Basic characteristics and printing principles of TPU materials
TPU (thermoplastic polyurethane) is a polymer material with excellent elasticity and wear resistance. Its hardness ranges from Shore 60A to Shore 95A, which can meet the needs of various applications from soft rubber to hard plastics. The soft segments and hard segments in the TPU molecular structure are alternately arranged, giving the material unique elastic recovery properties. In the field of FDM printing, TPU is the most commonly used flexible printing material. By adjusting the ratio of soft and hard segments in the material formula, finished products with different hardness and elasticity can be obtained. The rebound rate of TPU is usually between 40-60%, and the elongation at break can reach 400-600%. These characteristics make it an ideal choice for manufacturing flexible parts such as sealing rings, shock-absorbing pads, and protective sleeves.
The mechanism of influence of printing parameters on soft and hardness performance
The setting of TPU printing parameters directly affects the soft and hardness performance and mechanical properties of the finished product. The first is the printing temperature. It is recommended to adjust it within the range of 210-230°C. Higher temperatures can improve the bonding force between layers, but too high temperatures will cause excessive softening of the material. The second is the printing speed. It is recommended to print at a lower speed for TPU materials, usually in the range of 15-30mm/s. Low-speed printing can reduce the shaking and drawing of the material. Filling density is a key parameter that affects the hardness of the finished product. 100% filling can obtain the nominal hardness of the material, while a lower filling density will significantly reduce the actual hardness performance of the part.
Selection Guide for Applicable Scenarios of TPU with Different Hardness
Selecting TPU materials with appropriate hardness according to application scenarios is the key to ensuring part performance. Shore 85A-95A's hard TPU is suitable for mobile phone protective cases, industrial equipment crash pads, sports equipment accessories, etc. Shore 75A-85A medium hardness TPU is suitable for seals, pipe connection sleeves, cable protection sleeves, etc. Shore 60A-75A soft TPU is suitable for applications with high elasticity requirements, such as wearable device wristbands, medical rehabilitation aids, shock-absorbing gaskets, etc.
TPU printing common problems and solutions
Printing TPU flexible materials is more challenging than rigid materials. Common problems include plugging, wire drawing, interlayer delamination and surface roughness. Clogging problems are usually caused by moisture in the material or improper temperature settings. It is recommended to dry the material in a 60°C oven for 4-6 hours before printing. The drawing problem can be improved by optimizing the retraction distance and speed. It is recommended that the retraction distance be set to 4-6mm. The delamination problem between layers is mostly caused by the temperature being too low or the layer height being too high. It is recommended to increase the printing temperature by 5-10°C.
Post-processing and performance improvement of TPU parts
It is relatively easy to remove the support of TPU printed parts, but surface treatment requires special attention. Chemical polishing method has limited effect on TPU materials, and mechanical polishing is a more reliable processing method. It is recommended to use fine sandpaper to grind step by step, starting from 400 grit and ending with 2000 grit, to obtain a smooth surface. The long-term performance of TPU parts is closely related to the anti-aging properties of the material. It is recommended to conduct an environmental aging test before use.
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