10 Tough Questions: Part One - How to Choose Your Valve

Part One: Choosing the Right Fluid Dispensing Valve System

Is your current dispense valve system giving you accurate deposits with minimal maintenance — or are you applying inconsistent amounts of fluid and wasting too much time and money on downtime, rework, and cleanup?

This blog series discusses common problems encountered with typical dispense valve systems by asking some of the most common questions. It also offers helpful tips for improving valve performance. This first part in the blog series answers the top two questions we have encountered most frequently. We hope that you find this information helpful.

1. Are You Using the Best Dispense Valve for Your Fluid Application?

In most situations, best results will be obtained with a valve style and configuration carefully matched to the specific properties of the fluid being dispensed.

Thick Fluids

Thick materials like RTV silicone or heavy grease, for example, pose very different challenges than thinner fluids like adhesives or threadlockers. When using thick fluids, a high-pressure valve with a balanced spool design will provide good control. Also, look for a snuff back feature as it will prevent drooling and tailing and help reduce the rework and cleanup often associated with these more challenging assembly materials.

Thin to Medium-Viscosity 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. For critical applications, there is even a needle valve that seats the needle in the dispense tip instead of the valve body. By virtually eliminating dead volume, this design makes it possible to produce even smaller and more consistent micro-deposits.

Learn more about how to choose the right valve by downloading our Dispense Valve Selection Guide.

 

Tricky Fluids Like Cyanoacrylates (CAs)

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 cyanoacrylates, for example, wetted parts made of inert Ultra High Molecular Weight (UHMW) polymers are a good choice because they will not react with the fluid. Nylon or metal fluid fittings, however, should never be used with CAs because they absorb moisture and will promote premature curing. Use polyethylene or polypropylene fittings instead. Chemically inert, polyethylene-lined or PTFE FEP tubing are good choices for fluid feed lines.

Learn more about the right setup and maintenance for cyanoacrylate dispensing by downloading our Cyanoacrylate Dispensing Guide.

2. Are You Using a Dispense Valve System — or Just a Dispense Valve?

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 assembly line. A dispense valve system has four main components:

• The dispense valve
• A means of initiating the dispensing cycle
• A precision dispense tip
• 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. Optimum PTFE-lined tips work best with low-viscosity cyanos. They feature a special lining that prevents curing and clogging.

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.

Precision dispense tips should be of high-quality materials 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.

In the middle of coping with day-to-day production challenges, it can be difficult to calculate just how much poor valve performance is really costing you. However, doing so could save you money, increase production, reduce bottlenecks, and improve the overall quality of your products.

Next Up…Part Two: Troubleshooting Your Dispense Valves

In the next part of our series, we’ll look at how to set up your valve system for optimal performance by providing answers to some troubleshooting questions.

Have a question about how to choose the right dispense valve system to begin with? Don’t hesitate to email us at [email protected].