DeletedMemberx0938140
Well-known member
Hi everyone,
People on these forums don't seem to like talking about *feeding* issues. Maybe no-one else has feeding issues (Sheetfed). I've asked this question in different ways with no response, so I'll again try another angle and perhaps offer some observations I've made, which could help others.
h2. My Hypothesis
I believe that _stock conditioning_ is more important than _Pressroom Ambient Temperature and Humidity_ for successful high speed feeding on a sheetfed press. By that I mean that the _stock conditioning plays a much larger part_ and _greater gains can be had by simply conditioning the stock_ than by employing _Temperature & humidity controls__ in your pressroom.
h2. Definition
By _Stock Conditioning_ I mean the act of storing the paper stock prior to printing in room conditions which are controlled to allow the paper to arrive at a state which is favourable for positive sheet separation.
h2. Critical for
Thinner papers and less so for boards.
h2. Example
Ran a job the other day on a coloured bond (uncoated) at 80gsm weight. I was previously running all day 80gsm White Bond (uncoated). Running the previous jobs around 11,000-13,000 iph. A few stoppages, a couple of delivery prangs. Other than that quite consistent.
Opened a new pack of 80gsm Coloured bond. Whacked it straight in the press. I had to majorly change the setup of the feeder in order to feed the stock. In fact _I could have gone from 80gsm white bond to 100gsm gloss easier with less changes!_
So I got the job running and kept it running about 10,000 iph. Ran quite good, but I cooked it a little with the IR, only about 40% on an 18Kw Baldwyn dryer. It was only black and had a bit of solid on there. End of the day, wanted to finish cleanly. Gave it 10 minutes and turned it. _Changed the feeder settings dramatically 3 times!_ Couldn't feed 20 sheets in a row.
Knock off time. . .in frustration. Left the aircon on over night and let the _stock condition_ or what I _believe is what it was doing._
Next morning come in and feed the stock no problems at 10,000 iph. Also had to run another 300 over on fresh stock. That stock was already unwrapped on the bench. That ran through no problems. This time I didn't even switched on the dryer. Fed the stock through on second side at 13,000 iph no problems.
h2. Observations
1. When I was adjusting the feeder (separation fingers, blower height, blast settings, Feeder head height) I noticed the previous day that it just wasn't possible to separate the sheets. No matter what combination of air blast settings, finger position and head position you used it was _beyond the separation capability of the feeder head_. The sheets stuck together in sympathy and that leads me to think that the very temperature, humidity conditions _in the paper_ is what was the problem. We could have had a great ambient room temperature and humidity, but it would not have helped feeding that paper. . . unless it was previously conditioned well.
2. Cooking the paper too much on the first side removed a lot of moisture from the paper and changed the _conditions within the paper_ to an unfavourable one, leading to inconsistent response of the paper and thereby inconsistent feeding of the paper. The conditioning of the paper overnight returned the paper to _favourable conditions_ and which point it fed fine the next day. Although it was only at 10,000 iph - that was more of me _not trying to push my luck with it_. Possibly could have fed faster.
3. The stock that was left on the bench had time overnight to condition and thereby fed perfectly with no changes to the head. The previous day the stock was taken straight out of a packet and perhaps was why the amount of difficulty in initial feeder head setup.
h2. Final notes
I believe that more gains can be had by getting the paper stock to optimum temperature and humidity levels, than by completely controlling the pressroom temperature and humidity, since _between the sheets is where the rubber meets the road_.
_*Comments, objections, debates*_ I understand that I have only one example above and probably not enough to make a case. But this is a _*hypothesis I have*_ and I'd be interested to see what others think.
People on these forums don't seem to like talking about *feeding* issues. Maybe no-one else has feeding issues (Sheetfed). I've asked this question in different ways with no response, so I'll again try another angle and perhaps offer some observations I've made, which could help others.
h2. My Hypothesis
I believe that _stock conditioning_ is more important than _Pressroom Ambient Temperature and Humidity_ for successful high speed feeding on a sheetfed press. By that I mean that the _stock conditioning plays a much larger part_ and _greater gains can be had by simply conditioning the stock_ than by employing _Temperature & humidity controls__ in your pressroom.
h2. Definition
By _Stock Conditioning_ I mean the act of storing the paper stock prior to printing in room conditions which are controlled to allow the paper to arrive at a state which is favourable for positive sheet separation.
h2. Critical for
Thinner papers and less so for boards.
h2. Example
Ran a job the other day on a coloured bond (uncoated) at 80gsm weight. I was previously running all day 80gsm White Bond (uncoated). Running the previous jobs around 11,000-13,000 iph. A few stoppages, a couple of delivery prangs. Other than that quite consistent.
Opened a new pack of 80gsm Coloured bond. Whacked it straight in the press. I had to majorly change the setup of the feeder in order to feed the stock. In fact _I could have gone from 80gsm white bond to 100gsm gloss easier with less changes!_
So I got the job running and kept it running about 10,000 iph. Ran quite good, but I cooked it a little with the IR, only about 40% on an 18Kw Baldwyn dryer. It was only black and had a bit of solid on there. End of the day, wanted to finish cleanly. Gave it 10 minutes and turned it. _Changed the feeder settings dramatically 3 times!_ Couldn't feed 20 sheets in a row.
Knock off time. . .in frustration. Left the aircon on over night and let the _stock condition_ or what I _believe is what it was doing._
Next morning come in and feed the stock no problems at 10,000 iph. Also had to run another 300 over on fresh stock. That stock was already unwrapped on the bench. That ran through no problems. This time I didn't even switched on the dryer. Fed the stock through on second side at 13,000 iph no problems.
h2. Observations
1. When I was adjusting the feeder (separation fingers, blower height, blast settings, Feeder head height) I noticed the previous day that it just wasn't possible to separate the sheets. No matter what combination of air blast settings, finger position and head position you used it was _beyond the separation capability of the feeder head_. The sheets stuck together in sympathy and that leads me to think that the very temperature, humidity conditions _in the paper_ is what was the problem. We could have had a great ambient room temperature and humidity, but it would not have helped feeding that paper. . . unless it was previously conditioned well.
2. Cooking the paper too much on the first side removed a lot of moisture from the paper and changed the _conditions within the paper_ to an unfavourable one, leading to inconsistent response of the paper and thereby inconsistent feeding of the paper. The conditioning of the paper overnight returned the paper to _favourable conditions_ and which point it fed fine the next day. Although it was only at 10,000 iph - that was more of me _not trying to push my luck with it_. Possibly could have fed faster.
3. The stock that was left on the bench had time overnight to condition and thereby fed perfectly with no changes to the head. The previous day the stock was taken straight out of a packet and perhaps was why the amount of difficulty in initial feeder head setup.
h2. Final notes
I believe that more gains can be had by getting the paper stock to optimum temperature and humidity levels, than by completely controlling the pressroom temperature and humidity, since _between the sheets is where the rubber meets the road_.
_*Comments, objections, debates*_ I understand that I have only one example above and probably not enough to make a case. But this is a _*hypothesis I have*_ and I'd be interested to see what others think.
I realised that there will only be a few on board at the moment. It was handy to be able to format the post to make it more structured too. It'd be great if it supported the 'numbered/bulleted' point lists aswell to make points clearer to read etc.
