EJECTION

PARTS OF 2 PLATE MOLD1. Top plate2. Cavity plate 3. Core plate4. Guide pillar5. Guide Bush6. Core Back Plate7. Ejector pin8. Spacers9. Centering Bush10.Bottom plate11.Eje. Guide Bush12.Eje. Guide pillar13.Eje. Back plate14.Sprue pull & Ejector15.Ejector plate16.Sprue puller bush17.Return pin18.Stop button19.Sprue Bush20.Register ring21.Core insert22.Cavity insert

PLAY

EJECTIONEjection function of a mould is delicate since the part while solidifying shrinks to grip over the core tightly which makes smooth release without distortion, strain mark, break or damage of component very difficult.

Parting surface selected in mouldStraight surfaces of mould cavity & coreVacuum created by part sliding on core Undercut in part designDesign of ribs, boss and surface textureThin walled parts moulding

some design aspects that causeejection difficulty :--

EJECTION Various ways of minimizing ejection difficulties1.Apply releasing agent2.Polish core in the direction of ejection3.Provide suitable draft4.Decrease cooling time of moulding5.Decrease injection rate6.Decrease holding pressure7.Decrease holding time8.Slowdown ejection speed9.Decrease mould temperature10.Plating with low friction surface11.Provide air poppets to release vacuum

TYPES OF EJECTORS •Straight Pin Ejector•Stepped Pin Ejector•Sleeve Ejector•Blade Ejector•Stripper Plate

Ejector•Stripper Ring Ejector•Stripper Bar Ejector •Valve Ejector•Air Ejection

EJECTION TYPE

1. PIN EJECTOR

Pin ejectors are the simplest and most widely used ejection types to remove the moulding from core of the mould. Pin ejectors are hardened cylindrical Steel pins held in ejector plate and made to slide through the hole in core insert. Number of such ejector pins positioned on the core make smooth ejection of moulding during the forward ejection stroke,but mark of ejection will be visible.

Sleeve ejector is a hollow cylindrical pin similar to pin ejector. It is also held in ejector plate and guided over core pin. During forward ejection stroke the sleeve pushes the moulding out of the core pin which holds it. Best suited for ejecting bosses on a component.

EJECTION TYPES2. SLEEVE EJECTOR

mouldingSleeve ejectorcore pin

SLEEVE EJECTOR

CORE PIN

MOULDING -EJECTED

Sleeve Ejector Assembly

SLEEVE EJECTOR

CORE PIN

MOULDING EJECTED

EJECTION TYPES3. BLADE EJECTOR

For ejection of thin walled mouldings, instead of pin ejector rectangular blades of thickness equal to part and suitable width are used so as to increase the ejection area.

BLADE EJECTORHOLDER

PIN

LOCK PIN

STRIPPER PLATE EJECTION

•Best ejection arrangement for thin walled moldings

• Increased area of ejection because of all- round nature of ejection

•Suitable for multicavity moulds of cylindrical parts.

•No witness mark seen on part at ejection portion.

COMPONENT

STRIPPER PLATE

CORE

STRIPPER BOLT

STRIPPER PLATE EJECTION

COMPONENT

STRIPPER PLATE

CORE

STRIPPER BOLT

STRIPPER PLATE EJECTION

Stripper Ring Ejection

CORE INSERT

VALVE EJECTORCORE INSERT

MOULDING

VALVE EJECTOR

EJECTOR PLATE

AIR EJECTOR

MOULDING

CORE INSERT PNUEMATIC ACTUATION

VALVE EJECTOR

RAM

AIR VALVE EJECTORSEALNUT SPRING AIR VALVE 3 SLOTS

AIR

SEC-XX

AIR POPPET VALVETo break vacuum and ease ejection

AIR

STRIPPER

Poppet Valve

AIR

EJECTION REQUIREMENTS OF A MOULD

•The minimum Ejection required for a mould is arrived at by the following thumb rule : -

•Minimum Area of Ejection = 1 % of total lateral surface area of component in contact with Core.

ie. No. of ejector pins x Area of each ejector pin = sum of lateral surface area of component in contact with Core / 100

SELECTION OF EJECTORS• Pin Ejectors are easy to manufacture to high

accuracy and its corresponding hole in Core to slide also economically produce able.

• Provide more ejector pins than the calculated minimum

• Distribute the total no. of pins equally for uniform release.

• Parting surface ejector pins are more effective than face ejectors.

• Position no. of ejection pins near Bosses, Ribs and other obstructions.

• Thin walled components are better ejected by stripper or sleeve

• Transparent components are suitable for Blade or Stripper Ejection