SMAC is launching a new moving coil actuator (MCA) system that is designed to sort and reject parts at ultra-high speeds. Compared with conventional pneumatic cylinders and other devices commonly used, the system is claimed to have numerous significant inherent advantages, as outlined below.
Conventional pneumatic cylinders contain a number of static and dynamic seals. Due to the use and application of compressed air, the operational efficiency of these seals deteriorates considerably over time. This causes friction and stiction that causes the pneumatic system to slow, particularly when the cylinder cycle time is varied. The longer the period of time the cylinder system sits without moving, the higher the static friction breakaway force is required. It is not uncommon for this variation to be up to 50ms. The conventional pneumatic system is also highly dependent on the speed and reaction time of the solenoid valve used. General industrial DC solenoid valves have a variance of +/-10ms. With AC solenoid valves, this variance often doubles. Hence the total variation in cycle time can be up to 50ms.
In contrast, the SMAC MCA eliminates these problems because it runs on high-precision linear guides with static breakaway forces in the order of only 1 per cent of that of a pneumatic cylinder. Therefore total cycle time variation is under 1ms.
Due to the seals used in conventional pneumatic cylinders, wear is an inherent and significant problem. The life cycle of such a cylinder is on average around 10million cycles when used in applications where controlled impact and end-of-stroke cushioning is required. After this time the cylinder has to repaired or replaced, resulting in downtime and increasing costs.
The SMAC MCA will last around ten times longer when used in similar applications. This considerable increase in lifetime is achieved due to the dampening and cushioning being servo-controlled; it is the coil within the actuator that provides the programmed reduction in speed. The SMAC actuators are low-wattage devices – typically less than 2A at 24 or 48V - so heat generation is minimal and has no detrimental effect on life. Due to these advantages, SMAC MCAs are said to last between 10 and 25 times longer than conventional pneumatic cylinders and devices in similar applications.
Pneumatic systems are inherently noisy and inefficient. When pneumatic cylinders perform a high number of cycles in an enclosed space the noise and heat generated is significant (50degC or more), as the compressed air is exhausted to atmosphere. While a degree of crude silencing and muffling can be applied, the noise of the cylinder impacting at the end of stroke cannot be readily reduced.
SMAC's MCAs are extremely quiet in operation. The company says that no wasted energy is exhausted and the heat generated is relatively low (5-10degC). Overall, SMAC actuators run and perform much quieter, cooler and are far more energy efficient than pneumatic systems.
Compressed air is notoriously expensive to generate. Apart from the immediate costs associated with the hardware of cylinders, valves, fittings, tubing, silencers, air preparation equipment and other equipment, other significant additional costs need to be taken into consideration: the compressor, aftercooler, dryer, piping, etc. Also the cost of compressed air leaks is significant and should not be under-estimated.
However, the overall purchase and running costs of SMAC actuators when compared against conventional pneumatic systems is said to be highly favourable.
The SMAC moving coil actuators are also suitable for other demanding applications such as packaging, bottling, labelling, filling, parts handling, measuring and QC testing - to name but a few.