Dry vs. Wet Dog Food Extruder machine: What’s the Core Difference in pet food pellet machine Working Principles?

The core feature of a dry pet food processing machine is that it requires no additional water and relies on the self-heating of the raw materials. During operation, the screw rotates at high speed (typically 300-600 rpm), generating intense friction with the extrusion chamber. Simultaneously, a heating device assists in raising the temperature, allowing the raw materials to gelatinize and expand under high temperature (120-160℃) and high pressure (3-8 MPa) conditions. The humidity of the raw materials must be controlled at 10%-15% before entering the equipment. No additional water is needed throughout the process, and the finished product, after cooling, can have a moisture content as low as 8%-12%, with a shelf life of 6-12 months. This principle results in a relatively simple structure, eliminating the need for a water supply and drying system. The initial investment is 20%-30% lower than that of a wet extruder, making it suitable for producing ordinary dry dog ​​food, fish food, and other similar products.

A wet pet food making machine, on the other hand, uses an "external water supply + steam heating" operating mode. The equipment is equipped with a dedicated steam generator and water supply device. During production, steam or warm water is first injected into the raw materials to raise their moisture content to 18%-25%, and then they are extruded by a medium-low speed screw (150-300 r/min). The steam not only provides moisture but also quickly heats the raw materials to 100-140℃, reducing screw friction wear and resulting in more uniform gelatinization. Due to the high moisture content of the raw materials, the finished product requires a specialized drying process to reduce the moisture content to below 12%, thus necessitating additional drying equipment. This increases the overall production line cost by approximately 40% compared to dry processing. However, feed pellets produced using this method have a softer texture and a 10%-15% higher nutrient retention rate, making them more suitable for high-end pet food, livestock feed, and other similar products.

The core component designs of the two types of pet food extruder machines also differ due to their different operating principles. Dry extruders use screws with deep grooves and high-hardness materials to enhance frictional heating. The inner wall of the extrusion chamber usually has raised textures to further increase the coefficient of friction. Wet extruders have shallower screw grooves, focusing on raw material conveying and mixing. The extrusion chamber is equipped with steam injection ports to ensure uniform penetration of moisture and heat. In terms of energy consumption, dry extruders rely on frictional heating, resulting in 15%-20% higher energy consumption per unit product compared to wet extruders. However, they eliminate the energy consumption of the drying process. Overall energy consumption needs to be calculated in conjunction with production volume—dry extruders are more energy-efficient for small-scale production, while the steam heating efficiency advantage of wet extruders is more significant for large-scale production.

Producers need to determine the appropriate extruder based on the characteristics of the raw materials and the requirements of the finished product: if using low-moisture raw materials such as corn or soybean meal to produce dry pellets, dry extruders offer better cost-effectiveness; if using high-protein raw materials such as meat meal or fresh bone broth to produce soft pellets, wet extruders offer better gelatinization and nutrient retention. Understanding the core differences in the working principles of the two extruders is crucial to avoiding selection errors.

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