Need Help Head Strikes on 350gsm / 13oz canvas Media

[J4cko]

Hi Guys
Been using a wholesalers 13oz (350gsm) canvas for a couple of years now
13oz matte cotton canvas

Never had any issues until last week.
We run 42” rolls across 3 of our Latex 315 machines , and use 15 to 20 rolls a week.

This last week, we have started to get head strikes , in print runs , which when printed look like wavy vein like patterns , traversing in uneven vertical weave lines in the direction of the media

We are using 13oz (350gsm) cotton canvas

The canvas seems to be rippling as it exits the pinch rollers , just before the head passes over the canvas .

We have never had this problem before .
Been using same canvas media for 2 years

We know that suppliers sometimes change base material / coating and some farm the production out to 3rd parties , so each batch can be slightly different .this is not always communicated to the buyer .
All we know is that media was consistent until last week
Now all of a sudden we get this crinkling of the media as it exits the ping rollers

What we have noticed is that until last week, our printing was consistent and good

Now we see the media looking a little crinkled as it comes through the pinch rollers

We are printing on 10 pass and have used this almost generic canvas profile for years , without issue .

Now all of a sudden the media is Crinkling before the head even passes over
Because of this slight rippling , the head is clearly catching and causing these irregular wavy patterns

What we would like to know
Is what are our options ?

- Can we increase the platen gap ?
- can we reduce the heat ?
- can we increase the vacumm
- can we adjust the pass rate , relative to any of this changes ?

We thought initially the problem was specific to one machine. Now we know the problem is consistent with the 42” canvas media

Any suggestions as to how we make and test changes and outcomes in a controlled manner ?
As opposed to making random changes ?

Any advice and help apprecited

Kind regards
Jack

 

[dypinc]

Make them replace the media from another batch.

You can try to increase vacuum to see if that helps. Also is there a issue with humidity?

 

[J4cko]

dypinc
Thanks for the advice, much appreciated.
No real humidity issue. Pretty stable in the Uk, we dont get extremes.

We are trying to establish and separate and test batches now

Just cautious to start playing with media pre-sets, as that can be a long and winding path to nowhere sometimes.
The media was consistent across multiple machines until the last week or so.
We thought it was an issue with one machine, so had a tech out for half a day, testing pinch rollers and feed mechanism.
But as soon as we tried the media on other identical machines , the problem moved with it.

We have never used take up reels, in all the years we have printed.
All prints fall to the floor, and we have never adjusted vacuum settings since using the Latex machines ( maybe we are lucky !)

We believe the suppliers supplier have made a batch inconsistnt with previous batches, which all worked seamlessly, with little or no issues.
Everything points at the media...we just have to hope it is only specific to a small batch, as we are reliant on this material for a lot of our jobs.

We checked the platen, and it was pretty clear, and vac seemed to be working better
If we increase the Vacuum, will that not have a knock on effect to other settings ?

Any wise words appreciated
Thanks for contributing

 

[dypinc]

Changing the vacuum will have no effect on other media preset setting. Changing the vacuum slightly will have no effect on print quality. Changing the vacuum a lot might cause banding in the direction on media travel. You will see it if it does and if it does back off the vacuum amount.

 

[J4cko]

Thanks dypinc , really appreciate the suggestion...thank you