Introduction: How to Carve Liquid Plywood Patterns on a CNC Machine
In this tutorial I am going to be showing you a method that I have found works really well for carving wave relief patterns into plywood.
What is a wave relief pattern and why would I want one? It is a relief pattern carved into a material that is formed by simulating a wave and then projecting it into a 3d model that is then carved out on a CNC machine. They are not really useful for anything practical but when carved from plywood they create some really interesting and attractive patterns that are cool items to hang on walls or integrate into furniture like cabinate doors or coffee table tops. With that in mind this is quite a specific project and I don't expect that too many people will have access the equipment to make something like this but it will still hopefully be interesting to learn how the process works! Enjoy!
(Also I am entering this project into the CNC contest so if you enjoyed it I would appreciate a vote if you feel like it)
Step 1: Step 1: Creating the Wave Pattern
The first step is to create the wave like pattern that will be carved out of the plywood surface.
This pattern can be made a number of ways. The way that I am going to be doing it is to create a gray scale image of a wave using a program called ripple tank and then extrude that image into a 3d model to be carved out. You can adjust the wavelength and phase of the waves in this program and even simulate two waves colliding which looks really cool. Other ways would be to either 3d model one yourself (would take ages) or you can google images of waves and ripples and experiment with results from those. I have included all of the cool images that I have generated so far for you to use if you don't want to buy the software. The gray scale images of these waves are converted to 3d models in the next step.
Step 2: The 3D Model and Generating the G-Code
Now that you have the wave that
you want it is time to project it into a 3D model that can be carved out. There are as usual a great number of ways to do this. I will talk about the two that I know of. Firstly you can turn the 2D image into a 3D STL file using a program like Rhino (free 60 day trial) and then carve out the 3D model using a program like MeshCam or Fusion 360. This produces nice results and lets you have complete control over your toolpaths. Alternatively you can use PhotoVCarve or just VCarve which is what I prefer to use. This lets you import images and then generates toolpaths from the image. It has a free trial but leaves annoying watermarks on the image. I would recommend a maximum depth of around 5-7mm for good results in BB plywood as this exposes a nice amount of layers without making the wave valleys too deep and sharp. Once you have projected your image to a 3d model you can generate the G-code for your CNC machine. If you don't have a CNC machine (most people don't) then you can always go to a local machine shop or makerspace and there is a chance that they will carve some items out for you for a small fee. Alternatively there are some online resources but this would be expensive (postage and packaging for large items) and it might take some explaining to get what you want. For curved and organic shapes like this a ball nose end mill is required. I use a 3.175mm one for smaller more detailed waves and a 6mm one for the larger pieces. For a good surface finish that doesn't require much sanding I use a step over of 10 to 15% depending on time constraints. For my CNC (and X-Carve) I have found that with such a small stepover I can use a 10mm depth of cut and go up to 2000mm/min! (pretty fast for my hobby machine!) I have found that the best material to use seems to be high quality Baltic Birch plywood - not the cheap crappy stuff but the furniture grade birch stuff. This leaves really nice contour patterns with a nice contrast between layers when finished. Alternatively this might look quite nice if done is a heavy grain hardwood or in some sort of micarta layered material. Once the material is selected it is time to carve! So far I have only been testing small offcut pieces of material due to the high cost of this plywood but some point in the future I will try to make a coffee table top or something larger. I recommend starting on a smaller scale just so you can see what the patterns look like in real life and then slowly working your way up in size. Most of my carving on this scale only takes 1 or 2 hours but something larger could take up to 6 hours (with my amateur machine).
Step 3: Finishing the Plywood
After carving there is very little work to do if the wood comes out with a good surface finish (provided that you use the correct settings on the CNC) . Firstly I cut away the edges using my table saw and occasionally use a belt sander to round off the corners. I then give everything a light sanding with 200 grit glass paper to get rid of any grooves from the router then move onto using a 600 grit sanding sponge for the final finish. After that I give everything a good coat of boiled linseed oil to bring out the grain and contrast between layers. If I was going to use this for furniture I would give it a few coats of polyurethane yacht varnish but for these small tests its not worth it.
After all of that you are finished!
If you enjoyed this tutorial please vote for it in the CNC contest!
If you have any questions then please post them in the comments section down below!