Machining Metal Removal

on . Posted in Welding Engineering

Tags: Thermal Conductivity Welding Machining

Machining metal removal is the process of shaping, cutting, or removing material from a workpiece to achieve the desired shape, size, and surface finish.  This process is widely used in manufacturing and metalworking industries to create a wide range of products, from simple components to complex parts.  The primary goal of machining metal removal is to remove excess material, refine the workpiece's dimensions, and improve its surface quality.

Key Points about machining metal removal

  • Turning  -  Turning involves rotating a workpiece on a lathe while a cutting tool removes material from the workpiece's outer surface.  This process is commonly used for cylindrical parts like shafts and spindles.
  • Milling  -  Milling uses rotary cutters to remove material from a workpiece.  The cutter can move along multiple axes, allowing for the creation of various shapes, slots, and contours.  Milling machines are versatile and used for both simple and complex parts.
  • Drilling  -  Drilling is the process of creating holes in a workpiece using a rotating cutting tool called a drill bit.  It is a common operation for creating holes in metal components.
  • Grinding  -  Grinding is used to achieve fine surface finishes and tight tolerances.  It involves abrasive wheels that remove material by grinding or abrasion.  This process is ideal for achieving precise dimensions and smooth surfaces.
  • Electrical Discharge Machining (EDM)  -  EDM utilizes electrical sparks to erode the workpiece material.  It is suitable for machining intricate shapes and hardened materials that are difficult to machine with traditional methods.
  • Wire EDM  -  This is a variation of EDM where a thin, electrically charged wire is used to cut through the workpiece, creating complex shapes with high precision.
  • Abrasive Water Jet Cutting  -  In this method, a high-pressure stream of water mixed with abrasive particles is used to cut through metal.  It is suitable for cutting various materials, including metals, plastics, and composites.
  • Laser Cutting  -  Laser cutting employs a high-energy laser beam to melt, burn, or vaporize material from the workpiece.  It is used for precise and fast cutting of thin to thick metal sheets.
  • Plasma Cutting  -  Plasma cutting uses a high temperature, ionized gas (plasma) to melt and remove material from a workpiece.  It is commonly used for cutting thick metal plates and is often employed in industrial applications.

Each of these machining processes has its advantages and limitations, making them suitable for different applications.  The choice of method depends on factors such as the material being machined, the desired tolerances, surface finish, production volume, and the complexity of the part being manufactured.  Machining metal removal is a crucial step in the production of a wide range of products across various industries, including automotive, aerospace, electronics, and more.

 

Chip Thickness formula

\( CT =  2 \; IPT \; \sqrt{ \left( d \; RDOC \right) - RDOC^2 } \;/\;  d \)
Symbol English Metric
\( CT \) = chip thickness \(in\) \(mm\)
\( IPT \) = inches per tooth chip thinning adjustment \(in\) \(mm\)
\( RDOC \) = radial depth of cut \(in\) \(mm\)
\( d \) = tool diameter \(in\) \(mm\)

 

Cubic Inches Per Minute Removal Rate formula

\( IPT =  IPM \; RPM \; Z \)
Symbol English Metric
\(\ IPT \) = inches per tooth \(in\) \(mm\)
\( IPM \) = inches per minute \(in\) \(mm\)
\( RPM \) = revolutions per minute \(rev\;/\;min\) \(rev\;/\;min\)
\( Z \) = number of teeth on cutter \(dimensionless\)

 

cutting Feed formula

\( f_c =  f_t \; n \)
Symbol English Metric
\( f_c \) = cutting feed (IPR) \(in\;/\;rev\) \(mm\;/\;rev\)
\( f_t \) = feed per tooth (IPT) \(in\;/\;rev\) \(mm\;/\;rev\)
\( n \) = number of teeth \(dimensionless\)

 

cutting Time formula

\( t_c =  c_l \; f \)
Symbol English Metric
\( t_c \) = cut time  \(min\) \(min\) 
\( c_l \) = cut length \(in\) \(mm\)
\( f \) = feed rate (IPM) \(in\;/\;min\) \(mm\;/\;min\)

 

Inches Per Revolution Feed Rate formula

\( IPR =  IPM \;/\; RPM \)
Symbol English Metric
\( IPR \) = inches per revolution \(in\) \(mm\)
\( IPM \) = inches per minute \(in\) \(mm\)
\( RPM \) = revolutions per minute \(rev\;/\;min\) \(rev\;/\;min\)

 

Inches Per Minute Feed Rate formula

\( IPM =  RPM \; IPT \; Z \)
Symbol English Metric
\( IPM \) = inches per minute \(in\) \(mm\)
\( IPR \) = inches per revolution \(in\) \(mm\)
\( Z \) = number of teeth on cutter \(dimensionless\)

 

