Any owner of a printer or MFP has to eventually solve various kinds of problems related to both the hardware and software of the device. One of the fairly common problems is the following: why does the printer print faintly when the cartridge is full. This problem is, perhaps, one of the most urgent among all models of laser printers. If your printer began to print faintly, then do not rush to the nearest service center, because you can solve this issue absolutely on your own. The main thing is to treat it with all seriousness and responsibility, because. The sources of this problem can be very different.
In general, a light image is a consequence of the insufficient optical density of the laser device. This parameter depends on the charging voltage of the phototube, the power of the laser beam, the "blackness" of the toner, its amount transferred to the drum and the amount transferred directly to the paper surface. Of all the listed values, the amount of coloring matter transferred to the photo roller is of particular importance - it is on this parameter that the optical density of the print depends to a greater extent.
If you notice that your laser printer prints dull, then first of all pay attention to the settings of this device. This is a setting known as Economy Printing. The fact is that such a function helps to extend the life of the cartridge of the device, however, this is of little use, because. this may adversely affect print quality. This function helps the machine distribute the ink supply correctly. But when there is less than half of the toner in the cartridge hopper, this setting starts to save it, as a result of which the device produces poor quality prints. In this case, printed documents may become fainter. Therefore, any owner of a laser printer can be recommended to disable this function in advance, especially with its help you can save 40-70 additional pages on the strength.
But if you fail to simultaneously replace the elements described above for some reason, for example, for financial reasons, then you can resort to some other methods. It should be noted that the surface roughness of such an element as a magnetic roller can decrease due to the reasons that consist in the wear of this part and the filling of the "pores" on its surface with a coloring matter. What to do in the first case? It is impossible to cope with shaft wear, because. this process is irreversible. But the problem associated with its pollution can be completely solved, and on your own. To eliminate the filling of "pores" with toner, it is necessary to clean the roller using a strong solvent. After that, the printing printer should produce a fairly clear image. 
To clean the "pores" of the magnetic shaft, purchase an affordable product such as acetone. But at the same time, remember that you can not use excessive force, because. in this way, you can destroy the coating of the shaft and degrade its roughness. Also, do not forget that acetone is a toxic substance and, using it, all precautions must be observed, including ventilation of the room. After cleaning all the "pores" clogged with toner, you need to print a test document. If its quality completely suits you, then the problem is solved, otherwise you will have to contact the service center.
As practice shows, in order to solve the problem of pale printing after refilling the laser printer cartridge, it is also advisable to clean the doctor blade. The fact is that during the operation of the device for printing on the edge of this part, a strip consisting of pressed toner is formed over time. This strip, as it were, moves the doctor blade away from the shaft, which negatively affects the friction force, which gradually decreases. That is why, in order to restore normal printing, you need to clean this part. To do this, use dry, lint-free wipes, which, if necessary, can be slightly moistened with distilled water, if the build-up of the dye has not gone away during dry cleaning. If even a damp cloth could not remove them, then it is better to change the blade, or use acetone.
As you can see, the problem with the fading laser cartridge is solved quite simply. But if even after the manipulations the device prints pale, then perhaps the reason is in the device itself, perhaps this is the disease of your printer. Then we recommend that you familiarize yourself with the materials on a specific model by selecting it in the right drop-down menu.
Why doesn't the look of prints always look perfect? The new cartridge prints flawlessly, but after the first refilling, the print quality may be noticeably reduced. If the image looks faint, the print density has become too low. A little deeper into the theory, we can say that this parameter depends on a number of factors:
The first three factors are not related to cartridges: the first depends on the condition of the printer, the second - on the quality of the toner, the third - on environmental conditions and paper. But the amount of powder that falls on the photosensitive layer of the drum directly affects the print density. And the wrong thickness of the ink powder layer, which appears due to the wear of cartridge parts, is the main and most common cause of printing defects.
The Developer Roller (development shaft, magnetic shaft) charges the coloring powder granules with a negative charge. The toner adheres to the photoconductor due to the potential difference between the powder particles on the surface of the developer and the areas illuminated by the laser on the photoconductor. The greater the potential difference, the more powder will be transferred, the more saturated the color of the print.
The squeegee is a toner dosing blade that is designed to distribute the toner evenly over the developer.
The condition of these two parts plays a decisive role in the correct transfer of ink to the surface of the drum.
The new magnetic roller and squeegee have a perfectly flat surface, without protrusions and notches. During operation, toner residues accumulate on the surface of the blade, which leads to its curvature. Light stripes appear on the paper. The porous surface of the rubber roller becomes clogged with tiny ink particles over time, which also causes defects on the paper.
