Vismec is expanding its range of dosing solutions with two new models designed for dosing masterbatches and additives: the Perfecto gravimetric doser, completely updated for maximum accuracy, and the Flex volumetric doser.

Below, we highlight their advantages in terms of precision, color management, and production continuity.

What is a masterbatch for coloring plastic granules?

A masterbatch is a concentrate of pigments or additives dispersed in a carrier polymer, that is, a carrier resin that binds them and distributes them uniformly throughout the material.

The masterbatch is dosed together with virgin plastic pellets to give the finished product the desired color. This process must be carefully controlled, as inaccurate dosing can lead to problems in subsequent processing stages and increase production costs. Below, we outline the potential issues.

• Overdosing: it can cause significant color variations and substantially increase production costs, as masterbatch is considerably more expensive than virgin polymer. 
• Underdosing: it can result in colors that differ from the required specifications, uneven color distribution, and increased production scrap, with the additional risk of line stoppages while the formulation is recalibrated. 
• Variability between batches: if dosing is not accurate and repeatable, the final color may vary from one batch to another, creating a significant quality issue in industrial production. 

 

What are plastic additives?

Additives are substances added in small percentages to the polymer to modify its physical, chemical, or aesthetic properties. The following are the main types of additives. 

 

• UV stabilizers: they protect the polymer from degradation caused by sunlight, preventing yellowing, embrittlement, and color loss.
• Antioxidants: they slow down the oxidation of the polymer during high-temperature processing and over time, helping preserve its mechanical properties and appearance. 
• Flame retardants: they reduce the flammability of the polymer by delaying ignition and slowing flame propagation. 
• Antistatic and lubricating agents: antistatic agents reduce the buildup of electrostatic charges on the polymer surface, while slip agents reduce friction, allowing the material to move more easily during processing. 
• Functional fillers: materials such as talc, fibers, or calcium carbonate that improve properties such as stiffness and mechanical strength. 

Additives require even tighter dosing control than masterbatches. Even a small variation in the amount added can cause the material to fall outside specification, leading to reduced mechanical performance or production batches with non-compliant properties that must be discarded. 

Therefore, dosing systems must be capable of delivering consistent and repeatable quantities of additives – even at very low feed rates – without material stagnation or buildup that could affect subsequent doses. 

Perfecto gravimetric feeder: high-precision additive and masterbatch dosing

The new Perfecto doser is a gravimetric doser that controls the weight of every single dose of masterbatch and additives with extreme precision.  

It is Vismec’s preferred solution whenever accuracy and repeatability are top priorities, such as when dosing expensive additives or masterbatches in recipes with tight tolerances.

Precision and dose control

At the heart of the Perfecto dosing system is its high-performance weighing system:

• C3-class load cell with a 32-bit ADC converter – for high-precision measurement of every dose.
• 38,000 samples per second – this high sampling rate allows the system to adjust the dose in real time, even at low flow rates.
• Individual correction of each dose – the decoupled mechanical system allows for adjustments to each discharge, maintaining consistent accuracy over time.

The dosing chamber is designed without any accumulation points: each granule completes its full cycle, preventing stagnation that could compromise the accuracy of the next dose.

The twin-start screw, combined with a two-stage barrel, ensures a smooth, low-pulsation flow, with flow rates up to 15 kg/h for standard masterbatch and 9 kg/h for waxy masterbatch.

The screw is mounted on a double-row ball bearing and is decoupled from the high-torque stepper motor, a feature that extends the motor’s service life and maintains responsiveness and precision over time.

Quick cleaning and color changes without downtime

Perfecto is designed to reduce the downtime typically associated with color changes. 

The discharge hopper allows residual masterbatch to be removed without disassembling the doser, while the dosing assembly features a quick-release mechanism. The front access door, equipped with a magnetic latch, can be opened even when material is present, allowing visual inspection at any time.

The stainless steel hopper and feed throat, with internal separators designed without cavities, minimize dust buildup and simplify cleaning between production runs.

Flex: the volumetric doser that can be combined with Perfecto

Alongside the Perfecto gravimetric doser, the Vismec range also includes the new Flex volumetric doser. Without a load cell, Flex meters material based on volume, making it the ideal choice for stable, repetitive formulations where a more cost-effective solution is required. 

Flex shares the same quick-release dosing mechanism as Perfecto: a d14 screw conveyor, a mixing throat, and a stainless steel hopper, along with a dedicated touchscreen interface.

The two units can be combined: the same mixing throat can accommodate up to three dosing units, so it is possible to assign the critical additive to the Perfecto gravimetric doser and the base color to the Flex volumetric doser, optimizing both precision and investment on a single line.

Gravimetric or volumetric dosing: how to choose

The choice between the two technologies depends on the application. Gravimetric dosing is recommended where absolute accuracy, consumption control, and dose traceability are required, while volumetric dosing remains effective for established recipes and production processes with less stringent requirements.

Want to choose the dosing system best suited to your production line? Contact our team for a technical consultation and tailored advice.