Thursday, May 24, 2018
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Core Making Process

Type of cores

  1. Co2 core

2. Shell core

3. Quickset core

4. Cold box core

It is known as gas triggered processes .

Phenolic- urethane –amine gassed (cold box) process.

Principle ; The binder is supplied in  2parts .

Part 1- (Resin)

solvent based Phenolic resin .

Part 2 (Hardener) polyisocyanateMDI(methylene di-phenyldiisocyanate)

The resin are mixed with sand in the mixture and blown into a core box

An Amine gas (TEA –Triethylamine or DMEA-diethyl Ethlylamine) is blown into a core , catalyzing the reaction between part 1 and part 2 causing almost instant hardening

GAS GENERATOR

  • The Amine Catalyst are volatile, highly flammable liquids .Special generator are needed to vaporize the Amine and entrain it in air or Co2 The Carrier gas should be heated 30 to 40 deg C to ensure vaporization Controlled delivery of Amine by pump or timer is desirable
  • Cold box cores are produced in the machine. We are producing like crank case and cylinder block cores in this process

SAND

  • Clean silica sand of AFS 50-60 is usually used The sand must be dry ,more than 0.1% moisture reduces the bench life of the mixed sand . Sand temperature is ideally about 25’c.Clay should be 0.2% max.
  • Low temperature causes Amine condensation and irregular cure.
  • High temperature causes solvent loss from the binder and loss of strength

RESIN ADDITION

  • Total addition is 0.8%-1.5% depending on sand quality.
  • Normally equal proportions of Part 1 and part 2 are used

Mixing procedure ;

Batch or continuous mixer can be used.

Add Part 1 first and then Part 2 .

Do not over mix since the sand may heat and

loss solvents.

Bench life  1-2 hours  if the sand is dry.

Core blowing ; use low pressure 30-50 psi .The blowing air must be dry

   Core box material ; Aluminum and Cast iron

SHELL CORE

  • Shell cores are produced in the core shooter machine
  • Resin coated sand of AFS 60 -65 with resin % of 4% minimum is loaded in the machine hopper and blown at the pressure of 4-5 bar into the core box made cast iron
  • The heater are fixed on both core boxes. the heating temperature and curing time is set to our requirement depends upon the  core geometric and thickness of the  core
  • When the core gets cured at the set time the ejection pins fixed on the machine will eject the core from the core box
  • Based on the complexity and surface finish requirement . Shell process is selected

SAND PREPRATION

1. Add silica sand in the mixer 10kgs.

2.Pre-mix A and C oils110grms and 8grms

3.Switch on the Mixer

4.Add A and C oil mix to the sand

5  Add B oil to that mix 110grms

    Take out the prepared sand and charge the sand into the core box and by hand ramming pack well inside the core box . Remove the excess sand from the top of the box .Allow the stripping time for core till the sand gets hardened .(setting curing time is 3to 4 mints )

1.Oil A’ is act as Binder

2.Oil B ’is act as Accelerator

3 . Oil C’ is act  as Hardener

CO2  Process

  • Silica sand of AFS 52 – 58 with Clay content of 1% with sand moisture 1% max is used.

Sodium silicate oil is used as a binder and

Co2 gas as a hardener.

For easy collapsibility  of the core coal dust is used

For easy De- coring Saw dust is used

Hydrometer is used to check the specific gravity of the Sodium silicate . It

should be 1.8 – 1.9 grms/cc

Sand preparation

1 Silica sand – 100kgs free from moisture

2 Silicate oil –    4- 5%

3 Coal dust    –  1-1.5% thoroughly mixed  and taken for  production

After  filling the sand into the core box  co2 gas pass until core gets hardened

CORE COATING & DRYING

SPIRIT BASE CORE COATING

  • Clean the core that are to be coated
  • Mix the Mould Coat thoroughly with solvent
  • Stir the mix before use
  • Coat the core ( Except core print area) using brush or dipping as per Display Board
  • Burn the coated cores for removing the solvent from the core
  • Allow the core to cool to room temperature after burning

Water Base Core Coating 

 

1 Preparation of core coating mix Operator Beginning of the shift Water base core paste mix thoroughly and maintain specific gravity  1.35 to 1.40
2 Collect mixed core coating Operator Beginning of the shift Collect the required quantity from tank provided with stirrer
3 Core coating Operator After dressing the core joints Apply  uniformly by brush ,swap or by dipping and remove the excess coating in the cavities by brush
4 Coated core loading Operator After coating Arrange the coated cores in the oven  trolley

 

DRYING WATER BASE CORE

1 Starting the dryer Operator Beginning of the shift Switch on the air re –circulation fan motor combustion cum auto missing on air blower motor
2 Switch on the diesel pump Operator Beginning of the shift Set the air blower level to zero and open the diesel valve set at a level 4-6
3 Clean the burner Operator Beginning of the shift Watch for proper firing
4 Diesel coming through burner Operator Burner catches fire Set the blower level at point No 8
5 Set the temperature Operator Beginning of the shift Temperature indicator at 200 c+_10 .c
6 Set the trolley movement Operator Beginning of the shift 4 minutes per trolley
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Hi, I m Abhijeet Patil, an aspiring blogger with an obsession of all things mech. This blog is dedicated to helping people learn about Mech-Foundry technology.
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