Blister Packaging Problem

Hi MJ,

What seems to be happening is that the grain direction of both cards is the same direction,if one of the cards was grain long and the other was grain short, they will have less tendency to curl. I'm guessing that the original vendor had anticipated this due to their knowledge of the packaging industry, which may yield fewer pieces per sheet printed, thus resulting in the increased cost. I often encounter similar design flaws on a regular basis because, although in theory it should work as the engineer designed, In practical "real world" application and/or production, it is a nightmare, that could have been avoided if the engineer were more understanding of the machine process used to convert the material to a usable package.

When you say grain direction you mean the cardboard flute?? then yes... it is going to the same direction. I will try turning one of the cards horizontal, maybe it will have more strength to avoid the curl... alltough I doubt it will cause it looked really strongh to me.

To this point I will start a DOE but I need to gather a lot more information

The variables I have so far are the following:

Material: Laminate (compresion), corrugate (thickness), adhesive (types and layers), tray, flute direction

Process: Temperature, Time (press), time (cure), orientation (insert faces), nest geometry, Press strength

Other: Humidity

There has been some good advice given , and some that is not quite as helpful. The temperature contraction theory sounds good, and may be proven to be true, but the coefficient of expansion (contraction) for cardboard is not likely to be significant. The first variable that I would test would be humidity differential between the two different cardboards. If these are not being stored in properly controlled environment, this can be a serious problem when one is then heated and the other not.

About this time of year I get a rash of questions on rust in packaged parts from many shops, and Once we do a test for humidity in the packaging, the shops figure out what steps they need to take.

Heres a quick, non DOE experiment to quickly validate the humidity issue. Take 100 of both types of card stock and dry in oven at low temp, say 100 Degrees F or,some other suitably low temperature for a couple of hours (If they are in stacks, the centers will not dry out, allow an hour per inch of section) then take them to your machine and see if they curl, the % they curl, and the severity of the curl.

If dry, they wont feed in your machine, then retemper them both by putting them in a high humidity locker or something for 48 hours to get to same humidity level.

I'm thinking that you'll then figure out the controls that you will need to take on your storage and specification for both of these.

Another test you can do is given a suitable sensitivity scale , is to weigh 100 of both types of card,(not one at a time, 100= 1 sample) before putting in oven, then weighing after, the oven treatment. The loss on baking in weight will be an interesting number for you to use going forward. Do this from different boxes and you will be well on your way to solving this.

The idea of lay in the cards is also one i would investigate further, as is changing the adhesive to one requiring a lower temperature.

Finally, you might consider an after the the assembly "humidity temper" to see if it reduces the warpage. A tiny spray of micro dropletsmist might sufficiently remediate the superdrying from the high temp adhesive.

I don't have enough facts to ascertain if a coating on one side or both side of one of the stocks while none on the other may be a contributory factor- for thta, you can run the DOE . Id only use three variables, by the way, and the L8 taguchi matrix.

Your run sizes are too small for anything more ambitious...

milo

Hello Milo,

I do not want to get into your post too deep as you make some fair and good points.

Just one thing: You say "the first variable that I would test would be humidity differential between the two different cardboard's".

This is the most likely cause of the bending and twisting on application of the heated iron. I always had to keep my samples in the Factory atmosphere which was also more damp. If a sample was stored in the office, which was always hotter and drier, the samples would almost always 'move, and bend or twist and actually shrink! If they were stapled corrugated, the staples sometimes pulled through as they shrank.

I did not like to use corrugated for the surround of plastic packaging, as it was less stiff and was easily damaged and horrible to print! Always this corrugated card absorbs more moisture than solid flat card which will probably have some kind of non permeable finish on one side at least, with the other side laying flat on the sheet and stack underneath.

I would never have manufactured these products before doing a sample run of 500 to a 1000 items. 50,000 items is a disgusting waste of money time and effort! =

Take care my friend.

Hi babybear.

Thanks for your feedback.

As you confirm Humidity is important, and it is something usually uncontrolled, and as we saw , an afterthought in the consideration of factors involved.

My advice to dry it out may be wrong from the stand point of the process needing more not less humidity, but I gave it as a way to see "where they stood" in terms of comparing the materials.

I have seen humidity be the factor 90% of the time when paper or cardboard or packaging problems came up. So my idea will give them tools they can use to determine the status of the materials involved.

Thanks for sharing your experience.

milo

Hi Milo,

Cheers for the reply post my friend.

In an office it is relatively easy to control humidity or moisture. If you run a factory moulding plastic or something it is often 'pushed' out by the heat at least partly. But as the heat escapes, it pulls in new colder and more than likely moister air, but at the machine level where it is always hot, the air will be drier.

