Project 2

OBJECTIVE:

Creation of Mould for a cpu fan bezel using SolidWorks.

INTRODUCTION:

The injection moulding process involves heating & injecting plastic material under pressure into a closed metal mould tool. The molten plastic cools & hardens into the shape inside the mould tool, which then opens to allow the mouldings to be ejected or removed for inspection, delivery, or secondary operations.

Injection moulding is a manufacturing process that allows for parts to be produced in large volumes. It works by injecting molten materials into a mould. It is typically used as a mass production process to manufacture thousands of identical items. Injection moulding materials include metals, glasses, elastomers, and confections, although it is most commonly used with thermoplastic and thermosetting polymers.

WORKING:

The first stage of injection moulding is to create the mould itself. Most moulds are made from metal, usually aluminium or steel, and precision machined to match the features of the product they are to produce.

Once the mould has been created by the mould-maker, the material for the part is fed into a heated barrel and mixed using a helical-shaped screw. Heating bands melt the material in the barrel and the molten metal or molten plastic material is then fed into the mould cavity where it cools and hardens, matching the shape of the mould. The cooling time can be reduced through the use of cooling lines that circulate water or oil from an external temperature controller. Mould tools are mounted on plate moulds, which open once the material has solidified so that ejector pins can eject the part from the mould.

METHODOLOGY:

The injection moulding process requires careful design, including the shape and features of the part, the materials for the part and the mould, and the properties of the moulding machine. As a result, there are various considerations that need to be taken into account when injection moulding.

PROCEDURE

STEP-1: Deciding the tooling direction

• Selected the tooling direction which leads to minimum udercuts
• done draft analysis to check adequate drafts in the model
• core

• cavity

STEP-2: Scaling the model

Increased the model size by 0.6% to account shrinkage because ABS material shrinkage % is 0.6%

calculation

(0.6/100)+1 = 1.006

so 1.006 is the scaling value

STEP-3: Creating parting line

It is a core & cavity separating line or core and cavity meets at this line

STEP-4: Creating sutt-off surface

To close the holes and to create the core cavity surfaces

STEP-5: Creating the parting surfce

Surface which separates the core and cavity into 2 blocks in a mould

STEP-6: Creating core and cavity surfaces

Merge the parting surface with core and cavity surfaces

core surface

cavity surface

STEP-7: Creating core and cavity blocks

CORE

Edited the core block to match the slider block.

Created guide rails in core block.

Made a cut in the core block for bolts.

CAVITY

• Edited the cavity block to match the slider block.
• Edited cavity block as per rib rails.
• Edited cavity as per slider cuts.
• edited as per washers and gave 0.5mm relief.

SLIDER

Created slider block in such a way that it should not intersect with the component,gave suitable gap allowance

Created the wedge to properly interlock with cavity.

Given suitable fillets

WASHERS AND BOLT

Inserts

These are required where width of the cut is too small while the depth is too deep in a mold.

• Make a sketch of the required profile & split core block to make inserts
• maintain 60 mm distance b/w insert & base of the block.

• Made holes in core block & inserts to accomodate bolts

Ejection system

The ejection system in molding refers to the mechanism used to remove a finished plastic part from the mold cavity. The ejection system consists of ejector pins, which are located on the ejector plate and are used to push the part out of the mold cavity once it has been formed and cooled

Ejector pins

Ejector pins are long retracting pins that are used to push the solidified material out of the mold. Once the plastic polymer cools down in the mold, the ejector pins force the solidification out from the cast. They go back into the mold to get the thermosetting apparatus ready for the next round.

Procedure for creaion:

• Made holes in the core block for ejector pins
• using same sketch which is used to make holes created the ejecor pins
• made releief holes concentric to ejector pins
• D shaped head is created because of the inclined base of the pins

Ejector plate

The ejector plate is the floating plate in the ejector system. Its thickness is defined by the amount of force required to eject the part as well as the part/mold size. This plate also locks the ejector mechanism (pins or plate) in the ejector retainer plate.

Ejector back plate

This holds the ejector pins and is usually made of mild steel. It prevents the ejector pins from disengaging

Runner and gate system

A sprue is a channel through which to transfer molten plastics injected from the injector nozzle into the mold. It is a part of sprue bush, which is a separate part from the mold. A runner is a channel that guides molten plastics into the cavity of a mold. A gate is an entrance through which molten plastics enters the cavity.

Air vents

These are small channels provided in the mold block for the escape of air, which is traped inside the mold

Air vents are created in two steps to avoid defcts in the component such as flashing,1st step had depth of 0.02 mm which is big enough for air to pass but not big enough for plastic o pass. 2nd step had depth of 1 mm from this air pass to the channel of depth 1mm, through the channel air escapes out of the mold.

Cooling channels

theese channels aids to achieve uniform cooling throughout the mold so that defects such as warpage doesn't accur

Factors that affect the cooling of mold depends on the following:

• plastic material injected
• temperature of the plastic
• coolant used,temperature of coolant
• thickness of plastic component which is being molded

By considering these cooling channel is designed

DIFFERENT VIEWS OF THE MODEL

• ISOMETRIC VEIW

• CORE WITH SLIDERS

Conclusion

Created the Mould for a cpu fan bezel using SolidWorks.