Introduction: CNC Milled Reaction Diffusion Sculpture

About: Reza is a computational designer & creative engineer. He uses code to express himself, and creates tools and libraries to help others create. He is the author of ofxUI, one of the most popular addons for openf…

In this instructable, I'll be show you how to mill out the reaction diffusion sculpture shown above.


One of my goals during my residency at Pier 9 was to go larger and get more physical. I want people to be able to touch the generative forms I've been making & exploring with code. Furthermore, digital objects are volatile, they are so easily erased, deleted, and outdated. They don’t have the same impact as physical things.

Digital objects have no weight, when something has weight you're forced to think longer and harder about that object. Maybe its because you see it more often. Regardless, real objects are have presence. You can’t pirate or download an iPhone. The price of producing them makes society value them more than software. This is open to debate, but this notion has lead to get out of the screen and back into reality.

What is CNC Milling?

If you are not familiar with CNC milling, you've come to the right place. CNC stands for computer numerical control, and milling refers to the process of removing material from a piece of stock (block of wood or metal) using a rotary cutter or an end mill. When you combine these terms it refers to a computer controlled milling machine that can precisely perform milling operations (carve out material, drill holes, etc). If you're a visual person like me, jump to step 6 and play the video to see a CNC mill in action!

What is Reaction Diffusion?

I'm interested in generative systems. Specifically, in natural pattern formation and synthetic pattern formation (found by remixing / mashing up algorithms from the former). I love borrowing / remixing algorithms from nature and applying them to how design spaces, products and forms.

This past year (2014) I spent a lot of time studying and implementing n-body particle systems with various behaviors (flocking, electromagnetic repulsion and attraction, etc), voronoi patterns, and reaction diffusion. If you haven't read my previous instructable about reaction diffusion, check it out, I explain the phenomena in detail here!

In this Instructable, I'll show you how to:

  • Import a STL model into Inventor
  • Generate milling tool paths in Inventor
  • Prepare stock material for milling
  • Setup the stock on the DMS
  • Mill the pattern
  • Post Process the Sculpture
  • Sand & Prime the Sculpture
  • Paint & Finish the Sculpture

For this Instructable, You'll need:

  • Inventor HSM & Mesh Enabler
  • CNC Mill or Router (DMS @ Pier 9)
  • Measuring Tape
  • Table Saw
  • 2 Sheet of MDF (Minimum Dimensions: 2 FT by 2 FT by 1 INCH)
  • Large Clamps
  • Wood Glue
  • Disposable Gloves
  • Various Grades of Sand Paper (100 to 800)
  • Sanding Block (Flat piece of wood that fits in your hand)
  • Spray Paint Primer (See below for the brand I used)
  • White Spray Paint
  • Spray Booth
  • Disposable Dust Face Masks
  • Pier 9's Community of Awesome People

Step 1: Import the STL Model Into Inventor and Convert It Into a Solid

Now we are going to take the attached STL model and import it into Inventor HSM. This can be tricky sometimes because usually your model gets imported in the wrong orientation and you need to have Mesh Enabler (a plugin / addon for Inventor) installed. Click here to get Mesh Enabler.

  1. Click on the Inventor Icon (Top left corner) and then select open. Change the file type to any file.
  2. Navigate to the Minimal-Surface-1ft.stl and open it.
  3. After Inventor opens the file, you'll see that its not orientated properly, we'll fix this meow:
    1. Click on the Front face of the 3D Cube on the top right
    2. Click on the bottom edge of the 3D Cube
    3. Click on the bottom right corner of the 3D Cube
    4. Right Click on the home icon and set current view as home fit to view
    5. If everything went according to plan, you should see the model laying flat in the orientation shown in the fifth photo.
  4. Now right click on model and Click Convert To Base Feature. This feature will only be there if you have Mesh Enabler installed.
  5. Inventor will present you a popup titled: "Convert To Base Feature", make sure you have selected the option for Solid / Surface (Icon on the left) instead of Composite.
  6. Now you should have a solid surface that you can use in HSM!

Step 2: Generate Tool Paths in Inventor

Setting up your Stock:

  1. Click Setup to setup your stock material. This will allow you to set your work piece origin and set your stock size.
  2. When setting up your origin click on the bottom left hand corner point (on the top of the stock). This is illustrated in the second photo.
  3. Then click on the Stock tab under the CAM setup and make sure the stock material size (X & Y dimensions) matches the real stock you have. For this type of cut, its fine and recommended to have a piece of stock material that is thicker (Z-Dimension). Click OK!
  4. Now we need to setup a couple operations. These operations are responsible for milling away material from the stock. The first operation we are going to do is an Adaptive.

Roughing Pass:

  1. Click on the Adaptive button and then click on the Tool button (shown in the fourth photo).
  2. Before we select a tool, we'll need to Import the DMS tool library. Do this by right clicking on Minimal-Surface-1ft and Select Import Tools from Library. Navigate to the Pier 9 DMS HSM tool library (shown in the fifth photo) and press OK!
  3. Now you should see a bunch of tools (shown in the sixth photo). Select the 1/2 inch ball end mill (long).
  4. Click on the Passes Tab inside the Adaptive Operation
  5. Set your Maximum roughing stepdown to 0.25 inch
  6. Then click on the Linking tab inside the Adaptive operation and set your Maximum Stay Down Distance to 10 inches. Now we are done with this operation.
  7. You can simulate the operation to see how much time it will take. Remember that the time estimate is usually off by a factor of two or three (the actual time is longer).

