What is the best dispensing tip for a thick paste?

Medium- to high-viscosity fluids or particle fill materials have unique material properties that make them respond differently to dispensing system dynamics.

As a result, general-purpose dispense tips are not always the right choice for these materials. Let’s talk about how to choose a dispense tip for high-viscosity fluid.

What are the challenges of dispensing thick pastes?

When a thick paste passes from the hub to the cannula in a general-purpose tip, the material experiences backpressure from trying to force a thick material through a small cannula.

To overcome this backpressure, the dispenser has to increase actuating air pressure. This, in turn, can result in poorly controlled dispensing and excess material deposition. Additional pressure can even cause the material to separate in the barrel.

To solve these problems that occur when dispensing thick pastes, choose a tapered tip instead of a general-purpose tip.

Why is a tapered tip best tip for dispensing medium- to high-viscosity fluids?

• The smooth taper and wider diameter make even thick pastes flow more smoothly.
• The wider diameter enables a tapered tip to dispense the same amount of material in a fraction of the time compared to a general-purpose tip. This improves yields and productivity in the dispensing application.
• Tapered tips can be made with UV-blocking additives that prevent UV light from reaching the material inside. This stops UV-sensitive adhesives from curing inside the tip.

Figure 1: Nordson EFD’s SmoothFlow tapered tips are designed to deliver higher flow rates even with highly viscous materials. Some are made with UV-blocking additives, which prevents premature curing of UV-sensitive materials.