2. Material Selection

Blow Mould Design

Introduction IIT? All compound in blow mould is made of same material? why

No, each parts (like neck and shoulder, pinch off) have a seperate function

What is the common property for all componants in blow mould?

Have good thermal conductivity when parision in contact

List out the blow mould components

a) b) c) d)

Base plate Guiding members Neck and base inserts Mould cavity

Blow Mould Design

Base plate What is the function of base plates in blow mould?

Purpose of mounting the mould on the machine platen

IIT? Compressive forces are too high in base plate?

no

Which is right material for base plate

Mild steel

Guiding members IIT? Guide pin and guide bushes must be very accurate?

Yes for proper allignment

IIT? Guide pin and bushes will not wear and tear very fast

No wear very fast

Which material is suitable for guide pin and bushes

Case hardening steel

Neck and base inserts IIT? Neck and base constitute areas of heat concentration?

yes

Why neck and base insert should be made out of hardenable steel?

For welding of the open ends of the parision And cutting of the flash of takes place

How many cycle neck and shoulder of inert can be used

1,00,000 cycle

Cutting edges are not renovated (sharpen) in time what will happen?

Yield a thick parting line Do not cut the flash cleanly And make deflashing a difficult preposition

How much hardness recommended for hardened steel?

58-60 Rc recommended

Mould cavity Which material is suitable for mould cavity

Unalloyed medium C-Steel

IIT? C-Steel good thermal conductivity

No, poor thermal conductivity

Then, how heat is dissipated from C-steel (mould cavity)

Cooling can be placed fairly close to the cavity

IIT? Mould cavities for PVC require a corrosion proof surface? Why

yes chloring will corrode in pipe

What type of blow mould cavity material used for PVC

Hard chrome plate

What is the major problem if using chrome plating coated plate

Layer of Cr can peel off after some times

What is the restrication of cr-plated mould

Not required to produce large no of quanties

Which material is suitable for long run

Stainless steel

Aluminium alloy What are the major advantage of Al-alloy in making blo mould

Light weight, adquated hard and tough, easily machinable, very good conductor of heat

Al- alloy have excellent tensile strength? What is the adv. In mould (using this property)

Moulds with fairly long life

IIT? Steel inserts are not necessary for Alalloy blow mould

Yes

IIT? Al-alloy blow mould is good in thermal conductity

Yes. It is cooled superior to other mould components

What are the surface hardenss are provided to Al-alloy blow mould? To improvement

Chrome –plating, chemical Ni-plating

What is the major disadvantagen of Al-alloy based blow mould

Machining cost is expensive, time consuming processti

Zinc alloys what is the major adv. Of Zn alloys

Adv: free from blow holes Disadv: senstive to pressure even at low temp

Be-Cu alloys What are distinguished features of Be-Cu alloys

Excellent heat conductivity Adequate tensile strength Hardenablity Freedom from blow holes Dimensional accuracy Corrosion proofines

Brass-Bronze What is major disadv. Of brass bronze?

Restricted moulds Require no pinch off along the sidewalls

What are adv. Of brass and bronze

Good conductors of heat Cheaper than Be-Cu alloys Easy to machine Inserts for logo and scripts etc

Thermosetting resins What are the Thermosetting resins used in Blow moulding

Polyester, epoxy resin, impregnated with metal powders

IIT? Thermosetting resin bloq mould are not short lived?

No, short lived Use only small no. Of mouldings for trials at development stage of a new product

What is major adv. Of thermosetting resin

Simplicity of the process No special equipment Experimental moulds in a short time at a low cost