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Developing technology provides different possibilities in coloring the fabric and transferring the pattern to the fabric. Thanks to these techniques, it is possible to make more systematic and quality studies by making different applications.
Rotation printing process, which is one of the methods of transferring the pattern to the fabricstarts with the template preparation process. Template preparation is the first and most important step of the printing process. The work to be done during the template preparation process directly affects the print quality. The slightest mistake to be made will cause loss of length during the transfer of the pattern to the fabric, time loss by repeating the template preparation and increase in cost.
The tools and devices that must be present while making the Rotation Template are as follows:
- · Rotation template,
- · Lacquer,
- Sodiumbichromate,
- · caliber,
- · Each,
- · Rotation template opening apparatus,
- · Drying cabinet,
- · polymerization cabinet,
- · Mixer,
- Industrial type refrigerator,
- · Lacquer drawing machine,
- · Tape,
- · Tension rings,
- · Carrying clamp,
- · Distilled water,
- · The pattern taken into negative by color separation,
- · Exposure machine,
- · Tension rings,
- Template holding vessel,
- Pressurized water or stencil washing machine,
- stencil head,
- · Glue,
- Template head mounting machine,
- · Retouching bench,
- · Retouching lacquer,
Preparing the Template for Lacquering
rotation templates; They are hollow, solid porous cylinders made of chromium-nickel alloy, approximately 87–120 µm (micron) thick, with a circumference of 51–182 cm. Their height varies between 1280–3418 cm. However, the entire length of the template cannot be used for printing. The margin must be left. For example, the printing area of the 1980 cm template is used as 1850 cm. The circumference of the template also expresses the maximum rapport size to the fabric length.
There are hexagonal holes arranged diagonally at an angle of 60º to each other, allowing the printing paste to flow to the fabric on the rotation stencils. The template number varies according to the number and size of these holes. The number of pores per 1 inch (2,54 cm) determines the number of the template; this value mesh expressed as (125 mesh–135 mesh–155 mesh). As the mesh number increases, the number of pores in the stencil increases, and the holes become smaller and tighter. The smaller the mesh number, the smaller the holes on the nickel and the larger the hole diameter.
There are three types of template groups used in businesses.
These:
- Standard Template
- Penta Group Template
- · Nova Group Template
The fabric type, dyestuff (ronjan, reactive, disperse, etc.), pattern character, machine properties and printing speed play an important role when choosing a template during the usage process. Considering these features, it is determined which template group and mesh number will be used for the printing process. Different template groups can be used in a printing process, provided that the manufacturers are the same. Since this process is continuous in businesses, the choice is made easily with the experience gained. However, people who make these choices need to know the features that distinguish the templates from each other.
These features are:
- · Each stencil group has different paste permeability and hole diameters on the fabric.
- Standard stencils are generally used in lap motif patterns, Penta stencils are used in delicate detailed, screened and tone-tone patterns.
- · Nova stencils are mostly used in thick fabrics, when the amount of paste to be transferred onto the fabric is high and in patterns with fine contours.
- · Nova stencils are preferred in cases where high printing speed is required in the machine.
After the template selections are made, the template must first be prepared for the process called lacquering. The steps for this are:
- Opening the template
- Attaching the tension rings to the template
- Polymerization of the template
Opening the template
Businesses keep the template group and mesh numbers they work with in certain quantities in stock. Templates come to the business in boxes of 10 or 20 pieces. Boxes that will not be used immediately must be properly stacked and transported in warehouses. Deformations that may occur at this stage may cause permanent damage to the template and even loss of usability. For this reason, businesses make stacking and transportation in accordance with the instructions determined by the manufacturer companies. According to these instructions; Up to six boxes of the same template length can be stacked on top of each other. Boxes of different sizes are never stacked on top of each other.
Template boxes are not stacked sideways or with support boards in between. Template boxes are carried by two people opposite each other when they need to be moved from one place to another. Boxes that are stacked and transported taking into account these instructions are brought to the template flat and the opening process is started.
Template circles
These are the sections where all the steps from opening the template to the printing process are done by attaching it to the machine.
in itself exposure, lacquering and template preparation divided into sections. The general temperature of the template flats is regulated by special air-conditioned systems. According to this at 30 °C and 40–50% has a moisture content. with yellow light is illuminated. It is also extremely important that it is clean and free of static electricity. The static electricity that may occur may cause problems in the process flow as it will facilitate the transmission of the pollution in the environment to the template. From the boxes brought to the template circle, the templates are opened manually or with special tools, starting from the inside. The innermost template is the first one out of the box. Then all templates are removed in this order.
Attaching the tension rings to the template
The template that opens is in elliptical form. In order for the template to become fully rounded, special tensioning rings are attached. The diameter of these rings should be 1–2 cm larger than the inside diameter of the template.
Polymerization of the template
In order for the full circle form obtained by attaching to both ends of the template to be permanent, it is kept in the polymerized cabinet at 160-18000 C for 1 hour. The templates are carried with special clamps to prevent contamination and lubrication that may be obtained while being transported to the polymerization cabinet or to another department for a different process. The template coming out of the polymerized cabinet is ready for the lacquering process.
Lacquer Preparation and Lacquer Recipes
Rotation stencil lacquers are compounds that are resistant to mechanical (friction, impact, etc.) and chemical (acid, base, dyestuff, etc.) effects, and can be hardened by polymerization to obtain ceramic surfaces.
These compounds are used by mixing with metal ion sodium dichromate, which has high binding ability, which makes it photosensitive before being transferred to the stencil surface. While preparing the lacquer, 8-10% sodium bichromate is used. This rate varies according to seasonal conditions if the establishment is not air-conditioned. It is used at a rate of 8% in summer months in non-air-conditioned environments. Sodium dichromate added to the lacquer is mixed with a mixer and homogeneous distribution is achieved. If the prepared lacquer has a high viscosity, it is thinned by adding 10-15% distilled water. The emulsion is then rested in industrial refrigerators at +2 °C for 5 (two) hours. The aim is to rest the prepared lacquer in such a way that there are no air bubbles in it. These cabinets are also where the lacquer is stored before or after mixing with potassium dichromate and is maintained at the same temperature (+5 °C). Lacquers can be stored for a long time before being photosensitive by mixing sodiumbichromate. However, when it is sensitized to light, it should be consumed within 1-2 days. It breaks down if not used within this period.
Lacquering
The transfer of the emulsion, which is rested by adding sodium bichromate and making it light sensitive, on the template with different methods is called lacquer drawing.
It is carried out in air-conditioned environments at 20-22 °C and without daylight. Therefore, the template circles are illuminated with yellow light. If the emulsion is exposed to light before exposure, the lacquer cannot be separated from the stencil. In this case, the exposure operation will not be performed.
The emulsion is transferred to the template in two different ways.
1- Stripping
It is the method in which the lacquer is transferred to the template from the bottom up. The emulsion is drawn very thin. Thin coatings give better results on thin fabrics. Only the pores on the template are closed. There is no lacquer bleeding, but less quantity can be printed during printing.
2-Coating
It is the method in which the lacquer is transferred to the template from top to bottom. Lacquer is applied on the stencil in layers at thicknesses that can be expressed in microns. It allows printing in longer lengths compared to the stripping method. It gives better results on thick fabrics. Businesses can use one or both of the methods that are suitable for their production processes. Lacquer extraction can be done by machines or by hand. In manual lacquer drawings, the process is done from the bottom up and it is up to the habit of the drawer to ensure that the thickness is the same throughout the stencil. There is no such problem in machined lacquers. Other factors affecting the thickness of the removed lacquer besides being drawn by hand or machine are:
Viscosity
Flowability of the lacquer used
Speed
However, the machine drawing speed (min./mm). In emulsions drawn with the coating method, the speed of the machine is approximately 0,28 min./mm. The process is completed in approximately 18-20 minutes. In stripping, the process is completed in a few minutes.
Rachel
It depends on the use of double or single squeegee during the lacquer drawing process and the smoothness of the squeegee. Before starting the lacquer drawing process, the stencil is taped at both ends to prevent the lacquer from flowing inwards.
Lacquer Drawing Machine
They are the machines that perform the lacquering process on the template. These machines are divided into two groups according to the direction of pulling the varnish:
- 1-Machines that pull the lacquer from top to bottom
- 2-Machines that pull the lacquer both from the bottom up and from the top down
It consists of two main parts, where the control panel and the lacquer shooting process are performed. It ensures that the lacquer is drawn in the same thickness all over the template. The lacquer container has a capacity of approximately 1,5 kg and an average of 200–220 g lacquer is used for one template.
Drying the Template
It is the process done to dry the lacquer that is drawn on the template. In drying cabinets, the process is completed at 42–45 °C for 50–45 minutes at a maximum of 60 °C.
Stencil Dryer
Drying cabinets are cabinets in which heat is transferred by blown air conditioners. The temperature and humidity balance inside the cabinet is automatically controlled. In these cabinets, lacquered stencils at constant temperatures can be kept for several days without exposure. If the template cannot be kept in this cabinet, the place where it is stored after drying should be air-conditioned.
Placing the Template on the Machine
The template, which is dried by applying lacquer, is placed in the machine for exposure. During the placement process;
1-The air of the cylinder is deflated: the metal cylinder into which the template will enter, air is supplied (approximately 1 bar) through the inner tube so that the template does not move during the exposure process. The air supplied inside ensures the preservation of its cylindrical form by putting pressure on the upper cylinder. In this process, the surface of the metal cylinder is made porous in order to protect it from cracks that may occur.
2- Lacquer-coated template removed from the drying cabinet is placed in the cylinder.
3- With the movement given from the control panel, the fixing arm on the machine is lifted upwards. It is inflated by giving air to the cylinder.
Negative Placing
1-The fixed and inflated template is powdered so that the negative can be easily slid before the negative is placed.
2- Calculate how many times the negative will be slid on the powdered template. These intervals are determined by means of the digital measuring pen on the cylinder on which the template is placed and marked with rapport latches. For example, if the pattern working on the template that will have a pattern length of 185 cm is 18 cm, the negative will be shifted 10 times. performed.).
