The wide variety of materials employed and to be mixed in construction requires an excellent knowledge of suitable mixing processes. Choosing the wrong device for processing the material concerned can lead to serious structural damage or at least prolonged working hours and unnecessary physical strain on the worker.
Characteristics of the mixing material
As a rule it is not the finished mixed material upon completion of mixing that is the test for the mixing system but the components at the beginning of the mixing process. The mixing of what are normally two components, such as dry powder and liquid additive, for example, is what places the greatest load on the machine and will show whether the mixing paddle has the right geometry.
Which drive machine?
Firstly, you need to consider the basic question of whether to use a „power drill or hand mixer“. The classic power drill is certainly adequate for mixing small volumes of mainly liquid materials at a low rpm, with maximum mixing paddle diameters of 120 mm. You should not use power drills with an output of less than 500 W, however. When it comes to materials with greater viscosities (semiliquid), larger volumes of material or bigger diameter mixing paddles, the drive machine will be slowed down to such an extent that resultant lack of cooling will considerably reduce its life.
In comparison, hand mixers are specially designed for the heavy loads generated during mixing. The drive elements supply enough power and sufficient cooling for the motor even under heavy loads, and the special gear units guarantee a long life and optimum performance.
As a rule of thumb, the larger the volume of the material to be mixed, the bigger the diameter of the mixing paddle should be. In turn, the bigger the diameter of the mixing paddle, the lower the rpm and, as a consequence, the higher the drive power required.
Which mixing paddle?
For optimum mixing results it is important not only to select the right drive machine but the right mixing paddle as well. Your decision will be based on two factors: The volume of material to be mixed will determine the diameter of the mixing paddle, while the nature of the material will determine its geometry, i.e. the mixing method or action!
|From the bottom up (positive action)
The material is conveyed upwards through the middle of the mixing paddle from the bottom of the tub and flows down again at the sides. This method should be used for powdery and dry mixtures such as mortar, plaster, cement, and quartz- and pebble-filled materials. The mixing paddle works into the mixing material easily.
|From the top down (negative action)
The material is forced down from the top and then flows back up again at the sides. Any lumps are broken up by the high force generated by the drive and the user, without splashing. This method is ideal for thin-bodied materials such as paints, dispersions, materials containing fibers, and gypsum plaster. It involves greater strain on the drive unit and user.
|Parallel mixing action
The material is swirled on a single plane, the components only flowing up or down when the mixing paddle is moved accordingly. The suction effect results in optimal mixing results, according to the consistency of the material. This method is ideal for fillers. Fewer air inclusions in the material and, as a rule, higher shear forces, prevent the formation of lumps.