Die Design Strategies for Uniform Wall Thickness in PTFE Paste Extrusion

Uniform wall thickness is a core quality index of PTFE paste extrusion products, especially for precision PTFE tubing and thin-walled insulation profiles used in electrical insulation and precision fluid transmission. Uneven wall thickness will lead to inconsistent pressure resistance, insulation performance and structural strength of products, and cause dimensional out-of-tolerance in batch production. Die structure is the key factor determining material flow distribution and product molding size in paste extrusion process. Scientific die design strategies can effectively balance the flow velocity of PTFE paste in all directions of the die cavity, eliminate flow deviation, and realize high-precision uniform wall thickness molding PTFE TUBE.

The core principle of uniform wall thickness die design is to realize equal flow velocity and equal pressure distribution of PTFE paste in the circumferential and axial directions of the die. PTFE paste has shear-thinning flow characteristics, and the flow velocity near the die wall is low due to friction resistance, while the central flow velocity is higher, which is the main cause of uneven wall thickness. In view of this flow law, the optimized die adopts a gradient shrinkage flow channel design. The flow channel gap is reasonably adjusted according to the flow velocity distribution law, the resistance of the central high-speed flow area is appropriately increased, and the resistance of the wall low-speed flow area is reduced, so as to balance the overall flow velocity and realize synchronous uniform molding of the product wall thickness.

The concentricity and structural symmetry of the die core and die sleeve are the basic guarantee for circumferential uniform wall thickness. In traditional simple die design, tiny concentricity deviation will lead to inconsistent flow gaps in all circumferential directions, resulting in partial thick and thin wall defects. High-precision extrusion dies adopt integrated processing and high-precision calibration technology to ensure the absolute concentricity of the die core and die sleeve, eliminate circumferential flow deviation, and realize uniform circumferential wall thickness. At the same time, the die flow channel adopts a smooth arc transition structure to avoid right-angle dead corners and sudden changes in flow resistance, prevent material retention and local flow disorder, and ensure stable and consistent flow state of paste in the whole flow channel PTFE SHEET.

The length of the die sizing section is a key structural parameter affecting wall thickness uniformity. Too short sizing section cannot fully calibrate the product size and eliminate flow fluctuation, resulting in unstable wall thickness; excessively long sizing section will increase die friction resistance, cause material over-shear, and induce surface defects and internal stress. Through a large number of process verification, the optimized die design matches the length of the sizing section according to the product wall thickness and paste flow performance, ensuring that the material can complete stable shaping and dimensional calibration in the sizing section, and maintain consistent wall thickness tolerance in continuous extrusion production.

In addition, modular adjustable die design has become an advanced strategy for adaptive uniform wall thickness production. The modular die structure can fine-tune local flow resistance according to real-time production data, dynamically correct tiny wall thickness deviation, and realize precise control of high-precision products. Combined with paste rheological characteristics and extrusion parameter matching, the optimized die design fundamentally solves the industry pain point of uneven wall thickness in PTFE paste extrusion, greatly improves product dimensional accuracy and batch consistency, and provides reliable die technical support for high-end precision PTFE extrusion product manufacturing.