Single screw extruder and twin screw extruder comprehensive comparison: feed production selection guide

In the highly competitive feed processing industry, extrusion equipment directly determines the quality of feed products, production efficiency, energy consumption costs and profitability of enterprises. Single-screw extruder and twin-screw extruder are two mainstream core equipment in feed field, which are widely used in livestock feed, aquatic feed, pet food and special extruded feed production. Whether the equipment selection is reasonable or not directly affects the stability of the production line, the qualified rate of the finished product and the return on investment. Whether it is to build a new feed production line, upgrade the old equipment, or expand the high-end feed category, it is the key for enterprises to do a good job in equipment investment and optimize the production system to understand the core differences, adaptation scenarios and advantages and disadvantages of the two kinds of expansion equipment. This article will systematically compare single screw and twin screw extruder from the dimensions of equipment definition, working principle, core difference, advantages and disadvantages, application scenario, selection logic and operation and maintenance cost, so as to provide accurate selection reference for feed enterprises of all sizes.

Basic definition of equipment

Single screw extruder

Single screw extruder is the most basic and oldest extrusion processing equipment in the feed processing field. The core structure is that the heating barrel is equipped with a single rotating screw, and the processing, ripening and molding of feed raw materials are completed by mechanical operation. During the operation of the equipment, grain, protein, grease, additives and other feed raw materials enter the inside of the equipment, and the materials are compressed, rubbed, heated and cured by continuous rotation of the screw, and finally extruded through the die to make pellet feed or puffed feed.

The equipment has simple structure, few parts and clear operation logic. It can complete material transportation and ripening by friction force between material and screw and barrel, and realize starch gelatinization and protein denaturation with external heating device of barrel. After long-term industry iteration, the single-screw extruder technology is mature, stable in operation, suitable for the basic feed processing scenario with fixed formula and stable raw materials. It is the mainstream configuration of entry-level and middle-end production lines in small and medium-sized feed factories, and is mostly used for the production of conventional livestock feed and ordinary extruded products.

Introduction of Twin Screw Extruder

Twin screw extruder is a modern high-end feed processing equipment. The core structure is that the barrel is equipped with two parallel screws that mesh with each other. It can realize the same direction or reverse rotation according to the production requirements, and cooperate to complete the whole process operations such as material conveying, stirring, high temperature curing, pressure molding, etc. Compared with single-screw equipment, the twin-screw structure breaks through the limitations of friction transmission, forming a volumetric forward conveying operation mode, and has precise control over the temperature, pressure and material flow rate of the whole production process.

The equipment is equipped with adjustable modular screw assembly, which can flexibly adjust the structure according to complex formulas such as high grease, high moisture and high fiber, and adapt to various special raw material processing. The intermeshing structure of twin screws has automatic self-cleaning characteristics, which can effectively eliminate material residues and ensure production hygiene and batch stability of finished products. With excellent mixing effect, precise process control ability and strong formula adaptability, twin-screw extruder has become the core production equipment of high-end pet food, high-precision aquatic feed and special functional feed, and is the key equipment for feed enterprises to lay out high-end market and enhance product added value.

Comparison of working principle of equipment

Working principle of single screw extruder

Single screw extruder relies on single screw rotation drive to complete the whole process operation, material transportation, compression, ripening highly dependent on friction, simple process, low operating threshold. The mixed raw materials after pretreatment enter the feeding area through the hopper and are brought into the barrel by the rotating screw. As the screw groove depth gradually narrows from the feed zone to the compression zone, the material is continuously extruded and compacted, and the density is steadily increased to complete the basic conveying compression process.

In the ripening stage, friction heat generated by friction resistance of materials cooperates with auxiliary heating of the barrel to form a high temperature and high pressure environment in the barrel, which promotes sufficient gelatinization of feed raw material starch and effective denaturation of protein, greatly improving feed palatability and animal digestion and absorption rate. The cured material enters the metering and pressure stabilization area and forms a stable pressure under the constant speed push of the screw to prepare for extrusion molding.

Finally, the high-pressure material is rapidly extruded through the die head micropores, and the external pressure suddenly drops to make the internal moisture of the material flash instantaneously to form a loose porous expanded structure, and then the standard feed particles are formed by cutting, drying, spraying and other procedures. The core short board of this principle is very prominent: relying on friction feeding in the whole process, it is easy to have the problems of material slip and uneven flow rate when processing high fat, high moisture and low viscosity raw materials, resulting in uneven expansion degree and density of finished products and greatly reduced quality stability.

