NL2017143B1 - Printing apparatus - Google Patents

Abstract

The present invention relates to a printing apparatus, comprising: a laser configured to locally treat a substrate, wherein byproducts emanate from the substrate, and a by product discharge. The product discharge may comprise a blower and/or the product 5 discharge may comprise a suction unit. The product discharge may be connected to a water scrubber and/or the product discharge may be connected to a filter, such as an activated carbon filter.connected to a filter, such as an activated carbon filter.

Description

Patent center

The Netherlands

(21) Application number: 2017143 © Application submitted: 08/07/2016 © 2017143

Bl. PATENT (51) Int. Cl .:

B41J 2/435 (2017.01) B23K 26/00 (2017.01) B41M 5/24 (2017.01) B41J 2/47 (2017.01)

Application registered: (73) Patent holder (s): 15/01/2018 Tocano Holding B.V. in Delft. (43) Application published: - (72) Inventor (s): Martijn Joseph Boerkamp in Delft. (w) Patent granted: Venkatesh Seshaiya Doraiswamy 15/01/2018 Chandras cart in Delft. (45) Patent issued: 31/01/2018 (74) Agent: ir. P.J. Hylarides et al. In The Hague.

© Printing apparatus (57) The present invention relates to a printing apparatus, including: a laser configured to locally treat a substrate, receiving byproducts emanate from the substrate, and a by product discharge. The product discharge may include a blower and / or the product discharge may include a suction unit. The product discharge may be connected to a water scrubber and / or the product discharge may be connected to a filter, such as an activated carbon filter.

NL Bl 2017143

This patent has been granted regardless of the attached result of the research into the state of the art and written opinion. The patent corresponds to the documents originally submitted.

Printing apparatus

The present invention relates to a printing apparatus.

Conventional printing apparatuses use ink in various ways to print an image on a substrate, such as a paper. Commercially available printing apparatuses include toner-based printing apparatuses, liquid inkjet printing apparatuses, solid ink printing apparatuses and dyesublimation printing apparatuses. The use of ink has several disadvantages, one of them being the limited capacity of the ink cartridges. Another disadvantage is that e.g. liquid ink may be dry and clog the nozzle of a printing apparatus when the printing apparatus is not used for an extended period of time.

There are leg attempts to provide inkless printing apparatuses, and prior art inkless printing apparatuses include e.g. thermal printing apparatuses that work by selectively heating regions or special heat-sensitive paper. Monochrome thermal printing devices are used in cash registers, ATMs, gasoline dispensers and some older inexpensive fax machines.

WO-A1-2014 / 158019 or Applicant discloses an inkless printing apparatus that can be used with regular paper objects, i.e. that does not require the use of special heat-sensitive paper. This printing device is configured for the selective carbonization or at least a part of a surface of a paper object, more particularly of a sheet of paper, including receiving means for receiving the paper object, at least one laser for selectively heating one or more parts or the surface of said paper object to a level the heated part of said surface at least partly carbonizes and changes changes color, and control means for controlling the laser. The carbonization reaction on the one hand produces char that acts as a black pigment on the paper object. Furthermore, organic volatiles that are also produced by the carbonization reaction are condensed on the paper object where they function as an adhesive binder for the char, and in this way create a pigment on said paper object.

The printing device described in WO-A1-2014 / 158019 or Applicant obtained good results in a controlled testing environment. However, for commercial application, further challenges are needed to be solved. It is desirable that the printing apparatus is capable of dealing with a variety of circumstances, more in particular different paper types and paper conditions. Moreover, the permanence of the print should be of a high quality, even for the variety of circumstances encountered in practice. Permanency refers both to the print lasting over a long duration or time and resistance to being removed by abrasion.

The printing device of WO-A1-2014 / 158019 produces reaction products in the form of carbon-based char and tar-like compounds. Also byproducts such as smoke and organic volatiles are produced. The byproducts can condense on the paper object therefore causing unwanted color changes on the paper object. Furthermore, the byproducts can contaminate the laser optics or surfaces coming into contact with the reaction products. For example, when a transparent cover is used to obtain a low oxygen environment, this transparent cover may get dirty due to the byproducts, but also reducing the effectiveness of the laser beam that passes through said transparent cover. A consistent laser intensity is desirable in order to allow a controller to control the print quality. Last but not least, it is desirable that the printing apparatus can be used safely, without any discomfort, e.g. due to odor or even smoke development.

