Material Removal Processes

Question 1

What is Turning and what is it used for?

Answer 1

• Primarily used to produce parts of a cylindrical shape using a single point cutting tool mounted on a lathe
• Material is removed by moving the cutting tool either in a direction parallel to the axis of rotation or perpendicular.

Question 2

What is Milling and where is it used?

Answer 2

• Differs from lathes in that it is the tool that rotates whilst the workpiece remains stationary and is moved under the cutter by the machine table it is clamped to.

Question 3

What is the difference between down milling and upmilling?

Answer 3

• Upmilling is where the milling cutter rotates in the opposite direction that the material is being fed. This allows for faster machining and better surface finish, however the teeth experience greater shock.
• Down milling is the opposite. There is less mechanical shock, however, the piece must be secured properly to the base.

(Think downstream, upstream)

Question 4

What is drilling?

Answer 4

• Produces round holes in components.
• to produce very accurate holes of an exact diameter, and of a high level of roundness and straightness, a reamer is used.
• A reamer is similar to a conventional drill bit however the sides of the bit do the cutting not the end.

Question 5

What is grinding and what are the three main types?

Answer 5

• It is an abrasive method.
• Used where the workpiece material is hard to be machined effectively using other techniques or where dimensions are required to be very precise.
• 3 main types: Form grinding, centreless grinding, creep feed grinding

Question 6

What is form grinding?

Answer 6

• It is a type of cylindrical grinding where the grinding wheel has the exact shape/contour of the final product

Question 7

What is centreless grinding?

Answer 7

• Workpiece is supported by a blade

- Two wheels are used: One to grind the surface and one to regulate axial movement

Question 8

What is creep feed grinding?

Answer 8

• Can provide high rates of material removal

Question 9

What does CNC stand for?

Answer 9

Computer Numerical Control

Question 10

What makes up a CNC system?

Answer 10

• Machine Control Unit (MCU)

- Machine tool itself

Question 11

What makes up the MCU

Answer 11

1) Data processing unit (DPU) - Processes coded data and passes info on the position of each axis, its direction of motion and auxiliary control systems
2) Control Loops Unit (CLU) - Operates the drive mechanisms of the machine, recieves feedback about the position and velocity of the axes. the CLU takes information from the DPU.