Working principle of twin screw extruder

Twin screw extruder adopts meshing forward conveying principle, completely get rid of the limitation of friction feeding, greatly improve production stability and process accuracy. After the material enters the hopper, it can be quickly clamped and fixed by two synchronous meshing screws and actively pushed. The whole process does not depend on the friction force of the material. Common problems such as material slip and flow fluctuation are eliminated from the root to ensure uniform and stable feeding.

The equipment is equipped with a variety of modular screw components such as conveying, reverse, rolling, etc., which can form high-intensity shearing, stirring and rolling effects on materials during operation, so that grease, vitamins, functional additives and main materials are fully integrated. The material homogenization effect is far superior to that of single screw equipment. At the same time, it adopts partitioned independent temperature control design, which can accurately control the temperature and pressure of each section of the barrel. It is combined with a special exhaust structure to discharge excess moisture and volatile impurities in time, so that the raw materials can be cured more evenly and the nutrient components of the feed can be retained to the greatest extent.

Homogenized and cured materials are extruded from the die under stable pressure. The staff can accurately adjust the expansion degree, particle density and molding texture according to the product requirements, and easily realize the customized production of floating, slow settling and sinking aquatic feeds. The self-cleaning structure of twin screws wiping each other during operation can effectively avoid material residue deterioration, adapt to refined production scenarios with multiple formulas and high frequency conversion, and perfectly adapt to the processing requirements of various complex high-end feeds.

Comparison of equipment core differences

Mechanical structure design differences

Single screw extruder adopts integral fixed screw structure with few parts, simple structure, fixed operation logic and no complex modular components. The equipment is compact in size and occupies a small area, and the requirements for infrastructure such as installation site and power supply are extremely low. The simple mechanical structure makes the equipment have low failure rate and stable operation, which is very suitable for standardized and uninterrupted mass production operations, but the screw structure cannot be adjusted, the process parameter adjustment space is limited, and the production flexibility is insufficient.

Twin screw extruder adopts meshing modular structure, precise design, high integration, can freely combine screw components according to feed formula and production process, adapt to multi-scene production requirements. The equipment is equipped with independent temperature control, speed regulation, exhaust and other precision systems, with comprehensive functions and strong science and technology. The overall size of the equipment is large, and the requirements for installation space and supporting facilities are higher. Although the complex structural design improves the process flexibility and function expansion, it also raises the threshold of equipment operation and maintenance accordingly.

Material handling stability differences

Single screw extruder relies on the friction between material and equipment to complete the transportation, material speed, discharge depends entirely on the friction coefficient. When processing simple formula with moderate moisture and grease, the discharge is stable and the yield is uniform. However, in the face of high oil, high moisture and low viscosity raw materials, it is easy to have problems such as material slip, flow disorder and intermittent discharge, which directly leads to large quality differences between batches and cannot realize standardized and stable production.

Twin screw extruder adopts positive displacement conveying mode, meshing screw as precision pump actively push materials, not affected by material viscosity, grease, moisture. Whether the formula is simple or complex, it can maintain constant conveying speed and discharge volume, and the flow stability is extremely strong. Even if there is a small fluctuation in the quality of raw materials, the equipment can still maintain stable production, and the batch consistency of finished products is high, which fully meets the refined and standardized production requirements of high-end feed.

Homogenization effect difference of material mixture

Single screw extruder only has basic longitudinal distribution mixing ability, weak shear force, poor rolling effect, and can only meet the basic production requirements of simple livestock feed and low additive formula. For oil, crude fiber and functional additives, the dispersion ability is poor, and it is easy to cause the problems of ingredient aggregation and uneven ripening of materials, resulting in unbalanced nutrition distribution of finished products and inconsistent expansion degree, which directly affects feed palatability and animal digestion and absorption rate.

The twin screw extruder has the dual mixing ability of decentralized and distributed. The high intensity shearing and kneading effect produced by screw meshing can make all kinds of ingredients and main ingredients blend evenly, and the homogenization effect is excellent. Even for complex formulas with high fat, high fiber and multiple additives, it can completely eliminate the problem of ingredient agglomeration, ensure uniform ripening degree of materials, balanced nutrition distribution, and completely meet the production standards of high-end feeds.

Process control flexibility differences

Single screw extruder process parameters have strong correlation and weak adjustability, screw speed, material residence time, shear intensity and barrel temperature can not be independently adjusted, and parameters restrict each other. The equipment is only suitable for the production mode of fixed formula and fixed process. When changing feed category or formula, it is easy to cause the problem of substandard quality, poor process adaptability, and unable to support flexible production of multiple categories.