An object of the present invention is to provide a printing apparatus that is improved relative to the prior art and at least one of the above stated problems is obviated.

Such objectives as indicated above, and / or other benefits or inventive effects, are attained according to the present disclosure by the assembly or features in the appended independent device claim. Further preferred are the subject of the dependent claims.

In the following description preferred out of the present invention are further elucidated with reference to the drawing, in which:

Figure 1 is a schematic view of a printing apparatus according to the present invention;

Figure 2 is a side view of a printing apparatus according to Figure 1 for the printing industry;

Figure 3 is a perspective view of a printing apparatus according to Figure 1 for the coding industry;

Figure 4 is a flow diagram for operation of the printing apparatus according to the present invention;

Figure 5 is a schematic overview of operation steps of the printing apparatus according to the present invention;

Figure 6 is a schematic overview of a quality test unit of the printing apparatus according to the present invention;

Figure 7 shows schematic views of a paper product in successive carbonization steps;

Figures 8 shows graphs corresponding to the carbonization steps of figure 7; and

Figure 9 is a schematic overview of a by-product discharge of the printing apparatus according to the present invention.

The printing apparatus 1 shown in figure 1 is an inkless printing apparatus 1 according to a paper object 2 is printed by carbonization or said paper object 2. However, it is remarked that although figure 1 shows a paper object 2 in the form of a sheet of paper 2, the paper object 2 may include paper 2 in any form or shape, especially including cardboard 2 and cardboard boxes 2. It is furthermore remarked that the invention is not limited to the paper substrate 2 described in the expire, but may also include the printing of other materials which undergo a contrast change on their surface and / or below the surface when heat or fight is radiated on it. This contrast change allows a readable print on the material. Suitable materials include especially: paper, cardboard, cellulose based materials such as wood and cotton, textiles, glass, metal, plastics and mixture of the aforementioned materials with other materials in a sufficient quantity that their treatment leads to sufficient contrast change to enable carbonization.

Treatment by a laser 22 for most materials comprises carbonization.

Using a feed 8, eg including feed rollers 10, the substrate 2 is transported in a feed direction 12. Although substrates 2 in the form of cardboard boxes may be transported with roller tracks, also different type of feed 8, eg conveyor belts, may be used.

The printing apparatus 1 further comprises a controller 14 that comprises or is connected to a reference database 16. A user may provide the controller 14 with information using a user input 18.

The controller 14 is configured to acquire substrate characteristics and is configured to adapt operation of the printer, i.e. the laser 22, based on said substrate characteristics. The laser 22 is configured to emit a laser beam for locally carbonizing said substrate 2.

A pre-heater 20 may be provided for pre-heating the substrate 2 to a predetermined temperature below the carbonization temperature of the substrate 2. The advantages will be explained with respect to steps 126 and 128 in figure 4.

After the optional step of pre-heating said substrate 2, a radiative heat source 22 in the form of a laser is used for heating the substrate 2 to its carbonization temperature. The laser 22 emits a laser beam 23, which may be directed towards a printed part of said substrate 2 using a focus lens 24 and polygonal mirror 26, as also explained in WO-A1-2014 / 158019 of Applicant.

In order to prevent the focus lens 24 and / or polygonal mirror 26 from being contaminated due to byproducts 83, such as smoke, a byproduct discharge 77 may be arranged. The byproducts discharge 77 will be explained in more detail in figure 9. Byproducts within the meaning of this invention should be interpreted as undesired reaction products. These undesired reaction products may also include reaction products that are desirable in the paper, but that are undesirable when they emanate from the paper, such as carbon particles, carbon-based volatiles, gases and other particulate matter.

When the laser beam 23 heats to be printed parts of said substrate 2 to a temperature at or above the carbonization temperature of the substrate 2, reaction products 30 form a print 28. The reaction products include carbon-based char 32 and tar-like compounds 34 ( figure 5).

