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Brentwood Plastics Blog

PE Film Lead Time Factors

Posted by Joel Longstreth on Thu, Dec 08, 2016 @ 05:52 PM

The ship date for custom PE film involves much more than a first-come-first-serve queue.  An extruder who runs their
backlog in this fashion or has a salesman running the backlog is not long for this world.  

The primary consideration in setting up a backlog is minimizing scrap.  Clearly at loggerheads with customer's
urgency.  Keeping peace with all parties is an art.  The scheduler's agenda is to consolidate a sequence of films made out
of the same PE resin as long as possibleto avoid transition scrap.  With resin cost at about 75 cents per pound, every pound
of scrap is really about $ 1.00 lost factoring in labor, electricity and overhead.

A medium scale extruder puts out about 500 pounds an hour.  What would you do ?

It's best practices to have some leeway in ship dates.  We promise our orders for "week of _____ ".  A smart play is to promise
a Thursday ship date.  4 out of 5 chance it will ship early or on the date.  1 in 5 chance it will be a day late and so what ?  only a
day late.

It's also best practices to have a few dummy orders in the backlog to both act as a cushion for breakdowns and allow for opportunities.
If an order comes in with a ship date 3 to 4 weeks out for a resin running today, it makes common sense to tail it in to
avoid setup scrap instead of running it as a stand-alone 3 weeks from now. 

Distant secondary considerations are width and thickness changes ( there's the central theme of avoiding scrap again ) followed by pigmentation.  
Cleaning out after colors is time consuming and messy.  The line must be shut down, purged, what is called the screen pack / breaker plate must be changed.
The ordeal is followed by an expensive, frustrating waiting game while the remnants of the color clear out. 

Back in the day, we had a shrewd customer who went out of his way to pay his bills every Saturday.  A check for all invoices in the week would show up like clockwork on Monday morning.  Why ?  To tempt the film extruder to deviate from fundamental priorities.

Of course, there are justifiable exceptions but they are few.  Re-work of returned or defective product or doing an occasional favor for a good customer who is out of film and shut down.  

So now you know why:

Coextruded films have such extended lead times

shrink films have such a wide variation in MD / TD shrink ratios
( the order goes on the machine that needs work )

pigmented films have longer lead times

Are you wondering where is our proof that first-in-first-out doesn't work ?  That's easy.  The outfit we sold out to in 1984 ran orders in the sequence received.
It took them about 3 years to declare bankruptcy.

 

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Topics: LDPE film, polyethylene film, poly film

Clear Polyethylene Film

Posted by Joel Longstreth on Fri, Jun 07, 2013 @ 03:52 PM

 

20140128 130126The not subjective definition of LDPE film clarity is ASTM D 1003 which measures haze.  Haze is a measure of how much light gets through plastic film measured in percent.  There is an inverse correlation between the haze number and clarity of plastic film.  The lower the number, the more light gets through.

While a low haze film allows the consumer to see the product at point-of-sale, the amount of attention paid to the difference between a few points of haze is overdone.  Many PE film extruders tout their runway versions of clear film as the only film the discerning customer will pick up. Seriously ? 

What is often overlooked is the difference between haze and what is known as contact clarity.  In the above pic, note how the film appears clearer where it is in contact with the image underneath.

Someday I would like to meet the mystery shopper who does not buy bread, nuts and bolts, candy, carrots, paper towels or bottled water because the haze is 12 instead of 6.

https://www.youtube.com/watch?v=MIwLYp1qQCo

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Topics: LDPE film, clear PE film, polyethylene film, PE film haze

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