PRIVATE AND CONFIDENTIAL Issues with horizontal clearance: Issue Effect on Strip and Slit edge Effect on Knives Knives set too closely (Insufficient horizontal clearance • Deeper than normal nick • Small break • Jagged line between the two zones • Burr on bottom edge • Knives wear off too quickly • Unnecessary forced imparted to slitter head • Knives often chip Knives set extremely tight • Nick extending through most of the strip • Little or no fracture zone • Excessive Burr • Wavy Edges • Double Shear • Chipping of Knives • Spalled Knives Knives set too far apart (Excessive horizontal clearance) • No noticeable nick • Heavy roll over on the top of the strip • Heavy burr on the bottom of the strip • Knives act like bending dies • Reduced life of knives
Grinding of Slitting Knives Re-grinding of Slitting knives is a very specialized process and extra care should be taken as improper grinding can cause change in: • Microstructure of knives • Strength of cutting edge The above could lead to inferior quality of slitting along with a reduced life of the knives. For slitting knives, the re-grinding should be done on a cylindrical grinding machine and the Outer diameter of all the knives should be ground at the same time. Grinding wheel of a coarser particle size will invariable be softer and have a more open structure in order to be self dressing. This is ideal for the re-grinding of the outer diameter of the knives.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
PRIVATE AND CONFIDENTIAL
Issues with horizontal clearance:
Issue Effect on Strip and Slit edge Effect on Knives
Knives set too closely (Insufficient horizontal clearance
• Deeper than normal nick• Small break• Jagged line between the two zones• Burr on bottom edge
• Knives wear off too quickly• Unnecessary forced imparted to slitter
head• Knives often chip
Knives set extremely tight • Nick extending through most of the strip
• Little or no fracture zone• Excessive Burr• Wavy Edges• Double Shear
• Chipping of Knives• Spalled Knives
Knives set too far apart (Excessive horizontal clearance)
• No noticeable nick• Heavy roll over on the top of the strip• Heavy burr on the bottom of the strip
• Knives act like bending dies• Reduced life of knives
PRIVATE AND CONFIDENTIAL
Issue Effect on Strip and Slit edge
Poor Edge condition • Incorrect horizontal knife clearance• Incorrect vertical clearance or overlap• Separator disk - issues
Knives dull too quickly • Incorrect knife grinding practice• Incorrect knife selection• Speed mismatch• Incorrect vertical/horizontal clearance• Incorrect material selection of knives
Chipping of Knives • Too much vertical overlap• Incorrect alignments• Incorrect use of stripper rings• Incorrect material selection of knives
Marking on strip surface • Issues with knife design• Incorrect spacers usage• Issues with the use of coolant
Wavy edges on the strip • Incorrect vertical/horizontal clearance• Incorrect use of stripper rings
Common slitting problems and solutions
Table: Common slitting problems
PRIVATE AND CONFIDENTIAL
Grinding of Slitting Knives
Re-grinding of Slitting knives is a very specialized process and extra care should be taken as improper grinding can cause change in:
• Microstructure of knives• Strength of cutting edge
The above could lead to inferior quality of slitting along with a reduced life of the knives.
For slitting knives, the re-grinding should be done on a cylindrical grinding machine and the Outer diameter of all the knives should be ground at the same time.
Grinding wheel of a coarser particle size will invariable be softer and have a more open structure in order to be self dressing. This is ideal for the re-grinding of the outer diameter of the knives.
Care should be taken while synchronizing the below to obtain the proper surface finish of between 7-10 rms: