1.How do equipment accuracy and condition affect dimensional deviations?
Vibration and wear of the cutter shaft system: This is the primary factor causing width deviations. For example, in one case, cutter shaft vibration caused the product width tolerance to reach ±0.3mm, far exceeding the ±0.1mm standard. The causes are usually increased bearing clearance, excessive radial runout of the cutter shaft, or tool imbalance.
Control standards: Cutter shaft radial runout should be controlled to <0.01mm; bearing clearance should be controlled to 0.02-0.03mm using pre-tightening technology; residual imbalance in online dynamic balancing should be less than 0.5g·mm/kg.
Improper tool condition and clearance settings: Tool wear or unreasonable settings for upper and lower tool clearance and overlap will not only produce burrs but also affect the actual kerf width.
Control standards: The upper and lower tool clearance should typically be 8%-12% of the material thickness; tool overlap needs to be precisely adjusted according to the thickness (e.g., 0.03-0.05mm for thin plates below 0.3mm). The tool edge roughness should be less than Ra 0.4μm.
2.How do process parameters affect dimensional deviations?
Unstable tension control: Excessive tension fluctuations can cause the steel strip to stretch and deform or deviate during slitting, directly affecting the width consistency after slitting. Precision cutting requires establishing a linkage mechanism between tension and speed (e.g., V²·T = constant value).
Control standard: A closed-loop tension control system should be used to control tension fluctuations within ±5%.
Mismatch between cutting speed and material: Excessive speed will exacerbate vibration, while excessive speed may affect production efficiency. Different materials and thicknesses of cold-rolled coils have their recommended linear speed ranges.
Control standard: For example, for 0.3-1.2mm cold-rolled low-carbon steel, the recommended linear speed is 60-80 m/min. For every 0.1mm change in thickness, the speed should be adjusted by ±5%.
3.How do material properties affect dimensional deviations?
Incoming sheet shape and thickness unevenness: If the incoming sheet itself has camber, waviness, or uneven transverse thickness (wedge shape), the stress release after slitting will cause additional deformation and width fluctuations in the strip.
Residual stress: Residual stress inside the steel coil is redistributed during slitting, which may also cause slight changes in the strip size.
4.How do I determine if the deviation is "out of control"?
Before investigating the cause, it's crucial to confirm whether the deviation truly exceeds the standard. According to available information, there are specific regulations regarding the permissible width deviation of slit cold-rolled steel sheets (strips).
For example, for steel strips with a thickness between 0.4 and 1.0 mm:
When the width is ≤125 mm, the permissible deviation is +0.3 mm.
When the width is between 125 and 250 mm, the permissible deviation is +0.6 mm.
5.What are some quick troubleshooting tips?
Equipment Inspection: With the machine stopped, check the radial runout of the cutter shaft, tool clearance, and wear.
Process Inspection: Review production records to ensure tension and speed are within recommended ranges and exhibit minimal fluctuations.
Incoming Material Inspection: Conduct random checks on the thickness uniformity and shape of the raw materials.