The principle of operation of the cartridge is the same for all manufacturers, but the production technology is different. Developers Canon and HP are made of metal with a rubberized top layer, while Samsung is made entirely of rubber. Samsung and Brother blades are made of metal, while Canon and HP make blades from polyurethane. This polymer is stronger and more reliable than metal; only low-quality toner with large and “spiky” particles can damage such a squeegee.
The most effective way is to replace the squeegee and the developer (as a whole or just the shaft shell), and it is better to change both parts at the same time. The result appears immediately: the print density increases, the image becomes saturated. But if, when disassembling the cartridge, you see that these parts are not worn out or damaged, but simply dirty, then you can do without replacing them. Use a strong solvent to clean the pores of the magnetic roller and the surface of the doctor blade from excess toner.
Acetone is well suited for the developer, but isopropyl alcohol is not recommended: it dissolves the toner poorly and can worsen the situation by finally clogging the shaft pores with half-dissolved powder.
Do not wipe the polyurethane squeegee with acetone, it can reduce the elasticity of the surface: use special dry lint-free wipes. To remove dried toner, you can moisten it with distilled water.
When performing work, it is important to observe the following rules:
We have described the most likely reasons for the printer to print faintly after refilling. Changing the squeegee is easy, replacing the magnetic shaft is a more complicated procedure, there is a risk of damaging a rather expensive part.
But the reason for the decrease in optical density of printing may lie elsewhere: in HP and Canon cartridges, the appearance of light areas after several refills is usually caused by the deterioration of the photocell, and not by wear on the above parts.
It may happen that you have changed all the details, but the problem remains. So it's a bad toner. Or that you have not corrected the problem correctly, for example, you have damaged the magnetic roller during the cleaning process. Or maybe it was not in him at all, but in damage to the photosensitive layer of the drum. Inexperienced craftsmen, having incorrectly identified the source of the problem, change everything: from the key components of the cartridge to the printer itself.
If cleaning the doctor blade and developer does not help, the best way is to print a test page and contact the service center. By the nature of the defects, the master will immediately identify the cause of the appearance of discolored areas and offer the best ways to eliminate it.
Each specialist involved in refilling and restoring cartridges faces a situation in his work when cartridges of the same model, refilled with the same toner, installed in the same printer, give different optical print density. Some cartridges print normally, while the other part produces an image that is too pale. As you can see, in such a situation, the classic excuse like "bad toner" no longer works, and you have to look for reasons in a completely different place ...
As you know, Canon printers and Hewlett Packard printers based on them use a single-component magnetic development system. The principle of its work is as follows:
1) The development of the image created on the drum is carried out by the developing magnetic shaft. This shaft consists of two main elements:
Rod multipole permanent magnet;
Non-magnetic outer shell.
The bar magnet is inside and must be oriented in a very specific way relative to the drum unit and toner hopper. This orientation is ensured by a special curly lock and a corresponding bevel on the magnetic rod itself. The magnetic field formed by the poles of the bar magnet is oriented in such a way that its lines of force are most directed towards the inside of the toner hopper. This is done to ensure that the toner is picked up from the hopper. In addition, the lines of force also create a magnetic brush that ensures the contact of the toner with the surface of the photoconductor.
2) Image development, i.e. "sticking" of the toner to the photoconductor is carried out in an electrostatic way, i.e. the toner is attracted to the photoreceptor by electrical forces. The potential difference between the photoconductor and the toner itself helps to attract the toner to the areas illuminated by the laser. Thus, it turns out that the toner must carry an electrostatic charge.
3) The toner in laser printers is triboelectric, i.e. it is charged by friction. In Canon/HP printers, the toner is charged by its friction against the surface of the magnetic developing roller. To create this friction, the cartridge has a metering squeegee (Doctor Blade), and the surface of the magnetic roller itself has a special coating (note that the magnetic roller is very dark, almost black, although its edges are a well-polished shiny metal).
Thus, the magnitude of the electric charge accumulated on the surface of the toner particles is determined not only by the characteristics of the toner itself, but also largely depends on the friction force. And it, in turn, is determined by the quality and current state of the surface of the magnetic shaft and the dosing squeegee.
The amount of toner that is transferred from the hopper to the drum surface during image development is proportional to the potential difference between the toner particles on the magnetic roller surface and the latent image area on the drum surface (the area illuminated by the laser). The greater the potential difference, the more toner will be transferred to the image area, the greater the print density. In turn, the potential difference is the greater, the lower the potential of the exposed areas of the photodrum and the greater the potential of the toner particles.
