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banding caused by sculpted platen of 365

#1 geoff9156 3 months ago

Has anyone had the following issue, and a solution to it...

I am printing on a paper backed book binding linen called Iris, and am, on the whole, getting great results.

The issue I am experiencing is banding caused by the sculpted platen (as per attached photos) - that subtle set of dips and ridges around the vacuum suction holes.

If I start with no suction, the material warps with the moisture of the ink and the raised material bgets skimmed by the passing head. So I increased the suction a few digits at a time, to find the point at which the material doesn't warp - this happens when the suction is set to about 10.

The problem I have is that this level of suction is enough to cause the material to undulate up and down for each of the ridges in the platen, and this is causing banding on flat colours. It's definitely not banding resulting for the paper advance, nor any blocked heads. The banding can be seen as the cloth exits the machine and the distance between the bands exactly matches the ridges on the platen.

I've even tried to create my own completely flat platen, but it didn't work as planned.

Any thoughts?

Geoff

Attachments
   IMG_4655.jpg
   IMG_4657.jpg
#2 HP Daniela Ciolompea 3 months ago

Hi @geoff9156,

If you have seen banding on your prints, you should try increasing the inter-pass delay offset (the time delay between passes to allow for smoother drying). Also, you could try adjusting the substrate-advance compensation. This is a slight adjustment to the amount of substrate advance between print passes, to compensate for the characteristics of different substrate types. The printer normally performs this adjustment automatically but may need to be recalibrated for substrates not supported by HP, or for an unusual ambient temperature or humidity. Incorrect substrate-advance compensation may cause banding with fewer than 8 passes. I hope it helps.

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#3 geoff9156 3 months ago

#2 Hi Daniela

Thanks for the suggestion, but it's a vertical banding, not a lateral banding.

The distance between the bands exactly corresponds with the subtly undulating surface of the platen. I have observed that the suction pulls the substrate down enough that the ink hitting the surface is not even, which is causing the banding. If I back the suction off to the point where the substrate doesn't undulate, the substrate starts to cockle instead, resulting in other issues such as the head skimming the print surface.

I have worked on this with one of the local HP Latex providers and they too can't suggest a solution.

Sadly, I have already put this machine up for sale as I can't use it with the banding

Cheers Geoff

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#4 HP Daniela Ciolompea 3 months ago

Hi @geoff9156,

Coming back on this, what I think could help also are the following:

  • Align the printheads.

  • Reduce the vacuum level in steps of 5 mmH2O when printing on vinyl. Do not exceed the lower limit of 10 mmH2O for vinyl or 25 mmH2O for papers to avoid crashes and/or smears.

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The opinions expressed above are the personal opinions of the authors, not of HP.

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