The document discusses various hydraulic and pneumatic circuits used in machine tools and industrial applications. It describes the working of circuits for drilling machines, planning machines, shaping machines, grinding machines, pressing machines, forklifts, pick and place machines, and tool handling in CNC machines. It also discusses low cost automation techniques using pneumatic and hydraulic components, as well as hydraulic and pneumatic power packs used to power machinery.

1. Hydraulics and Pneumatics
Prepared by
David Blessley S
AP/Mechanical Engg.,
Kamaraj College of Engineering and Technology,
VIrudhunagar
Troubleshooting and Applications

2. Design of hydraulic circuit for drilling machine
Left Mode : When the DCV is shifted
to the left mode, the cylinder moves
downwards and carryout the drilling
operation
Right Mode : when the DCV is shifted
to the right mode, the cylinder moves
upwards i.e., retracts
Spring centered position: When the DCV is shifted to the spring centered position, oil
from the rod end regenerates with the pump flow and enters the blank end. This
effectively increases pump flow to the blank end. Thus the spring centered position
gives rapid extension of the cylinder.

3. Design of hydraulic circuit for planning machine
• Forward movement of table
• When the DCV is shifted to the right envelope mode, oil
flows from the pump into the left end of the cylinder and
the piston moves form left to right
• Oil at the right end return back to the reservoir through
DCV and the flow control valve. At the end of the stroke,
the pilot limit valve LV1 is actuated by the ram
movement. When LV1 is actuated, the pilot flow actuates
the DCV to shift its left envelope mode
• Return movement of table
• When the DCV is shifted to the right envelope mode, oil
flows from the pump to the right end of the cylinder and
moves from right to left
• Oil at the left side of the cylinder returns back to the
reservoir through the DCV and flow control valve. At the
end of the return stroke, the pilot limit valve LV2 is
actuated by ram movement. Which in turn actuates the
DCV to shift to its left envelope mode and the process
continues

4. Design of hydraulic circuit for shaping
• Forward stroke
• When the DCV is shifted to the right envelope, oil flows from
pump to the right end of the cylinder and the piston moves form
right to left
• At the same time, oil at the left side of the cylinder return back
to the reservoir through flow control valve which allows only
metered fluid to return back to reservoir
• This permits the forward cutting stroke to be carried out in a
slow manner. At the end of this stroke, the limit switch LS1 is
actuated by the ram movement which in turn actuates the DCV
to shift its left envelope mode
• Return stroke
• When the DCV is shifted to the left envelope, oil flows from the
pump into the left end of the cylinder through the flow control
valve and the piston moves from left to right
• At the same time, oil at thhe right side of the cylinder returns
back to the reservoir directly without any restriction and quick
return motion of the ram is achieved
• At the end of the stroke, the limit switch LS2 is actuated by the
ram movement which in turn actuates the DCV to shift its right
envelop mode

5. Design of hydraulic circuit for grinding machine
• Forward movement of table
• When the DCV is shifted to the right envelope mode, oil flows
from the pump into the left end of the cylinder and the
piston moves form left to right
• Oil at the right end return back to the reservoir through DCV
and the flow control valve. At the end of the stroke, the pilot
limit valve LV1 is actuated by the ram movement. When LV1
is actuated, the pilot flow actuates the DCV to shift its left
envelope mode
• Return movement of table
• When the DCV is shifted to the right envelope mode, oil flows
from the pump to the right end of the cylinder and moves
from right to left
• Oil at the left side of the cylinder returns back to the
reservoir through the DCV and flow control valve. At the end
of the return stroke, the pilot limit valve LV2 is actuated by
ram movement. Which in turn actuates the DCV to shift to its
left envelope mode and the process continues
It may be noted that the flow control valve is placed in a return line to the reservoir in order to obtain
the same speed of the piston during both strokes

