In the PVC foam boards production line, the problem of uneven thickness of the boards is prone to occur. If you've been struggling with how to fix uneven thickness in PVC foam boards, or if you're looking for troubleshooting steps to prevent this issue from arising, solutions can be implemented from the following aspects:

I. Adjust Mold Parameters

1. Regulate the Lip Gap: The size of the mold lip gap directly affects the thickness of the extrudate. An excessively large or small gap may lead to uneven board thickness. Therefore, the lip gap should be properly adjusted according to production requirements to ensure uniform thickness of the extrudate.

2. Adjust Flow Restrictors: Flow restrictors function to regulate the flow rate and distribution of the melt inside the mold. By adjusting the position and shape of the flow restrictors, the flow path and speed of the melt can be modified, thereby improving the problem of uneven board thickness.

3. Adjust Mold Temperature:Mold temperature has a significant impact on the fluidity and solidification rate of the melt. It should be set appropriately based on the properties of the production material and process requirements to ensure that the melt flows uniformly and solidifies quickly inside the mold.

II. Optimize Formulation and Process

1. Adjust Lubrication Balance: Lubrication in the PVC foam board system is divided into internal lubrication and external lubrication. Excessive external lubrication may result in poor plasticization, or cause a large amount of precipitates to adhere to the mold cavity and manifold core—leading to uneven wall thickness and occasional appearance of various defects on the surface. Insufficient internal lubrication, on the other hand, leads to poor material dispersion and uneven plasticization, making it difficult to control the product thickness (e.g., the foam board may be thicker in the middle and thinner on both sides). Thus, the dosage of internal and external lubricants should be properly adjusted according to production needs to ensure uniform flow of the melt during extrusion.

2. Excessive foaming agent dosage or insufficient foaming regulator dosage may lead to insufficient melt strength, resulting in uneven thickness of the foam board during extrusion. The dosages of the foaming agent and foaming regulator can be appropriately adjusted, or foaming agents and regulators with higher melt strength and viscosity can be selected to enhance melt strength and ensure uniform thickness of the foam board.

3. Control Calcium Carbonate Content: As the main filler in PVC foam boards, calcium carbonate affects the melt strength of PVC. Its content has a crucial impact on the board’s strength and thickness uniformity. The content of calcium carbonate should be properly controlled according to production requirements to prevent excessive amounts from causing reduced board strength and uneven thickness.

4. Stabilize Extrusion Speed: The stability and consistency of extrusion speed are vital to the uniformity of board thickness. It is necessary to ensure that the extruder maintains a stable extrusion speed during operation to avoid uneven board thickness caused by speed fluctuations.

5. Adjust Traction Speed: The speed of traction also affects the uniformity of board thickness. It should be properly adjusted based on production requirements to ensure it matches the extrusion speed, thereby preventing uneven board thickness.

III. Strengthen Equipment Maintenance

1. Regular Mold Inspection: During use, molds are subject to wear and corrosion, which may change their shape and dimensions. Therefore, the mold wear condition should be inspected regularly, and severely worn mold components should be replaced promptly to ensure the precision and stability of the mold.

2. Clean the Interior of the Mold: Residues and impurities tend to accumulate inside the mold, which can affect the fluidity of the melt and the thickness uniformity of the board. Thus, the interior of the mold should be cleaned regularly to ensure it is free of impurities.

IV. Other Measures

In summary, solving the problem of uneven thickness in PVC foam boards requires efforts from multiple aspects, including adjusting mold parameters, optimizing production processes, strengthening equipment maintenance, and implementing other measures. Through comprehensive implementation of these solutions, the thickness uniformity and product quality of PVC foam boards can be significantly improved.