Week 9 - Attachment Feature Creation - Challenge 2

 AIM: To create the dog house following the design principles

SOFTWARE USED: CatiaV5.

INTRODUCTION:

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