Week 8 - Challenge 4 - Coin Holder Design

Coin Holder Design

Create the Coin Holder Plastic component through the Class-A surface. Perform the Draft analysis on the model.

Understanding Draft for Plastic products

When developing parts for plastic molding, applying draft (or a taper) to the faces of the part is critical to improving the mold ability of your part. Without it, parts run the risk of poor cosmetic finishes, and may bend, break, or warp due to molding stresses caused by the plastic cooling. Equally important, an absence of draft may prevent parts from ejecting from the mold, damaging not only the parts, but possibly the mold itself a costly and time consuming detour.

Create the Coin Holder plastic component and perform draft analysis using Catia V5

1. Creating the tooling axis

Create Class A using scanned skin file for Coin holder-

Create a tooling Clearance in xz and yz plane-

As all the wall surfaces are perpendicular, there is no need for individual clearance. The normal line on the base surface will itself be the required clearance axis (Tooling axis)

Create the tooling axis-

• On the basis of the visual study create tooling axis normal to the base surface.
• For this it is necessary to consider holes and undercuts of the component.

Publish tooling axis and class A surface for convenience

2. Draft analysis

• Set the compass in the tooling axis.
• Analyse at 3 Deg minimum draft.

As this model shows many red region due to the perpendicual surfaces, it is advisable to contact the class A modeler and provide the required draft.

3.Creating Class B surface

Extract surfaces from the class A surface for base, top, sidewall and outer surfaces.

• Untrim and extrapolate these surfaces to get surfaces for Class B.
• Offset these surfaces with 2.5 mm and trim off them.

BASE

SIDE WALL

TOP SURFACE

OUTER SURFACE

Create B surface structure-

Mutually trim off all these surfaces to get B surface-

Give fillets according to class A to get final class B surface-

• Add the thickness 2.5 mm to fillet radius of A surface to get the outside fillets radius of B surface.
• Subtract thickness 2.5 mm from fillet radius of A surface to get the inside fillets radius of B surface.

This is important to get the uniform thickness, which further ensures that part will not have any plastic defects.

4. Creating Class C Surface

Create sweep surfaces from the boundary of class A with required draft with tooling direction.

HOLE

• During design it is important to consider the draft direction because it decides the parting line of mold.
• Outward draft is necessary because then only the parting line will be on B surface which is required.

5. Creating solid model

Use all A, B and C surface and trim off with each other to get final surface model

With the fill surface create solid model out of the surface model-

Draft Analysis

As already mentioned the red zone reprensents negative draft which is due to the class A surface.