Now back to the problem under discussion. So, when refilling cartridges, one often encounters the problem of a pale image. A pale image is, in fact, a low optical density of the print.
In general, the optical density of a print depends on the following parameters:
1)
The amount of charging voltage of the photoconductor. The lower this voltage, the higher the print density, and, conversely, a low density may indicate an overestimated voltage on the charge corotron;
2)
The power of the laser beam. Reducing the laser power leads to less discharge of the drum surface, i.e. to an increase in the potential of the illuminated area, and, as a result, to a decrease in print density;
3) The optical density ("blackness") of the toner itself, which is provided by the absorption of light by the dye pigment used in the manufacture of the toner. For the vast majority of modern original and compatible toners, the differences in this parameter are negligible;
4)
The amount of toner transferred to the drum during the development phase. The more toner is transferred, the naturally thicker its layer will be and the higher the print density will be;
5) The amount of toner transferred to the paper. This parameter is determined by many variables, such as transfer corona voltage, paper quality, environmental conditions, and so on.
Of all the quantities that affect print density, let's highlight the fourth item (the amount of toner transferred to the photoconductor). It is this parameter that can vary greatly in different cartridges, and first of all, depending on their physical wear.
The remaining parameters are not relevant to the topic of the current discussion. And therefore, if the printer is in good working order, is in good technical condition, operates under normal conditions (at the appropriate temperature and humidity), and when printing, paper of the appropriate quality is used, then only the amount of toner transferred remains a significant factor. Therefore, let's try to figure out what elements of the cartridge can affect this parameter.
According to their structure, photoreceptors can be divided into two types:
- single-layer photoreceptors;
- multilayer photoreceptors.
So-called "single-layer" organic photoconductors (in which the functions of generating and transporting charge carriers are combined in one layer) are relatively rare and are manufactured mainly by Mita. The question of the advantages and disadvantages of such photoreceptors is quite complicated and requires special discussion. But it is believed that a feature of single-layer photoreceptors is their high photosensitivity.
In multilayer photoreceptors, generation and transport functions are separated into different layers, which gives manufacturers much more freedom to improve each layer. This allows you to set the necessary properties of each layer, thereby "programming" the characteristics and parameters of the photoreceptor, making it, for example, more sensitive to light, or more wear-resistant, less sensitive to temperature changes, etc. It is multilayer photoreceptors that are currently most widely used, so it is expedient to discuss only them below.
The number of layers in a multilayer photoreceptor can be different - everything is determined by what characteristics they want to endow the photoreceptor with. But the classic variant, characteristic of the vast majority of modern photoreceptors of all brands, is
a four-layer photoreceptor deposited on an aluminum base made in the form of a drum (photodrum).
So, in this case, the photoreceptor consists of the following layers:
1) PL (Protective Layer)- a protective layer, 0.5 - 5 µm thick, serves to protect the surface of the photoreceptor from mechanical wear and the action of harmful atmospheric factors, corona discharge, etc. Currently rarely used in modern photoconductors.
2) CTL (Charge Transport Layer)- charge-transport layer (charge transport layer), 25 - 35 microns thick, serves to transfer charge carriers to the surface of the photoreceptor and locally reduce the surface potential.
3) CGL (Charge Generate Layer)- charge-generation layer (charge generation layer), 0.2-1.0 µm thick, serves to absorb exposure radiation and form an electron-hole pair.
4) GL- a primer layer, 10 - 20 microns thick, serves to level the surface of the aluminum substrate, and also performs the function of preventing dark charge injection from the substrate into the CGL layer, etc.
5. Substrate or UL- aluminum substrate (aluminum cylinder) polished up to grade 14. It is the basis of the photoconductor.
