Analysis of the reasons for the overall position of the carton printing
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The quality of carton printing is good or bad, and people usually understand two aspects. On the one hand, the clarity of the printing, including the consistency of the color, the pattern without adhesion, no ghosting, no leakage. On the other hand, the overprinting accuracy of multi-color printing should generally be within ±1 mm, and a good printing machine can be within ±0.5 mm or even ±0.3 mm. In fact, the printing press also has a very important printing quality index---printing overall position, that is, several colors are accurate, but they are inconsistent with the cardboard reference edge spacing, and the error is large. Because the quality requirements of the general carton are not strict, it is easy to be ignored. If the overall position error exceeds 3mm or 5mm, the problem is more serious.
Regardless of chain feed or automatic paper feed (post-push or leading edge feed), the reference edge of the overall print position is perpendicular to the direction of paperboard transport, and the overall direction (cardboard transport direction) is not easy to produce overall position (unless The cardboard runs diagonally). This article will analyze the reasons for the overall position of the automatic paper-feeding printing press after the paper-feeding method.
The paper feeding of the automatic paper feeding printer is to push the bottom sheet of the paperboard from the bottom of the paper to the upper and lower conveying rollers, and the upper and lower conveying rollers are forwarded to the printing portion, and the automatic feeding is repeated. paper. Analysis of the paperboard transport process can help us find the reason for the overall print position.
First of all, in the process of pushing the paper, the drive chain of the push cardboard should not have a large accumulation gap. The automatic paper feed press pushes the paper into a reciprocating linear motion. Most manufacturers use a crank (slider) guide mechanism plus a rocker slider mechanism. In order to make the mechanism light and wear less, the slider of the crank slider guide mechanism is a bearing. Because the gap between the bearing and the two slides is too large, the uncertainty of the movement of the pusher board will be caused, and the paper feed error will occur, causing the overall printing position. Therefore, how to ensure that the bearing is purely rolling between the two slide plates of the guide rod, and that the bearing and the two sliders have a large gap is the key. The double-bearing structure ensures that the bearing moves freely between the two slides without gaps, regardless of whether the bearing moves down or moves up the slide, so that the mechanism is light and wear-free and eliminates the gap.
The connection between the guide rod and the rocker and the shaft is easy to loose due to the force acting on the alternating load, which is also the cause of the gap caused by the pushing paper. The other mechanisms in the push-pull drive chain are gear transmissions, which improve the machining accuracy of the gears (such as grinding teeth and dents), improve the center-to-center accuracy of each pair of gears (such as machining wall panels with machining centers), and reduce the accumulation of transmissions. The gap improves the accuracy of pushing the paper to push the paper, thereby reducing the overall position of the cardboard printing.
Second, the moment when the cardboard is pushed into the upper and lower paper feed rollers, the paper speed is actually increased from the linear speed of the push paper to an instantaneous speed increase of the upper and lower paper feed rollers. This instantaneous pusher line speed must be less than the upper and lower feed roller line speeds (otherwise, the cardboard will be bowed). How much is small, the ratio of the speed of the two, the matching relationship is very important. It directly affects whether the speed of the cardboard speed is slipping, and whether the paper feeding is accurate, thus affecting the overall printing position. And this is exactly what the printing machine manufacturers can't notice.
When the speed of the main engine is constant, the linear speed of the upper and lower paper feed rollers is a fixed value, and the linear speed of the push paper is a variable, from zero in the rear limit position to zero in the forward maximum to the front limit position, from the front limit position. The zero is then reversed to the maximum to zero at the rear limit position, forming a loop.
Analytical method can be used to derive the linear velocity formula of push cardboard.
V=nπcos(α-α2)cosα2cosα11
C1 is the rear limit point of the rod end
C2 is the front limit point of the rod end
S is the stroke of the rod end (ie the stroke of the push board)
Where: V is the line speed of the rod end (ie the linear speed of the push board)
N is the rotational speed of the crank OB, which is a known amount
It can be seen from Equation 1 that V is a variable and varies depending on the position of C point (α2 is different). By calculation, the different speeds of the push board at different positions can be obtained. According to the proportional relationship between the line speed of the push paper and the line speed of the paper feed roller, after determining the linear speed of pushing the paperboard into the upper and lower paper feed rollers, the optimal position of the paperboard can be determined.
Of course, factors affecting the overall movement of the cardboard printing include factors such as the curvature of the cardboard, the surface roughness of the cardboard, the water content of the paperboard, and the gap between the upper and lower paper feed rollers, but the factors of the equipment are mainly manifested in the above two aspects.