Technical Guidance Troubleshooting for Milling
n Horsepower Consumption
This section contains the horsepower consumption formula and the explanation of the associated variables. A list of commonly encountered materials has been added to assist you when determining the required horsepower for a machining operation. Machine efficiency, drive type, and amount of time that the machine has been running can effect the horsepower and torque availability at the spindle. Without an extensive list of specifications, it is nearly impossible to predict the capabilities of a machine tool. Sumitomo suggests that unless the capabilities of a machine tool are well known, it is wise to limit the attempted operations to those that require no more than 65% of the machine’s rated horsepower. Please take the time to understand the power requirements of an operation before attempting it, unless you are very familiar with the tool, material, and especially the machine being used. *Note: If the material that you are machining is not found in this list, contact the material manufacturer for further information. Most material suppliers, or mills, have excellent technical resources available. However, if the material in question exhibits machining properties that are similar to a given material, use the corresponding “K” factor.
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n Horsepower Consumption Formula
'K' factors for some common materials are:
W x D x F K
Horsepower =
Material
'K'
Material
'K'
W = width of cut (inches) D = depth of cut (inches) F = feed rate (inches/minute) K = 'K' factor for material
Magnesium Aluminum
4.0 4.0 2.0 2.5 2.0 1.0
Stainless steel Free machining
1.0
Copper Brass Bronze
Others
.6
Titanium under 100,000 psi 100,000-135,000 psi 135,000 psi and over High-tensile alloys 180,000-220,000 psi 220,000-260,000 psi 260,000-300,000 psi High-temperature alloys Nickel base alloys
Malleable iron
.8 .6 .4
Cast iron Ferrite Pearlitic
1.5 1.0
Chilled
.6
.5 .4 .3
Steel up to 150 BHN
1.0
up to 300 up to 400
BHN .8 BHN .5
.4 .4 .4
up to 500 BHN .4
Cobalt base alloys Austenitic alloys
n Lead Angle Effect
The lead angle effect is a commonly known phenomenon in tool design. As the lead angle of a tool (the angle at which the insert is rotated away from its axial center line) increases, the actual thickness of the produced chip decreases from the programmed amount. This allows us to take advantage of increased feed rates over standard zero degree (90 degree shoulder) lead tools. By comparing the following lead angle figures, it is possible to increase the actual feed rate up to 30% over the suggested numbers (depending on the type of tool), thus increasing productivity. Tool Lead Angle 15 degrees 96% 20 degrees 94% 30 degrees 86% 45 degrees 71% To simplify this calculation we have included a chart that allows easy determination of programmed feed per tooth by choosing desired feed per tooth and then following the column down to the row that matches the lead angle of the tool that is being used. Example:Find the programmed feed per tooth for a UFO cutter (45 degree lead angle), when the desired feed per tooth is 0.006 IPT. Answer: Programmed feed per tooth = 0.0085 IPT n Programmed Feed Per Tooth vs. Desired Feed Per Tooth % of chip thickness from programmed feed rate
Desired Feed Per Tooth (IPT)
Tool Lead Angle
0.004
0.005
0.006
0.007
0.008
0.009
0.010
0.011
0.012
Programmed Feed Per Tooth (IPT)
15 20 30 45
0.0042 0.0043 0.0047 0.0057
0.0052 0.0053 0.0061 0.0075
0.0063 0.0064 0.0070 0.0085
0.0073 0.0074 0.0081 0.0099
0.0083 0.0085 0.0093 0.0113
0.0094 0.0096 0.0105 0.0127
0.0104 0.0106 0.0116 0.0141
0.0115 0.0125 0.0117 0.0128 0.0128 0.0140 0.0156 0.0170
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