Creating designs and artwork with an eye towards digital and CNC fabrication is different from producing work that will be printed or posted online. This checklist can help you prepare designs you’ve downloaded or received from other designers. It can also help you develop a clean workflow that will result in “CAM ready” geometry that goes smoothly from digital idea to physical thing.
Here is the list
1. Place Part Geometry on a Separate Layer
2. Reduce Line Weight
3. Geometry Should be Composed of Joined Vectors
4. Convert Specialize Curves into Standard Lines
5. Convert Fonts Into Curves
6. Simplify Overly Complex Vectors
7. Search for Irregular Vectors and Correct
Step 1: Place Part Geometry on a Separate Layer
Separate the part or object vectors from embellishment or raster information. You should create a layer where you have isolated the geometry that defines your object or part.
The two collections above have the same vectors, but the fill data on the left hides the underlying geometry. The same guideline is true for vectors that are only for visual effects.
The design on the left has additional vectors to help create
the illusion of an interwoven knot. For CNC geometry we want to isolate the vectors that describe our part.
Step 2: Reduce Line Weight
You should also assign the thinnest line weight supported in your drawing/drafting software to your part geometry. This will not only reduce visual confusion, but some of the drivers for our CNC tools use line weight to distinguish cutting and etching in their tool paths.
The circles above are all the same size, but the varied line weights can add confusion.
Step 3: Geometry Should be Composed of Joined Vectors
It is important that our geometry is comprised of joined vectors.
We can use four independent lines to represent a rectangle, but even if it looks like a rectangle, it is still four separate objects. Drivers and CAM software interprets each as an independent operation rather than one object.
This is also true for more complex geometry created from basic shapes where intersecting vectors have been trimmed. We still need to combine the vectors and join intersecting points for the vector be treated as a single piece of geometry.
Step 4: Convert Specialize Curves into Standard Lines
Splines and specialized curves should be converted to simple lines on the part geometry layer. Most CAM programs will have trouble importing vector information containing spline data. We want to create clearly definable geometry (basic lines and arcs).
Step 5: Convert Fonts Into Curves
If text actually forms a part of our geometry, it needs to be converted to curves or traced before it can be incorporated.
Like the other elements for our part, we should remove all fill data, and make sure our text elements are properly joined curves. We should note that once the text has been converted into curves, it will no longer be editable as text. If you want to make changes to text elements, you will need to convert the new text & integrate the new vectors with your part geometry.
Step 6: Simplify Overly Complex Vectors
Tracing font or other raster data brings us to another process. Simplify any object to the fewest nodes possible while retaining the object’s shape. Below is a font with a large number of nodes.
Compare the same vectors after the number of nodes has been reduced using the node reduction tool in CorelDRAW. You can accomplish the same thing in Adobe Illustrator using the “Simplify Path” sliders.
The goal when we are working with geometry for fabrication is to create the simplest geometry possible while preserving the integrity of the shapes in the design. Overly complex geometry will create problems when you try to import designs into the CAM software for many of the CNC tools at Pier 9.
Step 7: Search for Irregular Vectors and Correct
Another problem to watch for when reviewing geometry is irregular vectors and dots. One example of irregular geometry is a spline that loops back on itself. The object in the photo may look like it has a sharp point in the upper left, but if we zoom in, we find that the point is actually a loop. The loop will create issues if we try to import this design for a tool path.
Another common issue is small dots or dashes in our geometry. This can happen when the designer is using basic shapes and trim tools to create more complicated designs. This part began as a collection basic shapes which were trimmed to create the final part. The problem is a small line segment that was overlooked in the process of trimming and joining the geometry.
If you look closely, you can see the small line segment that was missed. These dots or overlaps frequently create problems when the design is imported into the CAM software for many of the CNC tools at Pier 9.