6. Design of hydraulic circuit for pressing
application
• Extension
• When the 4/3 DCV is shifted to the left mode, oil flows
from the pump to the blind end of the cylinder. Thus the
cylinder extends
• When the pressing operation starts, the increased
pressure of the oil opens the unloading valve to unload
the low pressure pump. i.e., only high pressure low flow
pump does the pressing
• Retraction
• When the DCV is shifted to the right mode, oil flows to
the rod end of the cylinder and retraction starts
• The pressure of the oil increases because of the check
valve keeps the high pressure oil
• Due to this, the unloading valve opens and unloads the
high pressure pump to the tank. i.e., only low pressure
high flow pump does the return stroke
• Cylinder locking
• When the DCV is shifted to the spring centered mode,
the pumps flow is directed to tank

7. Design of hydraulic circuit for forklift application
• Extension
• Pressure on the counter balance valve has been set
slightly above the required system pressure to prevent
the load from free falling
• Due to this back pressure, fluid available on the rod side
opens the counter balance valve
• Fluid coming out of the cylinder flows directly to the tank
through DC valve
• Retraction
• Flow in the reverse direction cannot occur without a
reverse free flow check valve
• When the load is to be raised, the internal check valve
permits flow for the retraction of the cylinder
• Cylinder locking
• At the centre position of DCV, pump is unloaded and the
piston is held locked by counter balance valve
• If the load is required to be held for a prolonged time,
then a pilot operated check valve to be used in addition to
the counter balance valve

8. Pneumatic circuit for pick and place applications
• Extension
• When the 5/2 DCV is shifted to its left mode by
energizing the solenoid, air flows to the blind end of
the cylinder through the flow control valve FCV1
• This extends the cylinder and so the actuating force is
applied on the cam of the gripper which in turn
actuates the gripper jaws to grip the object
• Retraction
• When the DCV is shifted to right mode by deenergizing
the solenoid, air flows to the rod end of the cylinder
through flow control valve FCV2
• This retracts the cylinder and the gripper ungrips the
object
Note: the extending speed of the cylinder and the actuating force can be
regulated by adjusting the air flow in the flow control valves

9. Pneumatic circuit for tool handling in CNC machine tools
• Cylinder operation
• When the solenoid of 4/2 DCV is energized, air
flows into the blind end of the cylinder and the
cylinder extends to clamp the workpiece/tool
• When the solenoid of 4/2 valve is deenergized,
the air flows into the rod end of the cylinder and
the cylinder retracts so that to unclamp the
workpiece
• Motor operation
• When the solenoid of 4/3 DCV is energized, air
flows into the inlet port of the air motor and the
motor rotates. This motor rotation is used to
rotate the tool
• When the solenoid of 4/3 DCV is deenergized, the
motor rotates in the opposite direction
Note: The operation of pneumatic cylinder and motor is synchronized based on the application requirement through part
programming

10. Low cost automation
• A technology that creates some degree of automation around the existing
equipment, tools, methods and people using mostly standard components
available in the market
• The main objective of this technology is
• To reduce machine investment cost
• To reduce the process time
• To increase productivity
• To have consistent quality
• Its application in manufacturing industries including material handling, loading,
feeding, pick and place functions, clamping, welding, painting, forming etc.,
• Machining operations like drilling, riveting, broaching, shaping etc.,
• Inspectional functions like marking, checking, gauging etc.,
• Assembly and packaging

11. Hydraulic power pack
• It is a self contained unit used instead of a built in power supply for hydraulic
machinery
• Its components are
• Reservoir
• Regulators
• Pressure supply lines
• Motor
• Pump
• Filters
• Pressure control valves
• Directional control valves
• Accumulators
• Coolers and heaters
• Power unit controllers

12. Pneumatic power pack
• It is a self contained unit used instead of built in power supply for pneumatic
machinery
• Components
• Reservoir
• Motor
• Compressor
• Air cooler
• Air dryer
• Valves
• FRL unit