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Nathan Selian: Mechanical Engineering
First Attempt
The first step of this project involved creating a rough sketch of the block’s features on which I could add dimensions. Using a set of dial calipers, I noted each dimension, rounding within 0.005” of their nominal values. Accuracy in this step was crucial since the gasket would have to align perfectly with the block's features and locating pins. Each measurement was added to the sketch until I had a detailed dimensioned sketch, although not over-dimensioned. From this dimensioned sketch, I was then able to design a CAD model of the gasket in SolidWorks.
Along with measurement, a significant component of this assignment was learning to use the GibbsCAM software to create G-Code that can tell the CNC machines what to do. Importing my SolidWorks model into GibbsCAM, I was able to tell the software what features to machine, how to machine them, what tool to use, tolerances, offsets, speeds, feeds, etc… Once happy with the result, I then used the software to generate the G-Code for the CNC mill to read.
Next, I brought my files to the EPIC workshop. Using machinist’s tape, I adhered the stock material to the work surface. This was plenty sufficient as the stock material was quite thin and bendy and would be virtually impossible to hold down using a vice or other fixture methods. Once adhered and the file loaded, I started the mill and let it do its work. When it was finished, I removed the part and as a final step cleaned up the edges with a de-burring tool.
CNC Machining Process
Second Attempt
Unfortunately, when I tested my gasket on the aluminum block in class, It didn't quite fit. This, I determined, was due to a single discrepancy in my sketch and measurements where a dimension was drawn between the wrong features on the sketch. This discrepancy is highlighted in red in the revised dimensioned sketch. To prevent this in the future, I will be more careful to draw dimensions between the correct features when creating dimensioned sketches.
After I determined where the discrepancy was, I updated my CAD model and re-machined a new gasket which fit perfectly. No extra measurement was necessary.
One unforeseen benefit to having this mistake is that I was able to get some extra practice using GibbsCAM as well as the CNC mill. The second time around, I found that it was much easier and more intuitive to set up the part in GibbsCAM. As well as being much easier, It also took a fraction of the time. Using the CNC mill again, I felt more confident and was able to run the mill almost without any instruction.
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