User guide

Appendix l B-4
Calculating Blade Interruption
Blade interruption is the length of time which the blade interrupts the extrudate
during the cutting process. Knowing blade interruption allows you to optimize
blade speed and design for specific applications.
You can calculate blade interruption for your application if you know:
• the cutting blade width
• blade speed (cutter rpm)
• extrudate cross section.
The rotary knife cut path circumference is fixed for each cutter model:
CSC Bushing Knife Cut Path Knife Cut Path
Model Diameter Diameter Circumference
1L 1.25" 10" 31.4"
As an example, calculate the blade interruption (in milliseconds) for an CSC1 cut-
ter running 1/4" (0.250") OD tubing. The blade speed is 718 rpm and the cutting
blade is 15/16" (0.937") width at the point where it passes through the extrudate,
and the cut path circumference is 31.4" for the CSC1.
Calculate the blade interruption time. The interruption time starts when the blade
makes its first contact with the extrudate and ends when the blade is totally clear of
the product (i.e. no longer interrupting it). Because we know the blade travel
speed, we can calculate the interruption time if we know how far the blade travels
during period of interruption. This distance is equal to the sum of the extrudate
outer diameter and the blade width at the point of contact.
Blade interruption = (Product OD + Blade width)
X 60,000
time, msec Knife circumference rpm