How to Pull an Impression on a Flexo PressThe key to getting a great looking image from a press run is pulling a good impression. While there are many opinions on this term and procedure, this article will focus on the process of bringing a substrate into contact with an inked plate and applying just the right amount of pressure to get the highest quality results.
Before you begin, make sure the main computer is set to "print". Turn off the printing at each individual station, using it's print button, making sure that the print indicator is not lit. Start the press in idle.
Begin by going to the first printing station and pressing the print button, which will start the printing process. Turn the vertical adjustment knobs, located on top of the station, clockwise so that the cylinder goes down and makes contact with the substrate. Try to keep the pressure even on both sides of the cylinder as you lower it. After the image has begun printing evenly across the entire width of the printing material, back off of the vertical adjustment, so that the image is barely printing.
Turn the horizontal adjustment knobs, located at the rear of the station, clockwise one-quarter of a turn, adjusting the plate so that it goes forward. Again, apply an even amount of pressure on each side as you make this adjustment. If it's not printing, that's where it should be for this step. If it is printing, using the vertical adjustment, back off one-quarter of a turn, then adjust horizontal knobs clockwise again.
Keep going up and forward one-quarter of a turn until the image is not printing. If only one side is printing, adjust that side only, until it is not printing. Once you have reached this step, return to the vertical adjustment. Bring it down until it makes contact and begins to print. Back off the horizontal adjustment until it quits printing. Once more, using the horizontal adjustment, bring it forward so that it starts printing evenly.
Give both vertical and horizontal adjustments a quarter turn. That should do it, and you will have pulled the optimal impression, for both screen and solid plates.
Go to the next station and repeat the procedure. After you have pulled an impression on the second station, turn off printing, and move to the next station. The printing should be turned off after you finish getting an impression on each station, except for the first one. This allows you to align all the remaining plates to the first, making it easier to get them in register.
The reason for adjusting both vertically and horizontally is to get just the right amount of pressure to distribute the ink evenly and cleanly across the surface of the substrate. If there is not enough pressure, it will cause "skipping", where the image will fade in and out. If too much pressure is applied it will cause "haloing", which causes an undesirable outline around parts of the image.
Using these procedures should save time and material, plus produce outstanding results
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