Wittmann’s new CARD (Compressed Air Resin Dryer) range offers injection moulders an efficient solution to achieve optimal and energy-efficient drying results, even with small material throughput rates, as low as 0.16kg/h.
Users of dryers expect carefree use of the equipment, with the operator’s job being more or less limited to filling the drying container and pressing the start/stop button, and everything else should ideally proceed in the background. This is precisely how the granulate dryers from WITTMANN work.
Whenever an unintended standstill of a production cell occurs, the aim of every user is to resume production as fast as possible. Here, the main focus always lies on the injection moulding machine and the automation system. Usually, the granulate dryer tends to be overlooked, which often means continued drying of the material with full heating capacity during the downtime and new startup. The consequence is not only that an unnecessary amount of energy is consumed, but also that the plastic material can be damaged. With the CARD compressed air granulate dryers from WITTMANN, this is prevented by what is called the SLEEP mode.
Automatic filling of the drying container proceeds directly proportional to the machine’s material consumption. While no material is extracted from the dryer, i.e. the drying container does not need to be refilled. In this case, the dryer’s control system registers the fact that the material loader used for filling the container has not shown any activity for a certain period of time. This period can be set on the CARD dryer (depending on the model). Then the dryer automatically reduces the heat output and quantity of air supply. This immediately protects the material and reduces the consumption of electricity and compressed air. As soon as the processing machine is restarted, it can continue to operate at once with dried material. The dryer starts to regulate the drying process at the right moment and raises the drying temperature as required.
The RAMPEN mode permits unlimited drying of sensitive materials, too, which tend to get sticky when heated. Here, the drying temperature is raised in two steps. If, for example, PC is to be dried, the material can be pre-dried at 80 °C for about 75 min following the initial filling of the container, and subsequently, the drying process can be continued at the desired temperature of 120 °C. In this way, the material, which is mostly stored at room temperature or in cooler storage halls, can be gently preheated at the first fill, before being completely dried at the target temperature.
The COUNT DOWN mode provides a signal output, which can be used for a machine startup. When production is started on a processing machine, it is very often important to know how long the material drying equipment has already been active and whether the material has been dried sufficiently. The COUNT DOWN mode shows the time which has already elapsed on its display panel and finally issues a signal when the preset period of time is over.
Depending on the model, the air quantity regulation in CARD dryers is controlled in an analogue or digital form via the temperature. Here, digital control provides a higher degree of precision, and the correct value for the temperature range to suit the material can be stored in the control system. For strongly hygroscopic materials such as PA, this automatic air supply control can be deactivated. This function is called the POWER mode, which permits a constant drying process with the necessary quantity of compressed air.
These innovative functions of the CARD dryers from WITTMANN not only contribute to energy efficiency but also provide a gentle drying process to protect the material.