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In the production of corrugated cardboard, the slotting process is the core link that determines the accuracy of the finished product. Burrs generated during the cutting process of the slotter knife not only affect the appearance of the carton, but also lead to unstable stacking, die-cutting misalignment and other chain reactions. This article combines the characteristics of the corrugated industry, from tool selection to intelligent monitoring, to provide you with an in-depth analysis of 10 practical experiences to help you overcome this industry’s persistent problems.
1. Accurate Tool Selection
In the corrugated cardboard processing process, the fan-shaped slotter knife with a special curved edge design is a key tool for precise cutting. The tool’s unique fan-shaped curvature structure perfectly matches the corrugated board’s wavy core layer, creating a continuous cutting path when rotating at high speeds. Compared with traditional straight edge tools, the wavy cutting surface of the arc-shaped slotter knife can reduce cutting resistance by more than 30%, effectively avoiding cardboard edge chipping. Its curved edge adopts precision grinding process, and the radius of the edge is controlled between 0.2-0.5mm, which not only ensures the cutting sharpness, but also prolongs the service life of the tool. In automated production lines, this specially designed slotter knife, together with the intelligent creasing system, can achieve efficient processing of more than 120 meters per minute, while ensuring that the error in grooving depth is controlled within the range of ±0.1mm, which significantly improves the molding accuracy of corrugated cartons.
2. Proper Blade Angle
The fine tuning of the blade angle has a significant impact on cutting results. Too small an angle will squeeze the paper fibers, while too large an angle will reduce the strength of the knife tip. After a large number of experiments, the front angle of the corrugated paper slotter blade is controlled at 18°±2°, which ensures sharpness and reduces fiber tearing. The back angle (the angle of inclination of the knife blade) is recommended to be kept at 5°-8° to avoid friction between the back of the knife and the cardboard, resulting in burrs. If dealing with E corrugated cardboard, the front angle can be increased to 20° to cope with its higher shear strength.
3. Dynamic Sharpening
Establishing a tool sharpening SOP (Standard Operating Procedure) is critical. The 5-minute maintenance rule for each shift means that for every 8 hours of production, a diamond grinding wheel should be used for micro-sharpening, focusing on repairing micro-notches on the knife edge. The use of laser tool setting instrument to detect the straightness of the edge, the error of more than 0.02mm immediately replace the blade, the strict implementation of this process may extend the life of the tool by 40%, the burr rate decreased by 25%.
4. Negative Pressure Dust Removal System
An industrial vacuum cleaner is added to the grooving unit to maintain a negative pressure environment around the knife blade. Experimental data shows that after the dust concentration is reduced from 15mg/m³ to 5mg/m³, the incidence of burr is reduced by 40%. The distance between the dust suction port and the knife edge should be precisely controlled at 3-5mm: too close will affect the chip removal, too far will discount the dust removal effect. It is recommended to choose the equipment with adjustable height of the dust suction port to adapt to different thickness of cardboard.
5. Pre-compression Wheel Synergy
A rubber pre-compression wheel is added prior to slotting to pre-compress the corrugated flute peaks at a pressure of 70% of the face paper thickness. This enables the core paper to deform in advance and reduces the lateral shear force during grooving. A case study of a packaging giant showed that the burr length of E-wafer after pre-compression was reduced from 0.8mm to 0.3mm. Note that the pressure of the pre-compression wheel needs to be dynamically adjusted according to the weight of the cardboard, and it can be increased to 80% for high weight cardboard to minimize burr generation.
6. Speed Matching
Establish a functional relationship between grooving speed and cardboard grammage: V = 12000 / (G^0.6) (V: meters/minute, G: cardboard grammage g/㎡)
For example, for 200g/㎡ cardboard, it is recommended to control the grooving speed at 85 meters/minute. Too fast speed is easy to lead to blade overheating and softening, too slow is to increase the extrusion time, will exacerbate the burr generation. After optimizing speed with this formula, productivity may increase by 10% and burr rate may decrease by 20%.
7. Tool spindle runout compensation
Tool spindle runout is an invisible killer of burrs. Using a laser interferometer to calibrate tool spindle runout on a monthly basis, the error needs to be controlled to within 0.015mm. A case study from an equipment manufacturer showed that for every 0.01mm increase in tool spindle runout, the burr rate increased by 15%. Regularly check the bearing clearance, it is recommended to replace the spindle bearing every 500 hours of operation to ensure the long-term stable operation of the cutter shaft and to minimize burr generation.
8. Humidity Management
Control the humidity in the production workshop in the range of 45%-55%RH. Too high humidity causes cardboard to soften and fibers to stick when cutting; too low makes cardboard brittle and prone to chipping. Equipped with online humidity monitor, with small humidification / dehumidification equipment to achieve micro-environmental control. Experimental data shows that after the humidity is stabilized, the cardboard bursting rate drops by 30%, and the burr rate is reduced simultaneously.
9. Tool sequence optimization
For multi-tool head equipment, it is recommended to arrange the knives in the order from thin to thick and from hard to soft. For example, cut E corrugated first, then B corrugated, and finally face paper. This arrangement reduces the cutting load on the subsequent cutterheads and has been proven to reduce the overall burr rate by 25%. If dealing with laminated cardboard, the knife sequence should be dynamically adjusted according to the hardness of each layer to ensure that the cutting force is evenly distributed.
10. Intelligent Monitoring
Deploying machine vision system, installing 2 mega-pixel industrial camera in the paper receiving department to detect the length of burr in real time. When detecting 3 consecutive cardboard burrs over 0.5mm, the following actions are automatically triggered: reduce the production line speed by 10%, send an early warning to the maintenance terminal, and start the spare tool warm-up program in order to control the burr generation.
The problem of corrugated cardboard grooving burrs needs to be tackled from the four dimensions of tools, processes, equipment and environment. It is recommended that companies establish tool life profiles, implement TPM (Total Productive Maintenance), and introduce intelligent monitoring systems, so that the slotting process can truly become a tool for improving carton quality. Through continuous optimization, you will find that: solving the burr problem not only improves product quality, but also significantly reduces the overall cost and enhances market competitiveness.
