Calculating Bore Diameters

Once the measurements have all been taken, a few simple calculations will provide detailed information on the internal diameter of the extruder barrel. Due to the design of the target and the NORMIN procedure, it is necessary only to know the reference diameter in order to calculate bore size at each measured point.

To track change in the barrel diameter, the user calculates the offset between the target center and the barrel center (the Target Centering Error or TCE) for each point measured. When TCE’s from two measured points are compared, the difference between them is an accurate measure of the difference in their diameters.

Note: These equations apply to the A-510 Target only.

1.	Calculate the Reference Diameter TCE (RDT). Calculate the target centering error for the reference location using the NORMIN readings taken at the reference location. This is the Reference Diameter TCE (RDT).
2.	Calculate the Measured Diameter TCE (MDT). Calculate the target centering error for each measured point using the NORMIN readings from each measured point. This is the Measured Diameter TCE (MDT). The formula is:   MDT  = Normal Reading + Inverted Reading 2
3.	Calculate the difference in diameter between each measured point and the reference location diameter. The formula is:   (RDT-MDT) x 2

Note: If the MDT is larger than the RDT, then the measured point diameter is larger than the reference location diameter.

To find the actual diameter of each measured point, measure the reference location diameter and use the formula below:

Measured Point Diameter = Reference Location Diameter + (RDT-MDT) x 2