posted January 19, 2004 07:21 AM               

I am having trouble writting a complete operator training manual for PE blown film. I have read the dynisco extrusion book (d dunning) and rauwendaal's polymer extrusion (amongst others) but am looking for specific traing info.

Also. The operators do not change the screw speed when altering the film gauge / width. It is all done on the nips. Dont think this is the right way to do it - any recomendations for discovering the right settings for difference jobs and the relationship (if any) between screw speed nip speed and film profile.

posted January 19, 2004 08:03 PM               

Welcome to the extrusion forum, get a copy of TAPPI's Blown Film Extrusion Manual, available from the bookstore at their web site www.tappi.org This is a really good resource. Get copies of the extrusion guides for the materials you use from your suppliers, these can be a useful source of information.

quote:

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The operators do not change the screw speed when altering the film gauge / width

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posted January 20, 2004 09:59 AM               

I think the reason the screw speed is not altered is just down to a lack of understanding / training and not limited by capacity / cooling. Do you have any ideas of how I could extrapolate the optimal settings of the rpm / nip speed for the different ranges that each extruder runs.

posted January 21, 2004 08:58 AM               

Lowering the screw speed will reduce output rate, and therefore reduce profits.

Therefore, nip speed is generally the dictator of thickness.

posted January 23, 2004 11:17 AM               

One important exception to my previous statement is that a line might be limited by the line speed of a bag machine, for example, in which case you would want to control thickness by screw speed.

This is not an optimal situation, but is somewhat common.

posted January 24, 2004 02:37 PM               

Joining the Society Of Plastics Engineers might be a good idea for you to consider- they have an excellent range of technical publications and hold regular seminars and technical conferences (ANTEC's), this "online" presentation may be of interest to you
Understanding Blown Film Process Variables and Bubble Geometry Online Presentation
May 27, 2004 http://www.4spe.org/trainingeducation/olt/040527.htm

As far as varying the screw speed goes, why do you see what your operators are currently doing, as a problem ?

If there are no quality issues with the product(s) that is/are coming off the line(s), why try and fix something that isn't broken?

Steve H