New in 2018: Automatically Program NC Code Based on 3D Surface Finishes

A previous article introduced a new computer-aided manufacturing (CAM) product in SOLIDWORKS 2018 and one of its key highlights: Tolerance Based Machining (TBM). As illustrated in the article, a hole pattern size tolerance drove the machining strategy selection. A change in the tolerance led to an automatic update of the machining strategy. The automatic selections and updates can cut typical CAM programing time from hours to minutes. In this article, let’s look closer at another type of annotation that can drive the machining strategies: surface finishes.

Figure 1 shows a mold design for an electric power drill housing.

Figure 1. A mold design for an electric power drill housing.

The surface quality of the mold will determine the plastic housing surface quality of the final product. Then how can you specify the quality requirements? In 2D drawings, you may define the surface finish symbols with 2D annotations as shown in Figure 2.

Figure 2. Surface finish symbols on a 2D drawing.

The challenge is that these annotations are attached to lines and curves projected on a 2D sheet, rather than attached to the desired target features on a 3D model. So it’s difficult for a machinist to fully understand which surfaces the symbols are controlling, especially for irregular or organic shapes in this power drill housing example. Furthermore, even if a machinist can understand the requirements, he or she has to look back and forth between a 2D drawing and 3D CAM program to manually extract the parameters and enter them into a CAM program.

SOLIDWORKS MBD and SOLIDWORKS CAM Tolerance Based Machining have provided a 3D angle to tackle these challenges. Figures 3 and 4 show the 3D Surface Finish Symbol tool from the Annotations menu command and the SOLIDWORKS MBD command bar.

Figure 3. The 3D Surface Finish Symbol tool in the Annotations command under the Insert menu.

Figure 4. The 3D Surface Finish Symbol tool on the SOLIDWORKS MBD command bar.

With this tool, you can define the surface finish symbols to the desirable faces directly on the 3D model as shown in Figure 5.

Figure 5. Define a surface finish symbol directly to the desirable face.

What if there are multiple faces sharing the same finish requirement? Figure 6 illustrates that you can show the leader line of a symbol and then drag and drop its anchor point to multiple desired faces.

Figure 6. Show the leader line, and then drag and drop its anchor point to multiple desired faces.

With that, we can complete several surface finish definitions to the target faces as shown in Figure 7. Please notice the cross highlighting from the symbols to the controlled features, which provides an intuitive visual confirmation of the design requirements.

Figure 7. Cross highlight from a surface finish symbol to multiple controlled faces.

Now that the 3D specifications are defined, we can move on to the machining step. On the SOLIDWORKS CAM TBM command bar, please first click on the Settings button as shown in Figure 8.

Figure 8. The Tolerance Based Machining Settings button on the SOLIDWORKS CAM TBM command bar.

On the settings dialog, as shown in Figure 9, please switch to the Multisurface Features tab.

Figure 9. Multisurface Features Settings.

You may notice the surface finish ranges, corresponding strategy and the color coding. Let’s modify these settings to better reflect the mold design requirements in this case. Figure 10 shows the dialog to adjust the ranges.

Figure 10. Adjust the surface finish ranges.

To delete a range boundary, hit the Delete key on the keyboard. To add a new boundary, type it in and hit the green + button. What’s nice here is that the boundary series is sequenced automatically.

Next, let’s adjust the strategies assigned to these ranges. You can simply choose from the strategies in the dropdown list as shown in Figure 11. These current strategies are driven by the SOLIDWORKS CAM technical database, which can be customized to allow more options. Of course, these strategies will lead to corresponding operation plans such as tool selections, speeds and feeds.

Figure 11. Assign the machining strategies for the new surface finish ranges.

To differentiate the surface qualities on different faces, I recommend a clear color coding. You can easily adjust them as shown in Figure 12. For example, I set tight requirements in red or orange colors just to catch machinists’ attention.

Figure 12. Adjust the color coding to differentiate the surface qualities.

Now let’s run the software to automatically assign the machining strategies and color codes according to the specific surface finish requirements. First, click on the Run Tolerance Based Machining button on the command bar to invoke the dialog as shown in Figure 13.

Figure 13. The Tolerance Based Machining Execution dialog.

Please notice that the ranges, strategies and color codes are inherited from the settings dialog as shown in Figure 12. However, you can still make adjustments for this local execution from the overall settings. Also among the five ranges, the black text lines indicate that the software has found surface finish requirements in these ranges, while the magenta text lines signal that none of the surface finishes fall into those ranges.

Next, switch to the Run tab and ensure these boxes are checked: “Recognize tolerance range,” “Recognize multisurface features based on surface finish,” “Apply color to multisurface features” and “Automatic Feature Recognition.” Figure 14 shows the necessary check boxes.

Figure 14. Necessary check boxes on the Run tab.

Now it’s time to hit OK and let the software automatically recognize the 3D surface finish symbols. Figure 15 shows the manufacturing feature tree and color-coded surfaces. Please notice that the 32 finish face is the tightest requirement and has been painted red. Its tree node show “Fine” as the machining strategy. The 63 finish face is painted orange, and its strategy is set to Area Clearance, Z Level. The 125 finish is a loose requirement, so it is painted green and shares the Area Clearance, Z Level method.

Figure 15. Automatically assign machining strategies, color codes according to the 3D surface finishes.

With the rule-based software, engineering changes are quick and easy to accommodate. For example, let’s say you add several more faces to a 200 finish requirement as shown in Figure 16.

Figure 16. Add more faces to a new surface finish symbol.

Just rerun the Tolerance Based Machining and you will see the updated result in Figure 17.

Figure 17. Updated machining strategy and colored faces.

You may find the new faces have been painted blue and linked to a tree node with a Coarse strategy in response to the 200 surface finish symbol.

To conclude, let’s remember that SOLIDWORKS allows 3D surface finishes to be defined to target features directly on a model. Then SOLIDWORKS CAM Tolerance Based Machining can analyze and act upon these surface finishes to automate the NC programing. You can customize the rules yourself, such as the surface finish ranges, matching strategies and color codes. Then the software can read the specific annotations attached to specific features to assign the strategies and color coding accordingly. Upon design changes, updating the machining preparations, operation plans and NC code programs can be as easy as a rerun of the Tolerance Based Machining tool.

If you have any comments or questions, please feel free to leave the min the comments area below. To learn more about how SOLIDWORKS CAM can help implement your model-based enterprises (MBE), please visit its product page.

About the Author

Oboe Wu is a SOLIDWORKS product manager with 20 years of experience in engineering and software. He is an advocate of model-based enterprise and smart manufacturing.

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