Best talks about which plastic base or wax base is better for MIM process binder
time：2020-06-23Views：285 Author：Best Seiko
Is the plastic-based adhesive or wax-based adhesive used in the metal powder injection MIM feeding process? What are the differences between plastic-based and wax-based adhesives in the mixing, injection molding, degreasing and sintering processes? The following is a brief introduction by Shenzhen Best Editor. 1. Wax-based binder in the mixing stage: 1. The mixing temperature is lower than 120°C, and the mixing time is shorter; 2. Sealed mixing and mixing, airtight design to reduce paraffin wax heating loss; 3. Plastic-based mixing Equipment, but the shear force should pay attention to temperature control. Plastic-based binders: 1. The mixing temperature is greater than 150°C, and the time for soft mixing is long; 2. The open-type kneading and kneading are used; 3. The wax-based mixing mixer is not available, and the shear force is insufficient; 4. The special powder is mixed Adopting nitrogen protection; 5. High shear force can fully soften the plastic base compound. In general, the wax-based binder is mainly paraffin wax, which has a low viscosity and is volatile; therefore, it is easy to mix, but it should also be noted that the temperature should not be too high (less than 120 ℃), with a gas-tight design to reduce volatile losses. Plastic-based adhesives are mainly POM, with high viscosity and low volatilization; need to use a mixer with high shear force, and the temperature is set higher (more than 150 ℃) to reduce the viscosity of the adhesive; because the temperature is relatively low High, and often open, in order to prevent some special metal powder from being oxidized, special circumstances need to use nitrogen protection. 2. Wax-based binder in the injection stage: 1. Good lubricity, slow firing speed can also be achieved, the hydraulic press can also be used for metal powder injection MIM; 2. Mold temperature and metal powder injection MIM material tube temperature is low; 3. Fast and easy shooting speed The shell effect caused by the separation of powder and glue is obvious. This is due to the low viscosity of the wax, so the parts with high polishing brightness are not easy to save their sand hole defects. Plastic-based binder: 1. High-speed motor can make plastic-based feed well; 2. Metal powder injection molding machine has high speed and injection pressure and long holding time; 3. Screw compression ratio is very important, and the screw length needs to be Short; 4. The mold temperature should be high (>120 ℃) to reduce the residual stress of the metal powder injection blank; 5. The temperature control of the material pipe should be more strict, and the temperature should be immediately reduced without injection operation to avoid POM cracking! The injection stage is similar to the mixing stage, and the high viscosity of the plastic-based binder also makes it difficult to injection mold metal powder. The wax-based adhesive can meet the requirements due to the low viscosity, low rate of fire, and low mold temperature metal powder injection molding machine due to its low viscosity and good lubricity. On the contrary, the fast rate of fire can easily lead to the separation of powder and glue, which leads to product sand hole defects. . Plastic-based adhesive requires a high-speed electric metal powder injection molding machine. The screw is short, the rate of fire, injection pressure, mold temperature is high, and the pressure holding time is long. In addition, the temperature control of the material tube should be more strict, and the injection operation should be immediate. Cool down to avoid POM cracking! 3. Wax base in degreasing stage (dissolution/thermal desorption): 1. Dissolution makes the product easy to deform; 2. The efficiency of the first removal is low, the safety of the removal equipment is poor, and the fire prevention and recovery of the solvent all cause environmental protection and safety problems; 3. The removal is suitable for huge parts , The structure must have a supporting plane. Plastic base (acid catalytic desorption): 1. Fast catalysis, suitable for meat thickness below 5mm, high efficiency; 2. Simple equipment and high safety; 3. The by-products are all gases (CO2, N2), easy to manage.