In order for the controller 14 to obtain relevant information regarding the characteristics of the substrate 2 and the environment, the printing apparatus 1 further comprises one or more than one substrate characteristics sensor 40, eg a substrate thickness detection sensor 42 and / or a substrate temperature sensor 44. Further information may be obtained from the controller using one or more than one environment characteristics sensor 46, which may be a moisture and / or temperature sensor.

The thickness of the substrate 2 may be measured by using magnetic resistance variation with respect to different substrate thicknesses, e.g. with a Voith LSC Caliper Sensor. A thinner substrate 2 should be marked with lower power to ensure that the surface marking without holes 38 can be with.

Surface quality and material of the substrate 2 can be measured by a gloss or roughness sensor which works based on measuring reflection from the substrate 2 for a given incident light, e.g. a Voith LSC Gloss Sensor. If the surface of the substrate 2 is very rough, there is a higher chance that the quality of the print 28 is not uniform, and a step of printing the substrate 2 with active feedback control (step 158 in figure 4) may be used.

The density of the substrate 2 may be measured using a contactless absorption sensor based on krypton radiation, such as a Voith LSC Basic Weight Sensor version 5112. If the substrate 2 has a low density, it should be marked with lower power to ensure that the surface marking without holes 38 can be with.

The moisture content of the substrate 2 can be measured by a transmission / reflection based moisture content detection sensor, such as Voith sensor version 5123. Moisture content also includes the power of the laser beam 23 and the speed of printing and it will be adjusted accordingly .

The color of the surface of the printed substrate 2 can be measured using a substrate color sensor. It can be a reflective sensor which measures the reflection of an incident light, such as a Voith LSC Color Sensor. The color of the substrate 2 will also vary the laser power and other process control parameters to reach the printing quality goals.

Based on the information the controller 14 obtained from the user via an input device 18 and further information obtained from the one or more than one substrate characteristics sensor 40 and / or by the one or more than one environment characteristics sensor 46, the controller 14 defined which settings are expected to provide the desired results. The controller 14 may consult a reference database 16. Typical settings that may be adjusted by the controller 14 are among others, the laser power, the dwell time of the laser per dot, the duty cycle of the laser, the laser wavelength, the pre-heating temperature, the relative speed between substrate and laser, the pulse repetition frequency, the overlap distance and the focus.

The Taser power "how much optical power is received from the laser 22 on the substrate 2. Increasing or decreasing the power of the laser beam 23 can change all the printing quality goals.

The "dwell time of laser per dot" represents the amount of time spent by the laser beam 23 for each dot. The dwell time in combination with the power of the laser beam 23 rated the energy received by substrate 2 for a unit area.

The "duty cycle of the laser" is the percentage of one period in which the laser is active with respect to the time when the laser is inactive.

The Taser wavelength "used according to the effect that the laser beam 23 has on the substrate 2. The amount of power absorbed from the laser beam 23 is dependent on the absorption spectrum of the substrate 2.

The pre-heating temperature can ensure that the speed of printing can be faster since the substrate is at a higher starting temperature. Furthermore, the preheating ensures that the substrate 2 can be marked more in the surface reducing the depth of carbonization.

The "relative speed between substrate and laser" represents the speed of the laser beam 23 as it scans across the substrate 2.

The "pulse repetition frequency" is the frequency at which the laser operates.

The "overlapping distance" defines the distance between the center of a dot (or line) or the next adjacent dot (or line) made by the laser. Reducing the overlap distance will reduce the depth of carbonization, and increase the resolution and the darkness of print.

Finally "focus": the type of focus lens 24 used the size of the dot that is printed, which will determine the resolution of the print. Higher resolution will enable higher quality of print 28.

A quality test unit 48, which will be explained in more detail using figures 6-8, is provided for testing the quality of the print 28, so that the controller 14 obtains feedback if the real results match the expected results. The reference database 16 may be updated based on the results.

In the shown embodiment, the quality test unit 48 comprises a light source 50, eg a LED array, which emits light towards the print 28. Some light will be reflected by the print 28, and the print quality sensor 52 may be a light sensor that measures the intensity of light in the reflected light beam 53. Based on the light intensity or reflected light beam 53, the controller 14 is able to assess the carbonization, as will be explained using figures 7 and 8.