It is also customary to divide photoreceptors into so-called "cold" and "hot" photoreceptors. Cold"Photoreceptors have a relatively low sensitivity to laser radiation. Therefore, when the surface of the photoreceptor is illuminated by a laser beam, only those charge carriers that are directly in the exposure zone are activated in the CGL layer. This leads to the fact that an insignificant amount of charges additionally "flows" from the CTL surface, directly surrounding the laser beam. As a result, the size of the dot (i.e. the size of the illuminated area) almost corresponds to the cross-sectional area of the laser beam. In other words, the illuminated dot has a minimum size. " Hot On the other hand, photoreceptors, on the contrary, are very sensitive to external radiation. Therefore, when they are exposed, not only the carriers located in the illumination zone, but also all nearby charge carriers are activated. As a result, the charge drains from the surface, much larger than the cross-sectional area of the laser beam. i.e. the illuminated dot turns out to be large enough.The image formed on the "hot" photoreceptors looks more saturated, i.e. small details become larger (the lines turn out to be "bold", the dots turn black, etc.). transmission of small details on "hot" photoreceptors leaves much to be desired. Therefore, "hot" photoreceptors are preferable to use in cases where text is printed predominantly. But for graphics, drawings, photographs, etc. it is better to use "cold" photoreceptors, although text they don't look as crisp and clear.
In addition, the use of "hot" photoreceptors leads to a greater consumption of toner.
charge shaft
The potential of the illuminated areas on the surface of the drum at the same intensity of the laser beam is practically independent of the initial potential of the charged surface of the drum, i.e. the impact of the charge roller and the decrease in charge sensitivity from wear of the outer layer of the drum (charge transport layer - CTL) is minimal. It follows that the problem of faint printing cannot be corrected by replacing the charge roller.
photoconductor
Based on the previous paragraph, one could conclude that a faded image cannot be corrected by replacing the drum, but this theoretical conclusion, unfortunately, is hindered by practice, which shows that in some cases replacing a worn drum with a new one can increase print density. Two factors contribute to this:
1)
A new drum may be "hotter" in its characteristics than the one that stood before, i.e. the charge generation layer (CGL) of this reel generates more charges and, accordingly, the latent image potential for this reel becomes lower. In addition, a larger number of generated charges leads to the fact that the point illuminated by the laser has a geometrically larger size. The generating properties of CGL are weakly dependent on the physical wear of the drum, so the "hot / cold" drum in most cases can be considered "innate" during production and unchanged during operation;
2) Reducing the optical transparency of the photoconductor (optical decay). The charge transport layer (CTL), which should be transparent to laser light, becomes dull with wear and therefore allows less light to reach the charge generation layer (CGL). This, of course, is typical for significantly worn drums, the degree of wear of which is close to critical.
Thus, it turns out that replacing the drum to solve the problem of faint printing can only work in two cases:
If the new drum, due to its characteristics laid down during its production, is capable of attracting more toner than the one that was installed before. Replacing a used drum with a new drum of the same type (manufacturer) will not give a significant increase in print density;
If the worn drum has a "matte" surface that strongly scatters laser light.
Magnetic roller and doctor blade
The potential of the toner particles on the surface of the magnetic roller consists of two components: the bias voltage applied to the magnetic roller and the charge received by the toner particles from triboelectricity, i.e. from their friction against each other, about the dosing squeegee and about the shell of the magnetic shaft.
The offset voltage set by the printer can be considered a constant value, and the only thing that needs to be done in the cartridge in order for this voltage not to decrease is to ensure stable contact. To do this, it is useful to clean the sliding contact pair of the magnetic shaft from contaminated conductive grease and apply a thin layer of fresh grease to it. Otherwise, the influence of this potential can be excluded.
The triboelectric charge of toner particles in reality is highly dependent on several factors. If we exclude from this list the triboelectric properties of the toner itself and environmental conditions, then there will be only two of them:
Condition of the dosing squeegee;
The state of the magnetic shaft shell.
One of the functions of the magnetic roller shell is to transport the toner from the hopper to the developing area. One of the functions of the dosing squeegee is to form a layer of toner on the surface of the magnetic roller. But both of these components together have another important function - the charge of the toner by friction when it passes through the contact point of the squeegee and the shell. To improve this process, the surface of the magnetic roller has a roughness, which increases the friction force, and the material of the doctor blade has a certain rigidity and an appropriate chemical composition.
In the process of long-term operation of the cartridge, the edge of the dosing squeegee wears out, and the surface roughness of the magnetic roller shell decreases. This leads to a decrease in the friction force, i.e. causes insufficient toner charge and, as a result, faint printing. Unfortunately, we have to state the fact that in modern HP/Canon monochrome cartridges this decrease in charging properties is already apparent during the first cartridge cycle, and after several refilling cycles it becomes very noticeable.
Solution
The problem of pale printing can be cardinally solved very simply - replace the dosing squeegee and the magnetic roller shell (or the entire magnetic roller). It is better to replace them at the same time in order to extend their service life and improve the print density immediately by a clearly visible amount.
However, if this option is not possible for some reason (lack of necessary spare parts or for financial reasons), then you can try to solve the problem of pale print and "little blood", i.e. without replacing the named components.
