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 (This entry)
- II)The corner contoured split
- III)Mechanism lead in and angled Isocline.
What is an Isocline?
For those unfamiliar with the term Isocline, here is the dictionary definition: i-soc-line, 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 I, The General Isocline Split
Here we have a moulded part with a full radius around the periphery of the wall-stock edge.
This is a close-up view of the radius following the outer wall-stock edge.
Common Poor-practice for Building Parting-line Split
The common poor-practice seen in the moulding industry is pulling off the parting-line split from the edge of the radius.Typically this is seen on somewhat vertical walls where the low draft angle doesn’t show much deviation from the radius edge to the true tangent apex of the radius (as compared to the die-draw).
From this close-up section below (and using iso-view above) you can see the designer selected the radius edge as the split for the mould.However based on the vertical die-draw axis (+Z) you can see that the radius actually bulges out past this split point to become slightly under-cut to die-draw.This causes a die-lock condition for the moulded part.
Several reasons why this goes unnoticed in the manufacturing process can be attributed to, but not limited to:
A)The undercut condition is very small and as the moulded part shrinks it releases itself from the under-cut and is no longer die-locked.
B)The mould was cut vertically in the Z axis so the cutter never actually cuts in the under-cut condition—thus leaving the customer with a blunted radius.
C)The mould is cut as shown but during hand polishing operations the top lip of the core is polished away leaving open draft—This then creates a mis-match condition where the core steel is stepped out past the cavity edge, and then polishing of the cavity edge is necessary to bring it over to the new core position.
Best-Practice for Building Parting-Line Split
First enter the Extract menu from either the traditional Menu button or through the Ribbon interface and choose Isocline.
Once in the Isocline dialog box:
1. We select the die-draw axis either using the default inferred vector selection, or any of the options in the Vector drop down list.If necessary you can then use the reverse vector orientation option. Note:after selecting the axis the dialog still shows 0 for the selection even though you have defined it, at this point hit OK to accept the vector selection.
2.In this case we make sure the Single option is selected as we only want one set of curves.(The family option lets you generate multiple sets of curves
between a range and angle step over.)
3.We then set the angle requirement--from the die-draw axis-- to create the isocline at.In this case when creating the outer parting split normal to the +Z axis we set this value at 0°.Then click OK to accept the angle and progress to the face selection dialog.
4.We then select all the faces we wish to process for Isocline creation.This can be done by single on screen selections, or the other selection options presented in the dialog box.Depending on how you intend to use the Isocline command in your process you may want to select all faces in body if you think the data will change enough that all faces need to be processed, however if you are quite sure it will only be these local faces to be accommodated then it’s best to only select the needed faces to reduce the amount of faces processed during updates.After selecting the faces needed in this set click OK.
You will be returned to the first Isocline menu again in order to create further Isocline definitions, but in this case click Cancel.
An Isocline representing the parting-split is generated (Red Line below).You can see the difference between A) the original radius edge, and B) the position of the Isocline split.
We now can develop a parting-split surface from the Isocline curve.
From this close-up section below (and using iso-view above) you can see that the parting-split surface lies at the 0° draft location of the radius and that the split now represents the outermost extent of the radius surface data.This split location ensures open draft to each half of the Core and Cavity.
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 firstname.lastname@example.org.