These machines are located downstream the annealing lehr, that is in the cold-end area of the plant.The main characteristics of this process, compared to the process performed by the burn-off machines, are the following:1) Higher quality of the items.After the moil removal, there are grinding and bevelling stations, and finally a fire polishing machine, in order to give the rim a fine finishing and, if required, a rim tempering.
2) Wider range of possible layouts, since the machine is located in an area that generally offers much more room than the hot-end area.
3) Higher costs. The above advantages must compensate the higher cost of this process, since the working stations (namely, grinding and bevelling) require tools that are expensive and with a working life that is not as long as desirable.
The producers of crack-off machines are therefore challenged to design new equipment providing high production speed and a continuously improved moil removal, so as to reduce the necessity of machining and consequently to extend the working life of the tools.
Antas can now propose a new technology that can achieve excellent results as far as the quality of the cutting is concerned. A laser unit is installed just next to the loading station of the VGL crack-off machines. The laser provides such a high quality cutting that, depending on the shape of the item currently produced and on the quality standard of the glass factory, a very reduced number of grinding stations must be in operation. Our experience shows that a typical full range of products can be easily handled by using zero to two grinding stations. The quality standards lead also to the decision about the use of a bevelling station: for high quality items it's recommended, while for ordinary articles it's not necessary.
When the process is performed without using working tools (neither grinding nor bevelling units), there is no need of washing and drying the items, since the laser does not generate any glass dust. Once the moil is fallen, the glasses are ready for the fire finishing of the rim.
The advantages shown by the use of the laser (the first VGL machine equipped with this unit is now working in normal operation since more than two years) have convinced Antas to revise the design of its VGL family of crack-offs. The original 16-station arrangement (with 32 or 48 chucks, i.e. 2 or 3 chucks each station) is no longer necessary, since the number of working stations has dramatically decreased. The new machine layout foresees a 10-station structure, that can be reduced even to 6 if the grinding and bevelling units can be omitted at all (that is for the Customers who do not manufacture top quality products).
The reduced size of the machine compensates the cost of the laser unit, therefore the investment for a crack-off equipped with laser is just slightly higher than a traditional machine, however the quality of the products is higher, the efficiency is higher and the operation costs are lower.