Molded plastics are often a blend of two or more materials. Colors (masterbatch) and other additives are often mixed (blended) with the raw plastic material prior to the molding process in molding plants. Many different types of blenders and dosing units have been used in this process; some with marginal and others with better accuracy. Some blenders are installed directly on the feeding throat of a processing machine and others are applied as a remote blender.

Remote and central blenders are often used to feed multiple machines with a blend of virgin resins, recycled material, masterbatch and other additives. The remote blenders are also used to feed a single processing machine to avoid transmitting vibrations from the processing machine to the blender aiming for high blending accuracy and longer life. They are also applied when direct installation on the feed throat of the processing machine is not desired. The blend is then conveyed from the floor standing blender to one or more processing machines by vacuum loaders or other loading systems, where separation of the blended components (due to different specific gravities, bulk densities and granule size) takes place. Separation can also happen in the storage bin installed on the feed throat of the processing machine. The product quality varies and the color grade changes from cycle to cycle when the blend separates. It is easy for the machine operator to notice the difference between the color grades, and this usually results in increasing the percentage of masterbatch to achieve a uniform color. The down side is the waste of expensive masterbatch.

Pumping liquid dies (ink or color) into the material flow on the feed throat of a processing machine is a messy method and rarely used in the plastics industry. Two blending methods (volumetric blending and gravimetric blending) are widely used to blend different materials including masterbatch. The volumetric blending method is far less accurate, when compared to the gravimetric blending method, but gravimetric blenders are more expensive. Gravimetric blending is more sophisticated and the majority of gravimetric blenders are sensitive to vibrations and, therefore, only applicable in a batch system.

The remote or central blending system is not the right type of equipment to be applied when different colors are used in different processing machines. Both the volumetric blenders and the remote blending systems are suggested when blending virgin resins with recycled plastics or blending different types of resins in high percentage and where tight tolerances are not required. It is suggested to apply a gravimetric blender directly on the feed throat of a processing machine when it comes to dosing masterbatch, which is normally blended in very low percentage (in many cases less than 1%). The accuracy of the gravimetric method, if not sensitive to vibration is very welcome, no separation can be expected and no loading system cleaning is necessary after changing colors.

The revolutionary gravimetric blending systems developed by LIAD (Leader In Advanced Dosing) have many advantages. It is in fact the most accurate way to go when masterbatch is to be blended with virgin resins, a blend of resins or resin / recycle mixture. The innovative ColorSave series are very precise MICRO-DOSING units capable of dosing the minimum possible quantity of one single pellet of masterbatch cycle after cycle. ColorSave series are designed for direct installation on the feed throat of a plastics processing machine. The weighing cells are not affected by vibrations transmitted from the processing machine. The precision load cell and the hoppers containing various materials are protected by an outer shell. External loads or forces do not affect the function or the accuracy of the unit. The ColorSave series do not require any setup time or maintenance. Experience has proven that the ColorSave series saves an average of 33% of masterbatch when compared to volumetric blenders mounted directly on the feed throat. In many cases the ColorSave was able to save more than 50% of the masterbatch. The simplicity of the units and the genius design with protected load cells in opened hoppers (no gates to open or close) insures high reliability.

The development of many gravimetric blending and dosing systems to cover the needs of plastics molders directly on the feed throat of the processing machine was not the only great achievement of LIAD. The leading company has also developed software to remotely control multiple blenders and dosing units from a central PC and to analyze the collected data from every unit. All blenders and dosing units developed by LIAD are equipped with interface for data transfer and the standard software is individually adaptable to cover to suit the operating system in different molding plants. The managing staff can observe the entire machine operation on a single or multiple screens. Questions like "how many tons of a specific material did we process in the last ---?" or "how many pieces of ---- did we make in red or blue during the last ---?" are easily answered. Machine down time and operation hours of the processing machine is directly readable whenever you need to know. Just ask for it and you surely have the answer right at your finger tips. Changing a parameter, increasing or decreasing the dosing percentage of an additive or masterbatch in any one of the units is enabled on the microprocessor on the unit and the central software in the manager's office.