Inches Per Tooth Feed Rate formula

\( IPT =  IPM \; RPM \; Z \)

\( IPT = IPR\;/\;Z \)

Symbol English Metric
\( IPT \) = inches per tooth \(in\) \(mm\)
\( IPM \) = inches per minute \(in\) \(mm\)
\( IPR \) = inches per revolution \(in\) \(mm\)
\( RPM \) = revolutions per minute \(rev\;/\;min\) \(rev\;/\;min\)
\( Z \) = number of teeth on cutter \(dimensionless\)

 

Inches Per Tooth Feed Rate (Chip Thinning Adjustment) formula

\( IPT =  CT \; d \;/\; 2 \sqrt{ \left( d \; RDOC \right) - RDOC^2 }  \)
Symbol English Metric
\( IPT_{adj} \) = inches per tooth chip thinning adjustment \(in\) \(mm\)
\( CT \) = chip thickness \(in\) \(mm\)
\( RDOC \) = radial depth of cut \(in\) \(mm\)
\( d \) = tool diameter \(in\) \(mm\)

 

Material Removial Rate formula

\( MRR =  c_d \; c_w \; f \)

\( MRR =  RPM \; c_d \; c_w \; IPT \; Z \)

Symbol English Metric
\( MRR \) = material removal rate  \(in^3\;/\;min\) \(mm^3\;/\;min\) 
\( c_d \) = cut depth \(in\) \(mm\)
\( c_w \) = cut width \(in\) \(mm\)
\( f \) = feed rate (IPM) \(in\;/\;min\)  \(mm\;/\;min\) 
\( IPT \) = inches per tooth  \(in\) \(mm\)
\( Z \) = number of teeth on cutter \(dimensionless\)

 

Motor Horsepower formula

\( HP_m = HP_s\;/\;n\)
Symbol English Metric
\( HP_m \) = motor horsepower (HP) \(lbf-ft\;/\;sec\) \(J\;/\;s\)
\( \eta \) (Greek symbol eta) = machine efficiency \(dimensionless\)
\( HP_s \) = spindle horsepower (HP) \(lbf-ft\;/\;sec\) \(J\;/\;s\)

  

revolutions Per Minute formula

Revolutions per minute needs to be at a constant speed to achieve optimum cutting.  The correct RPM can prevent high tool wear and poor workpiece quality that will result in higher tool cost.

\( RPM =  SFM \; \frac{12}{ \pi } \;/\; d_w  \)
Symbol English Metric
\( RPM \) = revolutions per minute \(rev\;/\;min\)  \(rev\;/\;min\) 
\( d_w \) = diameter of workpiece \(in\) \(mm\)
\( \pi \) = Pi \(3.141 592 653 ...\)
\( SFM \) = surface feet per minute \(ft\;/\;min\)  \(m\;/\;min\) 

 

Spindle Horsepower formula

\( HP_s =  MRR \; P \)
Symbol English Metric
\( HP_s \) = spindle horsepower (HP)  \(lbf-ft\;/\;sec\)  \(J\;/\;s\)
\( MRR \) = material removal rate \(in^3\;/\;min\)   \(mm^3\;/\;min\)
\( P \) = unit power  \(lbf-ft^2\;/\;sec^3\) \(kg-m^2\;/\;s^3\) 

 

Spindle Speed formula

\( s_s =  s_c \; d \; \pi \)
Symbol English Metric
\( s_s \) = spindle speed (RPM)  \(rev\;/\;min\)  \(rev\;/\;min\)  
\( s_c \) = cutting speed (SFM)  \(ft\;/\;min\) \(m\;/\;min\) 
\( \pi \) = Pi \(3.141 592 653 ...\)
\( d \) = tool diameter \(in\) \(mm\)

 

Spindle Torque formula

\( \tau_s = HP_s\;/\;s\)
Symbol English Metric
\( \tau_s \) (Greek symbo; tau) = spindle torque \(lbf-in\)  \(N-mm\) 
\( HP_s \) = spindle horsepower (HP) \(lbf-ft\;/\;sec\)  \(J\;/\;s\) 
\( s_s \) = spindle speed (RPM)  \(rev\;/\;min\) \(rev\;/\;min\) 

   

Surface Feet Per Minute formula

Surface feet per minute is time required to remove metal from a workpiece over a length.

\( SFM =   RPM \; d_w \; \pi \;/\; 12   \)
Symbol English Metric
\( SFM \) = surface feet per minute  \(ft\;/\;min\) \(m\;/\;min\) 
\( d_w \) = diameter of workpiece \(in\) \(mm\)
\( \pi \) = Pi \(3.141 592 653 ...\)
\( RPM \) = revolutions per minute \(rev\;/\;min\)   \(rev\;/\;min\)

 

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Tags: Thermal Conductivity Welding Machining