cnc machine component

8/8/2019 CNC Machine Component

1/22

CNCMachine

MachineComponents

Section (1)


2/22

CNC Machine Components:

1. Machine structure (Base, Column, Bed).2. Guideways.

3. Spindle & Spindle Bearings.

4. Ballscrews.

5. Torque Transmission units.

6. Tool Changing Mechanism.

7. Coupling & Connection.

Machine Structure:

Page 2 of22


3/22

Bed:

It is the means of holding and moving the work and tool. It comes under the linking structure and

generally made up of cast iron. it supports the table mounted on base guideways.

Table:

It is placed upon the saddle for the purpose of holding the work piece and moving it in desired

position in X axis on commanding. It is made up of cast iron.

Column:

This is vertical orientation made of cast iron, with column it is possible to move head up on

down and perform the process of cutting or milling.

Page 3 of22


4/22

Saddle:

The mechanical components of the machine must be rigid and strong to support the quickly

moving parts.

Page 4 of22


5/22

Page 5 of22


6/22

Cast iron used to be the material of choice for metal-working machines. Today, most

machines make liberal use of weldments of hot-rolled steel and wrought products such

as stainless steel to reduce cost and allow fabrication of more intricate frame designs.

Page 6 of22


7/22

Page 7 of22


8/22

Ballscrews:

The mechanisms that move the bed or spindle are called ballscrews. These change rotary

motion of the drive motors into linear motion and consist of a screw shaft and support

bearings. As the shaft turns, a bearing mount follows the spiral grooves in the shaft and

produces a very accurate linear movement that moves either the worktable under the

spindle, or the spindle carrier itself. These ballscrews are bolted to the base with the

bearing mount bolted to the worktable or spindle carrier.

Page 8 of22


9/22

Page 9 of22


10/22

S pindle

The spindle is machined and ground, mounted to its drive motor, and then bolted to the

movable spindle carrier. Each axis of motion has a separate ballscrew and set of ways in

most machining center.

Page 10 of22


11/22

CNC Machine Guideways:

Page 11 of22


12/22

High speed high accuracy linear guide way

1. Linear guide ways with zero backlash ensures consistent cutting surface on curve or slope

cutting.

2. Suitable for high speed travel and the power requirement is minimized.

3. By using rolling contact instead of sliding contact, linear guide reduces friction loss but

increases positioning accuracy.

4. The loading capacity is high on multiple directions. Cutting rigidity can be ensured.

Page 12 of22


13/22

5. Long service life is guaranteed by its high durability.

Hydrostatic Guideways:

Page 13 of22


14/22

Advantages of Hydrostatic Linear Guideways :

Superior vibration damping

Improved hard turning capabilities

Significantly longer tool life

Longer machine life

Increased axis speeds

Improved part roundness

Improved part surface finish

Page 14 of22


15/22

Linear bearings with balls, rollers or needles:

Because of the problem of metal to metal contact the relative high amount of friction is

generated, which exits between the faces in contact, typically 0.15 for lubricated steel sliding on

steel. A number of machines have flat roller bearings fitted to the carriages to provide a rolling

motion rather than sliding motion. The rollers are in contact with the guideways machined on the

bed of the machine.

To reduce the problem of machining an accurate form on the bed of the machine, hardened steel

rails with special guide forms (figure....) may be bolted on the casting of the machine tool.

Page 15 of22


16/22

Tool Changing Mechanism:

Page 16 of22


17/22

The CU system is a mechanical cam-driven tool changer that combines an intermittent

series of linear and rotary movements necessary to change the tool:

-cone gripping

-extraction (from the tool pocket and from the spindle)

-changeover

-insertion (in the tool pocket and in the spindle)-release

A mechanical tool safety lock on the gripper holder arm makes sure the tools are

transferred safely during the changeover phase.

Page 17 of22


18/22

Tool extraction station operated by a pneumatic cylinder

Rigid Coupling

Page 18 of22


19/22

This type of coupling has no flexibility or resilience, hence it is necessary for the shafts

that are to be connected to be in good alignment, both laterally and angularity, in order

excessive loads on the coupling, on the shafts, or on the shaft bearings.

Rigid couplings do not accommodate misalignment and consequently should not be

used indiscriminately.

Types of Rigid Couplings:-

1.1 Sleeve or muff coupling

1.2 Clamp coupling

1.3 Flange coupling

Easiest, lowest cost, for CNC

routers and cnc lathes, they are easily available, are self-aligning, do not damage the

motor shaft, and make a 100% connection from motor to screw, one trick when using a

solid coupling is to use a simple thrust washer, placed on the motor shaft between the

motor face and coupling, using a thrust washer will take any linear load of the screw,

allowing the motor, coupling and screw a total direct connection with almost zero end

play.

Page 19 of22


20/22

Driving System :

Page 20 of22


21/22

Types Of Drives:

Page 21 of22


22/22

Page 22 of22

cnc machine component

Documents