Slitter shaft check-up for your folder…
Are you experiencing slight ripping or nicking on the leading edge of the sheet as it passes through the slitter shafts or perhaps you can’t get good depth on the crease. Or you might be having problems with micro-perforating.
These are usually caused by incorrect pressure settings on the slitter shaft callipers. The simple answer to this problem is to check the couplings and bearings. This procedure can be done in about 2 minutes and will give you valuable information into why there are problems.
1. Put a piece of 100gsm stock into each side of the slitter shaft callipers and push a set of support collars out to each side so they are close to the ends of the shaft and tighten. Then adjust the callipers accordingly (not too tight that you cannot pull the sheet out without ripping the sheet and not too slack so that you can pass a sheet under a collar without applying any pressure).
2. Place your finger underneath the top shaft at one side of the shaft and gently apply upwards pressure. If the sheet now becomes slack this is am indication there is wear in the bearings and couplings.
3. The next step is to place 2 sheets between the collars and once again gently raise the top shaft and check to see if the pressure is tight. If you can put 3 sheets between the collars, apply pressure to the top shaft and the sheets become slack, this means the bearings and couplings are too badly worn to give a high quality crease. For every sheet that is not held this is equal to 0.1mm. Repeat this procedure on the opposite side of the shaft.
Why This Becomes A Problem
Although you set the callipers correctly, when a sheet of stock runs through the shafts, the top shaft lifts up so there is insufficient pressure pushing the creasing insert into the paper stock. The operator thinks, “let’s add more pressure in the calliper setting.” This may make a deeper crease but it also makes the leading edge rip slightly as the device has been placed closer together – but only temporarily. Because of wear, the lead edge of the sheet will push the shafts apart so what you get is a good crease over the balance of the sheet and a nick at the lead edge.
If there is excessive wear the couplings and bearings should be replaced as soon as possible. Check with your mechanic.
To get more information on this subject, or to book one of our technicians to come and give your machine a free check-up and test some of our equipment for you, contact us today.