A guide to troubleshooting label dies and related tooling

In general most problems can be divided into one or more of the following categories. These categories are shown in Figure 10.1. 

Within each of these three categories there are then a whole variety of parameters to consider when looking to troubleshoot and solve problems. Parameters as diverse as a damaged die, polluted or worn bearers, variations in liner thickness, incorrect web tension, excessive pressure on the pressure bridge, deflection of the rotary die or magnetic cylinder, stripping angle too sharp, or incorrect layout.

As can be seen, many factors may be involved. It is therefore necessary to try to work out what is happening. Use a process of deduction or analysis; work out what you can see from studying the tool, bearings, cylinder, web or pressure gauge. Assess which of the three categories in the chart may be the most relevant or applicable to the specific problem that is occurring. Narrow things down as much as possible and, above all, do not attempt to guess.

To aid the troubleshooting process . both for the operator and for the tooling supplier . proper die-cutting records should be kept. These should identify:

• The date(s) the die has been run

• The number of revolutions run on each date

• The date(s) the die has been returned for repair

• A description of the material being cut (type, caliper, liner) during each run

• The starting and ending pressure during each run.

For the press operator, there are then a number of first steps that can be taken if the die is not cutting correctly, including:

• Making sure the die was made for the material being cut. Check the liner thickness to make sure that it is uniform. If the die has been made for a different material, then a stepped anvil may help

• Checking the edge of the label for hairs. If it is cut cleanly, the problem may be the adhesive. Again, check that the correct material is being used. Also check to see whether the die is bouncing or flexing. Adjust the pressure if necessary.

• Check to see whether the correct magnetic cylinder is being used. Change if necessary

• Establishing whether the die stopped cutting from one instant to the next or gradually over time. If so, the anvil roller or magnetic cylinder may be worn. Try a different anvil. Proper lubrication will also greatly reduce the wear of the bearers of the die and the anvil roll surface.

Indeed, lubricating and wiping of the bearers will reduce the friction that causes thermal expansion.Thermal expansion of the bearers will cause the cutting blades to lift away from the anvil roller and can lead to fuzzy cutting or causing the labels to lift with the waste matrix.

Having set-out some basic troubleshooting pointers, let’s now look in more detail at the key problems that may occur during die-cutting process and assess the nature and possible troubleshooting solutions.

WASTE MATRIX BREAKING (REPETITIVE)

Damaged rotary die / flexible die. Check the cutting lines for possible damage. If a rotary die is damaged, send the die back for repair. In case of damaged cutting lines on a flexible die, use a spare flexible die or order a new one. Repairing of small areas of damage is possible by making use of special repair tools.

Worn cutting cylinder / flexible die. Try to finish the job with a plus (corrected) anvil roller or use an adjustable anvil roller system. For flexible dies, you can use a thin film (10-15 .) on the backside of the flexible die or a light coating of spray paint all over the backside or just in the area not cutting. This will lift the die slightly and may enable the job to be finished. In all cases, do not forget to reduce the pressure on the pressure bridge. Flex dies cannot be re-sharpened but some small areas of damage may be repairable with a special tool. Solid rotary cutting dies can be re-sharpened and small areas of damage may be repaired. After the job is finished, send in the rotary die for repair or to be replaced.

Polluted bearers. Check the die for pollution.There may be a build-up of ink, adhesive, paper or film particles that are interfering between surfaces in contact with each other.

Worn bearings. The condition of the bearings should be an integral part of the standard machine maintenance program. Check the bearings in the bearing blocks and replace if necessary. Check for excessive wear or lack of lubrication.

Incorrect position of the label shape in relation to the web direction. Check the position of the label shape and if possible adjust this to prevent the waste from breaking.

Waste matrix too narrow. Check the width of the waste matrix (gap across and around) on all positions as well as the waste along the outside edges.

DAMAGING OF LINER (RANDOM)

Pollution of anvil roller. Check the anvil roller for adhesive build up and paper/film particles.

Damaged anvil roller. Check the anvil roller for damages. If the anvil roller is damaged, send the anvil roller back to the tooling supplier for repair or order a new one.

