A clean cut edge is the be-all and end-all when cutting film on a roll. But how do you achieve this? Here are some recommendations for daily practice.
Tapes with a clean cut edge
Cutting like a pro – it’s not that difficult. Once you understand a few basic correlations. In this installment of our parting off series, we take a closer look at seven parameters. They have a major influence on whether the cut edge frays, whether the roll is crushed, whether dust or adhesive residue forms – or not.
The following topics are covered:
1. Rotational speed: fast is not always better
2. Immersion speed in the medium: High control instead of high pressure
3. Special case of a stationary blade
4. Lubrication of the blade: Always, if possible
5. Temperature of the blade: When in doubt, take a break
6. Ambient temperature: Lubricate a lot when hot
7. Winding tension of the medium: It is better to rewind once in a while
1. rotational speed: fast is not always better
A higher rotational speed is not always the better choice. The faster the roller turns, the more often the blade passes a point where it has already cut. This generates more friction and therefore more heat and tends to create more dust and more fringes as the blade repeatedly scrapes along the material that has already been cut. But: The slower the roller is turned, the less torque the motor develops – until at some point the point is reached where the blade can no longer penetrate, especially with tough material.
Our recommendation: A good middle ground for NEPATA slitting machines is a setting of 50 to 70 percent of the maximum speed.
2. immersion speed in the medium: high control instead of high pressure
Of course, you have to apply a certain amount of force. However, you must never press down too hard on the cutting unit. This would crush the material. In addition, the blade may even bend if too much force is applied. This would contribute to fraying. However, if you are too hesitant and do not have a firm grip on the cutting lever, you run the risk of the blade bouncing when it comes into contact with the roller and destroying the material.
Our recommendation: gentle pressure with a high level of control over the cut-off lever. This requires a strong hand, not necessarily strong downward pressure. If you notice that the whole thing is coming to a standstill, the rotational speed must be increased slightly so that more torque is available. For many media, a medium, fast speed is recommended (flock film, flex film, laminating film), for other materials rather low speed (e.g. magnetic films, reflective adhesive films). Tests and experience are required here.
Cut off foils
3. special case standing blade
As a rule, cutting with a moving blade is recommended, i.e. the blade rotates passively on the material. This results in less friction and therefore less heat in the medium, and the cutting performance is distributed evenly around the circumference of the blade. However, there are media that cannot be cut with a rotating blade, e.g. foam adhesive films. In this case, the blade on the NEPATA cutters can be blocked. The stationary blade ensures a higher cutting force in the system. However, there is considerably more friction. Again, this generates heat and the adhesive can smear.
Our recommendation: With small diameters, the problem with the upright blade is less of an issue. Large belts that require an upright blade should remain the exception with this type of parting off system. Do not carry out too many operations in succession. In between, the blade can be rubbed clean from time to time by cutting a less demanding foil or an empty cardboard tube. In addition, the blade position should be changed from time to time so that it is not always cutting in the same place.
Foam adhesive tape
4. lubricate the blade: Always, if possible
Lubrication is very important when cutting many media. It reduces friction and therefore heat generation. Less adhesive residue builds up on the blade. There are not only oil-based lubricants, but also water-based ones. These are ideal if you are concerned that the silicone could damage the adhesive strength of the film. With the automatic jaw lubrication system developed by NEPATA (((Link Schmiersystem))), very small amounts of lubricant are also sufficient, so that we have not yet had any negative experiences in daily practice.
Our recommendation: Use lubricant wherever it does no harm!
NEPATA lubrication system – tank
5. temperature of the blade: If in doubt, take a break
Each cut increases the temperature of the blade. If a large number of cuts are made in quick succession, the blade can become so hot that the cutting pattern is impaired. More and more adhesive can escape from the cut edges of the film until the individual layers fuse together.
This happens more quickly with tough materials, especially if the blade is used upright. In extreme cases, the blade may be deformed. However, we are talking here about hundreds of fast cutting processes, e.g. when producing very narrow strips.
Our recommendation: Give the blade a break after several cuts so that it can cool down sufficiently.
6. ambient temperature: Lubricate a lot in hot weather
Most films are more difficult to cut the higher the general temperature or the temperature of the medium. This is particularly true for adhesive films: adhesives change their viscosity in warm conditions and smear more easily. This is particularly important in non-air-conditioned rooms in summer, when it can be 35 degrees Celsius in the hall.
Our recommendation: Slow down a little at higher ambient temperatures and always lubricate carefully.
7. winding tension of the medium: it is better to rewind it once again
The winding tension is very important. Loosely wound media with loose, sliding windings are generally much more difficult to cut than tightly wound rolls (or linerless media). The loose windings lead to wave movement between the layers. The displacement results in one hundred percent fringe formation. But beware: Windings that are too tight are also problematic, as the roll then becomes too compact to be able to cut through the individual layers at all.
Our recommendation: If such material comes onto the machine, it is better to rewind it properly. Rewinding on a NEPATA machine under controlled web tension ensures that the winding tension is perfect for beautiful cut-off results.
Extra tip: Training and video “Cutting like a pro”
Of course, there are other parameters that have an influence on whether the cut edge is clean or whether there are problems when parting off. If you want to turn your employees into real cut-off professionals, we are happy to offer training courses NEPATA slitting machines and conversion centers with slitting unit to. Or take a look at our video “Cut off like a pro”.
Previous articles in our Abstech series:
