Standard Finishing
4Over

Announcement

Collapse
No announcement yet.

Which is more important, Stock conditioning or Pressroom Conditions?

Collapse
Canon
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Which is more important, Stock conditioning or Pressroom Conditions?

    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.

  • #2
    Re: Which is more important, Stock conditioning or Pressroom Conditions?

    Keep in mind we just launched the beta site today and not every active user has made it over. When we roll out to a larger audience more people will be registering and available to comment. This period is primarily to test out forum functionality.

    ...or maybe someone will stop by soon with some thoughts. ;-)

    Comment


    • #3
      Re: Which is more important, Stock conditioning or Pressroom Conditions?

      Eric,

      Yeah that's cool 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.

      Dwane.

      Comment


      • #4
        Re: Which is more important, Stock conditioning or Pressroom Conditions?

        Not to get off the subject but a double sided impo proofer I have used in the past, Grand Sherpamatic, REQUIRE the rolls of paper to be conditioned before use or you will fight headstrikes until the non-conditioned roll becomes conditioned to the room environment. I would suspect the same requirements for optimal running in the pressroom to be comparable. Here in South Texas we have temp and humidity changes such as hot and dry to hot and humid, letting the paper acclimate makes the most sense. Usually house sheets are stored in the pressroom environment, causing little problems, and those special order sheets that come in at the last minute for the rush jobs do seem to be the most problematic. Especially the text weight stocks.

        Comment


        • #5
          Re: Which is more important, Stock conditioning or Pressroom Conditions?

          Thanks for the response John!

          Well that's interesting. The last minute stock issues seem to be similar here too. We have hot dry to hot humid here in Darwin Australia too. Our pressroom is fully airconditioned but not humidity controlled. I was always taught at trade school that you need the stock to 'condition to the room environment'.

          However if your room environment is not optimal or consistent. Would not conditioning the stock to 'optimum' conditions and then bringing it into the pressroom be better?

          The imposition proofing issue is interesting too, that even on a machine as slow as a proofer (compared to a sheetfed press) that stock conditioning would be a problem. Incidently, the customer had problems feeding those same letterheads we printed through her laserprinter and wasted 1000 of them. They were 'skewing' in the machine.

          Dwane.

          Comment


          • #6
            Re: Which is more important, Stock conditioning or Pressroom Conditions?

            In my experience allowing paper to come to pressroom temp/RH is more crucial when printing four colour (or more) on 1 or 2 presses.

            It reduces the possibility of poor registration between colours of subsequent passes thru the press.

            As for poor feed, this can be attributable to numerous factors. Quality of feeder being the major influence.

            I remember running an Adast Dominant for 2 days on a 17,000 run of tinted 80gm - I was a broken man!

            We replaced it with a Komori Lithrone - same job two weeks later 1.5 hours - nuff said.

            Comment


            • #7
              Re: Which is more important, Stock conditioning or Pressroom Conditions?

              you cannont seperate the two honestly. If you don't have control over you press room enviroment and you don't allow stock to condition to that enviroment you will always have problems. Air, paper and steel transfer moinster and temperature at different rates. If your pressroom is swinging in temperature/humidity during the day faster than the stock can match it you will have problems.
              Matthew "LAMMY" Lamoureux
              918 Printery - Ad artem artium conservatricem conservandam

              Comment


              • #8
                Re: Which is more important, Stock conditioning or Pressroom Conditions?

                +> {quote:title=eyetech wrote:}{quote}+
                +> In my experience allowing paper to come to pressroom temp/RH is more crucial when printing four colour (or more) on 1 or 2 presses.+
                +> It reduces the possibility of poor registration between colours of subsequent passes thru the press.+

                Sure.

                +> As for poor feed, this can be attributable to numerous factors. Quality of feeder being the major influence.+
                +> I remember running an Adast Dominant for 2 days on a 17,000 run of tinted 80gm - I was a broken man!+

                Yeah, I've been there. . . many times

                +> We replaced it with a Komori Lithrone - same job two weeks later 1.5 hours - nuff said.+

                Could it be that the previous feeder had worn parts and was giving an inconsistent response? Was it an old press?

                Thanks for your response.

                Comment


                • #9
                  Re: Which is more important, Stock conditioning or Pressroom Conditions?

                  Lammy thanks for your response.

                  +> {quote:title=Lammy wrote:}{quote}+
                  +> you cannont seperate the two honestly. If you don't have control over you press room enviroment and you don't allow stock to condition to that enviroment you+
                  +> will always have problems. Air, paper and steel transfer moinster and temperature at different rates. If your pressroom is swinging in temperature/humidity+
                  +> during the day faster than the stock can match it you will have problems.+

                  Let's say however that the pressroom is not necessarily 'swinging temperatures', but it's just not optimum temperature. I was always told an optimum of 20 degrees Celcius and 50% humidity was the best conditions for a pressroom.

