Another technique for edge trimming on the folder (to continue from last weeks blog post) involves the use of extra thick cutting knives. Typically these are about 1mm thick and come in various diameters to correspond with the total thickness of the piece you are trimming.
The idea here is to run knife against knife and eliminate the counter knives altogether. Set the upper knife as shown, flat side facing in. If your folder has split collars (holders) for mounting the knives, be sure the knife holders are facing the correct way so as to avoid loosening of the collar while running. On older Baumfolders this won’t be an issue since the knives screw into the knife holder.
Placement of the pull-out wheels may differ from technique #1, so experiment. The bare minimum of pull out wheels is almost always better. Also, depending on the type of knife holder you have, you might have the option to add gripper bands. If so, try placing them on the outside of the knives as shown, gripping the waste. You might also try them on the inside of the knife, as well as trying to run with no gripper bands whatsoever.
As with almost all processes in the bindery, time spent on a little experimentation can go a long way toward improving folder productivity. I’ve produced excellent edge trim results with this method on a variety of signatures as well as with finished brochures although some folders took a little more trial and error than others.
This knife-against-knife technique also works extremely well when slitting 2 or 3-up jobs.
** A Word of Caution About Trimming on the Folder **
When using this technique or the technique we described in last week’s Bindery Success Blog post, you’ll need to keep an eye on the quality of the trim and establish a minimum acceptable quality. Many of the OEM trimming tools will handle the cutting but might leave a fuzzy edge which gets more raggedy with every passing sheet. The heavier the piece, the more noticeable the fuzziness and the quicker the dulling of knives.
If you need a guillotine quality edge trim or center trim, be sure to check out our Multi Tool for cutting, specifically engineered for this purpose. The Multi Tool will successfully trim folded stocks up through about .040” thick, whether text or cover.
In addition, the specially designed counter knife setup on the Multi Tool substantially reduces knife changes on long runs. Customers typically get 5-10 times the production life from these tools than from conventional OEM tooling.
More Tips for Better Trimming
Here are a few more easy items to check that can make or break your trimming job, no matter what type of knives you are using:
- Before mounting a new cutting knife, carefully clean the flat side of the knife and the knife holder where the knife is to be seated. This prevents knife wobble which in turn prevents premature wear.
- Be sure the slitter shafts are not bowed. A severe bow will prevent good, even knife contact, it will reduce life expectancy of the knives and you’ll be hard pressed to ever get a satisfactory cut.
- Buy quality knives. Cheap knives may look the same but poor manufacturing technique and low-quality material will show up right away in cutting results.
- Be sure there is no side to side play in the slitter shafts before you lock the knives and counter knives together! This is a very common oversight.