Finding the correct tool steel feeds and speeds is not just a matter of guesswork. You can save a great deal of time and money by learning the correct way to calculate the speeds and feeds. These are good starting point for injection mold making.
Solid Carbide Endmill Information
These figures are all for cutting mold steels, such as S-7, H-13, D-2 or P-20 with solid carbide endmills.
|SFM = 0.262 x D x RPMRPM = (3.82 x SFM) / D|
IPR = IPM / RPM or CHIP LOAD x F
IPM = RPM. x IPR
CHIP LOAD = IPM / (RPM x F) or IPR / F
Some basic terms are required before you can effectively start using any speed and feed chart or calculator.
Basic terms for speeds and feeds
Flutes(F) – Number of flutes
Diameter(D) – Cutter Diameter
Chip load – The amount of material removed by each flute of the cutter.
Feed Rate or Feed per tooth – The inches per minute of workpiece movement toward the cutter between each tooth
Inches Per Minute(IPM) – Number of linear inches the cutter passes through the workpiece in one minute
Depth of Cut (DOC) – The depth of cut of the end mill into the part surface axially. With CNC milling, it is measured in the Z axis direction.
Inches Per Revolution (IPR) – Feed rate of the cutter for each revolution of the cutter. In the inch system, the feed rate of the cutter can be calculated for each revolution of the cutter.
I.P.R. = Chip load x Number of flutes
Millimeters Per Revolution (MMPR) – Feed rate of the cutter each revolution of the cutter. In the metric system, the feed rate of the cutter can be calculated for each revolution of the cutter.
M.M.P.R. = Chip load x Number of flutes
Meters Per Minute (MPM) – The cutting speed of the end mill. This system is used in all countries that use the Metric system. MPM represents the rate of the surface of the cutter passes over the surface of the part. Cutting speed is measured in Meters per minute.
Revolutions Per Minute (RPM) – The spindle speed rate of the cutter. This value will be calculated from a selected SFPM or MPM.
Surface Feet Per Minute (SFPM) – The is the cutting speed of the end mill in the United States. It is the number of feet per minute that a given point on the circumference of a cutter travels per minute.
The following items must be selected by the machinist / programmer when using end mills.
SELECTING SPEED AND FEED RATES AND THE DEPTH OF CUT
SFPM – cutting surface speed
Chip Load – material removal rate
Depth of Cut – depends on specific part applications requirements
Considerations – cutting depth never to exceed flute length
Excessive depth of cut will result in tool deflection. As the depth of cut increases, use the largest diameter cutter available to maintain a depth to diameter ratio of 1 : 1.
Width of Cut – (maximum amount should not exceed 2/3 x Cutter diameter)