Irregular thickness of the liner. Measure the caliper (thickness) of the liner and compare this with the specifications of the material supplier. These measurements are indicative, as the caliper of paper is influenced by temperature/relative humidity.

DAMAGING OF LINER (REPETITIVE)

Pollution on the back of the flexible die. Clean the back of the flexible die carefully before mounting the plate to the cylinder.

Pollution / damage on the magnetic cylinder. Clean the magnetic cylinder carefully before putting on a flexible die. If the magnetic cylinder has been damaged or is malfunctioning (e.g. lifting or sinking of magnets), send the cylinder back to the manufacturer for repair. If repair of the magnetic cylinder is not possible or not economical, order a new magnetic cylinder from the tooling supplier.

Worn bearers; magnetic cylinder / rotary die. Send the rotary die or magnetic cylinder in for repair or order a new cylinder.

LABELS GO UP WITH THE WASTE MATRIX (RANDOM) 

Worn cutting cylinder / flexible die. Try to finish the job with a plus (corrected) anvil roller or use an adjustable anvil roller system. For flexible dies, you can use a thin film (10-15 .) on the backside of the flexible die or a light coating of spray paint all over the backside or just in the area not cutting. This will lift the die slightly and may enable the job to be finished. In all cases, do not forget to reduce the pressure on the pressure bridge. Flex dies cannot be re-sharpened but some small areas of damage may be repairable with a special tool. Solid rotary cutting dies can be re-sharpened and small areas of damage may be repaired. After the job is finished, send in the rotary die for repair or to be replaced.

Liner not correctly specified. Try to finish the job with a stepped anvil roller or use an adjustable anvil roller system to compensate for the error. If the liner is too thin, try to use a thin film (10-15 .) on the back of the flexible die. Finally, order a new flexible die with the correct specification or send in the rotary die to determine if the necessary adjustments can be made to the existing die.

Variation in liner thickness (calliper). The thickness (calliper) of a liner can be measured by making use of a micrometer. If the variation in liner thickness is too large, send the material to the material supplier for further inspection and evaluation.

Incorrect lay-out for stripping the waste. If possible, change the lay-out or call the tooling supplier for advice.

Material between bearer and anvil roller. Check the web width and its position between the bearers.

Damaged, polluted or worn anvil roller. Check the anvil roller. If the anvil roller is worn and/or damaged, use a back-up anvil roller. If a back-up anvil roller is not available, send in the cylinder for repair or order a new anvil roller. If the anvil roller is polluted, clean the cylinder.

LABELS GO UP WITH THE WASTE MATRIX (REPETITIVE)

Damaged/worn cutting lines. Check the cutting lines for possible damage. If a rotary die is damaged or worn out, send the die back for repair. In case of damaged cutting lines of a flexible die, use a spare flexible die or order a new one. Repair of a small area of damages on a flexible die may be possible by making use of special repair tools.

Pollution of cutting cylinder / flexible die. Check the die for pollution, adhesive build up and paper/film particles.

Polluted bearers. Check the die for pollution, adhesive build up and paper/film particles.

WASTE MATRIX BREAKING (RANDOM)

Pollution of anvil roller. Check the anvil roller for pollution, adhesive build up and paper/film particles.

Liner not correctly specified. Try to finish the job with a corrected anvil roller or use an adjustable anvil roller system to compensate for the error. If the liner is too thin, try to use a thin film (10-15 .) on the back of the flexible die or very light coating of spray paint. Finally, order a new flexible die with the right specification or send in the rotary die for making the necessary adjustments.

Variation in liner thickness (calliper). Measure the thickness (calliper) of the liner with a micrometer. If the variation in liner thickness is too large, send in the material to the material supplier for further inspection and evaluation.

Worn bearings. The condition of the bearings should be an integral part of the standard machine maintenance program. Check the bearings in the bearing blocks and replace if necessary. Check for excessive wear or lack of lubrication.

Incorrect web tension. Check the web tension and if possible adjust.

Stripping roll too small or stripping angle too sharp. Check diameter of stripping roll and adjust this if possible. If necessary, change the stripping angle under which the waste matrix is being stripped.