3- In the determined negative shift intervals, the middle axis is drawn on the template. The same axis is taken in the negative where the pattern density is the least.
4- After the axles are taken, they are taped by placing the negative on the first axle.
5- Afterwards, the pattern and negative numbers on the negative and which are not wanted to appear on the template are covered with dark tape.
6- During the exposure process, the unwanted places to see light are covered and masked.
Exposure Process
During exposure, the light emitted from the UV light source cannot pass through the black areas of the film on which the pattern is worked. The slide without the pattern passes through the regions. The emulsion in the places where the light passes through forms a chemical bond with sodium bichromate and clings to the template during washing. During the process, the areas where there is no negative on the template and where light is not desired are masked and the pattern is exposed to strong light. In which part of the template the process will be performed is determined by the locator bars located at the bottom of the machine. The process is completed by going back and forth only as much as the number entered on the control panel in this region.
Standard rulers prepared according to the number of colors are posed at the end of the template whose exposure process is completed. These rulers help the template to be properly adjusted according to the printing order in the adjustments made while placing the template on the printing machine.
Exposure Time
Pattern negative with equal size report around the template, edge control and closures are wrapped in the template. Axes are determined and the places that should not be exposed are closed and light is given by rotating the template. exposure time; It varies between 28-3 minutes depending on the mesh number of the template, the 6 characters of the pattern and the rotation speed of the template. For example, the exposure time is shorter in fine contoured motifs than in lap motifs.
Light
The light sources used in exposure are 2000-5000 watt UV lamps.
Exposure Machine
There are machines produced by different manufacturers to perform the exposure process on rotational templates. Basically, the process that all machines do is exposure. However, the technology and processing processes used are different.
These methods are:
- conventional method
- Injection method
- wax method
- laser engraving method
- Galvanic method
Businesses choose any of these methods by comparing their cost and ease of use.
The differences between the methods are:
Conventional method:
Negative work is done on the foil. Exposure is accomplished by wrapping the negatives in one piece and sliding them along the template. The fit of the axles and the correct repetition of the rapport depend on the hand habit of the working worker. After stencil exposure, it enters the washing and polymerization process.
Inject method:
In this method, the color separation processes of the pattern are prepared on the computer. No output on negative. The transfer of the pattern on the template is provided by sending approval to the machine working with the injeckt method connected to the computer. Transmission occurs by spraying the ink, which is impermeable to light, from the spray head, which works with Piazzo crystal technology, along the stencil. The ink transferred from the head during spraying is cold. The transferred pattern is exposed and the process is completed. The worker does not interfere with the template, except to place the template in the machine and confirm the pattern. After exposure, the stencil goes through the washing and polymerizing process.
Waxing method:
As in the injeckt method, the color separation processes of the pattern are prepared on the computer. No output on negative. The transfer of the pattern on the template is provided by sending approval to the machine working with the injeckt method connected to the computer. Transfer takes place by spraying hot wax (wax) with no light transmission from the spray head working with thermal heat technology. The transferred pattern is exposed and the process is completed. After the template exposure, it enters the washing and polymerization process.
Laser engraving method:
In the preparation of the template with this method, a special group of lacquers that do not contain sodium bichromate is selected. The template, which is cured in the polymerized cabinet by applying lacquer, can be stored in an air-conditioned environment without time limitation. The pattern is transferred to the template from the computer as in the injekt 30 method. However, there is no exposure process and the part where the pattern is transferred is illuminated with white light, not yellow. The parts with the pattern are burned with the help of laser over the template. This process continues throughout the template. Washing and polymerization of the template is not performed.
Galvanic:
They are systems in which motifs are made on unperforated nickel stencils by opening or coating the mesh with the help of acid, just like the mesh structure in conventional stencils.
Washing the Template
The exposed stencil is subjected to a washing process in order to remove the non-illuminated parts of the pattern. Tension rings are attached to both sides of the template. Then, in the boats filled with operating water, they are kept in water for a few minutes, and the parts that are desired to be poured are softened. The areas that do not receive light in the pattern are opened by washing with pressurized water or machines.
Template Washing Machine
Washing machines are machines that automatically wash the exposed template. It has a cylinder section on which the template is mounted and water spray nozzles located at certain intervals in this section. Pressurized water transfer is provided by attaching it on the template and the places that do not receive light are opened to ensure paint permeability. Washed stencils are kept upright for a short time to allow excess water to flow. Then, it is kept in the polymerization cabinet at 180 °C for 2 hours in order for the lacquer to harden well.
Numbering the Template
In order for the pattern to be printed in the most appropriate way, the colors and motifs must be processed in a certain order on the printing machine. The darkest color worked in the pattern is printed first, and the lightest color is printed last. BAccording to this order, the pattern number and the number of the screen printing order are written on the part where the pattern does not appear. However, this order may change in some cases.
Namely;
Since Matweiss prints have a more covering structure, the print order is determined from light to dark. The lightest colored top in the pattern is printed last.
If the darkest color in the pattern is to be printed as a plaster, it is printed as the last or penultimate template.
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