Wittmann: Blending with Perfect Accuracy Every Batch

GRAVIMAX 14V material blender

The model GMX 14V is the first of the WITTMANN GRAVIMAX blender series with their enhanced metering system for truly repeatable batch-to-batch consistency. The GMX 14V can blend up to 4 components with a total batch size of 2.2 lbs (1 kg) and a material throughput of up to 170 lbs (80 kg) per hour. The GRAVIMAX series of blenders provide single and multi-component gravimetric blending of up to 11,000 lbs/hr (5,000 kg/hr) for injection molding, blow molding and extrusion processes.

The GMX 14V represents a further development of its successful predecessor – the GRAVIMAX 14R – now with a completely revised design that gives it greater functionality in addition to a much more elegant look. Its construction is based on a new modular concept for the very best compactness. As a result, the hoppers and body fit precisely together to form one sturdy compact unit. The new corner windows of each hopper provide a full view for material inspection and detach quickly for simpler and easier cleaning access.

The enhanced “pinch” valve design and WITTMANN’s proven RTLS technology (Real Time Live Scale) provide high precision blending. RTLS is a unique 2-stage metering method achieving the most precise dispensing for batch-to-batch consistency and accuracy. This is achieved using progressively smaller dispensing algorithms to achieve the targetweight every single batch without any overshoot or “averaging” typical of other, less precise methods. The first step (free flow) allows quick dispensing to near target weight – approximately 95%. The second step (fine pulsing) is the controlled high frequency dispensing precisely to target. Only one kind of standard high precision valve is needed for the various materials i.e. pellets, regrind and additives.

Ensuring precise batch-to-batch accuracy with RTLS allows the operator to set the percentages exactly to the required minimum level. However, other blending methods constantly over and under dose which requires the minimum required level to be set higher to ensure any under dosed batch still meets the correct percentage. This results in overdosing all other batches, sometimes even significantly, causing tremendous excess material usage and increased cost. RTLS can pay for itself in an unrivaled short time.

The main technical improvements are to be found inside the GMX 14V:
• The PUR pinch valves have been replaced with highly precise wear-resistant stainless steel valves making the GMX 14V ideal for blending highly abrasive materials.

• The metering valve is integrated into the outlet of the hopper and features a self-closing mechanism to stop material flow when the hopper is removed.

• The self-closing discharge flap mechanism on the weigh bin prevents the release of material in the event of compressed air pressure loss.

• Two load cells are used for higher metering accuracy, resulting in even more precise metering of the material.

• An innovative laser sensor meters the amount of material in the mixer. This sensor is positioned above the mixing chamber outside of the material flow and thus, is protected from abrasion and contamination to guarantee permanent process security.

• The highly efficient mixer provides a homogenous material blend and the mixing chamber is designed for easy cleaning and prevents dead spots or material hang-up.

Full press release