posted January 28, 2005 11:23 AM               

I would like to know if someone can give the steps to optimise a blown film extrusion line. I know it's a lot but I need some advice to guide me in this process.

As example I want to optimise the production of a single layer film with 80%LLDPE/20%LDPE with a conventional extrusion line.

Thank you

posted January 29, 2005 09:09 AM               

If you put your priorities in order it would be helpful.

posted February 03, 2005 02:45 PM               

I want to identify all the key point of the extrusion line to have the best balance between output and film quality.
So in priority : 1-production rate, 2-film quality 3- thickness variation 4-color dispersion

posted February 03, 2005 04:42 PM               

Product rate is ultimatly limited by available horsepower to make and pump polymer melt. Horsepower is limited by the mechanical considerations of the extruder. So, in general, most extruders with the same diameter have similar horsepower installed.

Of the horsepower installed typically only 50% is used. A nice round number for converting the horsepower used into pressurized melt is 10 lbs/hr/hp. So if you have a 4 1/2" extruder with 250HP installed you should make 1250 lbs/hr of melt. This formula works over a wide range of materials and processes.

If your not getting the predicted output off your extruder the leading casue is lack extruder setup knowledge. Other reasons are; insufficient product cooling capability, overheating in the extruder, poor feeding in the extruder, and so on.

Please report on your available extruder horsepower, your production rate, and any limitations you are aware of. We can work from there.

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Best Regards,

Tom Cunningham

Extrusion Technical Services

posted February 03, 2005 05:15 PM               

quote:

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the steps to optimise a blown film extrusion line

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Are all the temp controllers working accurately.
Are all the heating elements OK.
Barrel/screw clearances.
Screw design and general condition.
Screw motor/drive/gearbox.
Die and adaptor(condition and cleanilness).
Bubble cooling(design/condition).
Collapsing frame.
Winders.

You should buy a copy of the "Film Extrusion Manual-Process, Materials, Properties" 1992 TAPPI (available from www.tappi.org )This is a very thick book that will cover all of the things you need to know about blown film)

Attending on of Allan Griff's extrusion seminars is a "must" too.

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Steve Hodgson

posted February 03, 2005 07:43 PM               

Output is first, while quality is second.

Hmmmm, I'm now wondering how many would agree to this. So, if I was a potential customer, and was informed of these priorities, I think I would shop for a different supplier.

This is exactly what's wrong with a lot of American production people these days. There also appears to be a propensity by the younger people entering the mainstream who learn to use buzz words about production, and rarely use the q word.

To me, this is kind of scary.

posted February 07, 2005 08:39 AM               

Just because rate is listed first doesn't mean quality is not important- most extrusion houses do pay a lot of attention to quality. But at the end of the day, rate is what makes money.

(By the way, what is "quality"? I just ask that rhetorically, because it means a lot of different things to different people!)