In a Printing cardboard factory there is not nearly as much heat. And also be an added source of humidity : IE : the Ink machines which use water as part of the off-set printing. If we had a big job coming up I would order the card, usually white lined basic 600/750 µ and keep it in the guillotine room which was drier and always had heat from south facing high windows. Leave it in there for a week or sometimes split the pallets take any plastic and or paper wrap off and split a pallet into four smaller ones. These little amounts would be ready for printing etc in about 3/4 days.

However, on some boards which were really popular, they could hardly manufacture the stuff quickly enough and we would sometimes get a duff lot in where there was either too much or not enough moisture in the board. This would always need splitting and the whole stack re-stacked and put into layers of around 75 mm (3"). This I found would leave flattened sheets ready for the guilly and printing, cut/ crease etc. But, on work in progress the usually small pallets or the wheeled printer runners should always be covered with a good thick sheet to keep the humidity from landing on it over-night and, of course to keep it clean for the next run through the print. Take care.

Hello Manufacturing Jedi,

Need to revise your title you may, since figure it out on your own you cannot! Hmmm, hmm, hmm (Yoda chortling)!

Seriously, we need to know many details such as:

• Thickness and composition of the "cardboard"
• Types (and if possible Mfg. and product number) of the adhesives you are using
• Coat weights of adhesives you are using
• Details of laminating operation (pressures, temps and line speed)
• Sizes of the "blisters" and spacing.
• Web details such as lamination entry and exit angles, and individual tensions of the two substrates being laminated.

The more of this information you can give, the better your chances we can give a working solution.

Mike

I am still gathering all of the information you asked for. This was not my project so It is kinda difficult to get because they are pretty angry and want to fix it themselves without help.

I will get this info and maybe more.

thanks

" it always curves to the upper section (the one where the hot plate goes down on)."

The hot plate expands the material on the hot side while the cold side remains stable. The glue then solidifies. As the "hot" side contracts, after cooling, it curls.

Heat/cool both sides equally.

The machine does not let us heat both sides... we already tried to heat the bottom side but it is very difficult without proper equipment.

Another material already worked with the actual process but as I mention it is more expensive and I really want to know why does it curl like that :( . I can't believe the vendor doesn't know jack about these kind of problems... Jesus Christ. Which takes me to another point: why are some vendors so ignorant about their products and processes? it really makes me mad...

Hello MJ,[p]

By "vendors" I assume you mean the people who have ordered the packaging? This can be a different packaging factory or the designer of the item in the pack?

You say it is not 'your problem' but, it would be nice to solve this problem and say "this is how to do it"?

I have not heard of corrugated packaging used with this molded plastic. We always used 'solid' card.

Take care.

It's the glue.

Try a more rubbery glue.

that is one of the suspects... What I need to do is to press it without the glue and tadaaaa! we have the culprit!!

What would you recommend? Can you believe they don't even know what kind of glue they are using?? A little bit more background: this was a major failure for packaging design, it is a new process for us and they decided to go ahead with production without maturing the process so they got the responsability to deliver 50k to costco... boy o boy they were shocked when they returned the 50k back home!! they must feel pretty stupid about this and I can't blame them.... for feeling that way that is.

Hello MJ,

I do not feel in the least sorry for this company. A couple of calls to like minded companies would have given them the answer. 50K? Wow! That is an awful lot of wasted card, time and effort! 1K would have made sense as a try to see if things worked ok surely?

Take care.

Hello MJ,

Hope you are well?

I was in Packaging but have forgotten a lot. But.............

I think it may be the residual dampness of the card which may be the problem. When heating just the 'top' of right 'side for instance it does what most card does when left by a heat source, curls.

How about having the hot iron the full size of the card.

And/or using a gloss or varnished card on the face next to the plastic on the hot side, so the liquid glue sticks to the gloss or varnish and does not soak into the card? You may have to have card varnished on both sides if you want the printed face varnished as well?

Just one of several thoughts. Hope it may help.

Good luck. And keep in contact please.

Sorry I didn't get where in the process the "blisters" come in. Does this curling of the laminated cardboard occur before the plastic is added?

I have done these blister packs, both 2 blisters and one blister and one cardboard. We never use glue. Glue shrinks inducing stress and therefore warpage. We did returns on 3 edges of the blister for the blister/cardboard to slide the cardboard in and stapled the open edge. For the blister/blister pack we used heat sealing - and did it all around all edges, no warpage.

Ed Galicki

San Diego, Ca.

Hello Guest,[p]

This is how I have done them in the past as well. But things have moved on since I did that and there may be a way to use a different glue, or as I suggested a full pack hot iron rather than half pack, which seemed to induce the bend or twist?

Take care.