MOLD DESIGN, EJECTOR PINS, SLIDER, INSERTS, AIR VENTS, & COOLING CHANNEL CREATION FOR CPU FAN BEZEL USING SOLIDWORKS 

MOLD DESIGN, EJECTOR PINS, SLIDER, INSERTS, AIR VENTS, & COOLING CHANNEL CREATION FOR CPU FAN BEZEL USING SOLIDWORKS

In this report mold design and creation of sliders for CPU Fan Bezel was done by creating each individual part in assembly workbench following step by step process to attain best results.

As there was the necessity of the sliders for the model, we should create washers and locking mechanism for the sliders.

Assuming the material for the model as ABS (shrinkage - 0.6%), the scale value is determined as (0.6/100) + 1=1.006 for the model.

MODEL

The steps followed and commands used for the core and cavity blocks creation are:

MOLD TOOLS

• Mold Pull direction:

The direction in which the core moves apart from the mold, based on the models and the features in the model the direction of pull is determined

• Draft Analysis:

Analyse draft angles of faces based on mold pull direction for moment of core and cavity blocks.

• Draft Creation:

The minimum draft should be 0.5 degrees, if there was no draft certain draft will be provided to the component.

• Scale:

Scales the model by a specified factor based on the material provided (Shrinkage factor)

• Parting Line:

Parting line separates the core and cavity surfaces. It is represented in blue line as shown below.

• Shut off Surfaces:

Create mold shut off surfaces, it prevents the flow of injected material by creating shut off surfaces.

• Parting Surface:

Create parting surfaces between core and cavity surfaces.

• Core & Cavity Blocks:

The Core and cavity block are created as individual parts in assembly by inserting the component as Core and cavity surfaces created for CPU Fan Bezel. The sprue location will be adjusted by rotating and giving mates with the planes of assembly.

Core

The core block is created using the core surface created and there will be 2 blocks internal and external block which are created considering the minimum distance between mold and the outer edge and the base of slider these two blocks are due to the parting line not on the same plane and combinedly these two blocks act as single core block.

Cavity

The cavity block is created using the cavity surface created and there will be 2 blocks internal and external block which are created considering the minimum distance between mold and the outer edge and the base of slider these two blocks are due to a curvature in parting line parting line not on the same plane and combinedly these two blocks act as single cavity block.

During the movement of blocks away from each other there will be rubbing of the blocks to avoid this relief should be provided.

During mold design of CPU Fan Bezel in the step of draft analysis we can clearly observe an undercut is present, to optimise the undercut sliders will be used.

In the above sectional view, we can clearly observe after completion of moulding process the part cannot be ejected due to the negative draft angle of the part, so hence the slider should be designed for that part.

Slider direction will be perpendicular to the direction of the pull which will be horizontal and these are separable from the core and cavity blocks as the sliders are movable, they should have a base for the movement form the model we can easily provide a base while creating the sliders.

The commands and steps involved in the creation of slider are:

SLIDER CREATION:

The commands used for creation of sliders are:

• REFFERENCE PLANE:

This command is used to create a plane, axis.

• SKETCH:

Using this command, we can create a new sketch.

• CONVERT ENTITIES:

It is a tool available in sketching workbench to project the sketch selected on the plane you are sketching and in this tool another option of intersection curve is there which is also used to project sketch.

• SPLIT:

It is available in features tab used to split the body in two pieces along the sketch based on applications.

• FILLETS

It is used to make fillets to edges of solid bodies.

• RECTANGLES:

It is also an entity used and available in sketching workbench to create a rectangle of different types like corner rectangle, centre rectangle, 3- point corner rectangle, 3-point centre rectangle and parallelogram based on their applications.

• CUT EXTRUDE

It is available in features tab used to remove material from a solid body along the sketch in which direction, we need based on applications.

• EXTRUDE BOSS

It is available in features tab used to add material from a solid body along the sketch in which direction, we need based on applications.

• MOVE FACE

It is available in mold tools tab used to move faces of a solid body.

• MOVE/COPY BODIES

It is available in mold tools tab used to moves, copies and rotate solid and surface bodies.

• COMBINE

It is available in mold tools tab used to add, subtract bodies.

• DELETE/KEEP BODY

It is available in mold tools tab used to keep or delete a solid body or surface body.

The sliders are created using the split option making the sketch as the profile of the undercut and the plane on which sketch is made.

These sliders are modified such that washers and locking mechanism will be correctly designed.

The core and cavity blocks are modified according to the shape of the slider after all modification using the combine command.

Washers and bolts are designed beside the slider base for this separate space is assigned on the blocks while modifying the blocks after slider design.

EJECTOR PINS & EJECTOR BACK PLATE CREATION:

As the part needs to be ejected form the core block after the injection process, we should design ejector pins such that the ejector pins will be pushing the part with the help of ejector and ejector back plate.

The heads of the ejector's pins are made based on the type of ejector pins, as the ends of ejector pins which will be in contact with the part to be ejected are in angled manner (Type-2) the heads of ejector pins should be in “D” shape.

After the design of ejector pins relief for the ejector pins should be provided both in core block and the ejector back plate.

The steps followed and commands used for creation of ejection pins and ejector back plate on core block are:

The Ejector pins will be present only on the core side, they will be near the ribs and features with more complex shapes at a distance of minimum 1 mm.

• Sketch:

The sketch is created on one of the suitable faces of core block, circles of diameter 3mm (standard)

• Core:

It is used for extracting cores from existing tooling split, using this command ejector pins will be created.

• Providing Relief:

To provide relief for the ejector pins a sketch with circle of diameter 6.95mm (Standard for 6mm diameter ejector pins) will be created on the same face used for creation of sketch of ejector pins.

• Extrude Cut:

The sketch created for providing relief will be cut extrude from an offset distance of 12mm (Reference table) from the face used for sketching along the length of ejector pins.

SPRUE, RUNNER & GATE CREATION:

Sprue is a channel through which metal or plastic is poured into a mould trough this the molten material will be passed through the gate through runner system which will connect the sprue and gate, gate is a channel which will connect the runner and mold cavity.

AIR VENT CREATION:

Air vents need to be designed for the mold for removal of trapped air in the blocks for this a gap of 0.02mm will be provided on the core block with a way for the air to be passed out the block.

COOLING CHANNEL CREATION:

Cooling channels are required to provide uniform cooling for the part to avoid defects during solidification for this we need to provide inlet and outlet ports for the coolant to pass through the core block.

The final assembly of the model after creation of Ejector pins, ejector plates, air vents and cooling channels for the mold blocks will be.