7. Computer Controlled Machining¶
Individual Assignment¶
- Make (design+mill+assemble) something big
For this week’s individual assignment, my biggest struggle was probably deciding what to make. Initially, I wanted to make some shelves, but I could not figure out how to make all the press fit things line up when I was laser cutting and several of my classmates who had already milled were forces to sand down several of their pieces so that it would fit, and I did ot want to run that risk. Then, I decided to make a table with curved legs and a bigger top than bottom, but then some friends helped me realize that it would then be too top heavy. Next, I decided to make the top and bottom of the table the same size, but that still did not work because the shapes of the legs did not allow me to add dogbone fillets (more on that later). I decided to switch the leg design to be like Elle Hahn’s because hers was very successful. However, when I did that, I did not like how it looked and it felt too similar to her design, so I decded to go back to my leg shape and change the pressfit component to allow for dogbone fillets. Although this all sounds like a lot of work, once I figured out how to do it, it all went very quickly. For example, once I learned how to use Aspire once, it took me around a quarter of the time the next time I tried. I also already feel very comfortable using Fusion 360 and laser cutting, so those steps were simple too.
Shelves¶
As mentioned previously, I initially wanted to create shelves.
Designing¶
To design my shelves, I looked at previous Fab Academy documentation to see if anyone else had made shelves before. I came across David Tian’s documentation and tried using it as a reference of where the slots needed to be. However I did not want it to be the exact same as his, so I had to add my own features. I wanted to make the design parametric, so that I xould easily resize it. This came in handy when I had to laser cut it because the slot thickness needed to be different.
This was the final design I tried to laser cut:
I made many many alterations to that design after I laser cut because not all the slots lined up.
Laser Cutting¶
Everytime I laser cut the shelves, I scaled it down significantly. One major issue I came across was with units. I exported the Fusion 360 file as a dwg and then downloaded it into CorelDraw on the laser cutter computer. When I downloaded it, there was a popup about converting units that I did not rreally read. That was a bg mistake. That computer had CorelDraw default units as inches, but my computer had Fusion 360’s default units as millimeters. This caused my design to be HUGE when I imported into CorelDraw. I was very confused because I kept scaling my design down enough that the slot would be press fit with cardboard and messing around with the parameters, and it still was really big in CorelDraw. Once I figured out my mistake, the sizing was much better and I used the option to put a scale factor to resize it. I still had to change the slot size parameter in Fusion460 too becausze if I only scaled it down, the shelves would still be too big and waste a lot of cardboard. Another issue that was more minor was that construction lines appear in the dwg file in CorelDraw as just regular lines, and since I used several construction lines in my design, I needed to use the Virtual Segment Delete tool to remove them. In addition, a good thing to check is the size of the lines in CorelDraw because they should all be hairline in order to vector cut. That is what it defaulted to, but that is important to check.
When I was laser cutting, there was an issue with the Autofocus button that would not allow the machine to be autofocused. I asked Cooper Cumbus about this issue because he had just laser cut on that laser cutter. He showed me how to focus it manually, which is definitely an important skill to know how to do. There is a little spring right by the laser, and you have to use the joystick to lift the laser up until the end of the spring is just barely touching the material.
This is what you need to do:
Make sure to lift the spring up when you are done:
Here are the laser cut pieces:
I laser cut again and here are the pieces:
I tried using blue tape to assemble it to see where the msitakes that needed to be fixed were:
Eventually, as it got closer to the next Wednesday, I did not want to get behind, and since the shelves had so much room for error when milling due to the many press fit slots, I decided to switch to something else. Several of my classmates had milled their designs on the CNC machine and were tasked with sanding all of their press fir slots until they fit, and with my shelves that would have been very tedious.
Table¶
I decided to make a small table instead to use as a plant holder. I was inspired by Tyler Russell who made a stool, but he used 0.5 inch wood instead of 0.75 inch, so Mr. Dubick called it a planter since people cannot sit on it. I went home and told my mom this story, and she wanted me to make a “planter” too.
Designing Type 1¶
I wanted it to be a cool-looking but relatively simple-looking table, so I started out trying to make one of those tables where the top is bigger than the bottom with several legs connecting the two circles. Some friends pointed out to me that havigng it be top heavy would not be very sturdy, so I decided that if once I milled, it was too top heavy to stand up, I would be okay with just flipping it over and having the top be smaller than the bottom since both circles were similar sizes anyway.
The most difficult part of creating this design was creating an asymmetrical arc where one end was not linear with the other end. I tried several different techniques in Fusion 360 to do this and ended up using a Fit Point Spline. However, when I exported the Fusion 360 file as a dwg and brought it into CorelDraw, the arcs did not appear, so I asked ChatGPT. I ended up tracing over the Fit Point Spline with the 3-point-arc tool and then deleting the Fit Point Spline. This worked.
