Automatic knife positioning can reduce a repetitive setup task, but it does not approve the finished roll. The stored position can be correct while the incoming web, printed image, edge guide, core layout or job revision is different from the last run. Before the operator commits a full mother roll, convert the customer's finished-roll requirement into a controlled slit map, check the references on the machine and measure every lane on the first web. Automation should make the approved method repeatable. It should not replace the approval method.
Start with the finished rolls the customer will use
Write the output specification before entering knife positions. Record the number of lanes, nominal width of every finished roll, permitted width tolerance and the required edge trim on both sides. Add the core inside diameter and width, maximum finished diameter, winding direction, face-in or face-out requirement, artwork orientation and labels or metres per roll. A total web width alone does not define the deliverable.
Use the customer's approved drawing, applicator requirement or physical reference roll where one is available. Mark which edge is the operating reference and show the web's running direction. If lane widths are not equal, identify every lane separately. This avoids a setup that adds up correctly across the web but sends one roll in the wrong position or orientation.
Check the arithmetic as part of job preparation. The lane widths, internal trims and two edge trims must reconcile with the planned usable web. Keep any allowance for web wander or printed register visible rather than hiding it inside one nominal dimension. If the numbers do not reconcile, stop before the roll reaches the slitter.
Turn the requirement into a controlled slit map
Prepare one slit map that shows the operator side, drive side, web centre or reference edge, printed-image position, trim widths, knife positions, lane numbers and core positions. Use the same reference convention on the drawing, machine recipe and inspection record. A position measured from the operator edge cannot be compared safely with a value stored from the opposite side without an explicit conversion.
Identify the approved cutting method as well as the position. Razor, shear and crush slitting use different hardware and setup controls. The slit map should name the blade or knife IDs where tooling is controlled, the holder positions, overlap or engagement method where applicable and the approved safety and maintenance procedure. Automatic movement does not correct an unsuitable blade or worn cutting edge.
Give the map a job number and revision. When artwork, lane arrangement, finished width, trim or core format changes, issue a new revision and decide whether the stored recipe remains valid. Do not let an operator select a familiar customer name and assume that every roll under that name uses the same layout.
Check the incoming web before trusting stored positions
Measure the actual mother-roll width and compare it with the job record. Confirm that the web is threaded to the intended reference, the edge guide is active in the correct mode and the guide sensor is reading the specified edge or line. A knife bank can move to its programmed coordinates while the web itself runs several millimetres away from the position used when the recipe was created.
Check the printed image against the web edge and the slit references. If the print has shifted across the substrate, the lane widths may measure correctly while the cut moves against the artwork. Compare both outer lanes and at least one internal reference. After a splice, material-width change or new roll, repeat the reference check according to the approved job procedure.
Record any correction to web position separately from a correction to knife position. Moving both at once can produce an acceptable sample without showing which reference was wrong. The next shift then inherits a setting that cannot be explained or reproduced.
Match cores and rewind lanes to the same map
Set the cores from the lane identification, not by eye after the knives have moved. Verify core inside diameter, actual core width, shaft or mandrel location and the required gap between neighbouring rolls. Mark non-equal lanes physically so that a roll is not packed under the wrong size after rewinding.
Align the core to the intended slit web and check for planned overhang or inset. A correctly slit web can still make an unacceptable roll if the core is too wide, too narrow or displaced. Record the customer rule for core exposure, label direction and roll identification on the same release sheet used for width checks.
Confirm the rewind arrangement and tension grouping for the real lane pattern. Narrow and wide lanes may not behave the same way. The machine configuration, substrate, adhesive construction and finished diameter need to be reviewed together. Use the equipment manufacturer's procedure when setting shafts, chucks, tension and winding controls.
Measure the first web before full production
Run enough material at a controlled condition to stabilise the web, then stop or sample by the approved safe method. Measure every finished lane and both edge trims with the agreed instrument. Check the result against the slit map, not against the values shown on the machine screen. Mark the samples with the job, roll, lane, running direction, date and operator.
Inspect the slit edge, printed-image position, core alignment and winding orientation at the same time. Where the job has a liner, laminate or sensitive film, include the relevant edge, dust, curl or damage check. Measure the first completed roll again if winding tension or finished diameter can affect the width reading or edge condition.
Hold the first roll until the width and orientation record is complete. If one lane is wrong, do not average the readings or release the other rolls without tracing the cause. Check the web reference, recipe revision, knife holder, core location and measurement method, then repeat the approval sample after correction.
Save a recipe only after the physical result is approved
PRATI's current information describes automatic blade positioning on finishing equipment, including FASTCUT on SATURN Next and manual or automatic positioning on DIGIFASTone. The maker also describes job-support functions such as MAKE READY and ETICKET on SATURN Next. Confirm the available configuration and functions for the individual machine rather than assuming that a product-family description applies to every installation.
Save or update the job recipe only after the measured roll agrees with the approved map. Keep the recipe name, revision, machine, knife arrangement, web reference, core layout and first-roll record linked. Note any manual offset and why it was required. A silent offset can make the next repeat job faster to start but harder to diagnose.
Royal Coat represents PRATI finishing technology across India, Bangladesh, Sri Lanka, Nigeria and Kenya. For a slitting review, send the mother-web construction and width, printed layout, slit map, finished-roll sizes and tolerances, core data, winding orientation, present knife system, machine details and samples showing the problem.
Questions from production and purchasing teams
What to ask about automatic slitting setup verification
Does automatic knife positioning guarantee the finished-roll width?
No. It positions the configured knife holders, but the actual result still depends on the correct job revision, web reference, incoming web, cutting condition, cores and measurement of the first roll.
What should a slitter slit map contain?
Show the running direction, operator and drive sides, reference edge or centre, printed image, every lane and trim width, knife position, core position, winding orientation, job number and revision.
Why can the lane widths be correct while the print-to-slit position is wrong?
The whole printed image or web can move across the machine while the distance between knives remains correct. Width and print register therefore need separate checks.
When should a stored slitting recipe be rechecked?
Recheck it after any layout, artwork, material, web-width, trim, core or machine change, and whenever the web reference or first-roll measurement does not match the approved record.
How should the first finished roll be approved?
Measure every lane and both trims, verify print position, edge quality, core alignment and winding orientation, identify the samples and hold the roll until the recorded checks pass.