Manufacturing

Process of a

Piston

INTRODUCTION

A piston is an important component of

reciprocating engine helps to convert

energy obtained by the combustion of

fuel in cylinder into useful mechanical

power.

It is like a disc which reciprocates within a

cylinder.

It is either

moved by the

fluid or it

moves the

fluid which

enters the

cylinder.

MANUFACTURING PROCESS

Casting

Heat treatment

Machining process

Pin fitting and Inspection

CASTING

The foundry is the beginning of the piston.

At the foundry the die is prepared by heating

it to operating temperature for approximately

one hour.

This process allows the die to readily accept

the molten material when it is poured.

The molten material used for Piston is 10%

Silicon content Aluminium or Aluminium alloys

PROCESS

The process starts by heating the material to 700 degrees Celsius.

The material is then scooped up with a ladle from the crucible (the pot that holds the molten material).

This is then poured into the die through the sprue.

The material is then allowed to cool before it is removed from the die.

HEAT TREATMENT Heat Treatment is the controlled heating and

cooling of metals to alter their physical and

mechanical properties without changing the

product shape.

Heat Treatment is often associated with

increasing the strength of material, but it can

also be used to alter certain manufacturability

objectives such as improve machining, improve

formability, restore ductility after a cold working

operation.

MACHINING PROCESS

Open end bore machining

Rough outer diameter turning

Grooves forming

Semi finish hole boring

Circle grooving oil hole drilling in 3rd

groove and skirt

Ring grooving and chamfering

Final outer diameter turning

Deburring and cleaning

Tin coating

Finish pin hole boring

PIN HOLE BORING

At this stage of the piston manufacturing

process, the casting has the gudgeon pin

hole rough machined.

This is carried out on a simple lathe.

The pin borer is only a rough machining

process which allows the reamer to enter

the gudgeon hole later.

CNC TURNING

Turning of the casting is carried out on CNC machinery.

This equipment is the most accurate and fastest available for this application with very tight tolerances and extremely fast spindle speeds. The following operations are performed on this machine:

Open end bore machining

Rough outer diameter turning

Grooves forming

DRILLING AND GRINDING

Drilling includes all oil holes in places such as the gudgeon pin bosses and oil ring grooves.

Slotting is done where slots are placed in the skirt or in the oil ring groove.

Grinding involves the final size being machined on the piston.

Semi finish hole boring

Circlip grooving oil hole drilling in 3rd groove and skirt

Ring grooving and chamfering

REAMING

The final machining process for the piston is

that of reaming.

This process involves the piston being placed

in a bath of oil and reamed at different sizes

to reach the final size required.

Since the pin boring process is only rough it is

necessary to ream the pin bore a number of

times to achieve the surface finish and size

required.

DEBURRING AND TIN

COATING

Before coating, the pistons should be

thoroughly cleaned to remove any soap or

phosphate residue, water spots, machining oil,

dirt, etc. picked up during the manufacturing

process.

For optimum results a mechanical type

cleaner (e.g. spray) is recommended.

Recommended methods for applying Tin

Coating to pistons are either screen print or

spray techniques.

PIN FITTING AND FINAL

INSPECTION

At this stage the piston is cleaned, inspected

by the instruments, fitted with the appropriate

gudgeon pin, stamped with the pistons

oversize and any other markings, and then

sent to dispatch.

Finally, the piston is wrapped and placed in

the shipping container with the ring set and

sent to the customer.