VMI introduces advanced system for bodyply stocksplice handling

VMI's new advanced system for bodyply stocksplice handling does not only prevent interference between splices of two different plies, but also does this in a scrap reducing way and a way that is expected to reduce the dispersion of uniformity figures. 

In VMI tire building machines, bodyply stock splice detection is part of the standard functionality. This system measures the position of all stock splices in the bodyply. If a stock splice would end up too close to one of the ends of a bodyply, the system automatically cuts off a piece of material to prevent this stock splice to be too close to its machine splice in the tire.

This current system only prevents interference between stock- and machine splices in the same bodyply. It does not prevent possible interference between stock- and machine splices between bodyply 1 and bodyply 2, although this interference can also influence the tire quality.

The system described below, does not only prevent interference between splices of two different plies, but also does this in 1) a ‘scrap reducing’ way and 2) a way that is expected to reduce the dispersion of uniformity figures.

Both bodyply 1 and bodyply 2 are checked for stock splices:

1. No stock splices may occur in the (materials own) machine splice area.
2. No stock splices may occur in machine splice area of the other material, where the difference of the spot positions has been taken into account.
3. No stock splices may occur in the area’s where stock splices of the other bodyply are situated.

Figure 1: No machine-splices are allowed in the yellow areas of bodyply 1 and bodyply 2.

Pieces of material are being cut off, to prevent splices in the yellow area’s, as can be seen in figure 1. When scrapping of material will not only be used to prevent interference of splices within one ply (situation 1 above), but also to control the interference between two plies (situation 2 and 3), a considerable increase of the amount of scrap material that is being cut out may be expected, compared to the current situation.

Scrap can be reduced by dynamic adjustment of the machine splice position of the body plies on the drum. The machine splice will not be made on the position that is defined in the spec. The control software will calculate the centre of gravity of the machine splice and all present stock splices. The machine splice will be made on a dynamic position, in a way that the calculated ‘centre of gravity’ is on the spedified position. This offers the control system more possibilities to apply the bodyplies and to pick the solution with the lowest amount of scrap. This solution, where the ‘centre of gravity’ of all bodyply splices is always on the same position in the tire, might also have a positive influence on the stability of the tire uniformity.

[1] Joint in the material, made during preparation of this component.
[2] The position where leading and trailing end of a ply are joint after apply on the building drum.

Figure 2: The stocksplices in bodyply 1 give two possible positions for the machinesplice to position the centre of gravity in the spec position.