To eliminate extrusion handover marks, it is important to understand that these marks usually appear at the point where one extrusion cycle joins the next, or where material transfer is not perfectly smooth during continuous production. They can be caused by inconsistent temperature, unstable pressure, poor melt flow, die design issues, contaminated material, or improper machine settings. To reduce or eliminate them, a systematic approach is needed from raw material preparation to final process control.First, the raw material should be kept clean and dry. Moisture, dust, and contamination can interrupt the melt flow and create visible lines or defects at the handover point. If the material is hygroscopic, proper drying before processing is essential. The drying temperature, time, and airflow should match the material requirements. Even a small amount of moisture can lead to surface blemishes, bubbles, or weak bonding at the transition area.Second, temperature stability is critical. The barrel, adapter, die, and melt channel must all be heated evenly. If one zone is too cold, the melt may thicken and cause a mark when the flow restarts or changes. If the temperature is too high, the material may degrade, creating discoloration or rough surfaces. It is best to check all heating zones and ensure that the temperature profile is suitable for the specific resin or compound being used. A stable melt temperature helps the material move smoothly through the die and reduces sudden changes at the handover point.Third, pressure and screw speed should be controlled carefully. Unstable pressure often results in inconsistent output, which can leave a visible line where two sections of material meet. Operators should maintain a steady screw speed and avoid unnecessary fluctuations. If the process includes start-stop movement, the transition should be as smooth as possible. Proper back pressure can also help improve melt uniformity and mixing, which reduces the chance of marks.Fourth, die and tooling conditions should be inspected. A worn, dirty, or poorly designed die can easily create handover marks. Build-up of material inside the die may interrupt flow and leave streaks or lines on the product surface. Regular cleaning and maintenance are necessary. In addition, the die design should promote balanced flow so that material enters the shaping section uniformly. If the flow paths are uneven, the handover area may become more visible.Fifth, line speed and cooling conditions should be optimized. If the cooling rate changes too quickly, the surface may set before the flow is fully stabilized, making marks more noticeable. On the other hand, insufficient cooling can allow the material to deform. The take-off speed, cooling water temperature, air flow, and contact pressure should all be matched to the product requirements.Finally, process monitoring and operator training are very important. Small changes in raw material, ambient temperature, or machine condition can affect the appearance of the product. By recording settings, checking product quality regularly, and making adjustments based on actual results, extrusion handover marks can often be greatly reduced or eliminated.In summary, eliminating extrusion handover marks requires clean material, stable temperature, controlled pressure, proper tooling, balanced cooling, and careful process management. A consistent and well-maintained production system is the best way to achieve a smooth surface and high product quality.