Fault analysis and solution of screen printing press

In screen printing.As a result of the whole process more, and ink, substrate material is very widely used, its performance is more complex.In particular, the printing methods and techniques are directly related to the audio quality of screen printing.

The following are several common failures in screen printing, and analyzed the causes of the failures and solutions.

One, tension network tension is inconsistent resulting in screen printing multicolor set

Cause analysis: multi-color overprint in silk screen printing machine, found that appeared in print on a color image, the phenomenon of relative displacement, it is in the screen printing misregister failure phenomenon, is checked to determine a set of silk box used when stretched mesh tension is inconsistent, and machine mesh spacing adjustable too large, the scraping scraping board printing pressure, causing all kinds of printing image position change, misregister fault phenomenon.

Troubleshooting: clean the screen, after dry to stretch the network again, require in a set of screen, the tension of each screen to keep the same, the tension difference should not exceed 1N/cm. at the same time, pay attention to readjust the network distance for 2~5mm.Printing products meet the requirements of a set of qualified.

It should be pointed out that in screen printing, it may also be screen printing screen frame deformation caused by the color plates of the image and text position is not uniform.Or deer due to the screen and mesh frame paste is not strong, part of the result of the change in the position of the text and text.It is also possible that the screen plate on the printing table with the positioning of the gap error or fixer is not fixed, part of the glue, resulting in the printing of all colors of the board positioning and standards.Or the substrate material is not stable, in the substrate will cause overprinter error phenomenon.

One, screen printing appeared premature screen tear

Reason analysis: Screen printing machine in the appearance of screen tear quickly.It was found that the scraping plate was too close to the edge of the frame due to the excessive edge pressure of the scraping plate.

Troubleshooting: adjust the distance between the scraping plate and the edge of the screen, to ensure that there should be at least 15cm space, as for some small screen, can be solved by reducing the distance between the screen.

Spots appear on screen prints

Cause analysis: during the printing process of screen printing machine, due to the uneven thickness of the ink layer of the printing image, the ink should not be squeezed out of the place where the ink leak, there will be spots on the printing.There are many reasons for the phenomenon of spots, the inspection found that the cause of spots here is due to the ink mixed with small pieces of hard, in the solvent softening adhesion to the screen hole, together with poor ink mobility, ink is difficult to pass through the mesh, resulting in the spot fault phenomenon.

Troubleshooting: the ink with a fine screen filter, and screen plate clean and then start printing, spots can be eliminated.

It should also be pointed out that there are spots on the printing fault phenomenon, may also be caused by the four bumps of the printing table.In printing, the ink thins where the printing table bulges and thickens where the ink sinks, creating thick blobs.In addition, the substrate on the back and printing table dust, will also cause spots fault phenomenon.Therefore, items should be excluded when checking.

Iv. The image edge of screen printed matter with ink whiskers caused by the adhesion of villi on the screen

Cause analysis: In the process of screen printing, there will be defects in the image edge.There may be three reasons for the failure of this ink beard phenomenon, one is the adhesion of villi in the screen, the second is caused by electrostatic effect;The third is the poor ink suitability ink drawing caused by.

Troubleshooting: first check the screen, and clean the screen.If the machine has an electrostatic elimination device, you can eliminate the ink caused by static, or you should eliminate the electrostatic effect.Then boot printing, printing found that the image on the smooth, ink must fault phenomenon has been eliminated.If the above measures are taken, ink must still not be eliminated, the ink should be adjusted or replaced.

Five, screen printing press plate photosensitive layer off the fault

Cause analysis: during the printing process of screen printing machine, the defective image on the printing products caused the waste products.Through analysis, it is believed that this is due to the screen plate photosensitive layer off.And why the template photosensitive layer will fall off, this may be due to the adhesion of film layer or due to the network spacing is too large.

Troubleshooting: First check the size of the network spacing.It is found that the screen spacing is too large, and the screen tension is slightly lower, in the squeezing-ink plate pressure squeezes, resulting in local photosensitive film off.Therefore, the need to choose a higher tension screen, and reduce the screen distance (adjusted to the appropriate distance), for fine printing, the screen distance is 1~3mm;For ordinary printing, the network distance is 2~6mm.Then start printing, find the trouble phenomenon troubleshooting.

It should also be noted here that the cause of poor adhesion of photosensitive film layer and the use of corrosive ink or cleaning agents, will also cause the template photosensitive layer off.Therefore, if the above measures (to adjust the distance between the grid) failed to eliminate the phenomenon of failure, can only replace the new ink or cleaner.

Six, screen printing ink or color bar

Reason analysis: In the process of screen printing, the pattern printed on the substrate sometimes appears inconsistent color depth or regular color bar fault in the pattern.Analysis of the reasons for the above faults, mainly due to the printing speed is not uniform, coupled with the different pressure applied on the scraper, resulting in screen ink leakage more or less, so in the substrate to form the imprinting depth and shallow;Secondly, because the scraper ink bending Angle is not consistent, so that the printing pressure is not consistent, resulting in screen plate ink leakage is not equal, so in the substrate formed different patterns;In addition, due to the screen plate is not smooth or flat plate, also in the substrate printing so that the scraping plate pulsations, in the substrate formed on the color bar fault.

Troubleshooting: According to the above analysis, carefully check the causes of the faults and take targeted measures to eliminate them.As a result of squeezing-plate pressure printing, bending Angle is different, resulting in different printing pressure, so there is a large pressure on the printing, the pattern color is dark, small pressure on the pattern color is light inking phenomenon.At this time, it is necessary to readjust the pressure of all kinds of ink scraping plates, so that the tilt Angle is consistent and the pressure applied is uniform.Then boot printing, inking on the substrate pattern of the fault can be removed.

Seven, screen printing substrate appears double

Cause analysis: In screen printing, partial or total images on the substrate appear double image phenomenon called double fault.In particular, small area images and lines are more obvious.Analysis of the causes of this kind of double fault, tension network tension, make the layout slack seriously, when the scraper operation pressure is a little high, in front of the scraper running direction of the cutting edge, the layout relaxation, the image on the page will be shifted, the image printed on the substrate appears double;When the scraper is in operation, the plate also moves forward (the amount of clearance), resulting in inconsistent positioning during printing of all colors, resulting in double image on the substrate;When the first scratch, the substrate did not get a full pattern, so that the image is not clear, when the second repeat scratch, due to the plate or substrate displacement will also produce double fault;The artificial leather or plastic cloth on the printing pad is not tight enough, and the pressure of the scraper is high during operation. As a result, the artificial leather or plastic cloth will relax in front of the cutting edge in the direction of the scraper, which will force the substrate on the printing pad to move along with it. As a result, double image will be generated in printing.

Troubleshooting: Take appropriate measures based on the above analysis of ghosting.If the cause of ghosting is due to the locator clearance is too large, it should be adjusted between the locator and the screen location courtyard.After the adjustment, fix the position, and then start up the printing, and the ghosting fault will no longer appear.

The printing platform is not flat or the suction is too large to leave mark marks on the printed matter

Cause analysis: In the process of screen printing, marks are usually left on the prints due to the uneven printing platform and too large air holes or the vacuum passing in the air pumping process.

The attached

Troubleshooting: It can be solved by adjusting the vacuum degree of air extraction. If the vacuum degree cannot be adjusted, it can be solved by placing a piece of paper between the printing platform and the substrate, such as kraft paper.Because the vacuum can be reduced when the paper is placed, this method can also avoid the blowhole mark left on the print.