Heidelberg Windmill: Uneven pressure

Hi everyone
For a while (as I think this wasn’t always like this, not sure though), my OHT prints unevenly. Its always on the gripper side where the paper lies in press. Printed with the long side lying in the gauges (See the picture). So this means, less pressure on the right side, especially right and down, from point of view of machine and printing person. Its always the same, with lead type, polymer or magnesium plates. When I put paper under the packing at that spot (“Zurichtung”), pressure gets better. Inking seems good to me, so it can’t be the roller height.
I remember reading once in another thread, that pressure can indeed get uneven the more used the machine gets. But somehow I cannot believe this, as everything is made of steel?
Also you always start with putting your form in the right lower corner, shoudn’t most pressure be there then? How is pressure “distributed” on the windmill?
What reasons can there be and what to do about it?
I hope you understand what I mean.

Thanks for your ideas and help. I would just like to understand, as I don’t get the logic of it.


image: OHT_Druckunregelmässig.jpg


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Try turning your packing 180 and see if your pressure issue changes location

Hi Jes
Thanks for answering. I was at the atelier this afternoon, thinking about what reasons it can be. I think I have the reason/solution: The “table” on which I close the form, “marbre” in french, is a plate of thick steel, but in the middle it’s “concave” (?) Means, it is out of steel, but the middle part is not as thick as the outer parts. So now I found out that this “marbe” isn’t totally even anymore, over the years. (It “sags” (?) a little bit in the middle.) Of course this affects the form, then the pressure etc. And this also explains why it was always on the same area. I honestly never questioned the flat level of this “marbre”, as it seemed so solid to me.
That was a very interesting afternoon for me. Learning about my tools and my machines.

Try turning your Marbe over and see if that changes anything.

Hi Jeff
Thanks. Yes, that’s of course what I did before writing my comment from 19 nov, and it did change, thats how I found out this is the reason ;-). Maybe I didn’t put it in words accurately. I will get a new “marbre” or something else that is completely even. So problem solved :-).

‘Marbre’ en français, ‘stone’ in English. When I lived in Paris, I got a nice piece of stone from a shop on Bd Saint Germain in paris, they specialize in kitchen worktops. I had a piece of granite cut to my specifications and it works well. Bon courage…

Hi Thomas
Good idea, will think of that. Thanks for sharing your knowledge and your experiences.