Wittmann’s Gravimax blenders have long been helping plastics processors develop and manufacture innovative mouldings. The dosing technology provides repeatable accuracy and boasts advanced features, including touchscreen control terminals and an OPC UA interface for automatic quality reporting.
Wittmann
Wittmann’s Gravimax blenders have significantly improved over the years, boasting numerous functions to ensure easy operation and consistently high-quality parts.
They’re available with various throughput rates and touchscreen control terminals, with all parameters being set and retrieved via the display. The ambiLED signal mounted on the front of the Gravimax visualises the appliance’s status, allowing the operator to save the compound formulations together with the appropriate blending processes.
These can be passed on to other appliances on the shop floor either by USB stick or by special GraviLog software.
Gravimax accuracy and repeatability
Gravimax’s popularity with the UK’s technical moulders is accuracy and repeatability, expressed via Wittmann’s RTLS (Real Time Live Scale) weighing technology.
RTLS is a metering process carried out in two steps, becoming more and more accurate until the target weight has been reached. After a rapid metering phase and before reaching the target weight, any residual quantity is added by several short ‘fine’ metering impulses. This way, any overdosing of ingredients is prevented.
Gravimax also plays a key role in in-house polymer regrind and post-use recyclate (consumer or industrial). Whenever regrind is created during production (for example, from additional reject or start-up parts), the Gravimax responds accordingly by increasing the regrind fed in by a predetermined amount, reducing virgin material consumption to a minimum and saving cost.
An OPC UA interface for automatic quality reporting is available on all Gravimax blenders, via which process data can be retrieved for each batch.
Gravimax’s dosing accuracy, repeatability and ease of use have taken it centre stage, according to Dr Stephen Pepper, Managing Director at Rugby Plastics. The technology has helped the company get its design and manufacturing over the line to win orders on multiple occasions.
“The Gravimax is ideally suited to technical moulders such as ourselves,” says Stephen. “It typically comes to the fore as part of a ‘high-end’ solution for demanding applications.”
A recent Rugby Plastics project to mould a bifold patio door component required that the right-angle elements of the component be made to 90 degrees exactly. “Any deviation in angularity – however small,” notes Stephen, “would make the rest of the door construction redundant.”
Without treatment, reinforcement or additives, many polymer-based components are typically subject to creep, shrink or relaxation after the ejection from the moulding process and the cooling thereafter.
“In this case, we used three chambers of the four-chamber Gravimax,” explains Steven. “A base polymer, a regrind stream and a special inorganic material dosed at a sufficient %, so that its function minimises the natural tendency of the polymeric material to distort on cooling. By using this material combination with the Gravimax, we could fulfil the brief and mould the engineering components to a tolerance of less than 0.5 of a degree – fit for purpose.”
Another project – a manually operated hydraulic pump – involved moulding and assembling 19 separate components in various colours. In this case, the Gravimax could include virgin polypropylene, colour variants and 40 talc-filled additives to aid dimensional stability for the components to assemble perfectly.
“The key with the Gravimax is that it helps guarantee production consistency and reproducibility”, claims Stephen.
Rugby Plastics Gravimax is part of an injection moulding business that currently deploys 25 machines from 15-750t in locking force with a maximum part weight of 4.8kg. The company has recently invested in edge equipment and systems, including Wittmann 4.0 and Temi+ MES packages.