Door Arm Rest Week 8 Challenge

CONSTRUCTION and DRAFT ANALYSIS of DOOR ARM REST

Draft analysis technique is used to analyze whether our part model created in CAD is manufacturable or not. The part should get easily removed from the mould or die. No part can be ejected from the tool if it is having straight 90 degree angle from its base surface. A small draft angle is provided to each and every area of the component and we are providing a direction in which components should eject in order to easily remove the component from the tool.

Draft Angle is the amount of taper given to the molded parts perpendicular to the parting line. As the plastic cools it shrinks and sticks to the mould surface and therefore need draft angle while ejecting, and to avoid damage. Normal draft angle is 3 degree. Increasing draft value will increase manufacturing cost.

TOOLING AXIS

In order to perform analysis, we need to create tooling axis and in order to do that we need to check class A surface first. We need to check whether all the surfaces are closed or not using boundary option. Once inspection is complete, we need to create separate geometrical set for tooling axis. We need to choose the axis in such a way that all the pockets, holes, sections etc. should get covered. For example, once inspection is completed, we concluded that Z axis is the tooling axis. Now we take reference point and create an intersection. Later we draw two lines on intersection profiles and create bisecting line using the two lines,tyhis is our main tooling axis. Here we have a another tooling axis (side core axis) in the Y direction to form the pattern on the surface. We form side tooling axis by extracting surface and creating a line at the centre.

Class B surface creation

Now we extract class A surface to create first half of class B surface. We extract the surface, then untrim it along with one more surface and then extrapolate it . Later it is offset to required command and trimmed togather.

The second half is similar to first half which is extracted, extrapolated,offset and trimmed togather.

In the third half both the previous parts are trimmed and joined togather.

For pocket, extract the class A pocket surface and untrim it. Extrapolate all the surfaces and offset all the surfaces and trim it.

Now we apply fillet to class B surface.

Class C surface creation

Here outer boundary of class A surface is extracted using multi extract option. Then sweep command is used with draft direction and main tooling axis is used as reference to create the surface.

After creating Class C surface , now join both class A & C surfaces.

Now all the surfaces are trimmed togather to form one whole surface part. Close surface option in oart workbench is used to convert it into solid body.

Once draft analysis is done we can see that due to the inclination in the class A surface, some portion in the class A pocket area has draft angle less than 3 degree.