical Device Assembly Processes

Thank you for your interest in Adhesive Dispensing Ltd air-powered dispensing technology.

For a confidential discussion of how air-powered dispensing can help you
improve your medical device assembly processes, we invite you to contact our experienced Application Specialists at 0800 094 9058 or [email protected]


Medical device assembly is a demanding task that requires precise control of every step in the production process. Many devices require assembly fluids like adhesives, RTV silicones, epoxies or lubricants to be applied in very small, accurate amounts -- but the squeeze bottles, medical syringes, dental picks and other manual tools often used to apply these materials do not provide a high level of control.

Variations in the amount of fluid applied to each part means more rework, more rejects, and
lower yields. In addition, the repetitive movements associated with manual applicators can cause hand fatigue or more serious injuries like Carpal Tunnel Syndrome, especially when using silicone and other very thick materials.

If your production operators find it difficult to apply consistent amounts of fluid, or if they
experience hand fatigue from constant squeezing or trying to push thick materials through thin dispensing needles, air-powered dispensing technology may be the solution you are looking for.

This paper addresses:

� Common problems with manual fluid applicators
� How air-powered dispensing technology works
� A new tool for preventing hand fatigue
� How air-powered dispensing technology can eliminate hand fatigue and variability problems

Common Problems with Manual Fluid Applicators

While manual fluid application with medical syringes, toothpicks and brushes, or dipping parts into containers of fluid may produce acceptable results in some assembly processes, medical device manufacturers often encounter one or more of the following problems.

Poor Process Control

Manual tools that require the individual operator to determine how much fluid to apply cannot provide the accuracy and repeatability needed to consistently meet specifications and ensure reliable device performance.

Hand Fatigue & Safety Issues

Repetitive squeezing or pressing motions with thumbs and palms is tiring, and can lead to serious injuries � especially when thick materials like silicone must be applied through small gauge needles. And in processes where open containers are used, there is the risk of hazardous fumes and skin irritation.

Variations in the Amount of Fluid Applied

Because manual fluid applicators rely on individual judgment to control the amount of fluid applied, results can vary from operator to operator, and facility to facility. What one worker thinks is too little fluid, another may think is too much. In some applications, the operator can be so busy just trying to push fluid through a syringe and get it in the right place that it�s difficult to worry about putting a consistent amount on each part as well.

Low Productivity

When prototypes or small production runs are being made a few parts at a time, extra time can be spent on the fluid application process to ensure acceptable results. In high-volume production environments, however, operators grow tired and slow down, and it becomes more difficult for them to maintain control over the amount of material applied.

High Reject Rates

When a device will be used in a surgical procedure or inserted into a human body, there is no
room for error. Too much or too little fluid, or unwanted application onto nearby components, can all result in costly rejects, lower yields and reduced profitability.

Fluid Waste

Over application and disposal of fluids that become contaminated in open containers wastes
expensive material and increases production costs.

How Air-powered Dispensing Technology Works

Air-powered dispensing systems make it simple to apply virtually any fluid used in medical device assembly in accurate, repeatable amounts. They do this by using a combination of controlled air pressure and a precision timer to control the amount of fluid applied. By taking the guesswork out of the fluid application process, they enable any operator to apply the same amount of fluid on every part, every time.

These systems operate on compressed air (nitrogen may also be
used) and electricity. The fluid to be dispensed is contained in a
disposable syringe reservoir. The top of the syringe is connected to the dispenser console by a flexible air line, and a precision dispense tip is threaded onto the bottom of the syringe.

The following figures show a typical system setup and control

Typical Air-powered Dispensing System Setup

Typical Dispenser Control Panel

In air-powered dispensing, the amount of fluid applied is determined by a combination of air pressure, dispense time, and tip size. In general, thick fluids and larger deposits require higher pressures, longer dispense times and larger tips. Thin fluids and smaller deposits use lower pressures, shorter times and smaller tips. The following figure shows the effects of different pressures, times and tips on deposit size.

Effect of Different Times, Pressures and Tips on Deposit Size

NOTE: Dot sizes are proportional - not to scale

To make a series of identical dots, or fill cavities with consistent volumes of material, the user adjusts air pressure to achieve the desired fluid flow rate and sets the size of the deposit with the digital timer. Dispense time, which is the simplest and most precise way to adjust deposit size, is adjustable in 0.1, 0.01, or 0.001-second increments, which ensures exceptional

Unlike manual applicators, no repetitive motions or awkward hand positions are involved. To
apply a dot or fill a recess, the operator simply holds the syringe like a pen, places the dispense tip in position, and taps an electric foot pedal to initiate the dispense cycle. Tapping the pedal again produces an identical deposit. When making stripes, the timer is turned off and the operator controls the dispensing cycle with the foot pedal.

A New Tool for Preventing Hand Fatigue

Silicones, epoxies and other thick fluids can be extremely difficult to dispense with medical syringes and other manual tools. Hand fatigue is a common problem, because of the tremendous effort needed to push thick material through a small orifice.
In most applications, the hand fatigue issue is easily eliminated by using a standard 0-100psi air-powered dispenser and a tapered polypropylene dispense tip that is specially designed for fast, smooth application of thick fluids.

However, in processes that require small amounts of very thick
fluids to be applied through very small tips, even 100 psi may not be sufficient. For these applications, there is a new dispensing tool that effectively increases the output of a standard 100psi dispenser into 700psi of fluid dispensing pressure.

The tool consists of a lightweight aluminum retainer containing a disposable syringe reservoir
and an oversized piston. When the dispenser is actuated, air pressure is applied to the top of the piston. The piston�s large surface area increases the pressure on the fluid inside the syringe up to 7 times, in effect converting 100 psi of input pressure into 700 psi of dispensing pressure. The result is fast, controlled application of thick fluids through dispense tips as small as 0.004� in diameter. In addition to reducing the risk of repetitive stress injuries, these new high pressure tools also increase yields by helping workers produce more (and more consistent) parts in less time.

How Air-powered Dispensing Technology Can Resolve

Hand Fatigue and Variability Issues

Better Process Control

An air-powered dispenser�s precision controls and digital timer provide exceptional control of
deposit size and allow dispensing parameters to be documented, so that results can be duplicated each time a particular product is produced.

Less Operator Fatigue, Fewer Injuries

Using controlled air pressure instead of repetitive squeezing or pushing motions to apply fluid greatly reduces hand fatigue and the risk of serious injury, especially in applications where thick fluids are used. Eliminating open fluid containers also reduces fumes and the risk of dermatitis from contact with fluid.

Elimination of Variability in Critical Dispensing Processes

Removing guesswork and subjectivity from the dispensing process means that every operator �
even in different facilities -- applies the same amount of fluid to every part, every time. Operators can then concentrate on putting fluid in the right place, instead of worrying about how much to apply.

Fewer Rejects and Higher Yields

Uniform fluid deposits improve device consistency and cosmetic appearance, so that operators
can produce more good parts in less time.

Less Waste

By keeping fluid contained in a closed system and applying the correct amount every time, air powered dispensers help reduce production costs by eliminating contamination and waste.


Air-powered dispensing technology offers medical device manufacturers a cost-effective way to:

� Reduce hand fatigue and variability
� Increase yields
� Lower production costs

Simple to set up and operate, air-powered dispensing systems eliminate guesswork and enable
any operator in any facility to apply a precise, consistent amount of fluid on every part, every time. They can be used to improve a wide variety of assembly processes, and have the  flexibility to handle many different fluids.

For more information on air-powered dispensing technology, or to discuss your specific assembly application in strict confidence, please contact ADL�s Fluid Application Specialists at 0800-094-9058 or [email protected].

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