Twin-screw extruder supports independent regulation of all parameters, which can adjust throughput, screw speed, partition temperature, exhaust volume and shear rate separately, and accurately control the ripening degree and residence time of materials. The equipment can complete multiple processes of mixing, dehydration, curing, modification and molding in a single production line. By adjusting the screw combination and process parameters, it can quickly switch to multi-category and multi-formula production. The process flexibility and adaptability are far superior to single screw equipment.

Difference between finished product quality and category adaptation

The single screw extruder has poor controllability on the expansion degree and particle density of the finished product, and the batch quality fluctuates obviously. It is only suitable for producing conventional sinking livestock feed and low-end economic pet feed. The equipment can not accurately control the expansion effect, it is difficult to produce high-stability floating aquatic feed, the starch gelatinization rate and nutrition retention of the feed are general, the palatability and digestibility are at a medium level, and only suitable for the popular low-end feed market.

Twin screw extruder can accurately control the expansion degree, density and molding texture of feed, stably produce floating, slow sinking and sinking aquatic feed, and can process high-end pet food and functional special feed with high meat content and no grain. The finished starch is fully gelatinized, the nutrition is intact, the granules are uniform and full, the digestibility and palatability are greatly improved, and the added value of the product is high, which fully meets the strict quality requirements of the high-end feed market.

Energy consumption and capacity performance differences

In the simple formula and standardized basic feed mass production scenario, the single-screw extruder has small structural resistance, lower energy consumption per unit finished product, and outstanding cost-effective advantages in mass production. However, in the production of complex formula, problems such as material slippage, uneven aging and high rejection rate will greatly reduce the effective production capacity, increase the comprehensive energy consumption and production cost, and cannot adapt to the efficient production of complex materials.

The instantaneous energy consumption of twin-screw extruder is higher in no-load and simple production scenarios, but in the production of highly difficult and complex formulas, the energy consumption optimization of qualified products is realized by virtue of the advantages of stable transportation, extremely low rejection rate and high effective production capacity. The material matures evenly, the production loss is extremely low, and the comprehensive energy efficiency and production capacity advantages of long-term large-scale production are significant, which can offset the basic energy consumption cost through high quality and high production capacity.

cost input variance

Single screw extruder purchase price is low, supporting equipment is simple, installation debugging, site use cost is very low. Equipment parts and components have strong versatility, low price, low capital and labor costs for later maintenance and parts replacement, low investment threshold, and are suitable for small and medium-sized micro-feed enterprises and start-up factories.

Twin screw extruder belongs to high-end precision equipment, R & D, manufacturing, installation and commissioning of the early investment is high, precision control system and modular screw assembly raised the initial cost. However, the equipment has high production capacity, low loss, strong product premium ability, long-term comprehensive production income far exceeds that of single-screw equipment, and the return on investment is higher, which is suitable for large-scale and branded feed enterprises.

Single screw extruder advantages and disadvantages and application scenarios

Equipment core advantages

The core advantage of single screw extruder is high cost performance, low cost of early procurement and late operation and maintenance, greatly reducing the entry threshold for feed production, and is the first choice for enterprises with limited budget. The equipment has simple structure, convenient operation, simple training for ordinary personnel, and controllable labor cost. Parts durability, versatility, low failure rate, short downtime, can ensure long-term continuous and stable operation of production lines.

In the mass production scenario of simple formula such as conventional livestock feed, the energy consumption per unit output of equipment and the cost of consumables are lower, and the cost performance of mass production is outstanding. Small size, flexible installation, no need for site modification and complex supporting facilities, suitable for small and medium-sized factories and limited site scenarios. The technology is mature and stable, and high yield and low failure operation can be realized under fixed formula mass production conditions, with strong practicability.

Main short board of equipment

The core short board of the single-screw extruder is that the processing performance is limited, the material mixing accuracy is insufficient, and the nutrition distribution of the finished feed is uneven, which cannot meet the high-end feed quality standard. Poor compatibility of raw materials, processing oil content of more than 12%, high moisture, high fiber materials, easy to slip, flow disorder, aging problems, production stability greatly reduced.

