Turning - Processes & Materials in Manufacturing

Chipmaking process - material removed from a workpiece by a tool. An engine lathe is used to rotate a workpiece at a selected rpm. "Chips" are produced when the tool shears the workpiece.

Advantages:

• Good dimensional tolerance
• The tooling is universal
• Able to machine hardened materials
• Different surfaces are able to be machined (mirror)

Disadvantages:

• Slow process
• Energy intensive
• Excessive waste
• Surface quality is affected

Variables in Chipmaking process:

Independent(variables you can adjust)

• Tool/workpiece hardness
• Tool/workpiece material
• Cutting speed
• Depth of cut made
• Condition of the machine used

Dependent(variables measured)

• Type of chip
• Surface finish
• Temperature change in the tool and workpiece
• The force between the tool and workpiece

The cutting speed (V) is given by the follow equation: V = (pi * D0*N) / 12
Where...

• V is the cutting speed in feet per minute (fpm)
• D0 is the diameter of the workpiece to be cut measured in inches
• N is the rotational speed measured in revolutions per minute (RPM)

Cutting time in minutes is given by: t = L / (f * N)
where...

• L is the length of the cut in inches
• f is the feed rate in inches per revolution (in/rev)

Chips will always be thicker than the depth of the cut.

As friction increases between the chip and tool, the chips become thicker, warmer, and the energy required will increase. The same results will occur if the rake angle decreases.

Profilometer: measures the surface finish.

Fluids can be sprayed on the workpiece during turning process to:

• Reduce friction
• Improve tool life
• Reducing temperature
• Wash out chips