What Causes Hot Melt Stringing? 8 Causes and Control Guide
Hot melt filamentation is the elongation of a thin fiber at the moment when the glue flow must be stopped. The most common control areas are actual application temperature, product viscosity profile, nozzle cleanliness, gun–surface distance, on-off timing and line speed. The problem should not be tried to be solved by simply increasing the temperature without taking measurements.
Threading; In case closing, packaging, assembly and similar hot melt applications, the glue in the nozzle forms a thin thread as it separates from the surface. These threads can cause a dirty appearance on the product, sensor and conveyor pollution, unplanned downtime and unnecessary consumption. Although the symptom may be the same, the cause may lie at different points on the machine and adhesive side.
What is hot melt threading?
When the application pulse ends, the glue flow is expected to stop cleanly. If the flow does not break fast enough, a fiber-like wake forms between the nozzle and the surface. It may be accompanied by “tailing”; However, in diagnosing both symptoms, the application video, nozzle appearance and the pattern on the part should be evaluated separately.
8 possible causes of hot melt threading
The value seen on the panel may not represent the actual temperature at the nozzle tip. Sensor, hose and gun areas should be checked separately.
Working viscosity of the product; If the temperature, waiting time and application system are not compatible, clean break may become difficult.
Carbonized debris, partial blockage, or damaged tip disrupts the flow pattern and delays droplet breakout.
Unnecessary distance between the gun and the surface can increase the extension and drift of the hot glue in the air.
Delayed valve closure, irregular pressure, or a trigger pattern that does not match line speed can create a tail.
Keeping the glue hot in the boiler for too long may affect product properties and flow stability.
Cold, dusty or coated surfaces may change the spreading and breaking behavior of the glue.
If the line speed, open waiting time, surface and strength expectations are different, the existing hot melt may not offer the correct process window.
15-minute controlled test plan
- Check the physical condition of the nozzle and filters with the safe stop procedure.
- Record the product code, lot, boiler filling level and hot waiting time.
- Verify actual application temperature with calibrated method instead of set values.
- Take short video with current settings; Determine the start and end point of the thread.
- Change a single variable in small steps within the limits of the technical sheet and test again with the same number of samples.
- Evaluate the result with thread length, line cleanliness and adhesion strength.
How does choosing the right hot melt affect spinning?
The hot melt family is not a single product. EVA and polyolefin based products and reactive hot melts; It has different process windows in terms of viscosity, open waiting time, heat resistance and surface compatibility. Jowat's official hot melt approach also emphasizes product selection based on application area and process requirement. You can match your application with hot melt adhesive guide; You can review packaging glue solutions for your packaging line.
A mere “thread lost” result is not enough for permanent improvement. Adhesion strength, consumption, line speed, accumulation in the nozzle and process stability throughout the shift should be monitored together.
What Causes Hot Melt Stringing? 8 Causes and Control Guide hakkında merak edilenler
Does hot melt spinning occur because the temperature is low?
Low actual application temperature may be one of the reasons; However, high temperature, long hot hold, nozzle problem and timing may also cause similar symptoms. First, the actual temperature should be measured and compared with the product technical sheet.
Should the temperature be increased to dissolve the stringing?
It is not recommended to increase the temperature without measurement and technical sheet verification. Excessive thermal load can increase glue aging, odor, carbonization and maintenance requirements.
Does a dirty nozzle cause threading?
Yes. Partial blockage, carbonized debris, or a worn nozzle tip can disrupt the flow pattern and cause stringing and tailing.
Can the problem be solved without changing the hot melt product?
If the cause of the problem is adjustment, distance, timing or maintenance, improvement can be achieved without changing the product. If the product process window does not suit the application, an alternative should be evaluated with a technical trial.
Technical resources and verification
The content has been prepared in Turkish with the technical experience of Koçak Endüstri, based on the following manufacturer resources.
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