Nordson_EFD_Medical_Device_Assembly_White_Paper.pdf - 第4页

2. Are You Using a Dispense Valve System – or Just a Dispense Valve? www.nordsonefd.com 4 Taking a “system” approach to fluid dispensing and carefully evaluating all the details – even something as small as a fluid fitti…

1. Are You Using the Best Dispense Valve for Your

Fluid Application?

3 www.nordsonefd.com

For most medical device dispensing applications, a well-designed, general-purpose

diaphragm or piston valve that can handle a range of fluid viscosities is a good

choice.

In most situations, however, best results will be obtained with a valve style and

configuration carefully matched to the specific properties of the fluid being

dispensed.

Difficult Fluids Such as Medical-grade Cyanoacrylate

Wetted internal parts, as well as any fittings and tubing that come in contact with

the fluid, should always be carefully chosen for compatibility with the fluid being

dispensed.

When working with the cyanoacrylates used in catheters and stents, for example,

diaphragm valves with wetted parts made of inert, Ultra High Molecular Weight

(UHMW) polymer are a good choice because they will not react with the fluid. Nylon

or metal fluid fittings, however, should never be used with cyanoacrylates because

they absorb moisture and will promote premature curing. Use polyethylene or

polypropylene fittings instead. Chemically inert, polyethylene-lined or PTFE FEP

tubing is a good choice for fluid feed lines.

Thin to Medium Fluids

Thin fluids like solvents and watery adhesives have much different requirements,

especially when very small deposits are needed. For these applications, needle

valves are often recommended because shutoff occurs close to the valve outlet or

dispense tip. This is an important design feature because it minimizes dead volume

that can cause dripping or oozing.

When applying fluids in critical applications such as needle bonding, there is even a

needle valve that “seats” the needle in the dispensing tip instead of the valve body.

By virtually eliminating dead volume, this design makes it possible to produce even

smaller and more consistent microdeposits.

Thick Fluids

Thick materials like sealants or the RTV silicones used to bond pacemaker

assemblies, for example, pose very different challenges than thinner fluids like

adhesives or solvents.

When using thick fluids, a high-pressure valve with a balanced spool design will

provide good control. Also look for a snuffback feature – it will prevent drooling and

tailing, and help reduce the rework and cleanup often associated with these more

challenging assembly materials.

Best results will be obtained when the

valve design is matched to the properties

of the fluid being dispensed.

Diaphragm valves

with inert wetted

parts are a good

choice when working

with reactive fluids.

Needle valves minimize dead

volume when making very small

shots of thin fluids.

Needle Seat

Piston valves have snuffback to

keep thick fluids from drooling.

2. Are You Using a Dispense Valve System – or Just

a Dispense Valve?

www.nordsonefd.com 4

Taking a “system” approach to fluid dispensing and carefully evaluating all the details – even something

as small as a fluid fitting – will help prevent many problems on your medical device assembly line.

A dispense valve system has four main components:

 • Thedispensevalve

 • Aprecisiondispensetip

 • Ameansofinitiatingthedispensingcycle

 • Afluidreservoir

The greatest accuracy, reliability, and production yields will be obtained when all four components are

engineered to work together as an integrated system. This approach will also simplify qualification and

validation processes.

A valve paired with a dedicated valve controller will typically provide faster response time than a valve

triggered by mechanical means or a remote PLC. A dedicated controller will also allow deposit size to

be fine-tuned with much greater precision than other methods, and can be interfaced with the assembly

line’s main PLC.

Tips should be of high quality to ensure unobstructed fluid flow, and matched to the specific fluid and

volume being dispensed.

Fluid tanks should always be fitted with constant bleed regulators, to maintain steady fluid pressure and

prevent variations in deposit size as the fluid level moves from full to empty.

An integrated dispense valve

system with valve, dispense tip,

valve controller, and fluid tank.

5 www.nordsonefd.com

3. Does your application require valves that must meet CIP

or SIP standards?

Proper coating placement, coverage, and thickness are critical in medical applications.

Manual tools and spray systems that allow only coarse adjustment may not provide

the controlled, consistent coverage needed to achieve predictable process results and

reliable device performance.

Aseptic valves feature a smooth fluid flow path that is free of any entrapment areas.

FDA-compliant wetted parts make the valve suitable for CIP (Clean-In-Place) and SIP

(Sterilize-In-Place) medical assembly processes.

Aseptic dispense valve wetted components can be made of 316L stainless steel or

PTFE, to conform to biopharmaceutical regulations in medical assembly processes.

Internal threads can be removed to provide a smooth, easily cleaned fluid flow path,

free of entrapment areas and the valve fluid body can be made electro-polished to

increase corrosion resistance.

Aseptic valve shot sizes can range from 0.5 microliter deposits to a continuous flow

rate of 60 milliliters per second. These dispense valves close after each cycle with a

fast, clean cut-off that eliminates drips.

Similarly, aseptic spray valves also feature a fluid flow path that is free of any

entrapment areas—a critical consideration in sterile and aseptic fluid applications

that use low- to medium-viscosity fluids. An aseptic spray valve works best with a

small gauge dispensing tip to produce uniform round spray patterns. Alternatively,

some aseptic spray valves can be fitted with fan air caps for a wider area of coverage.

Aseptic valves and aseptic spray valves offer medical device manufacturers an

accurate, cost-effective coating method that can increase yields, reduce production

costs, and improve process control.

Aseptic valves meet FDA regulations while

providing accurate consistent shots.

The unique design of the aseptic spray

valve is critical for sterile fluid applications.

•Salinesolutions

•OpticalMonomers

•Pillcoatings

•Stentcoatings

•Siliconeoils

•Solvents

•Reagents

•Pharmaceuticalfluids

Compatible Fluids