I recently had the honour to work together at a customer to do trial runs and operator process training. We teamed up with two specialists Mr H. Medemblik from BHS corrugated and with Mr D. Murfitt from Crespel & Deiters (starch specialists).
This resulted in a very successful cooperation and very good light weight board production in different combinations. This also gave us the possibility to give a joint training pointing out several things to the operators and management. With as main topic, less heat, less starch.
The corrugator we used was not the youngest one and could be described as a middle aged lady with a couple of face lifts and all the other cosmetic stuff. A steam system that is not always very reliable and E flute corrugator rollers that are also due for a full cosmetic rebuild 🙂
We focused in getting flat E flute board, with no post-warp and no wash boarding neither honeycomb.
The papers used where Modo Northern light Flexo 120 as coated fully bleached (100 percent fresh fibre), combined with 80 gsm Modo Northern Light / 100 MNL and as inner liner we used 100 MNL
This pictures shows 120/80/100 combination. Nice board and no postwarp.
As you can see these are very low grammages and these fully bleached virgin fibre liners have the tendency to pick up heat very fast and have an build in natural humidity barrier. ( so they do not like water/ starch to much). So the risk one has poor bonding due to excess starch is there always.
When we started the corrugating we first monitored the settings and state of the equipment. We noticed relatively high amounts of starch and a bit to much preheating an about all positions (SF and DB) whilset running Flexo preprint coated liner 120gsm combined with MNL 100 as fluting and MNL 100 as inner liner.
After one day we ended up using a gap of 0,12 on the ( in stead of 0,20 ) DF with 0% preheating so liner went in to hotplates at around 27 to 40 degrees Celcius..
Same actions were taken at the single facer where we went to minimum possible gluegap and reduced drastically the preheating of liners and fluting.
So finally we arrived to following process parameters:
Process temperatures and glue gaps
- 200 m/min
- SF liner 80- 90°C
- Fluting 75- 85°C
- web 85-95°C
- Glue gap on mechanical minimum.
- Temperature liner before hotplates 27 (uncoated) 40 degrees coated
- DF 117- 122°C Sensor (130-130-135-135°C hotplate temps)
- DB gluegap: 0,12 mm
The very stable one bag mix from Crespel & Deiters performed very well – the parameters for this high-performance wheat starch based glue were 55-60 seconds Stein Hall viscosity (18-20 sec. Lory cup), 57 DegC gel. point and (oven) dry substance of 22.70%. Even at what we would consider a bit high temperature of the starch in the glue pan (38 degrees) it sill performed very well.
This cooperation has again taught us that using iodine pictures is so very helpful.
While running at 180 m/min making perfect board we increased the speed to 200 meters and the board started to delaminate:
Iodine pictures showed us again what was happening:
So the iodine pictures showed it why we had a bad bond at 200 meter. Too much glue and not enough heating. First reaction of operators before making iodine picture was putting even more glue…..
This irregular glue-lines on the liner where caused by an excess vibrating of the arm holding the interfic shoes.
After fixing this the problem disappeared and the road is open to higher speeds than 200 m/min.
So making iodines is very important, it show the soul and conscience of the corrugator and help us to take the correct decisions.
Another tool that is also very handy and I dare to say a must is an absolute humidity measuring device.
This will give us peace of mind and we will not be afraid of postwarp.
This corrugator still had some issues like a doubt on the parallelism and some irregular belt porosities but these where just some things to add to the list to be checked along the road.
I would like to thank Mr Medemblik and Mr Murfitt for their perfect help for the commen goal: GOOD BOARD!