Servo Knife Unit

The servo system gives very high cycling rates as there is no target to obstruct the core. An encoder measures the speed of the inside ply. The operator enters, on a touch screen keypad, the core inside diameter and the width of the inside ply. This synchronises the cutting unit to the core speed. The operator can then enter the required cut length and the machine will cut this exactly at all speeds. Fine tuning of cut length and/or speed can be done while the machine is running if, for example, the operator has entered the wrong information.

When the knife is cutting a ‘bullet’ on a rod inside the tube prevents the tube being crushed under the cutting force. This ‘bullet’ is released to travel at the same speed as the tube and requires your winding mandrels to be hollow. The smallest diameter for the mandrel is limited to 25mm by the need for the through rod connected to the ‘bullet’. The carriage speed is determined by the tube itself, so any belt slip does not affect the cut length.

The cutting carriage is datummed close to the discharge end which helps to get the cut tubes clear of the machine, particularly on short length work. A small conveyor may be provided to further assist on short length discharge.

The knives are brought in to cut via a second servo drive. The advantages are there is little noise, the cut is the same at all speeds and the knives can be programmed to move through the wall thickness plus a clearance distance. All these features help when cutting short lengths at speed. The cut off unit is mounted on a separate base so that the approach angle of the tube to the knives can be matched and the tube can be set to go through the middle of the opposed knives.

This is very important to ensure a good quality cut. The tube is supported until the cut is complete and is then released to fall in an orderly way. A collection table may also be included.

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