Methodology for New Tooling?

[Stephen Marsh]

I am interested in how folk that live and breath narrow web flexo labels work out their new tooling, any constructive feedback would be great… I am of course open to specific links to further info.

Trying to keep it simple for now, lets just say that we have a 6 colour narrow web press with the following variables (cylinder width being equal and not a factor, say 10” or 253 mm):

060 gear / 7.5” repeat (190.5 mm repeat) = available print cylinders x4
061 gear / 7.625” repeat (193.675 mm repeat) = available print cylinders x6
120 gear / 15” repeat (381 mm repeat) = available print cylinders x6

Our final label size is approx. 4” x 1” narrow edge leading (100 mm x 25 mm narrow edge leading) and the job is 6 colour.​

What is the thought process and steps that go into how you would then estimate the creation of the die/knife?

For example, am I right in assuming that you would rule the 60 gear print cylinders out of hand as there are only 4 and the job is 6 colour? Then we are left with 61 and 120 cylinders that we have 6 of, they can both hold the same across, however around one is roughly double the other.

Please let me know if I have missed any specs or other required info.

This is not a test, it is a request to further my basic level of education – so please take it easy/slow and don’t leave out anything thinking that the knowledge is assumed. Thanks in advance for your help!


Stephen Marsh

 

[Tim-Ellis]

Hello Stephen,

It's a simple thing but you'll need to make sure you also have 6 identical anilox's. Printers don't always have full sets of everything.

Now your 061 gear tooling is going to cost less than the 120 gear tooling but (please correct me if I am wrong) if your page is wider than it is long, you might suffer from press bounce.

Hope this helps.

Cheers

Tim

 

[Stephen Marsh]

Thank you Tim, this is all hypothetical at the moment. I am trying to better understand how one decides to create a tool. The cylinder gearing is known, the cylinder width is also known, as is the number of colours and the final label size and whether it is narrow or wide edge leading.

So how/why does one decide that the step and repeat plus gaps are a given value? I get that one can’t step more labels around the cylinder than the depth available, however what are the extact steps and processes that one takes to come to a final answer?

So, from what you say – all else being equal, the smaller the gear value to get the job done would cost lest in tool making, which is an important but one off cost. What if the larger tool was used, would this offer advantages when reprinting or reusing the same tool for other work? For example, the larger gear tool should use slightly less substrate and press time, are these potential benefits outweighed by other factors?

Thank you for mentioning anilox, it was my impression that these would/could vary in bcm volume depending on the plate content/colour and that all else being equal would not matter (or did you mean something else?). Again, presume nothing in pre-existing knowledge – I am keen to learn.


Stephen Marsh

 

[Bill W]

Your figures quoted using 60 teeth equals a 7.5 repeat as an example, means you are using 1/8" tooling with 8 teeth equaling 1 inch of repeat. If I understand correctly narrow edge leading means you label is 4 inches in the press run direction. Most dies are made with an .125" gap between labels so the matrix will strip cleanly and to minimize material waste. This means if your label is 4 inches in the press direction, adding the gap would make the repeat of one label plus gap be 4.125". Since 8 teeth equal 1 inch of repeat a die would need to have 33 tooth as would be the plate cylinder. Plate cylinders would have to be multiples of 33, 66, 99 etc. in order to have additional images running around the press. None of the tooling listed is a multiple of 33. If you use the 120 tooth plate cylinders you can get 3 images in the press direction with 1" gutters. (Divide 15" repeat by 4, which give you 3 die cavities with 3 inches left. There will be 3 gutters so divide 3 inches by 3 which gives you 1" gutters.) This then would require die tooling of 40 teeth (5"x 8) or some variable of 40 teeth e.g. 80; 120. However one needs to realize that 1" of gutter x 3 per repeat is a big waste of material. One can run different size print cylinder and dies, as long as they are a variable of each others teeth size. Quite often this will be done because dies are more expensive than print cylinders. Anilox's are not bought based on either print cylinder or die cylinder size. They are controlled by what the press manufacturer has made in the press. The only consideration for anilox's is the volume and line count.

Generally when spec'ing plate cylinder and die sizes, one starts with the label size in the press direction, adds the gutter and then multiplies it by 8, if the press is 1/8" pitch as yours appears to be. This allows one to discover the repeat of one cavity. Once this repeat is ascertained a decision can be made as to how many cavities one wants to be in one repeat of the plate cylinder / die cylinder. Obviously with more cavities the plate cylinder and die are larger in repeat which = more $$$ to purchase. Remember that plate cylinder and die costs are mostly a one time purchase, but wasting material by having too large of gutters will be a cost that has to be covered or absorbed each time the label is re run.

 

[Stephen Marsh]

Thank you Bill W, great stuff I really appreciate it… I have read this many times and feel that I now have 100 more questions!


Stephen Marsh