Machined Tiny Turtles for Arts and Crafts

These were a fun little experiment to try and learn a bit more about programming a desktop CNC machine in Fusion. These are really cool for gifts and showing friends and family what can be done with an affordable CNC machine. These only take a few hours depending on how fast the machine being tasked can handle the feeds and speeds.

• Computer with CNC programing software (I used Fusion as it is CAD and G-code programming in one software)
• The wood of choice (I just used some scrap wood)
• CNC Machine (I have a Comgrow Robo)
• End mills and engraving bits
• Double-sided tape (can be optional)
• stain/oil (I used grapeseed oil)
• Superglue (optional)

This step will be the hardest step and potentially the most time-consuming depending on the knowledge of programming a CNC machine.

1. The first step in getting started is to grab a model to machine. A model can be created by using CAD software or browsing a website collection of models such as Thingiverse. (Different models will have different levels of difficulty in machining). The model that I am using is originally from louisersr71. The model had a gap at the end of the shell so I remixed it and included it in this step.

2. Now, the model has to be inserted into the software. If Fusion is being used the model has to be inserted and then converted into a mesh. If you do not know how to do this there are lots of wonderfully helpful videos on youtube such as this one: Video

3. If you are using Fusion make sure the stock that is being cut is also modeled in Fusion. I am not familiar with other programming software but I assume you have to create the stock too.

4. It is now time to officially start doing the program. I am not going to get really in-depth with this because that would take forever but you have to create a profile for the machine and profiles for the cutters. Then have to create a setup for the origin, stock, and models. After that, make a roughing pass (this gets rid of the majority of the excess material). I used the additive roughing that Fusion offers. Make sure that some material is left so there can be a finishing pass ( I left .1 mm of material). After that, I used a parallel pass and this removes the rest of the material and leaves a nice finished model. These are the basic tool paths that I used but there are tons more things that can be done depending on the model and what needs to be done with it. Once the programming is done make sure you double-check and make sure there are no errors or any problems that are going to happen

* Note

For roughing, I used a 3.175 mm four flute bit running at 700 mm/min at an rpm of 10,000 and a maximum depth of cut of .6 mm

For finishing, I used an engraving bit running at 1,000 mm/min at an rpm of 10,000 and a maximum depth of cut of .1 mm.

I left around 2 mm of material on the bottom for me to cut out the model by hand to make sure the turtles didn't break since they are so small.

This next step is pretty easy. To begin with, get the stock that is going to be cut. Next, take the stock and secure it to the bed of the machine with clamps or other various methods. The position of the stock on the machine's bed will be determined by how you have it set up in the programming software. If the stock is small and a small vice is not available double-sided tape works great. Now, insert the milling bit that will be used for roughing. (3.175 mm four flutes for me) and find the origin (The point where the machine will start). The origin should have been determined by the setup when the programming was being set up.

*Note if a computer is being used to send the G-code to the machine make sure that the X, Y, and Z are set to zero. I used this method and the program I used was CNCjs which is free and extremely useful.

This is step is my personal favorite since it is so fun to watch. Now that the origin is set you can export the G-code from the software of choice and load it onto the machine either through an SD card or a computer. Then click go and the machine should be off and running. Make sure to clean the chips up every so often with a vacuum just to make sure everything is running correctly. Then once the roughing pass is complete now it is time to finish up the part. This will involve a tool change which will require resetting the z height for origin since the bit will most likely be a different size than the first bit that was used in the roughing pass. This can be achieved by using a piece of paper or a leveling tool. If there is any confusion on how to do a tool change here is a great video.

*Note: For the finishing pass, I used a 20-degree engraving bit with a .1mm tip

To finish up the turtle, some cutting by hand was required to remove the material that was not cut with the machine which was around 1 mm or two. If you are cutting it out, do not cut super close to the turtle or you might risk breaking it because of how small they are. Once the turtle is cut out some sanding is required. It should take an hour or less depending on how good it needs to look. Then once the sanding is done make sure any dust is removed from it and then stain or oil can be applied to the turtle to give it a darker or shinier look. For my turtle, I used a grape seed oil to shine it up. After that, I added a layer of superglue just to give the turtle some strength and it adds some shine to it. Then I 3d printed out a backplate from black Petg plastic and glued the turtle onto it using a small drop of superglue. Then the final step for this was to create a chain that was actually pretty simple. Just needs some wire, wire cutters, needle-nose pliers, and a small diameter to wrap the wire around to make a spring. Then cut the spring on one side to make little Cs and then just link the Cs together and close the gap with the pliers. Then connect the chain to the backplate and the other side of the chain to a wire loop, and that is how you make a simple key chain with a beautifully machined turtle.