SURFCAM calculates Feed Rate using the following formulas:
IPR Feed Rate = Feed Chip Load * Number of Flutes * Chip Load Factor
IPM Feed Rate = IPR Feed Rate * Spindle Speed
Feed Chip Load
The initial value for Feed Chip Load is taken from the Chip Load Per Flute value in the Tool Library.
Number of Flutes
This is a value from the Tool Library for the number of flutes in the tool.
Chip Load Factor
This is a value from the Material Library associated with the material being cut and the material from which the tool is made. Spindle Speed is the previous parameter on this tab.
If you override the calculated Feed Rate value, the Feed Chip Load value will be re-calculated as you enter the new Feed Rate value.
In the second column, select either Inches per Minute (IPM)/Millimeters per Minute (MMPM) or Inches per Revolution (IPR)/Millimeters per Revolution (MMPR). The selection determines the Post output code for the Feed Rate.
Inverse time feed rates are calculated in the post processor based on the desired feed rate and the actual length of the move. When these feed rates are used, the NC code must have a feed rate programmed on each block. This is to maintain a constant feed rate, in inches per minute, across the part. Check the machine tool documentation for the feed rate type requirements.