DAMAGING OF LINER (REPETITIVE)

Damaged rotary die / flexible die. Check the cutting lines for possible damages. If a rotary die is damaged, send the die back for repair. In case of damaged cutting lines on a flexible die, use a spare flexible die or order a new one. Repairing of small areas of damage is possible by making use of special repair tools.

Stepped anvil roller. Check if by mistake a stepped (plus) anvil roller is being used or if an adjustable anvil roller needs to be reset to a zero position.

Incorrect calliper of liner. If the liner is too thick, the cutting lines will cut too deep into the liner, thus damaging the silicone layer. Use a stepped (minus) anvil roller or use an adjustable anvil roller system to compensate for the difference. Finally, order a new flexible die with the corrected specification or send in the rotary die for the necessary adjustments to be made.

Too much pressure on the pressure bridge. Reduce the pressure on the pressure bridge and reset, then start again.

HIGH PRESSURE ON THE PRESSURE BRIDGE

Worn cutting cylinder / flexible die. Try to finish the job with a plus (corrected) anvil roller or use an adjustable anvil roller system. For flexible dies, use a thin film (10-15 .) on the backside of the flexible die or a light coating of spray paint all over the backside or just in the area not cutting. This will lift the die slightly and may enable the job to be finished. In all cases, do not forget to reduce the pressure on the pressure bridge. Flex dies cannot be re-sharpened but some small areas of damage may be repairable with a special tool. Solid rotary cutting dies can be re-sharpened and small areas of damage may be repaired.

After the job is finished, send in the rotary die for repair or to be replaced.

Flexible die too low / drop too small (rotary die). Flexible die height or the drop (distance between bearer and top of the cutting line) of the rotary die do not match the liner thickness.

Incorrect liner thickness (caliper). Check if the liner thickness is correct.

Stepped anvil roller. Check if by mistake a stepped (minus) anvil roller is being used or that an adjustable anvil roller needs to be reset to a zero position.

Front material too thick. Check that the thickness of the front material (compressed) does not exceed the actual height of the cutting line.

Pollution of the bearers. Check the die for pollution, adhesive build up and paper/film particles.

NO (BAD) CUTTING IN THE MIDDLE OF THE WEB

Deflection of the rotary die / magnetic cylinder. If the diameter of the rotary die / magnetic cylinder is too small this may lead to bending (deflection) of a cylinder. If possible, change the layout of the flexible die or use cylinders with a larger repeat size.

Deflection of the anvil roller. If possible use an anvil roller with a larger repeat size.

CUTTING TOO DEEP IN THE MIDDLE OF THE WEB

Aligning, centreline. Check if the rotary die/magnetic cylinder and the anvil roller have been aligned correctly.

Worn bearings. Check the bearings in the bearing blocks and replace them if necessary. (Checking of bearings should be integrated into the maintenance program of the machine).

Shaft diameter. Check if the shaft diameter corresponds to the inner diameter of the bearings in the bearing blocks.
CUTTING ONLY ONE SIDE

Wrong gear. Check the pitch of the gear if the magnetic cylinder or rotary die is not cutting on the gear side.

Damaged/worn bearers. Check if the bearers of a rotary die or magnetic cylinder are worn or damaged. To check the cutting result, try to put the flexible die onto another magnetic cylinder. If the bearers are worn or damaged, send in the cylinder for repair or order a new one.

Pollution of bearers. Check the die for pollution, adhesive build up and paper/film particles.

INCORRECT LABEL DIMENSIONS

Wrong specifications on tool. Compare the specifications of the label (order form) against the order acknowledgement or packing slip. (The solid rotary or flexible tool will arrive with samples in the box but will demonstrate the cutting performance only. They are not accurate for size.) If the specifications/dimensions of the flexible or rotary die are incorrect, contact the tooling supplier for resolution.

Incorrect web tension. Tension in the web can affect the size of the label in the web direction. If the label size in the web direction is too small, tension may be too high. If the label size is too long, then the tension may be too low.

FINALLY...

If it still not possible to solve the particular die-cutting or tooling problem, then it may be time to get in touch with the tooling supplier.