Using a light source 50, it is possible to obtain increased accuracy, but the skilled person will also understand that reflected ambient light may be used. As the quality test unit 48 is normally enclosed in a housing of the printing apparatus 1, a light source 50 may be desired when the print quality sensor 52 is a light sensor 52. However, the skilled person will understand that the print quality sensor 52 may also be an infrared sensor, that measures the heat profile of the carbonized substrate for acquiring print quality information. In that case, a light source 50 may be absent.

In order to increase the permanence of the print 28, an electromagnetic radiator 54 may be used in order to cause the tar like compounds to polymerize and interlink. The polymerized and interlinked tar compounds 36 are indicated in Figure 5 has linked triangles. The electromagnetic radiator 54 may comprise a UV source 56 and / or an electron beam generator 58.

A further increase of the permanence of the print 28 may be obtained when the reaction products 30 are compressed into the substrate 2 using a compressing unit 60. The compressing unit 60 comprises a first compressing roller 62 and a second compressing roller 64 that may be pretensioned using a compression spring 66. The compressing rollers 62, 64 exert a compressive force 68 on the reaction products 30 that form the print 28 on said substrate 2.

A final step or even further increasing the permanence of the print 28 may include the step of using an applicator for adding a coating 76 on the reaction products 30 that form the print 28 on said substrate 2. The coating 76 preferably functions as a binder for the reaction products 30. The printing apparatus 1 comprises a coating reservoir 70, from which a conduit 72 transports coating 76 to coating nozzles 74 that are configured for spraying the coating 76 on the reaction products 30 that form the print 28 on said substrate 2.

Please note that the applicator can be used before or after printing. If used before printing, the applicator may apply an agent that promotes bonding of the reaction products 30 in a successive printing step, i.e. carbonization step.

In order to prevent the focus lens 24 and / or polygonal mirror 26 from being contaminated from byproducts 83, such as smoke, a byproducts discharge 77 (figure 9) may be arranged. This byproducts discharge 77 may also be useful to prevent any discomfort or health risks for a user, e.g. due to odor or even smoke development.

Figures 2 and 3 show of a printing apparatus 1 according to the present invention for the printing industry (figure 2) and the coding industry (figure 3) respectively. Like reference numbers as in figure 1 are used for the figures shown in figures 2 and 3. Therefore a detailed description of these is omitted here.

The printing apparatus 1 or figure 2 is configured to print large amounts or sheets or substrate 2. Substrates 2, such as sheets or paper are tasks from the input stack or paper 4, and transported along the feed direction 12 through the printing apparatus 1. The printed sheets or paper are collected in an output stack or paper 6.

On the other hand, the printing apparatus 1 or figure 3 is a coding printing apparatus configured for printing prints 28 on cardboard boxes that form the substrates 2. The cardboard boxes 2 are transported in the feed direction 12 using a conveyor 13.

In order to elucidate the operation of the printing apparatus according to the invention, successive operating steps will be described using a flow chart or figure 4. The operation starts with a "step of the feed moving the printed substrate forward" 114.

It is necessary that the controller 14 or printing apparatus 1 is informed about the substrate characteristics, such as thickness, surface roughness, temperature, moisture, etc. Some information, such as the chosen substrate type, may be indicated in the optional 'step of user inputting substrate characteristics' 116. Other substrate characteristics, such as the moisture level and temperature of said substrate, are obtained by the 'step of substrate characteristics sensors acquiring information' 118.

The operation further comprises the "step of environment sensors acquiring information" 120, which may be performed simultaneously or following step 118. One or more than one environment sensor acquires information about the environment, such as temperature and moisture levels.

Based on the information about the current characteristics of the substrate and the environment, the operation performs a 'step of the control unit acquiring information from reference database' 122. Information of earlier test results and pre-set conditions may be stored in this reference database 16.

Subsequently, the operation is continued with the "step of the control unit setting characteristics such as laser speed, laser power and overlap distance" 124.

