Unigraphics NX Best Practices : Wave Geometry Linking
Technical
Written by Murali Krishna M   
Friday, 28 November 2008 12:32

Here is one of the best methods we use in Unigraphics NX software to create linked parts.


Let us take an example of Left Hand (LH) and Right Hand (RH) parts which are symmetrical and opposite to each other. In this case, instead of remodeling the opposite hand part separately, it is better to link to the original part using wave geometry linker in Unigraphics NX.


First complete the first model (either LH or RH which is desired or shown on the drawing). Then create a new part with opposite hand part number. Add the the original CAD model to the structure of new part through add component option of assemblies.

 

The first feature in new model has to be extracted face from original part through wave geometry linker. If no flat face or edges available, then you have to depend on datums. Instead of creating a fixed datum plane in new part, wave link an existing datum plane from original part. Again this is also through wave geometry linker option. If face is linked, then create a datum from this in new part.

 

However, the preference is to link the datum from original part to reduce number of features and file size. Once the datum plane is available for mirror, use wave geometry linker “mirror body” option to create the opposite hand part. Make sure you are using right plane in view of mirror plane.

 

This way, the opposite hand part will have 100% associativity to the original CAD model. Even if the original model is moved/rotated, the opposite hand part will update automatically.

Nesting the parts while machining using CAM

While working on a recent CAM project using CAD model, we found few interesting techniques. In the first job, we requested the operator to use a 1/4″ Ball nose cutter of 1″ long. We were expecting there could be some tool flexing because for the first cavity profile cut. But he used almost 1 1/2″ long cutter. Finally, once the machining is done there is a clear cut draft left on the part which is almost 3 degrees. Also, there was not enough overpass of ball nose at the bottom of the part leaving a radius there. It was not too bad other than doing some manual cleanup of the part after machining.

In our second batch of CAM, we nested four parts as shown on image from two separate CAD models. So, we have to make a single pre-machining block to make two separate parts of quantity two each. Also, we tried to machine only up to 4 mm around the part using 1/4″ cutter. This saved us almost 50% of machining time as we eliminated machining unneeded stock. Also, we ensured the cutter overhang is only 22mm just more than nose overpass. This didn’t cause any tool flex and squeak.

Nesting the Parts example

Nesting the Parts example

 

Another interesting thing is after doing the rough cut with 1/4″ cutter, we lost the datums where we set original zero. So, for finish cut we have not changed X and Y coordinates. But, asked the operator to reset Z with respect part top surface which was intentionally left unmachined before. This helped us in quickly running the finish cut using 1/8″ cutter without much time on reference point set.

Hope you found this article useful. Please share your comments below.