Hot Melt Troubleshooting: Processing Issues

When a hot melt adhesive line is running smoothly, everything just works — clean bonds, consistent flow, and reliable performance at speed. But when something goes wrong, even small processing issues can snowball into costly downtime, wasted materials, and customer complaints.

From foam build-up and air bubbles to uneven flow and high applicator pressures, hot melt processing problems are more common than many factories realise. The challenge is that these issues rarely have a single, obvious cause. Instead, they often stem from a combination of adhesive selection, line setup, substrate condition, and environmental factors.

To help production teams quickly diagnose and prevent these problems, we’ve created a Hot Melt Troubleshooting: Processing Issues Hints & Tips Sheet — a practical guide to the root causes behind the most common issues and the corrective actions you can take.

Here’s a snapshot of the processing problems we cover:

Lack of Substrate Penetration

When adhesive sits on the surface instead of properly wetting out, bond strength suffers. You may see pop-opens, weak tear, or bond failure during storage. Our guide explains what typically causes poor penetration — and how to resolve it fast.

Foam Build-Up in the Adhesive

Foaming during application is more than a cosmetic nuisance. Foam introduces voids into the glue line, reduces adhesion, and destabilises flow. It’s often a symptom of moisture, contamination, or processing conditions — all covered in the tips sheet.

Applicator Drooling

Drips, tails, and unwanted adhesive deposits can create mess, waste, and inconsistent bonding. Whether caused by temperature control, system pressure, or wear, we break down the most common triggers and how to stop drooling at the source.

Uneven Applicator Flow

Wavy, inconsistent, or thin glue beads can compromise bond quality and cause operators to chase problems up and down the line. Our guide highlights the underlying issues — from nozzle blockages to tank stability — that influence flow uniformity.

Air Bubbles in the Hot Melt

Bubbles trapped in the adhesive reduce contact area and can weaken the bond. They often point to environmental issues or changes in the adhesive itself. The hints sheet covers how to identify the cause and eliminate bubbles before they reach the substrate.

Applicator Running at High Pressure

If the system is compensating with pressure, something upstream is restricting flow. Left unchecked, high pressure can damage equipment, increase wear, and lead to sudden failure. We cover the most common reasons for rising system pressure and the simple checks operators can perform.

Get the Full Hints & Tips Sheet

This blog post only scratches the surface. The Hot Melt Troubleshooting: Processing Issues guide provides:

• Root causes for each issue

• Practical corrective actions

• Preventative measures

• Operator-level checks

• Setup considerations that improve long-term reliability

If your team wants to reduce downtime, boost bond performance, and make your hot melt line more reliable, download the free hints & tips sheet using the form below.