To measure your profile variations, cut a one foot section.  Measure wall thickness  with a hand micrometer every one inch. Calculate using above formula.

The calculated value represents the sum of all the variations around the pipe subtracting out machine direction variations. These variations can be caused by an eccentric die, uneven cooling, non-uniform heater zones, etc.

2. Determine the short-term machine direction variation

(Highest Measurement – Lowest Measurement)/Avg. of all Measurements  X 100 =  ___________ % (1 – 3 % Industry Avg.)

To measure, cut 40 foot section of pipe in half in the machine direction. Using a hand micrometer, record the thickness every foot. Compute using above formula.

These variations are shorter than one minute in duration. They are caused by screw or pressure surges, uneven blending, puller slippage, saw timing, etc.

3. Determine the long-term machine direction variation

(Highest Weight – Lowest Weight)/Average of all Weights  X 100 =  ___________ % (1 - 5 % Industry Average)

To measure, record the individual weights of 30 coils or links. The measurements must be of identical product, diameter, and length. Compute using above formula.

These variations are typically several hours in duration, they are caused by changes in resin batches or regrind ratio, screen pack build up, changes in water flow, puller drive variation or vacuum take changes, etc.

Calculate using the 'RMS' formula above.

5. Estimate your total annual scrap due to off-gauge material.

Lbs. per year__________

6. Estimate the time required to get within spec on startup.

_________ Minutes

Collect Economic Data

7. Extruder Throughput ________________ lbs./hour

8. Average Number of Startups Per Day ______________ #/day

9. Annual Startup Time __________ hrs/year

(6) x (8 )÷ 60 x 330

10. Price of Resin__________ $/lb.

11. Conversion Costs__________ $/lb. ($.15/lb industry average)

To calculate conversion costs, add annual energy costs, maintenance expense, manufacturing and administrative overhead and equipment depreciation. Divide the sum ($/yr.) by annual throughput (lbs./yr.).

12. Margin__________ $/lb. ($.06/lb industry average)

Margin = Sales Price - (Price of Resin + Conversion Cost)

13. Hours of Extruder Operation/Year __________hours/year

7,884 hours/year = 90% capacity utilization

Calcualte Potential Savings with Gauging

14. Projected Profile Variation __________ %

(1) x 0.50

Profile variations are typically cut in half with on-line gauging.

15. Projected Short Term Machine Direction Variation __________ %

(2) x 0.90

Short-term machine direction variations cannot be directly reduced with on-line gauging. The gauge can be used as a diagnostic tool to remove some of the causes of these variations.

16. Projected Long Term Machine Direction Variation __________ %

(3) x 0.10

Long term machine direction variations are virtually eliminated by closed loop automatic control of screw or speed.

Reducing product variation enables thickness target shift (down-gauging) while maintaining the minimum spec.

20. Projected Annual Savings Due To Scrap Reduction__________ $/yr.

(5) x [(11) + (12)] x 0.50

Scrap is typically reduced by 50% with on-line gauging. (Assumes line is production limited.)

21. Projected Annual Savings Due To Reduced Startup Time__________ $/yr.

(9) x (7) x {(11) + (12)} x .50

Startup time is typically reduced by 50% with on-line gauging. (Assumes line is production limited.)

Bottom Line Savings

22. Total Projected Annual Savings With Gauging = __________ $/yr.

(19) + (20) + (21)

23. Payback Period = __________ months

{50,000 ÷ (22 )} x 12

Footnote:  A fully configured NDC Infrared System with complete automatic control of pipe wall thickness can be installed for less than $50,000.