posted May 20, 2004 09:50 PM               

I have designed these types of monitoring sheets for years. The objectives of the sheets should be to provide set-up conditions, and control items. Each monitored item should have a set point, and allowable minimum and maximum values. An additional sheet should be provided to log process set-up changes and excursions outside limits. These items are typically recorded once per hour. MDSD of raw materials should also be issued.

At the top of the sheet (entered one time):

Product
Lot
Raw Resin grade, lot, package being used
Raw Resin generic type (HDPE, LLDPE, etc.)
Raw Resin melting point.
Raw Resin degrades dangerously? (Y/N) (If yes, conditions and instructions)
Purging instructions.
Extruder #
Screw Design or number
Die design or number
Cooling setup
Visual characteristics of the product (Black, glossy, embossed)
Common process related quality problems and remedies.

Some of the items to monitor:

Date
Time
Package or part (amount produced)
Operator
Feeder settings (if any)
Throat water on (Y/N)
Zone Temperature Setpoint / Actual (Barrels, adaptors and die)
Screw RPMs
Screw Amps
Head pressure
Short term pressure variation
Screen mesh installed
Screens last changed
Melt temperature
Coolant temperatures
Haul off speed.
Product temperature

I'm sure others can think of more. Too many and the operators will ignore the whole process. Try to limit the list to important items that have an influence. A general policy should also be set on who is allowed to change settings. Often I see that this type of monitoring just becomes a recording exercise. Operators should be reminded that the purpose is to control the process and to provide a consistant product.

Good luck,

posted May 22, 2004 07:16 AM               

I'd actually add:
Date of last screw pull.
Screw measurement.
Screw measurment limits.
Barrel measurement.
Barrel measurement limit.
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