The equipment process adjustment ability is weak, the production parameters cannot be independently adjusted, and the formula adaptation is single, which is not suitable for frequent production change and multi-category production mode. The expansion degree, density and texture of finished products are easily affected by raw materials and equipment conditions, with large batch differences and high rejection rate. At the same time, long-term friction feeding will accelerate the wear of screw and barrel, and long-term use will continue to reduce production accuracy and finished product stability.

Best case scenario

Single screw extruder is suitable for small and medium-sized feed factories and start-up enterprises, focusing on standardized, fixed formula of basic feed production. The core products include conventional sinking pellet feed for pigs, cattle, sheep, chickens, ducks and other livestock and poultry, low-complexity ruminant supplementary feed, and low-fat, simple formula economical basic pet feed. It is suitable for ordinary feed processing scenarios that only require basic grain ripening without precise density and texture requirements, and for enterprises with low cost, high mass production and fixed production mode.

Twin screw extruder advantages and disadvantages and application scenarios

Equipment core advantages

Twin-screw extruder production accuracy, comprehensive performance leading, excellent shear mixing ability can achieve uniform dispersion of complex ingredients, finished nutrition balance, texture unity, quality far superior to single-screw equipment. Raw material adaptability is very strong, can stably process 25%-30% oil high oil formula, high humidity, high fiber and various new composite materials, breaking through the traditional expansion equipment raw material processing limitations.

The equipment can accurately control the expansion degree and particle density, and customize the production of various aquatic feeds, high-end pet foods and functional special feeds. Self-cleaning structure can reduce material residues, improve production hygiene level, facilitate production change, adapt to small batch, multi-category, refined flexible production. Stable equipment operation, extremely low scrap rate, outstanding economic benefits of large-scale production, which can help enterprises to lay out high-end market, improve product premium and core competitiveness.

Main short board of equipment

The main shortcomings of the twin-screw extruder are concentrated on the investment and operation threshold, the equipment purchase price is high, the investment pressure of fixed assets in the early stage is high, and it is not friendly enough for small and micro enterprises with limited funds. The equipment structure is precise, the components are complex, the maintenance process is complicated, professional technicians are required to repair, the replacement of accessories and operation and maintenance costs are higher, and the threshold for talent training is higher.

In the simple formula mass production scenario, the energy consumption of the equipment is higher than that of the single-screw equipment, and there are problems of waste of energy consumption and low cost performance. The equipment is large in size and occupies a wide area, and the requirements for site space, power supply load and supporting infrastructure are higher. Enterprises need to have perfect production supporting conditions to operate stably.

Best case scenario

Twin-screw extruder mainly produces high-end high value-added feed, which is the core production equipment of aquatic feed, high-end pet food and special functional feed. Suitable for all kinds of precision density control aquatic feed for fish, shrimp and crab, high-end pet food with high meat and no grain and low sensitivity, functional feed containing probiotics and special protein, special feed for young animals and customized feed for animals. Accurate adaptation to large-scale feed enterprises, high-end export-oriented factories, and modern flexible production lines that require frequent production changes and multi-category synchronous production.

Core basis for equipment selection

Combined with production product type selection

Product type is the core basis for equipment selection. The main conventional livestock sink feed, low-end economic pet feed, and simple fixed formula enterprises, choose single screw extruder can be low-cost stable mass production. Enterprises mainly engaged in high-end aquatic feed, high-nutrition pet food and special functional feed, which need to accurately control expansion degree, density and nutrition retention, and have complex formula and high fat addition, must select twin-screw extruder to ensure the quality of finished products reaches the standard. Enterprises need to combine existing products with future new product layout, match and adapt equipment, and avoid performance redundancy or insufficient capacity.

Combination of budget and ROI selection

Small and medium-sized enterprises with limited budget, focusing on low-end circulation market and pursuing short-term rapid return to capital shall give priority to single-screw extruder. Low equipment investment, low operation and maintenance cost, short return period, and adaptation to lightweight business model. Large-scale enterprises with sufficient funds, high-end premium market layout and long-term development are suitable for investment in twin-screw extruder. Although the investment in the early stage is higher, with the premium of high-quality products, low loss and high production capacity, the long-term return on investment far exceeds that of single-screw equipment. When selecting models, it is necessary to calculate the overall cost of ownership for 3-5 years, rather than just looking at the purchase unit price.

Selection of raw materials and formula requirements

Raw material stability, single formula, low oil and low humidity, fixed production conditions of the production line, single screw extruder cost-effective. For enterprises that need to change formula frequently, process complex materials with high oil, high humidity, high fiber and multiple additives all the year round, and the quality of raw materials fluctuates slightly, the adaptability and stability of twin-screw extruder are remarkable, which can effectively avoid the quality problems caused by raw material fluctuation and ensure the continuous stable production of production lines.

