Electronic autoleveller is used for achieving an automatic adjustment with two different criteria of speed variation:
- feed rate variation, for all autolevelling standard applications
- variation of the delivery speed when the machine requires steady feed rate like in case of linkage with other machines with the same throughput speed (for example, in the after-card drawframe combined with a set of cards).
The first system, previously analysed, is most frequently used in this process stage. Its operation is schematised in Figure: a mechanic feeler detects the thickness of the material fed, the variations are transformed into electric signals and sent to a control unit which, with a suitable delay corresponding to the passage of the material from the feeler to the drawframe, determines the variation of the feed rate and therefore of the draft. The electronic autoleveller does not set definite limits to the possibility of adjustment but in relation to the correct detection and to the speed limit of the intersecting comb head, the suitable adjusting range applicable varies between 25% and + 25%. It is also possible to store the maximum and minimum drawing limits beyond which the machine no longer complies with the technological operating conditions allowed for each material.