The 'step of pre-heating the printed substrate' 126 and 'step of checking if the substrate is pre-heated to a predetermined temperature below the carbonization temperature of the substrate' 128 aim to bring the substrate 2 at a desired elevated temperature . The radiative heating source, ie laser 22, now only has to increase the temperature of the substrate 2 from the elevated temperature already obtained by the pre-heating to the carbonization temperature of the substrate 2. Due to the pre-heating, the printing speed whether the printing apparatus 1 is improved relative to a printing apparatus from the substrate 2 would have been heated from a room temperature or about 20 ° C to the carbonization temperature of the substrate 2.

Next, the operation tests the quality of the print 28 based on a sequence of steps, including first a 'step of printing test dots' 130, followed by a' step of measuring and checking if the desired darkness is obtained '132 and a' step of measuring and checking if the substrate is free of holes' 134.

Only if a 'step of measuring and checking if the consistency of the darkness is okay' 136 provides positive results, the operation continues with a 'step of printing the entire substrate with determined and set print characteristics (such as laser power, overlap, print speed, etc.) 138.

If the "step of measuring and checking if the consistency of the darkness is okay" 136 would provide negative results, the operation continues with a feedback controlled operation. This feedback control comprises the further steps of a 'step of printing feedback controlled dots' 146, a 'step of the control unit setting characteristics such as laser speed, laser power and overlap distance' 148, a 'step of printing test dots' 150 , a 'step of measuring and checking if the desired darkness is obtained' 152 and a 'step of measuring and checking if the substrate is free of holes' 154. Finally, a' step of measuring and checking if the consistency of the darkness is okay '156 has been performed. Again, only if the 'step of measuring and checking if the consistency of the darkness is okay' 156 provides positive results, the operation continues with a 'step of printing the entire substrate with determined and set print characteristics (such as laser power, overlap , print speed, etc.) 138.

Preferably, one or more of the "steps of discharging byproducts" 140 (figure 9), and "steps of increasing permanency" 142 (figure 5) are executed before the "step of finishing printing operation" 144.

If the "step of measuring and checking if the consistency of the darkness is okay" 156 would provide negative results, the process continues with the "step of printing the entire substrate with active feedback control" 158.

Preferably, one or more of the "steps of increasing permanence" 160 (figure 5) and "steps of discharging byproducts" 162 (figure 9) are executed before the "step of finishing printing operation" 164.

It is remarked that the 'steps of increasing permanency' 142, 160 are identical for both the 'normal', ie step 138, and 'active feedback controlled', ie step 158, printing of the substrate 2. Likewise, the 'steps of discharging byproducts' 140, 162 are identical for both the 'normal', ie step 138, and 'active feedback controlled', ie step 158, printing of the substrate 2.

The "steps of increasing permanency" 142, 160 are now further explained using figure 5. The successive steps should preferably include a pre-heating step 102, a carbonization step 104, an irradiating step 106, a compressing step 108 and a coating step 110.

In the pre-heating step 102, the pre-heater 20 heats the surface of the to be printed substrate 2 to a desired temperature below the carbonization temperature of said substrate 2. Preheating the substrate 2 increases the speed of printing, because a smaller temperature rise is required to obtain the carbonization temperature of the substrate 2.

In the next carbonization step 104, the laser 22 emits a laser beam 23 that increases the temperature of the substrate 2 to the carbonization temperature. The carbonization process will start, and carbon-based char 32 (denoted with circles in the figure 5) and tar-like compounds 34 (denoted with triangles in figure 5), are formed as reaction products 30. These reaction products 30 have a dark color that contrasts with the substrate 2, and in this way form the print 28 on the substrate 2.

In the irradiating step 106, the electromagnetic radiator 54, which may be a UV source 56 or an electron beam generator 58, electromagnetic waves towards the reaction products 30. This causes the tar-like compounds 34 to polymerize and form links with each other.

A chemical reaction produces products which increase the cohesiveness and adhesiveness of the print 28 within the substrate 2 matrix. The polymerized and interlinked tar compounds 36 (denoted with linked triangles in Figure 5) are bonded and therefore better resistant to wear, further increasing the permanence of the print 28.

