Marking issue

[jhm]

Hey guy's
I'm having issues marking in my ovens on the lower side of the web. There's no marking at make ready speed but around 800 fpm marking gets really bad. When I open the oven doors and inspect the web all looks good. There's a nice wave threw the nozzles and doesn't seem to be touching any where. I just started working for a new company and the press is a Harris M-300 36" press. The problem only occurs on heavy gloss stocks 100-140lbs paper. Oven marking isn't something I ever really had to deal with other than give them a quick clean and go. I noticed the velocity valves on the back of the ovens are set at high velocity. I'm wondering could turning them down help with my marking issues. Any suggestions would be great!
Thanks JHM

 

[Bagfoot]

Are you sure you are marking in the dryer? Could it be from an angle bar or on the former?

 

[jhm]

Yes I'm sure. I was getting a consistent mark and e-stopped the press. When I looked at the printed web that was in the press the marking was from the former board back to the tilt-box which is roughly 30' fro the ovens. When I hit my e-stop it takes about 30' to come to a complete stop. I actually put a marker on the web until the moment I hit the e-stop and measured the distance traveled so I'm confedent my marking is in the ovens.

 

[Cornishpastythighs]

Copied from a troubleshooting guide, may give you some ideas
Web Marking Cause:
1. Grater roller points too dull
2. Web bustle wheels touch
image areas
3. Improper air flow
4. Chill roll too warm
5. Web temperature too low to
drive off solvents
6. Press speed or job type
beyond dryer capabilities
7. Non-absorbent stock
8. Ink film too thick
Solution:
1. Install grater roller with sharper points
2. Move wheels so they touch only non-image areas; apply TEFLON®
tape to make wheels less abrasive
3. Adjust airflow through oven; adjust web tension
4. Reduce temperature for post-chill roll temperature of 90° F or less;
recommended temperature is 72-75° F. CAUTION: If chill rolls are too
cold, condensation can occur. Reduce oven temperature to minimum
necessary to get web through chilling and press folding operation
5. For impingement dryer, adjust flame tips to impinge properly; for
velocity forced air dryer, raise air temperature; decrease press speed;
increase air circulation; consult ink manufacturer for faster drying ink.
CAUTION: Paper will burn at 451° F and can scorch at lower
temperatures
6. Consult dryer manufacturer
7. Consult paper manufacturer; change stock
8. Reduce ink film; raise air temperature in dryer; reduce press speed to
increase oven dwell time; consult ink manufacturer for faster drying ink

 

[D Ink Man]

How many zones are there in the oven and what are the temperature settings and actual temperatures measured. Also, what is your web exit temperature. How long is the oven, feet?

D

 

[BeauchampT]

Just throwing this out there, but.... do you have a short smoke tunnel on exit of dryer? I have seen marking come from the web exiting the smoke tunnel and still fluttering. It would look like it was coming from your dryer but is actually just afterwards.