Good mortar requires good equipment, and good equipment requires careful comparison. While learning from advanced European technologies, it's also crucial to build your own brand. Investors often make several misconceptions when choosing equipment, including: 1) choosing the cheapest equipment; 2) buying from large manufacturers; 3) directly importing equipment from Germany or Italy; and 4) insufficient understanding of the equipment, purchasing any dry-mix mortar equipment listed on the market without proper knowledge. Many such blind choices occur.
Material mixing requires considerable expertise. The market offers a wide variety of dry-mix mortar mixers. Is the mixing uniform? Are there any dead zones? Does the so-called "flying knife" effectively work? Is the motor power appropriate? With such a diverse range of options available, and investors new to the industry lacking in-depth understanding, this can lead to increased operating costs and potentially substandard mortar. Reducing costs in every small step leads to increased profits every second.
The mixer is the key to producing dry-mix mortar and the core component of the entire equipment system.
A dry mortar mixer consists of a mixing drum, drive shaft, motor, mixing blades, a cutting tool, inlet, outlet, observation door, sampler, safety switch, and venting device. The purpose and task of these components is to uniformly mix all the materials.
Mixing Drum: Dry mortar mixing drums on the market are available in vertical and horizontal types. Vertical drums are generally not used because dry mortar materials have different specific gravities. When mixed in the same space, heavier materials (sand) sink to the bottom, while lighter materials (additives) float. This is not visible to the naked eye, but it is the actual process. Therefore, horizontal drums are widely used.
Drive Shaft: Horizontal mixers are available in single-shaft and double-shaft types. In the future, triple-shaft and quadruple-shaft mixers may appear. Double-shaft mixers are generally used for mixing feed or in industries where the uniformity of materials is not critical. A twin-shaft mixer naturally creates two three-dimensional spaces during operation. When raw materials enter the mixing tank, they are separated into these two spaces. Whether it's cement, sand, or additives, they won't be evenly separated into both spaces; one side might have more and the other less. If additives enter the mixing tank and one of the mixing blades happens to rotate and carry them away, the other side will be completely unmixed. Even with long mixing times, the required uniformity cannot be achieved. Therefore, twin-shaft mixers are rarely used in the dry-mix mortar industry unless there are objective reasons, such as collusion between machinery manufacturers and a certain authoritative industry department to monopolize procurement. In such cases, if consumers don't follow the direction, project approvals may be problematic. Errors in the upper-level design are normal; it's all human manipulation. Even without the incentive of profit, it's impossible to avoid detours.
Mixing Blades: Blade types include boiling type, pear-knife type, and spiral blade type (HSS series dual-operation high-efficiency mixers were exhibited at the 6th China (Shanghai) International Dry-Mix Mortar Technology and Products Exhibition on November 30, 2010). In a boiling-type mixing process (relatively ideal), the success depends on the manufacturer's engineers' thorough understanding of mechanics and the precise application of the lifting force. Excessive lifting force results in heavier materials being thrown further and lighter materials closer, while insufficient force fails to lift the material. This is not boiling but rather a "pear-knife" type. As the name suggests, the pear-knife type operates on the same principle as a pear-shaped mixer used in rural areas. The blades only allow a small portion of the material to tumble once at the bottom of the mixing tank. The longer the mixing tank, the longer it takes for the material on the left and right sides to mix completely, sometimes failing to mix at all. This type of mixer is less than ideal for the dry-mix mortar industry. (Spiral) The dual-speed mixer is the most ideal type of dry mortar mixer. Its spiral blades rotate at low speed, circling the bottom of the mixing drum (completely eliminating dead zones), bringing all materials one by one to the central shaft. The high-speed central shaft has more than ten flying blades (11kW, adjustable speed, extendable), instantly breaking up the incoming materials. In terms of feel, practicality, and energy saving, this mixing method far surpasses the mixing methods of German and Italian mixers. In the dry mortar industry, mixing only takes 2-3 minutes, making it the most ideal and scientifically sound mixer. A senior PhD, upon seeing this mixer, sincerely remarked: "The level of domestic mixing equipment is beyond what developed countries can imagine. Savings mean profits, and lost resources mean lost wealth."
The flying knife device: First, consider how often the material, especially clumps (in the early stage of coagulation), actually encounters the few flying knives on the mixing drum during mixer operation. Theoretically, the material should be broken up by the flying knives, but in reality, less than 50% of the material is actually hit during mixing. Therefore, the material not hit by the flying knives may remain clumped, or additives may remain concentrated and poorly dispersed. Second, consider the spacing between the mixing blades on the mixing drum to prevent them from hitting the blades during rotation. This spacing creates dead zones; more flying knives mean more gaps and more dead zones. Finally, consider uneven mixing. Some manufacturers extend the mixing time, but this disrupts the original particle size of materials, especially sand and vitrified microspheres. It also shortens the lifespan of the mixer blades and drum walls. Furthermore, the improvement in material uniformity from increased mixing time is only relative, not absolute, because the mixer's structure determines the uniformity of material mixing. Therefore, based on these three observations, the few flying knives fixed on the mixing drum are essentially ineffective, serving little purpose, and even representing a long-term waste. Statistics show that a 5000L dry mortar mixer has 6-8 blades, each with a power of 7.5kw, totaling 45kw for 6 blades. This results in a daily electricity consumption of 1080 kWh, or 324,000 kWh over 300 days. At 0.6 yuan per kWh, this totals 194,400 yuan over 300 days. Furthermore, the high failure rate of the high-speed blades, manufactured with immature technology, increases maintenance costs and impacts production schedules and project delivery times. Hundreds of thousands of yuan can be wasted annually during operation. The blades on the mixing drum wall are the direct culprit for this significant waste of electricity and operating costs. In contrast, a dual-speed mixer with over ten blades on the central shaft uses only a single 11kw adjustable motor. This effectively disperses materials, allowing for speed adjustments to accommodate different materials during mixing, protecting the materials from damage. Its function far surpasses that of the small blades on the mixing drum wall. Structurally, the efficiency of a central shaft equipped with numerous cutting blades far exceeds that of a conventional mixer. Even operating continuously for 300 days, its power consumption is only 79,200 kWh, a quarter of the 324,000 kWh consumed by a less efficient mixer.
Motor power: 5000L dry mortar mixer (ordinary mortar): A typical mixer feeds 3 tons of material at a time, with a main shaft power of 55 kW and 6 cutting blades totaling 45 kW. Mixing time is 4 minutes, requiring 720,000 kWh per year (300 working days), producing 324,000 tons of mortar. A dual-operation high-efficiency mixer feeds 2 tons of material at a time, with a main shaft power of 45 kW and 12 cutting blades totaling 11 kW. Mixing time is 2 minutes, requiring 403,200 kWh per year (300 working days), producing 432,000 tons of mortar.
