Material bars are made ready for processing on a lateral material storage facility (sloping surface). The FMB bushing-aligned bar loading magazine is used to handle bars with individual, hexagonal or quadratic outer contours, which may have either hollow or solid cross-sections. FMB currently offers the Kontur 70, a magazine for bars up to 3.2 m in length and an external diameter of between 20 and 70 mm. The bar materials used are generally steels, aluminium and brass.
The lateral material storage is of variable length and not only holds the bars ready for processing, but also feeds a specified number of bars, in order to ensure the automated production of the required parts with as long an interval as possible between manual interventions.
From this reserve in the magazine, the individual bars are separated out and deposited in half shells adapted to their profiles. In the storage facility, three axially moving bushing units, each fitted with two guide bushes, are threaded onto the material bar. The guide bushes are fitted with a locating hole corresponding to the profile of the material bar. In order to be able to receive the bars securely ready for processing, the bushing units are turned by an alignment device in advance to the specified resting position of the profiled material bars. The material bar is the pushed by a pusher through the hole in the lathe spindle, where it is fixed in place on the spindle end next to the tool by a clamping device, usually a collet or a chuck.
Once the bar is delivered, the turning process begins, during which the end of the bar is usually clamped in place for machining. The whole of the bar rotates during the turning process, as is the usual practice. The rotation speeds reached depend on the diameter and profile of the material bar. On completion of the turning process, the collet or the chuck is released, enabling the loading magazine to push the material bar forward through the spindle by the required length of the part. After the bar is reclamped in place, the next processing cycle begins. The remnant piece at the end of the processing cycle is pushed by the new material bar being fed from behind, through the clamping device into the working space of the lathe.
In order to provide optimum guidance, the gap in the spindle stock of the lathe for passing the bars through must be adjusted to the profile of the material bar. This is done by two spindle liner tubes with the appropriate guide bushes.
When processing “long bars”, if the original bar length is greater than the length of the spindle, part of the bar remains outside the lathe during the turning process and needs to be guided as it rotates. In the case of the FMB bushing-aligned bar loading magazine, this is between 1400 and 1800 mm. The bar loading magazine not only needs to arrange and feed the material bars, but also needs to assume a guide function for the bars. A bar clamped at only one end by the collet of the lathe would naturally tend to swing out and create vibrations that would have a negative impact on the turning process, and in extreme cases could damage the whole system.
For this reason, it is necessary to take constructive measures to prevent such vibrations in the loading magazine. The stable overall structure of the loading magazine and guidance in profiled bushings ensure that these vibrations are damped or prevented entirely. It is also possible, where the material bars rotate outside the centre of gravity, to weight the bushes statically with counterweights to reduce the vibrations caused by imbalance.
Übersicht