Gemata’s Spraystar spraying line is modular both mechanically and operationally. The mechanical modularity allows you to adapt the line to the needs and any constraints of the customer, while the modularity in the management of the line allows for a simple and intuitive use, with the operator interfaces that reflect the actual physical composition of the line.
The interfaces are based on a system of icons that recall the controlled component, thus facilitating both the general understanding of the various pages and the actual use of the line.
The control of the entire line can take place in any of the various panels present at each cabin and the operator has various synoptics that allow him to easily control the entire process.
The main synoptic displays the overall status of the line (including the various cabins and tunnels present in the line itself) through icons and histograms designed to allow the operator to understand at a glance the progress of production and the immediate identification of any anomalies.
Line synoptic
Dryer synoptic
Scrubber synoptic
Machine parameters and recipes can be modified remotely and the data collected by the line, both during preparation and during processing, are made available to remote systems for analysis and / or recording.
The relevant operations carried out by the operator, the modifications of the processing parameters, the variations of the physical parameters and the adjustment operations carried out automatically by the line are recorded and made available for subsequent analysis, for data logging or for the creation of graphs.
Recipes can be limited to a particular cabin or tunnel, or collect data across the line; in addition, the authorized operator can decide whether the loaded recipe can be modified during processing or if it must be performed as it is.
In the cabin, octagonal in shape to reduce the stagnation of fumes and the volume of air to be sucked in, the distributor shaft has been placed outside the cabin, freeing the internal volume from any mechanical part that could generate dripping, accumulation of dirt or other conditions that can cause contamination of the leather surface.
Smart Spray Control (SSC)
The Gemata SSC economizer, unlike the other systems, does not just consider the projection of the gun nozzle on the work surface of the leather, but manages the entire imprint of the flame.
Generally the economizer considers the guns as a point, corresponding to the nozzle, which moves along the circumference defined by the movement of the carousel. When this point is superimposed on a leather the gun is activated, while when the point “comes out” from the leather the gun is deactivated. In order to work the edges correctly, it is necessary to “widen” the leather, or to extend the image of the leather in order to anticipate the activation and postpone the deactivation of the gun.
The guns used in the spray booths generate a flame that has an elliptical section (flame imprint), the angle of which depends on the rotation of the carousel. It is easy to realize that the amount of color sprayed by a gun placed on the edge of the leather that ends up on the leather itself depends a lot on both the shape and the orientation of the flame: considering only the central point, the widening of the edge must therefore be done to excess, causing unwanted sprays in many areas close to the actual edge of the leather.
As previously mentioned, the Gemata economizer manages the entire flame imprint and not just the central point. For each gun, therefore, its current position and flame orientation (linked to the angular position of the gun) are considered. The imprint thus obtained is compared with the leather and if the intersection of the two figures has a sufficient area. If the percentage of the imprint superimposed on the leather is higher than a threshold chosen by the operator, the gun is activated.
Traditional system
SSC Gemata system
If only the projection of the nozzle is considered, it is necessary to widen the leather to work the edges correctly, but unwanted sprays are generated; with the Gemata system the problem does not arise (avoided sprays highlighted in green color).
The gun is triggered only when some of the color ends up on the leather, eliminating sprays in the leatherless areas. With this approach, guns with flames of any shape can be handled.
The Gemata economizer completely avoids “empty” spraying and works correctly all the edges of the leather thanks to a single parameter: the minimum overlap threshold. The choice of the overlap threshold influences the final outcome of the processing and the amount of product saved. To guide the operator in choosing this parameter, the estimate of the percentage of the spraying area not superimposed on the leather is provided: simply, based on the processing of the test sample, the operator evaluates whether to reduce the threshold to obtain a better edge coverage or whether to increase it to reduce product waste.
By varying the overlap threshold, you decide how the edges will be processed, also checking the quantity of product used.
Resolution of the reading bar
Lately there has been a push to increase the resolution of the leather reading with the aim of limiting product waste. From the considerations made, however, it is clear that a high resolution in the measurement of the position of the leather, however precise it may be, does not solve the problem related to the shape of the flame: the model based on the central point of the flame is not able to manage its rotation and in any case forces the operator to widen the edges, to widen, with consequent unjustified sprays. The Gemata economizer, capable of managing various resolutions, is able to reduce product waste even with low resolutions, thus limiting system costs.
The effect of the resolution in the reading of the leather has a negligible influence in the calculation of the overlap between flame and leather.
Color circuits
In the Gemata line, the SSC economizer is fully integrated into the line control and is also able to manage the gun power supply color circuits, up to three color circuits for each gun group.
The preparation of the color circuits, the washing of the guns and the color change are particularly easy and quick to carry out. The operator, in fact, can decide to work a batch using the second color circuit of the first group of guns while simultaneously:
• prepares the color on the first circuit of the same group of guns,
• prepare the first circuit of the second group,
• retrieves the color from the second circuit of the second group and washes the guns of the second group.
All this without interrupting production, from a single page of any panel of the line.
Number of arms of the carousel
An alternative solution proposed for the reduction of product waste is the increase in the number of guns, up to carousels with 24 arms, which allows for lower rotation speeds and, therefore, greater precision in the instants of activation / deactivation of the guns. Even this solution is not able to compensate the limits of the flame modeling at the central point only, and in addition it accentuates the unequal coverage between the right and left sides of the transport.
The uniform deposit of color occurs when all the guns pass everywhere with the same speed; the density of the color deposited is strictly linked to this speed: the slower the gun, the more color will be deposited, and vice versa. The carousel rotates at a constant speed but, in the area where the transport speed has substantially the same direction as that of the carousel, the gun moves more slowly compared to the leather and therefore deposits more color; in the area with opposite speeds, vice versa, it deposits less color.
This effect is all the more marked the lower the speed of the carousel is: the sum of the two speeds is increasingly influenced by the point at which it is calculated. This is a purely geometric effect, independent of the type of guns or their atomization pressure.
The difference in coverage is not symmetrical with respect to the center of rotation of the carousel. This prevents correct compensation even when using two cabins with carousels that rotate in the opposite direction.
In booths with many guns, therefore, there is a greater diversity in the deposition of color on the leather. Gemata, aware of this problem, recommends using a lower number of guns, guaranteeing an acceptable speed for the carousel such as to minimize this distortion.
Taking two points like those in the figure, you can see how the difference between the speed of the gun with respect to the leather (colored arrows) diverges as the ratio between the transport speed and that of the carousel increases.