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Doctor blade and doctor blade flaws

Posted: Thu Oct 14, 2010 7:00 pm
by Robinr
Dear All,

On a current thread on booklets there are two apparently totally conflicting statements - from people who know their stamps very well. I hope they'll forgive me paraphrasing:

1. Those vertical ink lines that pop up now and then on pieces, blocks, etc., are (and are invariably referred to as) doctor blade flaws.

2. If the line is vertical it cannot be a doctor blade flaw. These flaws are sloping or slanted because the blade wipes the cylinde sideways as it rotates.

Could somebody please explain exactly what the doctor blade does, and which of these statements is correct? There must be a LOT of dealers misdescribing choice blocks, and a lot of misguided write-ups one way or the other.

Or are they both right?

Thanks a ton, Robin R.

Transfer from previous board: original post 1459

Posted: Thu Oct 14, 2010 7:05 pm
by Barry_Smith
There is a description of Doctorm Blade Flaws at http://www.thetenoclockshow.co.uk/compo ... Itemid,54/

The flaw can be either horizontal or vertical on the pane (depending on the direction of printing) AND always slopes, but so little it is very hard to detect. If you have a number of consecutive booklets with the faw it is easier to see the slope when you put them all together.

The Doctor Blade itself is very well described at http://pdf.polestar-group.com/elearning ... rblade.pdf

Transfer from previous board: original post 1462

Posted: Thu Oct 14, 2010 7:10 pm
by Robinr
Hi Barry,

Many thanks for a prompt and totally helpful explanation!

So, both are right! The line APPEARS to be vertical but is in fact slanted, and is vertical on upright-printed sheets and sideways on sideways-printed sheets.

I like the idea of collecting from the same sheet to see how far the flaw extends. I wonder whether that resulted in somebody buying dozens or hundreds of the cookbooklets!

Cheers, Robin Restall

Transfer from previous board: original post 1464

Posted: Thu Oct 14, 2010 7:15 pm
by robinT
I have seen complete sheets with more than one doctor blade flaw on - from top to bottom.

Quite obviously 'printers waste' which 'escaped'

Ber very careful going down that road.