The decrease in the surface roughness of the magnetic roller occurs for two reasons:
Physical wear of the magnetic shaft;
Filling the "pores" on the surface of the magnetic roller with toner.
If it is pointless to fight physical wear and tear, because it is irreversible, then the problem of contamination of the magnetic shaft can still be overcome. Clogging of the "pores" of the magnetic roller with toner can be eliminated by cleaning the roller with a strong solvent. Acetone can be attributed to such solvents available to any person. It is the cleaning of the magnetic roller with acetone that can solve the problem of pale printing for some time.
However, when carrying out the cleaning procedure, it is necessary to follow a few basic rules:
Do not apply excessive force, as this may damage the coating of the magnetic roller, i.e. worsen its roughness;
It is necessary to remember the toxicity of acetone, and therefore you should follow the rules for working with it (well ventilate the room in which the work is carried out, and it is also advisable to use protective gloves when working).
Isopropyl alcohol is also known as a toner solvent, but it is not very suitable for cleaning the magnetic roller. The fact is that isopropyl alcohol is not a very strong solvent, and therefore, instead of cleaning, on the contrary, it can clog the “pores” of the magnetic roller with dissolved toner.
Practice shows that along with the magnetic roller, it is also desirable to clean the dosing squeegee. During operation, a strip of pressed toner usually forms on the edge of the dosing squeegee. This strip "pulls" the squeegee away from the magnetic shaft, which reduces the friction force. Therefore, to restore normal printing, it is necessary to clean the squeegee. It is believed that the use of any solvents (and acetone in the first place) can disrupt the chemical composition of the squeegee and lead to a deterioration in its elastic properties. Therefore, it is most often recommended to use dry, lint-free wipes for cleaning the squeegee. If dry cleaning does not work, and toner build-up remains, then you can moisten the cloth with distilled water and repeat the procedure. If this does not help, then you will either have to leave the squeegee without further cleaning and put up with possible defects, or change the squeegee to a new one.
However, our experience says that, despite all the prohibitions, the use of acetone to clean the squeegee gives a very good effect. Especially if you need to choose between installing a new squeegee and cleaning the old one.
In principle, there is another "popular" way to restore the roughness of the magnetic shaft, which is used with varying degrees of success by individual specialists. We are talking about sandblasting or surface treatment of the magnetic shaft with fine sandpaper. But the result obtained in this way is extremely unstable and requires certain practical skills that can be developed, as a rule, by "killing" several magnetic shafts. Therefore, we would not recommend this method for practical use.
Source World of Peripherals PC-6 "09
Pale prints cartridge HP 36a, 35a, 78a, 85a and Canon 712, 713, 725, 728.
A problem often faced by many users of laser printers– printer after . This often happens with cartridges. HP 36a, 35a, 78a, 85a And Canon 712, 713, 725, 728. The problem may be either in the printer or in the cartridge. Consider a common case - the printer is new, recently purchased and in good working order. Cartridge just refilled with fresh quality toner, and he prints faintly. Most likely the problem is with the cartridge.
A common cause of faint printing in HP and Canon printers is the condition of the magnetic roller or doctor blade of the cartridge.
The main purpose of the surface of the magnetic roller is to transfer from the hopper to the developing area. The purpose of the doctor blade is to create a layer of toner on the surface of the magnetic roller. An additional function of both is to electrify the toner as it passes through the point of contact between the surface and the blade. In order to improve performance, the surface of the magnetic roller is roughened, and the doctor blade is made with a suitable shape, hardness and composition.
During the operation of the cartridge, the edge of the doctor blade is ground off, and the magnetic roller loses its roughness. The toner is not charged enough, resulting in faint print.
The best solution to the problem is to replace the magnetic roller and doctor blade. You can try to reanimate the cartridge without replacing parts. What is needed for this?
1. Disassemble the cartridge and inspect it carefully.
2. Clean the surface of the magnetic roller from the toner. This can be done using a strong solvent such as acetone.
3. Inspect the surface of the doctor blade - it must be clean. If there is toner on the surface of the blade, gently clean with a cotton swab and solvent.
4. Completely remove the old one toner.
When cleaning, it is necessary to act carefully, without exerting great effort, so as not to damage the surface.
It may be that the magnetic roller or doctor blade is not only dirty with toner, but also worn out. Unfortunately, the physical wear of the magnetic roller and blade is irreversible. In this case, there is no alternative to replacing the shaft and blade.