Combination of market positioning and quality requirements

The main low-end circulation, price competition as the core of feed enterprises, single screw equipment can meet the basic quality needs, effectively control production costs, improve price competitiveness. Enterprises focusing on brand, high-end and export markets have strict requirements on feed palatability, digestibility, appearance texture and nutritional balance. The high-quality products produced by twin-screw equipment can support the high-end positioning of brands, create differentiated competitive advantages and seize high-profit market share.

Selection of production capacity and site conditions

Small and medium-sized production lines with narrow space and weak infrastructure are suitable for small and convenient installation of single-screw extruder, which is suitable for small-scale mass production and saves space resources. Modern production line with large-scale mass production, multi-category flexible production, sufficient space and complete power supply, suitable for twin screw extruder, relying on high production capacity and high adaptation characteristics, realizing large-scale and diversified production and improving overall operation efficiency.

Combined with enterprise long-term development planning selection

Equipment selection needs to take into account the current capacity needs and the next 3-5 years development plan. Most start-ups focus on basic feed production at the initial stage, and choose single screw equipment to reduce initial investment. After the scale expansion, product upgrading and layout of high-end market in the later period, twin-screw production lines can be added to form a production system with high and low matching. Some enterprises directly arrange twin-screw equipment, arrange high-end track in advance, reserve product upgrade space, and avoid secondary investment in later equipment iteration.

Equipment operation and maintenance and comprehensive benefit analysis

Initial investment and overall cost

Single screw extruder has obvious advantages in comprehensive investment, the purchase price is only 40%-60% of the same specification twin screw equipment, simple supporting, convenient installation, low construction and labor costs, site depreciation, low capital pressure, and low cost operation mode. Twin-screw extruder early procurement, installation investment is higher, but the equipment life is longer, the production loss is extremely low, the product premium ability is strong, the long-term comprehensive operation cost is lower, and the income is higher.

Operating energy consumption and labor costs

Under the simple formula production condition, the single screw extruder has lower energy consumption, no need for professional technicians to be on duty, ordinary operators can complete the operation and maintenance, and the labor cost is low. In complex formula production, twin-screw equipment has higher energy consumption per hour, but the effective production capacity is large, the rejection rate is almost zero, and the energy consumption cost per qualified product is better. However, twin-screw equipment needs professional technicians for operation and maintenance, and the cost of labor technology is higher, which is suitable for large-scale high-value production scenarios.

Equipment maintenance and downtime losses

Single screw extruder has simple structure, universal accessories, daily cleaning, replacement of worn parts, simple operation and maintenance, low cost and short downtime. However, long-term friction feeding will accelerate the wear of screws and barrels, and the wear of wear-resistant materials will be faster when processed. With its self-cleaning structure, the twin-screw extruder has less material residue, small daily operation and maintenance workload, high continuous production stability, and low unplanned downtime losses. However, there are many precision components of the equipment, and the cost of regular maintenance and replacement of accessories is higher, requiring professional technical team to support the operation and maintenance work.

Summary and recommendations

Single screw extruder and twin screw extruder have no absolute advantages and disadvantages, the core lies in scene adaptation, the key to selection is to match the enterprise production mode, product positioning and development planning. With the advantages of low cost, easy operation and low operation and maintenance, single screw extruder is the best choice for mass production of basic feed. It can adapt to small and medium-sized enterprises with limited budget, single product and mass market, and can help enterprises to invest low, return quickly and stabilize mass production.

Twin-screw extruder has the core advantages of high precision, high adaptation, high quality and high flexibility, which can solve complex formula processing problems, produce high value-added feed, and help enterprises build differentiated market competitiveness. It is the core equipment for large-scale and branded enterprises to upgrade production capacity and layout high-end market. The long-term investment value is significant.

For factories with small production capacity, fixed formula and basic feed, single screw extruder shall be preferred to control cost and stabilize production capacity. Deep cultivation of aquatic products, high-end pets, special feed track, the pursuit of high quality and long-term profitability of enterprises, priority layout of twin screw extruder. Large-scale comprehensive feed enterprises can cooperate with two kinds of equipment for production, guarantee the basic mass production income with single screw equipment, lay out high-end and high-profit market with double screw equipment, realize the optimal balance between cost and benefit, and comprehensively improve the market competitiveness and profitability of enterprises.