NX Mold Wizardry – Part 1
NX Routing Mechanical Notes
NX Mold Wizard: Impressive Commands
This 3-part article will discuss a few of the commands within NX Mold Wizard functionality that indicate the level of sophistication of the software product. Part 1 will cover the preliminary step that aids not only the mold maker, but also the designer/engineer.
Analyzing Part Mold Flow
In this step, we will investigate part geometry for moldability and look for potential problems in mold flow. We’ll work with the chassis pan from the remote control toy car that was created by Siemens Education Services in the 90’s.
What to Look For
Primary consideration is given to draw direction and part geometry that can’t be formed by mold geometry moving in that direction. The part we’re investigating will have some areas where inserts, slides, or lifters will be necessary in order to form the geometry.
We’ll also look for excessively thick or thin areas. The thick areas are where drastic temperature differentials during cooling might create stress build-up, sink marks, or other problems.
Decisions Must Be Made
We’ll eventually need to decide where to gate the part and how the molten material will flow the best. Cycle times need to be as short as possible. We want to alleviate cooling of the material before it reaches the more remote regions of the part. That could create knit lines and weakening of the structure.
For those who haven’t designed molds for decades, we can rely on Siemens’ Mold Wizard to do this. A Molded Part Validation license is available as a separate, much more affordable application. Additionally, there is an advanced Mold Wizard add-on: Easy Fill Advanced.
Mold Wizard Application
After installing Mold Wizard and starting NX, the Mold Wizard application can be turned on under File->All Applications.
The Mold Wizard tab should be visible in the NX Ribbon Bar.
1. Select the Run Flow Analysis command in the Part Validation group.
2. Choose a single gate located on the bottom along the center plane of the part.
Once selected, choose OK and Mold Wizard starts the process. A subroutine is spawned called Moldex3D. Eventually, a dialog like the one below will appear offering many options for the analysis.
Next, we will run multiple analyses and compare to get a better idea of the entire mold press setup. To keep this simple, select the Analyze now… button. A status dialog like the one below will appear and update the estimated time to completion.
After a minute or two, the analysis is complete and a popup will appear.
Display Flow Analysis Results
We’re now ready for the next step: Display Flow Analysis Results.
Once selected, a dialog appears providing many forms of analysis.
Melt Front Time
These functions provide graduated surface coloration with a legend of the corresponding values for that characteristic. As that dialog appears, the geometry of the part will immediately become color coded. This indicates the default display result: Melt Front Time.
You’ll also note at this time that the Rendering Style is now set to Face Analysis.
We’re going to turn on the options for Air Trap and Welding Line to give us indication of potential problems. These are available as long as the dialog is open.
Indicators appear in the graphics area on the geometry showing us where there might be concern. There do not appear to be any weld lines. However, there seem to be many points where air could trap inside the cavity and cause a short shot or vacant bubble in the part. Air vents will solve these problems.
While we’re in the Gate Front Time function, we’ll take a quick look at the animation that’s available that shows the actual flow of the material relative to a time interval we can input. We’ll drag this out so we can watch it more closely using the number 50.
The animation below can help the designer understand much about the part. It also gives insight as to whether the part would mold better with some ribs to help the flow. In addition, it can tell the mold maker how effective the gate position is.
Since we’re only gating the part in one location, the Gate Contribution command is of no use.
The next icon over, Pressure Drop, gives us an indication of how fast it will flow, perhaps based on how thick the passageway is or where there might be a bottleneck. As a designer/engineer, I find it impressive that we can investigate this without spending a nickel on mold materials or a minute on machining a single chip off.
The next three icons are indicative of temperatures at various states of the cycle. The most profound is Average Temperature on this chassis pan.
That color differential is screaming at us that THERE IS A PROBLEM! Rotate the part. You can do this while this analysis is going on. Notice that the whole front end of this part is solid.
Maximum Cooling Time
To highlight the obvious dilemma in this part, the Maximum Cooling Time function proves to us that this part must be redesigned before we work on it. It shows us that the area in between the front wheels will still be molten while the rest of the part has cooled to the point of being frozen. You might not have initially noticed that.
Choose OK in the dialog. The display will then revert back to the normal Shaded with Edges style. The data of that analysis will save in the part file. You can simply choose Display Flow Analysis Results again and the coloration and animation is immediately available.
This is only one small facet of the Mold Wizard application that can provide huge benefits to users who deal with molded part considerations. There will be tremendous savings from eliminating or reducing the rework of molds down to a rare occurrence. Manufacturing and the managers like the sound of that!
This concludes Part 1 of the Mold Wizardry blog series.
Part 2 – Initiating a Mold Project, will show how Mold Wizard can create an entire assembly containing more links than a sausage factory!