CNC Machinery Module Objectives: Define Machining. Recognize the main machining processes. Calculate the cutting and rotational speeds for turning and milling.

Basics of Machining Have you ever think how these parts are produced?

Machining Machining is one of the manufacturing techniques used to produce parts. The modern types of machining techniques include the use of CNC (Computer Numerical Control) machines. To understand CNC basics, let’s have a look at the conventional machining.

Here we can see how a small gear could be produced:

Machining is a class of material-working processes that involves using a power-driven machine tool to shape metal. The most important conventional machine tools that shape materials to a size by cutting away unwanted portions, are: Turning (Lathe) machine. Milling machine.

Turning machine and its main parts Turning (Lathe) Machine The primarily function, of the turning machine is to produce a cylindrical surfaces. Turning Machine Turning machine and its main parts

Turning Machine Operations Some important turning machine operations are: 1. Facing: Is to remove a small amount of material (around 1 – 2 mm) from the end of the workpiece to produce smooth and true face and also to bring the workpiece to the desired length.

Facing

2. Parallel Turning Is to move the cutting tool parallel to the workpiece axis in order to reduce its diameter.

3. Drilling Is to make a hole having a specific diameter and depth in a material. Drilling could be done by special drilling machines, milling or turning machine. Drilling using a drilling machine Drilling using Lathe machine

4. Threading To make spiral or helical cuts on a material. These cuts are usually found on bolts (external threading) or nuts (internal threading). Thread in technical drawing External Thread (outside) Bolt Internal Thread (inside) Nut

5. Recessing To make a groove having a specific width and depth into the material. Internal Recess External Recess

Taper cutting on the turning machine 6. Taper cutting To increase or decrease the diameter of the workpiece in a uniform rate. Tapered Part Taper cutting on the turning machine

Name The Following Turning Operations ?

Milling Machine Milling is to use a rotating multitoothed cutter into the workpiece to remove material, in order to make gears, slots, holes, pockets and many different shapes.

Vertical Milling Machine Generally Milling machines are classified into : 1. Vertical milling machine The spindle positioned perpendicular to its worktable. Vertical Milling Machine

Horizontal Milling Machine The cutting tool positioned horizontally and parallel to the worktable. Horizontal Milling Machine

Parts of Milling Machine

Examples of Milling Operations milling.avi milling machine operations.wmv

Example of Milling Operations

Turning and Milling Cutters Available in different shapes, and made of different special materials. For example: High Speed Steel (HSS). Tungsten Carbide. Milling Cutters Turning Cutting tools

Cutting Speed and Feed Cutting speed (Vc) The cutting speed is the speed at which the circumference of the work part moves along the cutter. The magnitude of cutting speed is determined by the: 1. Material of the work part. 2. Material of the cutter. 3. Infeed (surface quality, roughing, finishing). 4. Life of the tool. The cutting speed is chosen from tabulated values.

Rotational Speed (n) Once the cutting speed is chosen, the rotational speed has to be calculated. The following formula can be used to calculate the rotational speed: Where, Vc: the cutting speed in (m/min). d: the work part diameter in (m). n: the rotational speed in revolution per minute (RPM) (Rev/min).

Infeed Speed (Vf) Vf = n x f Together with the cutting movement, infeed allows a continuous chip removal during several rotations. The infeed speed (Vf) is indicated in mm/min. The following formula is used to calculate the infeed speed: Vf = n x f Where: Vf: the infeed speed in mm/min n: the rotational speed in revolution per minute (RPM). f: the infeed in mm/rev; chosen from tabulated values.

Examples Example 1: How many number of rotations (n) are required, if the diameter to be machined is 12 mm and the cutting speed is 283 m/min? Example 2: Calculate the cutting speed for turning if the cutting is done on 60 mm diameter workpiece and at number of rotations of 1500 RPM?

Example 3: Calculate the cutting speed for milling if the milling tool diameter (d) = 50 mm and the number of rotations (n) = 520 rev./min? Example 4: Calculate the number of rotations (n) if the milling tool diameter = 12 mm and the cutting speed Vc = 120 m/min.