                  If you're not hitting that 'optimum range' but your stock is in the 'best range', is it not better to have the stock in the 'best range or conditions' if the room is unable to hit that range?

                  Comment


                  • #10
                    Re: Which is more important, Stock conditioning or Pressroom Conditions?

                    Lammy is correct IMO. If you have correct humidity pallet wrapped paper introduced to a low humidity environment what do you get - curly paper. How about frozen paper in a "normal" environment what do you get - trouble feeding. What about "correct" paper into a room where the A/C is broken - printing trouble.

                    How about some poor pressman whose feeder is facing the open doors of a shipping bay in the mid-winter in Michigan? BIG trouble.

                    The two either mesh or you get trouble somewhere. Basic science. Been there and done that. Get it right or back to school of hard knocks.

                    Edited by: Chilbear on Aug 30, 2007 8:14 PM

                    Comment


                    • #11
                      Re: Which is more important, Stock conditioning or Pressroom Conditions?

                      Chilbear,

                      Thanks for joining the discussion. How about this situation (which I can only relate to my own experience and situation).

                      You're only running a single shift and which point the airconditioning is running and it does around 22-23 degrees (without the IR cranking). However after the shift the air-con goes off and all the stock in that room begins to become more humid and the temperature also increases 3-4 degrees (celcuis).

                      When starting in the morning, the aircon goes on, and the room quickly cools and becomes dryer, however the stock takes much longer to 'condition to the room' as a result the room conditions and the paper stock are not the same temperature and humidity. From what I understand at least overnight is required to condition stock to the room.

                      However, if the stock were kept in controlled conditions in another room (which is smaller & cheaper to run redundantly) and brought into the press room after the pressroom is cool and dry enough, perhaps that would maintain the 'equilibrium between paper and stock'.

                      Of course if you're AC 24/7 no problems.

                      Your thoughts. . .

                      Comment


                      • #12
                        Re: Which is more important, Stock conditioning or Pressroom Conditions?

                        Could be just the design of the Adast feederhead - not enough control for separation/forward blast - no front side blow, no antistatic device. It was old but it didn't like tinted bond - white bond no problem. Go figure!!

                        However, to fly in the face of the current postings (which BTW I agree with)...we have a roller shutter door to the end of our pressroom - it's open all year, our pressmen like it that way! - and we have no rh or temp control.

                        However our feed problems are negligible (we regularly run at 13k/ph) and always attributable to incorrect feeder settings (my staff hate me using that phrase - but in all situations where feed problems have arisen it has been the case that the feeder needed adjustment).

                        Our paper comes from Spain, mainly. And yes occasionally when our UK weather does its worst - we get edge curl, but this does get trimmed off anyway.

                        Comment


                        • #13
                          Re: Which is more important, Stock conditioning or Pressroom Conditions?

                          Conditioning is not a stock only issue IMO. We have run almost frozen paper into a press (it was stored on a truck in mid Winter) delivered in the early AM, it ran but was erratic to say the least. Conversely you must have discovered that a press runs differently at startup in a cooler room than it does what at correct temp. It is all about shrinkage and swelling of rubber materials.

                          Fooling with one variable (paper) may get you through the issue but this is not then a quality discussion but a band aid solution. I paid the price to run AC 24/7 cooling the room slightly in anticipation of the increase from the heaters. Expensive oh yea put production continued and was consistent.

                          So the real question from an owner prospective I guess is - what cost the company more/less the wasted press time or the cost of a/c even if you turn it on using a setback thermometer starting at say 6am? Of course the room should not be allowed to get more than 5 degrees out of normal IMO again.

                          Comment


                          • #14
                            Re: Which is more important, Stock conditioning or Pressroom Conditions?

                            > {quote:title=dwanehollands wrote:}{quote}

                            > However, if the stock were kept in controlled conditions in another room (which is smaller & cheaper to run redundantly) and brought into the press room after the pressroom is cool and dry enough, perhaps that would maintain the 'equilibrium between paper and stock'.


                            yes that should actually work.
                            Matthew "LAMMY" Lamoureux
                            918 Printery - Ad artem artium conservatricem conservandam

                            Comment


                            • #15
                              Re: Which is more important, Stock conditioning or Pressroom Conditions?

                              Do you think it effects dot gains also?

                              Comment

                              4OverStandard FinishingDuploSmartsoft (Presswise)AleyantCanonKBA
                              KBAKBA

                              What's Going On

                              Collapse

                              There are currently 5159 users online. 84 members and 5075 guests.

                              Most users ever online was 6,597 at 10:25 AM on 04-20-2018.

                              Working...
                              X