Production decisions
Splicing rolls: cut both lengths together
When a roll runs out, splicing on the next avoids rethreading the entire web through the machine. But a splice only works if both edges match perfectly. The trick is not to cut well twice, but to cut just once.
In a printing press or web converting machine, the roll runs out. Always. And when it does, there are two options.
The first is to thread the new roll from scratch: feed the web through the entire machine path again, roller by roller, unit by unit. On machines with many rollers, that means a long time with the line stopped.
The second is to splice: join the end of the roll that is running out to the beginning of the new one, and let the web itself pull the next length through the entire machine. The path is already threaded; you just have to use it.
The second option is much faster. But there is one condition: the splice must be made properly. A crooked splice, a step or a protruding edge catches on a roller, tears the web or jams the machine. Then you have lost more time than you hoped to save.
How it was done, and why it failed
The starting method was familiar in many workshops: an aluminium plate with a groove to guide the utility knife, and everything else done freehand.
Over the years, the groove had been wrecked. Thousands of blade passes over a soft material had widened it, and the knife was no longer guided: it wandered. The cut came out uneven, and an uneven cut cannot make a clean splice.
But there was a second, less obvious problem: the web was not clamped. One end was cut, then the other, and then they had to be brought together by hand. Each step was another opportunity for something to move.
The key idea: overlap and cut just once
If you cut both ends separately, you have to get it right twice. And even if you do, you still have to bring them together afterwards without any movement.
The solution is to change the sequence:
- Overlap the two ends, one on top of the other, on the table.
- Square them against a side stop, so the cut is at 90° to the edge of the web.
- Clamp them with quick-release pressure bars.
- Cut both together, in a single pass, following the guide.
Because both lengths are cut together, one edge is the exact negative of the other. There is nothing to get right twice: if the cut deviates by a tenth of a millimetre, it deviates equally on both, and they still match perfectly.
It is the same principle carpenters use when they cut two pieces together to make them fit: you are not looking for a perfect cut, but two identical cuts.
After cutting: join without releasing
This is the second half of the method, and it is just as important.
The bars keep clamping both lengths while the joint is made. The offcuts are removed, only the edges next to the cut are lifted, splicing tape is placed underneath with the adhesive facing up, and the edges are lowered onto it. They stick in place, edge to edge, without overlapping.
Another strip is then applied to the top face. The result is a butt splice with tape on both sides: no step, no overlap thickening the web, and a joint reinforced on both sides.
Keeping the web clamped throughout is what makes the splice come out the same every time, whoever makes it.
Where to splice
A practical detail worth knowing if you work with valuable material.
When the web carries expensive elements—in this case, tickets with an RFID inlay inside—the splice is not made in the middle of the product. It is made in the blank leader or trailer at the beginning or end of the roll, which is there precisely for operations like this. No chip is wasted, and the joint only has one job: to let the web pass through the machine without problems.
And if the printing on one length ever needs aligning with the other, the table can accommodate visual references, such as laser-engraved marks.
What happened afterwards
The table was built in 2021. Today it is used daily across three shifts, shared between two machines: it passes from one operator to another.
What they value most is precisely what you do not see: the operation is so simple that it leaves no room for error. Overlap, square, clamp, cut, join. The cut comes out perfect, and so does the joint, whoever makes it and whatever the time of day.
The takeaway
If your line makes splices by hand:
- Cut both lengths together, overlapped. Two identical cuts always match; two good cuts do not necessarily match.
- Square against a stop, rather than by eye.
- Keep the web clamped throughout the process, not just during cutting.
- Guide the knife with something that will not wear out through use.
- Butt-join with tape on both sides, to avoid a step.
- Splice in the blank section if the product is valuable.
A properly made splice is the difference between saving the rethreading time and losing the afternoon clearing a jammed machine.
At 7Axis Industrial, we design and manufacture production tooling that makes a manual operation come out the same every time, whoever performs it.