The basic working principle of dry mortar mixer is to achieve uniform mixing by using mechanical motion to cause convection, shearing and diffusion of dry powder materials of different components in the mixing drum.
The working principle of horizontal ribbon mixer is that the material is mixed under the push of ribbon spiral blades. The outer ribbon pushes the material from one end to the other end, while the inner ribbon makes the material move in the opposite direction. The inner layer of material is pushed to one side and then rolls from the inside to the outside, while the outer layer of material is pushed to the other side and then rolls from the outside to the inside. During the convection process, the material flow permeates and changes position to mix [3]. The main shaft of the mixing device of the twin-shaft zero-gravity mixer (taking Nanfang Road Machinery as an example) rotates to drive the blades to generate a three-dimensional motion trajectory of two large and two small continuous cycles. In the turbulent junction area between the large and small cycles, the material generates strong convection; the periodic rotation of the blades generates shearing action on the material; the inclined installation of the blades causes the material to generate a normal velocity along the blades outward, forming diffusion. The intense relative motion of the mixed materials maximizes energy utilization, ensuring that all materials in the mixing space are stirred at all times during the process, eliminating dead zones.
Mixing speed is a key parameter affecting mixing uniformity, energy consumption, and equipment wear. Different materials and mixer types have corresponding suitable speed ranges. For example, the suitable speed for ordinary masonry mortar in a ribbon mixer is 40-80 rpm, while a plow-type mixer may require a high speed of 200-280 rpm to break up the fibers when processing crack-resistant mortar containing fibers. The speed-affecting mechanisms include: low speed to prevent cement from flying, medium speed to promote additive dispersion, and high speed to break up fiber clumps. Mixing uniformity exists within a 'speed range'; too low a speed leads to insufficient mixing, while too high a speed may cause materials to adhere to the walls (forming a 'sluggish layer') or even segregate due to centrifugal force, while significantly increasing energy consumption and equipment wear.
Some mixers employ special designs to optimize the working process, such as installing internal scrapers to simultaneously remove material adhering to the drum wall during mixing, preventing clumping and facilitating material discharge.
