Spray power issues

[Paultheprinter]

Hello,

i have suffered with a problem for some time when i finnish backing up say 40,000 sheets coated 130 gsm, the spray from the first side buiilds up on the impression cylinders and l
deposits large flat leaves of powder, these are sometimes 30 -40 mm in diameter and always in non image areas of the sheet. This seems to have got worse recently and is only more apparent on thinner stocks 170 gsm and less. The press is a 2001 SM 74-5 and the spray varn fine coated 1.5 micron. Any help appreciated as i can find a thing

Paul

 

[keldrewett]

Re: Spray power issues

Change suppliers. Varn has been having problems.

 

[Paultheprinter]

Re: Spray power issues

Thought as much ! just so happened that this occured after they seemed to re package there spray into different weights. There was the 1.5 r the 230 r and the 350, then overnight they changed to coated fine, coated medium and coated course! and then problem after problem, You would think a company of varns size would be able to control there manufacturing processes and deliver a useable product to the market ! when i questioned Litho supplies sales team about the issues i got the usuall, no other account has flagged up these issues!

Paul

 

[Hawdkoar Printer]

A good practice is carefully monitor any changes that occur to the consumables you use, as you found out what is a small change to Varn, can make a huge difference to you in the pressroom. Secondly always trust your observations and not some Litho supply person, other vendors may not have caught up to the problem as fast as you.

 

[Sfdp2300]

Have you had any problems with excessive spray powder building up in your deliveries with this varn?
We use Varn as well (R27) and over the past year or so we have notice alot lot build up in the delivery at a faster rate than normal which in turn starts to drop like little bombs onto our printed sheets.

 

[Albert Noel]

we've been having the same exact issue that the OP is having.
i'm glad i'm not the only one. we are using varn r27.

didnt know they changed to multiple versions

 

[printr640]

i have had this problem before. it is from powder buildup in the delivery thus creating powder bombs that fall onto the sheet.
watch inside the delivery as the press is running to see if you notice this issue; if so you need to stop and have the press helper give the delivery a good blow.
my guys blow the delivery every weekend. however we still sometimes have this problem and i have noticed that it happens when the press trips off and all the fans turn off and on from start ups the vibration causes powder bombs to fall onto top sheet. so i have gotten into the habit of pulling the top 2 sheets when we have trip offs on the first pass only to prevent problems when backing up.