The compressing step 108 comprises the step of a compressing unit 60 exerting a compressive force 68 on the substrate 2, also compressing the reaction products 30. The compression will increase the density of the reaction products 30 and interlocks the reaction products 30 with the substrate 2. The reaction products 30 will function as a binder for the carbon-based char 32 and further improved the permanence of the print 28 on said substrate 2.

Finally, a coating step 110 may be performed, a coating 76 is arranged on the print 28. This coating 76 may function as a binder between the reaction products 30, bonding them to the substrate 2 and creating a barrier to prevent the print 28 from being smudged.

Although the best results are obtained if the carbonization step 104 is followed by all three steps of irradiating 106, compressing 108 and coating 110, the skilled person will understand that each independent step already contributes to an increase of the permanence of the print 28. Also the pre-heating step 102, which contributes to an increased speed of printing, is optional.

Figure 6 shows a quality test unit 48. A light source 50, for example a LED array, emits light. The light beam 51 emitted from this light source 50 reflects on the print 28 and the reflected light beam 53 is received by a print quality sensor 52 that is a light sensor. By comparing the intensity of the light emitted from the light source 50 and the intensity of the light received by the light sensor, ie print quality sensor 52, it is possible to determine the amount of light absorbed by the print 28. Based on this information , it is possible to determine different phases 104a-104d or the carbonization step 104.

As indicated in figure 6, the quality test unit 48 is capable of testing during the carbonization step 104, i.e. while the laser 22 emits a laser beam 32 towards the substrate 2 and reaction products 30 are formed, defining a print 28.

The carbonization step 104 comprises four phases: a first phase 104a, a second phase 104b, a third phase 104c and a fourth phase 104d (figure 7).

In the first phase 104a or carbonization step 104, the laser beam 23 is still warming up the substrate 2 to the carbonization temperature.

In the second phase 104b or carbonization step 104, carbonization has just started, and print 28 will still have a brown color, and is still getting darker, i.e. it is changing color from brown towards black.

In the third phase 104c or carbonization step 104, the reaction products 30 reach deeper into the substrate 2, and the print 28 has obtained its maximum darkness. In this third phase 104c, the carbonization is preferably stopped.

In the fourth phase 104d or carbonization step 104, the laser beam 23 has burned through the substrate 2, leaving a hole 38, which is undesirable.

Figure 8 show three graphs, each having the time T on the x-axis. In the top graph, the V indicates the voltage of a photodiode or the light sensor, i.e. print quality sensor 52. In the center graph, indicates the output of the laser. In the lower graph, B indicates the percentage of blackness of the print 28.

In the first phase 104a, the substrate 2 is still it is original color, eg white, and reflects most light or light beam 51 that is emitted by the light source 50. In the second phase 104b, the print 28 is getting darker, which can be seen in B increasing in the lower graph. Less, less light is getting reflected towards the print quality sensor 52, i.e. the light sensor. This results in the voltage V or the photodiodes or the light sensor decreasing. Once the print 28 is not really getting darker anymore, the voltage V will get constant again (third phase 104c). Both V and B show a flat line.

In the third phase 104c, optimum darkness of the print 128 is obtained. When the darkness B does not increase anymore, and the voltage V is getting constant, the controller 14 makes sure the laser beam 23 is stopped from heating that specific spot on the substrate 2.

