MACHINING ON AUTOMATIC MACHINES

The efficient lathe turning of parts in large and very large batches is currently possible thanks to specialized machines. These machines are called automatic lathes. Their construction is designed to allow continuous work without operator intervention. Automatic operations require the installation of peripheral equipment called bar feeders. These are used to guarantee the continuous and stable feeding of the material for machining without the need to stop the process.

The scope of treatment on automatic lathes for various materials is very wide and includes both hard-to-machine materials and plastics. However, the main materials machined on automatic lathes include free machining steel, stainless steel and non-ferrous metals.

Automatic lathes are usually used to produce small parts, mainly rotating parts with diameters less than 32 mm. These usually include various connectors, bushings, nipples, rollers, axles, screws, nuts, nozzles and many others.

The most popular type of automatic lathes in this sector is the Swiss-type screw machine. Its characteristic feature is a design with a moving spindle. The material is guided with the guide sleeve and supported and driven by the spindle installed after the sleeve. Movement in the Z axis is performed by the material, not the tool, which allows the positioning of the entire tool head directly next to the support point in the guide bushing. Such a solution ensures the maximum rigidity of the system and allows very fast processing, especially for parts with an unfavorable relation of their length to diameter, i.e. slender parts which usually cause vibration problems.

During element processing on metal cutting machines with moving heads, a few important issues should be considered. This should always start from the drilling and internal turning performed on the main spindle. This will ensure higher stability, as the material is fully supported in the guide bushing along the whole diameter. The next operation should be external turning on the main spindle. If possible, cutting should reach the full depth in a single pass, without reversing the tool. This helps to obtain higher stability of the process and shorter operations. It is followed by milling, preferably face milling which generates lower cutting forces and the stability and power of spindles in automatic machines is limited. In order to machine the external diameter in the last stage prior to cutting off, a very effective method of back turning is applied – also preferably in a single pass. The last operation on the main spindle is cutting off. This is performed after the part has been clamped on the auxiliary spindle. The closer the two spindles are to each other, the lower the part overhang is and the better the surface finishing. After the part has been cut off, it is finished on the auxiliary spindle which usually covers internal machining and the finishing of the second face.