Week 9 - Project 1 - Door Trim Lower with Engineering Features

DESIGN OF CLOSED SURFACE AND TOOLING AXIS

AIM:Create the rib for the Drill Handle considering the design rules

PROCEDURE:
Part I
* Import the .STEP file into CATIA V5.
* fit the object to screen. Save the file into CATPART
*Open the file save it.

*use varnier tool to check the flat surfaces.

CREATING TOOLING AXIS
*By changing orientation and select a axis at which maximum part is visible.

*choose a surface and use point [•]

point >on surface >select a Surface >'0'

Choose line [/]

line point-direction select points Select axis

* The created line is the tooling axis Publish it.

Part II:


Offset → select the Class A Surface

*Click on the other side, so we obtain the.offset of A surface of 3mm which is considered as class B

*Fillet all the edges of required dimension

*class B surface is ready - Publish it

Part III:

* Make surface A visible and make boundary limit as required.

Sweep-> Using boundary and surface>90>and give okay

Now Join the Surface A &C.

*Use extrapolate . and completely check there is no open boundaries

*C surface is created and Join A+c and publish it

*Make the b surface visible and just extrapolate the extra edges

*Trim the extra surfaces and the required part of 3 mm thickness is created

*Go to Part Modelling Close surface → fill
* So the surface model is converted into part model.
Draft Analysis is made on both sides "3

DESIGN OF DOG HOUSE

DOG HOUSE

Dog house is an engineering feature used in plastic trim design. Dog houses are used as supporting feature. Sometimes other engineering features like snaps; locators etc. are mounded on them to increase their strength. Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from mould cavity. Dog house and other engineering components are built on B-surface.

DESIGN CONSIDERATION FOR PLASTICS:

1.WALL THICKNESS:

Thick sections waste material and are simply uneconomic. So solid shapes that would do the job well in wood or metal must be transformed to a 'shell' form in plastics. This is done by hollowing out or 'coring' thick parts so you are left with a component which regardless of complexity is composed essentially of relatively thin walls joined by curves, angles, corners, ribs, steps and offsets. As far as possible, all these walls should be the same thickness. Wall thickness guide range is 0.75 mm to 3 mm for reinforced materials 0.5 mm to 5 mm for unreinforced materials.

WALL THICKNESS(W)=0.70*(NOMINAL THICKNESS OF PLASTIC MATERIAL)

2.CORNER RADII

Properly designed corners will make a big difference to the quality, strength and dimensional accuracy of a moulding. But there is another benefit too. Smooth curved corners help plastic flow in the mould by reducing pressure drops in the cavity and minimising flow-front break-up. Internal radii should be at least 0.5 and preferably 0.6 to 0.75 times the wall thickness.

CORNER RADII= (0.6-0.75) * (NOMINAL THICKNESS OF PLASTIC MATERIAL)

3.DRAFT ANGLE:

Tooling must be cleared for easy ejection of the component, from the core cavity. In order to clear tooling certain value of draft is given to the component. Minimum of 2-3deg is provides on all plastic components.

DRAFT ANGLE=2-3 DEGREE

4.FILLETS:

Fillet on the inner side = 0.25 * Thickness of the plastic material Fillet on the outer side = 1.25 * Thickness of the plastic material Fillet on the coring edges = 0.25 * Thickness of the plastic material Coring thickness = 0.40 * Thickness of the plastic material

DESIGN OF HEAT STAKE