The 'steps of discharging byproducts' 140, 162 are now further explained using figure 9. The carbonization reaction on the one hand produces reaction products 30 that are either gaseous or mixed within the air, such as char like substances, and byproducts such as smoke and organic volatiles. These gases and airborne particles will contaminate the substrate 2 when condensing back to the substrate 2. If the byproducts 83 contact the substrate 2 after emanating from the substrate 2, they can condense and cause a hazy glow next to the print. Hazy glow may also occur due to the heat energy stored in the byproducts 83 and therefore it is desirable that they are removed from the print area without allowing it to interact with the print area. Preferably, the removal is performed in a direction substantially perpendicular to the plane or the print area in order to eliminate the chance of interaction. Furthermore, the gases and airborne particulate matter will contaminate surfaces, such as but not limited to optical components of the laser 22, such as focus lens 24. Byproducts discharge 77 comprises a blower 78 with a blowing pump 80 configured to blow substantially clean gas 82 towards the print 28, Moving any byproducts 83 such as smoke away from the printed area on the substrate 2. The byproducts 83 are drawn into a suction unit 84 that is powered by a suction fan 86. The byproducts 83 are transported from the suction unit 84 via a conduit 88 towards a water scrubber 99. The water scrubber 99 serves to sediment the particulate matter that is present in the byproducts 83. This can be later collected and cleaned from the printing apparatus 1. The byproducts 83 are transported via a conduit 92 from the water scrubber 99 towards an activated carbon filter 94 that serves to remove any odors from organic volatiles present in the byproducts 83. This way, clean odo urless gases can be passed out of the printing apparatus 1 via outlet conduit 96. Additional process steps may be added to ensure that the gases in outlet conduit 96 meet the air quality standards required in offices / relevant environments where such printing apparatuses 1 are used. Instead of or in addition to activated carbon filter 94, a (not shown) electrostatic filter may be applied.

It is to be noted that the when additional gas is pumped though blower 78, it removes the oxygen and other gases present in the vicinity of carbonization and may create a low oxygen environment. This has an additional desired effect or preventing smoke 83 from forming. The low oxygen environment can also be created by creating a vacuum using suction unit 84. Furthermore, a transparent cover can be placed on top of the blower 78 and suction unit 84, such that the components of the printing apparatus 1 are completely sealed off from the print area.

The printing apparatus 1 may further comprise a detector 98, 100 configured to detect characteristics of the byproducts 83 and / or of reaction products 30 formed in the substrate 2. The controller 14 is preferably configured to adapt operation or said printing apparatus 1 based on the detected characteristics of the byproducts 83 and / or of reaction products 30 formed in the substrate 2. Both detectors 98, 100 shown in figure 9 are arranged in the byproduct discharge 77. The first detector 98 is arranged downstream or said suction unit 84, and the second detector 100 is arranged downstream or filter 94.

The function of detectors 98, 100 is to understand the composition, temperature and other relevant properties of the reaction products 30 and / or byproducts 83 which consist of smoke, organic volatiles and other gases. The controller 14 may stop or optimize the carbonization reaction to produce the least amount of byproducts 83 or to stop the printing completely if the level of byproducts 83 produced is too high for the filters 94 to handle or detect if the filters 94 are clogged or damaged . For this latter function, detector 100, which is arranged downstream or filter 94, is used.

Although they show preferred embodiment of the invention, the above described are only intended to illustrate the invention and not to limit in any way the scope of the invention. Applied claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of claims and are in no way limiting the scope of claims. Furthermore, it is particularly noted that the skilled person can combine technical measures or the different expiry while leaving out others. The scope of the invention is therefore defined solely by the following claims.

Claims (11)

Conclusions A printing device comprising: - a laser configured to locally treat a substrate; - wherein by-products arise from the substrate; and - a by-product discharge. A printing device according to claim 1, wherein the by-product discharge comprises a blower. 3. Printing device as claimed in claim 1 or 2, wherein the by-products discharge comprises a suction unit. 4. Printing device according to one of the preceding claims, wherein the by-product discharge is connected to a wet-dust remover. 5. Printing device according to one of the preceding claims, wherein the by-product discharge is connected to a filter. The printing device of claim 5, wherein the filter comprises an active carbon filter. A printing device according to claim 5 or 6, wherein the filter comprises an electrostatic filter. 8. Printing device according to one of the preceding claims, further comprising: - a detector configured to detect characteristics of the by-products and / or reaction products formed in the substrate; and - a controller configured to adjust the operation of the printing device based on the detected characteristics of the by-products and / or reaction products formed in the substrate. The printing device according to claim 8, wherein the detector is disposed in the by-product outlet. 5 10. Printing device as claimed in claim 8 or 9, wherein the detector is arranged downstream of the suction unit. A printing device according to any of claims 8-10, wherein the detector is arranged downstream of the filter. 1/8 co 2/8 \ O 3/8 Oxl 114 5/8 MO 6/8