The shape of the carton and the strength of the cardboard will affect the structural strength of the carton. Generally, the higher the carton strength requirement, the relatively higher the relative cost of the cardboard. However, the carton manufacturer often neglects the cost burden of the cardboard strength destruction during the processing.
Corrugated board strength Each corrugated board manufacturer invests in expensive manufacturing equipment and a large amount of manpower in the manufacturing process. It is precisely controlling every link and wants to manufacture the same or higher quality corrugated board at a lower cost than the industry. .
Enhance the rigidity, compressive strength and impact strength of corrugated paperboard and the core paper type, type of corrugation, corrugation height, bonding strength and corrugation strength under the general requirement that vertical compression strength (ECT) is greater than burst strength (BS). All are closely related.
The process of printing and cutting to destroy the strength of damaged corrugated cardboard boxes during the process of printing and cutting, how to minimize the extent of damage to the cardboard or not to cause damage, will undoubtedly greatly improve the strength of the carton and reduce the cost.
In the process of printing and cutting, there are several parts where the cardboard is easily damaged when it passes through. 1. Feed roll
2. Print plate
3. Print and cut various parts of the Pull collar
4. Rotary die cutter This article only discusses the effect of the paper feeding process on the strength of the carton on the Flexo press.
General Flexo printing machine paper feeding method 1. Kickboard type (kickboard push and upper and lower feed roller clamping combination)
The speed of the kickboard and the speed of the feed roller cannot be maintained at the same speed, and the length of the paper cannot be extended. It is necessary to completely rely on the feed roller for clamping and transmission. The paperboard strength is destructive and has gradually been eliminated.
2. Leading edge paper feeding (suction suction wheel and upper and lower paper feed roller clamping combination)
The speed of the transfer wheel and the speed of the feed roller can be maintained at the same speed, and the length of the feed paper can be extended to assist the feed roller to transfer the paper. The destructiveness of the cardboard strength can be controlled and reduced. Now mainstream equipment is widely used.
3. Leading edge paper (suction conveyor wheel directly extended to the printing unit)
No upper and lower feed rollers hold the paper directly to the printing unit. The strength of the paperboard is minimally damaged, and new types of equipment have not yet been commonly used.
In order to ensure the accuracy of the paper feeding speed through the printing press, the paper feeding wheel is still an indispensable device in the existing equipment. It has enough clamping force and reduces the damage to the paper board strength. Wheels should consider factors:
1. The actual radius of the outer diameter A feed roller is different from the actual feed radius of B, C, and D. The change of the feed point radius of each feed point in the feed roller pressure point causes a difference with the surface speed of the lower feed roller.
When the outer diameter is too small, the same drag force must be tighter.
2. Hardness The surface hardness of most new feed rollers is between 30 and 35 degrees.
Long-term use will gradually become hard due to factors such as time, exposure to heat and light, and abrasion. It must be checked regularly to avoid damage to corrugated cardboard. When the hardness exceeds 40 degrees, it should be replaced.
â—† The relationship between the surface hardness and clamping tightness of the paper feed roller of the C board (set pressure 40PSI does not reach the strength of the damaged board)
3. The frictional force of the contact paperboard holding the cardboard is generally 1.2mm to 2.0mm, which prevents the paperboard from slipping when passing through the feed roller. The higher the coefficient of friction of the material of the feed roller, the greater the same degree of clamping can have a greater drag force. The shape of the surface of the lower paper feed roller (smooth surface, cross pattern, horizontal grain, etc.) has a significant difference in drag force. Improper guttering on the surface of the feed roller can affect the supporting force or the deformation space.
â—† The maximum pressure reference value of various corrugated paperboards (feed roller pressure point pressure)
The above is a general paper board reference value, and the five-layer cardboard (eg, B/C) is subject to pressure at a lower value (40 psi).
4. Causes of increase in clamping pressure due to rigid flexing during high-speed operation 1. The thickness variation caused by the carton cover pressure line cannot be reliably transmitted.
2. Cannot extend the paper to the printing unit. Due to insufficient friction, it is necessary to hold the grip tighter to increase the drag force.
3. The cardboard stack has too much weight to increase and must be gripped tighter to increase the drag force.
4. When the stack of cardboard is dropped on the paper moving table, the grip must be tightened to increase the drag force.
5. The position of the rear backplate is large under the cardboard, and it is necessary to hold the stack cardboard more tightly to increase the drag force.
Conclusion In the face of fierce competition in the corrugated carton industry, more and more factories pay attention to the upgrading of production technology, relying solely on their own bit by bit to accumulate, and often rely on others' experience and technology as a shortcut, but now many problems lie in the equipment. Bad, it is tricky to improve. Choosing equipment that is truly suitable for your production needs is a topic that cannot be ignored in the face of competition. (Longsheng Industrial (Taiwan) Co., Ltd. You Lichuan)