1.What is the impact of the core material?
Insufficient material strength
The core is usually made of paper (kraft paper, fiber paper), plastic (PVC, PP) or metal (steel, aluminum). If the material selected is of low strength (such as insufficient thickness of paper core, poor quality of plastic core), or there are material defects (such as excessive moisture content of paper core resulting in reduced strength, and loose welding of metal core), it is easy to deform when subjected to the weight of the coil or external force.
2.What influence does the structural design have on the core?
Unreasonable structural design
Poor uniformity of core wall thickness: Local thin wall thickness will cause local collapse when subjected to force.
The core length does not match the roll material: When the core is shorter than the roll width, the edge is easily deformed due to concentrated force; when it is longer than the roll material, the protruding part is easily damaged by collision.
3.In what cases is deformation caused by improper force?
Abnormal winding tension
During the production process, if the winding machine tension is too large or uneven: ◦ Excessive tension will cause the coil to exert radial pressure on the core, causing the core to be "squeezed" and deformed (such as ovalization, concave in the middle). ◦ Uneven tension (such as left and right tension deviation > 5%) will cause excessive force on one side of the core, resulting in eccentric deformation.
Unbalanced force during stacking or hoisting ◦ During stacking, if multiple layers of coils are stacked too high, the bottom core needs to bear the weight of all the coils above. Long-term pressure will cause the core to bend axially or collapse radially (especially paper cores). ◦ During hoisting, if the contact area between the hoist (such as hook, forklift) and the core is too small, or the hoisting point is off-center, local stress concentration will occur, causing the core to be "cracked" or "bent".
Shock and vibration during transportation
If the coil is not firmly fixed during transportation, it will shake with the bumps of the vehicle, and the coil core will repeatedly rub or collide with the fixing device (such as baffles and ropes), causing local deformation; continuous vibration during long-distance transportation may also cause fatigue damage to the coil core.
4.What influence do environmental factors have?
Temperature and humidity changes
Paper cores are sensitive to humidity: in high humidity environments, paper absorbs moisture and expands, its strength decreases, and it is easily deformed by pressure; in low humidity environments, paper becomes dry and brittle, its impact resistance decreases, and it is easy to crack.
Plastic cores may soften and lose strength in high temperature environments (such as in summer carriages), and they cannot withstand the weight of the rolls and deform.
Storage time is too long
When the rolls are stacked for a long time, the cores continue to be subjected to radial pressure, especially for thick specifications (such as thickness > 0.8mm) and wide width (such as width > 1.2m). The gravity will cause the cores to slowly undergo plastic deformation (such as changing from round to elliptical).
5.What impact will operating process problems have?
Core installation deviation
If the coaxiality deviation between the core and the main shaft of the coiler is too large during production (such as skewed installation), the core will generate additional centrifugal force due to "eccentric rotation" during the coiling process, causing deformation.
Improper coil unloading
If the coil is directly dropped from a high place during unloading, or the core is pried with a hard object, it will cause an instantaneous impact on the core, causing local damage or deformation.