Finishing Pass:

  1. Click on Parallel and then click on Tool. Select the 1/4 inch ball mill (long). See photo 9!
  2. Click on the Passes Tab inside the Parallel Operation and set your stepover to 0.0375 inches. For an even finer finish you can enable: Add Perpendicular Passes.
  3. Then click on the Linking tab inside the Parallel operation and set your Maximum Stay Down Distance to 10 inches. Great! We are done with the tools paths.
  4. You can simulate the tool paths and make sure they look right and don't take too long. Do this by Right clicking on the Setup Operation and then clicking Simulate (All).
  5. If you want to see the stock getting milled away, make sure to clock the icon next to the stock option in the simulation options.

Renumbering Tools:

  1. Click the tool library icon located on the top right of the screen.
  2. Then select your first tool (1/2 inch ball mill long). Right click on the tool and select Renumber Tools. Press Accept.

Post Process:

  1. Right click on the Setup Operation and then click Post Process (All).
  2. Under Post Configuration, select DMS fagor 8055i M5xS_R5.cps (If you are using another type of CNC Router, remember to select the Post Configuration that corresponds to your CNC!)
  3. Now lets set the Program Name. The DMS will only accept program names that are 6 numbers (no alphabetical characters!). Lets name this one 100111.
  4. Now we'll leave a Program Comment, so that when we view the file on the DMS, we are sure that its the same file we generated. I wrote down: "Minimal Surface"
  5. Almost Done! Click post and save the file.

Create a Setup Sheet (Optional):

  1. Now we are going to generate a Setup Sheet (this contains a summary of the machine operations you'll be making and what tools you'll be using). Remember that the tool numbers in the Setup Sheet do not correspond to the tools in the Pier 9 Tool Library we used earlier. For example the 1/2 inch ball mill (long) is tool 20 in the library but in the Setup Sheet its tool 1.
  2. Right click on the Setup Operation and then click Generate Setup Sheet (All), then save the sheet to a folder on your computer.
  3. If you are using the DMS at Pier 9, save the program to a USB drive and print out the setup sheet for reference. Also note what the original tool numbers were so when you get to the DMS, you have an easier time finding the tools you'll need.

Step 3: Prepare Material for Milling

  1. Take a sheet of MDF and cut it (preferably using a table saw for precision) into 1FT by 1FT squares (its okay if the sheet is a little larger, but it shouldn't be smaller than 1 FT). You'll need at least 2 squares, and ideally 4.
  2. Take whats left of the sheet and cut another square (1.5 FT by 1.5 FT). This will be our base plate and will be used to hold the stock material down to the CNC bed.
  3. Laminate (aka glue) the sheets of MDF together with wood glue. (As shown in the 3rd & 4th photos). Make sure your sheets are square by using a square and scrape pieces of flat wood/MDF.
  4. Use clamps to apply pressure to the sheets (As shown in the last photo).
  5. Let the glue dry over night to ensure it has dried and the sheets are bonded properly!

Step 4: Setup Stock Material on the DMS

Back in my day, the DMS had a spoiler board which you can screw into, Now there is a fancy inch thick layer of clear acrylic with nicely spaced (taped) holes you can use to clamp your material down.

If your CNC has a spoiler board, use a drill to screw down the base plate to the spoiler bed (with brass screws). Make sure that your piece is squared up and properly aligned.

Step 5: MILL

Follow the instructions in the Pier 9 DMS User Manual to use the DMS to mill out the piece. I'd highly recommend taking a look at this instructable: before getting on the machine.

Step 6: Post Processing

After the DMS has magically milled your stock material into a fantastically faceted sculpture you'll want to remove it from the bed and prepare it for finishing (by hand).

  1. Unscrew the brass screws using a drill.
  2. Use the table saw to trim off the excess material (edges of the base plate sticking out).
  3. Use 100 Grade sand paper to remove the facets.
  4. Once the facets have been removed the the surface roughness looks even, go up to 200 grade sand paper and repeat.
  5. Keep moving up the grades until you have a surface finish that resembles the second photo.
  6. Screw a wood screw into the back of the sculpture and hang the sculpture (as shown in the fourth photo).

Step 7: Sand & Prime & Sand & Prime

Now we are ready for priming. Make sure you get atleast two cans of Rustoleum automotive primer. MDF soaks up paint and primer like no other.

Evenly apply a coat of primer to the surface of the sculpture. Its okay if the coat turns out a bit patchy. We'll be sanding the sculpture again after painting. Repeat the sanding operations from the previous step until you have a smooth surface. Then apply another coat of primer to the sculpture. Then sand the sculpture again, this time starting sanding with 200 or 400 grade paper until the surface is smooth (and like really really smooth). Then prime it again. Then sand it again until you've achieved a surface finish like in the last photo.

Step 8: Sand & Paint & Sand & Paint

Now we are ready for painting. Make sure you get at-least two cans of Krylon Flat White. We'll be applying multiple coats of paints.

Evenly apply a coat of paint to the surface of the sculpture. Repeat the sanding operations from the previous step until you have a smooth surface. Then apply another coat of paint to the sculpture. Then sand the sculpture until the surface is smooth (and like really really really smooth). Then paint it again. Then sand it again until you've achieved a surface finish like in the last photo.

Step 9: Reflect

Congrats, you're done. Now bask in glory. If I missed a step or didn't describe enough, please leave a comment below. Thanks for reading! Happy Making.