BN-20 chrome mirror polish tunnelling

[Hugh Potter]

you’ll get this on pretty much any metalised (chrome, brush etc.) film, usually when they’ve not been used in ages. They effectively stretch on the roll and when you then try to lay it flat, it tunnels. will happen on a plotter too if you run it in, I’m 99% certain that heat is not the deciding factor here.

I often have this issue as I don’t use chrome much, when I get a roll off the rack it’ll do the above!

[Chris Jarvis]

Thanks Hugh,

I’ve worked out what the problem is:

I cut a wider roll down to two narrower rolls, cutting from the backing paper side.
If I have the original roll edge on the right side (cap head end) in the machine, there is no tunnelling/rippling.

When my new cut edge is on the right side, it tunnels right across from right to left, every time.
It must be because my cut is forcing the edge of the material away from its backing paper just enough to start it tunnelling when it’s near the heated area on the printer?

The reason I cut the full width roll down, is because the ‘wavy sea’ shape of this material concerns me as it come close to the print head/carriage at various points on the carriage traverse. I thought a narrower roll would lessen this. The jobs I print are all pretty small, so the narrow roll width is ok for me.

The thing is, by trying to remove a problem, I’ve created another!

At least I understand what’s causing the problem now, and how to avoid it happening from now on.
I’m happy to say I have successfully printed a couple of jobs since the penny dropped.

Chris