Push-pull chain moves 8-tonne loads in and out of oven

Aluminium engine blocks can develop residual stresses due to differential cooling during the casting process. This can cause the distortion of critical features during machining and make it difficult to maintain dimensional tolerances. Prior to machining, therefore, many manufacturers stress-relieve cast aluminium engine blocks by using a heat treatment process.

It is for this purpose that the Aerotherm Group was commissioned by Ryobi Aluminium Castings in Northern Ireland to design and manufacture a stress-relieving oven. Essential to the design of this system is the mechanism that pushes the skillet of engine blocks into the oven and out again at the end of the four-hour cycle.

With a static load of 8 tonnes, the push/pull mechanism needed to be exceptionally strong and withstand high temperatures - and without substantially increasing the footprint of the overall system. The Framo Morat Linear Chain family was a clear front runner given these parameters, resulting in Aerotherm working with the UK distributor R. A. Rodriguez on the design and specification of the mechanism.

Two Framo Morat products are used in combination for this application: a Framo 60PSG Linear Chain (pictured above) that is driven by a Framo AG160 Compacta geared motor (pictured right). In addition, a Framo chain guide was also supplied by R. A. Rodriguez and shipped separately for early installation on the factory floor.

The design of the precision chain links on the Linear Chain enables it to push as well as pull heavy loads. A special profile on the links, with interlocking fingers at one end, enables the chain to roll up for efficient storage in one direction and form a rigid thrust device in the other.

In the magazine the chain is stored spirally within a narrow chamber making it a good choice for the Ryobi application where space is limited yet the maximum stroke is 6.5m long. The device provides high positioning accuracy, constant stroke speed and shock-free motion.

As standard, the chain can easily withstand the oven temperature of 250degC required by this application, but Framo Morat also offers a high-temperature chain option suitable for temperatures up to 560degC.

For the oven loading/unloading mechanism the Framo Linear Chain is complemented by the equally neat Framo Compacta slip-on geared motor. This product is said to be significantly lighter than competitive geared motors, but it provides the same output torque and speed. Framo Compacta geared motors achieve this through the use of a spur and worm gear transmission combined with performance-optimising motors.

Aerotherm's Dave Taylor comments: "The Linear Chain system on the stress relieving oven at Ryobi is working very well. And with the help of R. A. Rodriguez we have also been able to retrofit a higher-powered motor to the Compacta that enables the system to drive the 8 tonnes load at a greater speed of 50mm/s."

Follow the links for more information about Framo Linear Chain and Framo Compacta geared motors.