1. The basic structure of scoring and slotting unit

The purpose of slotting is to cut a certain width and depth on the flap of a cardboard. When making the carton, the knife must be diantled when the height of the carton exceeds the maximum distance between two slotting knives, and the position must be adjusted accurately, otherwise it will cause the equipment and tools damaged, also reduce production efficiency and increase production costs.

The scoring and slotting unit is composed of slotting unit, scoring unit, angel cutting unit and trimming unit. The slotting unit consists of an upper slotting knife, a lower slotting knife and a scrap knife. Of those, the lower slotting knife has four round steel plates, and the distance among them is exactly the thickness of the upper slotting knife. The scrap knife is used to remove the paper scraps left in the lower slotting knife to avoid shut down due to paper jam. Generally the scrap knife is made of copper.

Some slotters have two scored shafts, while others have one. Similarly, some slotting machines have two slotting shafts, while others have one. Two scored shafts are used for initial and secondary scoring, or pre-creasing and scoring, respectively.

There is a row of scoring rollers on the scored shaft. These steel scoring rollers have different shapes according to different purpose. When processing heavy gram cardboard, high pressure scoring roller should be used , so the scoring accuracy can be ensured. When the flute height increased, the width of the scoring should also be increased, so as to avoid the inner layer cracks .The scoring can be flat or have a 0.5mm to 0.4mm raised.

2.Introduction of each part’s

Scoring unit: The  is to scoring several lines out of the cardboard to facilitate formation.

Angel cutting unit: Mainly divided into knife holder, blade and anvil. The  is to remove the excess pieces of paper at both ends of the tongue joint.

Trimming unit: It is mainly divided into two semi-circular steel trimming knives respectively, whose  is to cut off the excess paper edges. Basically not use any more.

Double shaft knife holder: Mainly used to narrow the width of slotting.

Pre-creaser: Also called crushing roller, it is to install a pair of metal scoring rollers directly in front of the slotting knife. Its main  is to make pre-creasing adjustment for scroing, in order to facilitate the formation of the carton, and prevent score cracking. If pre-creaser with power, it can better achieve a certain degree of pre-pressure and line speed.

3.Process details in production

Anti-cracking crushing roller: The gap should be less than the half of the thickness of the cardboard, and the standard is not to crush the cardboard.

Scoring roller: The gap is about the half of crushing roller, the standard is not to crush the cardboard.

Slotting knife: The gap of upper knife embedded the lower knife is about 3mm, the gap of clamping is about 5mm, and the upper holder or lower holder should be taped with sponge to anti-skid.

Trimming knife: The upper knife should touch the lower one for more than 6-10mm, and should be sealed vertically.

4.Factors to notice in order to ensure the scoring and slotting effect

It is very crucial for carton’s logistics performance and formation that whether the scoring and slotting is good . When the scoring is skew, carton formation will not be square enough.

If the slotting edge is too deep, it will break the surface layer, the compressive resistance of empty carton will be reduced. Poor scoring or slotting will affect the production efficiency of the post-process, so the scoring must be straight and deep. The slotting edge should be ooth, not rough.

In order to achieve good slotting and scoring effect, we must pay attention to the following factors:

●Slotting knife wear

Slotting knives are consumables among the printing components. The major problems may occur including slotting knife is rough and wear, and failing to cutting off the paper scrap. The main reason is the slotting knife wear. After the slotting knife used for a period of time, the blade wear and tear, getting thinner, and there will be a large gap between the upper and lower knives, resulting in the paper is no longer being cut but tore. Then the edge of the paper is easy to break and become rough. So we need to check the slotting knife regularly, and screw must be fastening on a regular basis.

●Slotting depth

Slotting knife is divided into upper knife and lower knife, the depth of upper and lower knife is different, so is the cutting effect. Conventional production of single wall cardboard and double wall cardboard has a certain standard cutting depth, single wall is shallow, while double wall is deep.

In addition to paying attention to the depth of the slotting, the scrap plate of slotting knife holder should also be noted. When the scrap plate is worn, the paper is easy to get stuck in the slotting knife, resulting in the expansion of the lower knife holder, which leads to a larger gap between the upper and lower knife, resulting in rough slotting edge and rupture.

●Scoring roller gap and scoring depth

Scoring is divided into pre-creasing and scoring. Crushing roller is mainly to destroy the flute, that is, after the flute crushed, it is conducive to scoring. Generally, the gap of crushing roller is half of the thickness of cardboard, that is to say, if the thickness of cardboard is 6mm, the gap of crushing roller is 3mm, so as to make it more matching. Scoring depth in general should not crush the cardboard. The depth can be adjusted according to the thickness of the paper and the crushing roller.

●Slotting paper guide shaft

The paper guide shaft of the slotting knife holder plays a transfer role in the slotting process, if the height difference between the paper guide shaft and the lower slotting knife is too large, the cardboard can not be supported in the slotting process, which exacerbate the run-out. Paper guide shaft is to ensure the cardboard oothly transferred to the stacking unit, so the role of the paper guide shaft is also very critical.

5.How to solve the score cracking by adjusting scoring ?

             ●Improved plans of scoring equipment

Pre-creaser improvement: Some of the all factories do not have pre-creaser, it is highly to consider converting a pull paper roller into pre-creaser. And this can be also applied to those whom having pre-creaser, in this way, the probability of score cracking will be greatly reduced after two pre-creasing.

Scoring roller improvement: The width and depth of the scoring should be reasonably calculated. You can also make the scoring roller larger, so that the run out of the scoring roller will be reduced, that will be conducive to scoring.

1) If two pre-creasing are selected, pre-creasing gap must be gradually reduced, and put them in order from large to all, and check if the pre-creasing position is correct.

2) The scoring roller pressure should be gradually increased, in principle of not cracking the cardboard.

3)To regularly check the scoring depth, and to correct the roundness and balance of the scoring roller.