There are common poor-practices in the moulding industry, in this series we will shed light on some.
They often occur due to:
Lack of internal company best-practices; attempting to rush though a project to meet the common compressed deliveries of today’s industry; lack of available tools in competitor software products; lack of awareness by the designer; or sometimes due to lack of training in the functions/tools available to the designer.
In this series we will cover several scenarios where the right feature functions, and the right training, can create a better finished product and more stable steel conditions.Stable steel conditions allow the mould to stand up to high production volume and eliminate production downtime due to pulling the mould for repair.Having more of the finished parts being passed through QC inspection, and having less downtime of the mould, both contribute into a lower life cycle cost of the project.
The scenarios we are going to cover in this series include:
- I)The general Isocline split
- II)The corner contoured split
- III)Mechanism lead-in and angled Isocline (This Entry)
What is an Isocline?
For those unfamiliar with the term Isocline, here is the dictionary definition:i-so-cline, noun, a line connecting points of equal gradient or inclination.
Where to find it
The Isocline Feature can be found several ways.If you are familiar with the traditional NX menu you will easily find it under Menu->Insert->Derived Curve->Extract
If you are more comfortable with the NX Ribbon style interface first you will need to have the Advance Role loaded, or your own customized Role where you have already added the Extract Curve to your ribbon. In the Advanced Role you will find it in CURVE->More Gallery->Derived Curve group->Extract Curve
There is always the command finder where you can search the Isocline feature and access it directly.
Use:Part III, Mechanism Lead-in and Angled Isocline
Note:If unfamiliar with the Isocline feature and its use, please refer to Part I and Part II of this series where it is described in more detail.
Here we have a part with a full radius around the periphery of a dog-house type feature that will need a mechanism to de-mould it.
Poor-practice When Generating a Lead-in Parting-line for a Mechanism Split
A poor-practice when a designer creates the split line of a part is that they will generate it only in the main die-draw +Z axis.While this is the required split to have an open draft condition for the core and cavity halves, this doesn’t necessarily create good conditions for a side action mechanism.Below is an iso-view of the part with a +Z axis Isocline curve.
When using this Isocline for generating side-action mechanisms a 90° steel condition only exists if we were to extrude the curve with no draft angle.This does not work well for side action mechanisms due to the mechanism needing to have lead-in draft (also referred to as break-away angle).
The need for lead-in means the Extrusion must be drafted based on the Mechanism Pull Axis.In the picture below the draft angle has been set to 20° to illustrate a point.(Typically in the industry 5-7° is considered a good angle).
You can see with the Iso-view and the following section what this does to the steel condition on the cavity.
Best-practice for Generating a Lead-in Parting-line for a Mechanism Split
We first need to generate an angled isocline curve that will be perpendicular to the lead-in angle.This ensures that the steel condition will be 90° all around the feature.
Start the Isocline command.
1.Set the type of Vector method.
2.Select the axis for the Vector (In this case the - X-Axis)
3.Reverse the axis if necessary.(In this case we reverse it to point –X)Then click OK.
4.Set the draft angle to be the compliment of the angle we want for lead-in.In this case we want a 20° lead-in later, so we set the Isocline angle to 70° (90°-20°).Then click OK.
5. 6. 7.Select the surfaces to generate the Isoclines on.(There are options in the dialog box for selecting all faces, but in this case we are being very specific about where this parting takes place)
8.Click OK to view Isoclines.
This picture below shows the original +Z axis Isocline split of the whole part (Red thick line) compared to the Isoclines we now generated based on the Mechanism Pull Axis (Blue lines).Two 70° conditions exist because of the convexity of the surface.We are only going to use the outer most line for our Extrusion.
9.Select the outer Isocline
10. Specify the Mechanism Pull Axis (This needs to be the same as the Axis used to generate the angled Isocline.
11.Set the Extrusion length
12.Change the DRAFT option from ‘None’ to either ‘From Section’ or ‘From Start Limit’
13.Enter the desired lead-in angle (this is per-side, not an included angle measure).Then click OK.
You can see with the new Iso-view below and the following new section that using this method ensures the lead-in split we want splits the geometry at the true 90° position.
If you would like to learn more about this operation and other advanced operations, you should attend one of our advanced NX CAD courses. To arrange for advanced training please contact your Account Manager, or contact us directly at[email protected].