Here are some pictures throughout the designing process:
Laser Cutting Type 1¶
Since the legs of the stool were so long, and there were four of them, I did not want to waste cardboard, so I started out only cutting both of the circle and one leg just to see if the leg was sized correctly. It worked first try!
Then, I wanted to double check to make sure it would work just to be safe, so I scaled the whole design down and laser cut all four legs and both the top and bottom.
This also worked first try, which was a nice refresher after my difficulties with the shelves.
Preparing for CNCing¶
Tyler Russell helped me out with setting up my design in Aspire.
1.Set up material size and settings.
2.Select whatever components of the design you want to deal with first. I selected all of the components, but later Andrew Puky pointed out to me that I should not select the inside grooves that time because I would have to select a different setting for those.
3.All of my design was Profile cut, not Pocket cut, so I selected that option.
Profile-cuts along line
Pocket- shaves out shaded area
Profiles and pockets have to be closed.
4.Select outside, inside, or on the line.
Outside: exact vector size
Inside: vector - diameter
For everything except the grooves in the circles, I chose outside, so that the vector size would be exact, but I chose a different setting for the grooves in the circles.
5.Add tabs to keep wood from moving when the machine is finished with cut. Aspire has an option to automatically add tabs, but it is important to never put a tab on the corner, so I needed to remove some of the tabs it created for me. For a four-sided object, four tabs is generally good. My tabs would not appear at first, and I kept getting this error message:
To fix the error, I needed to ungroup all the components and then use the Join tool that Tyler recommended to join the components together and remove open spaces. Sometimes when importing a dxf file into Aspire from Fusion, the lines can be unconnected, which does not allow tabs to be added properly.
6.I also decided to add ramps using the default value, which Elle recommended. Ramps keep the bit from going straight down. Instead, the bit goes at an angle. They lead to less stress and more life for the tool.
7.The next thing I needed to do was add a dogbone fillet to all the inner right angles of my design. Dogbone fillets allow press-fit components to fit together nicely and work better with a rounded bit. I had to ungroup each individual component to add the dogbone fillets. This is where I ran into an issue with my design because I could not put dogbone fillets on the end of each of the legs because there was no rigth angle to apply them to. Tyler pointed out that if I milled my design how it was, then the wood pieces might not fit together properly, and the circles could slide down the legs which no piece to stop them. I had to adjust my design to fix this.
I went back to Fusion 360 and fixed my design. My updated design ended up looking too much like Elle’s, so I had to fix it again. I laser cut one of the versions and once I knew that the legs would line up, I reshaped them to be how I wanted them to be and then exported that Fusion 360 file to Aspire as a dxf. Then, I repeated the previous process, and it was much faster. Andrew decided to mill with me, so he added his design to my file. In the file linked at the bottom of this page, you can see our final combined design.
CNCing¶
Andrew and I milled our design together and worked together with the help of Elle Hahn and Angel Fang to learn how to use the CNC machine.
Andrew, Angel, and I went down to the shed to get wood, and as we selected our piece of wood, we used the thickness testers that were milled in the group assignments for this week.
We determined that 0.496 was the most accurate thickness for our wood.
1.First, we needed to open the Aspire file on the computer connected to the CNC machine.
2.Then, we needed to brad the wood down to the machine using plastic brads. Bradding the wood down to the machine ensures that the wood will not move while cutting, which helps keep us safe. The brad nailer was empty when we needed to use it, so we had to load the brads.
Here is a picture of us putting the brads in the wood:
3.Next, we needed to do an aircut to make sure that the cut would be over the wood. We also had to change the machine bit to the 1/4” compression bit since that is the one we chose to use.
Aircut:
4.Then, once we were sure the cut was going to occur in the correct place on the wood, we were ready to go.
5.Once finished, we vacumed the wood dust.
These are the finished pieces being taken out:
Assembling¶
Here are the final CNCed pieces:
Here are the pieces partially assembled:
Cooper Cumbus helped me assemble my table because it was difficult to get everything to line up at the same time.
Here is the finished table!
I was happy with the final result, and my mom was also happy. Currently, the plant table is being used to hold one of my mom’s many plants.
Group Assignment¶
Our group assignment for this week was to complete our lab’s safety training and test runout, alignment, fixturing, speeds, feeds, materials and toolpaths for your machine. My group this week was all the girls doing Fab Academy: Zaina Gibrine, Elle Hahn, Jenna Chebaro, Kathryn Wu, and Angel/Zijia Fang. Since there were so many of us working in a group, I ended up having to do less work than I have in previous weeks since we just divided and conquered all the necessary topics. I looked at speeds and feeds. Here is our full group documentation for this week.
Speeds and feeds in CNC machining determine the cutting tool’s performance, efficiency, and longevity.
Spindle speed (RPM) refers to how fast the tool or workpiece rotates and is based off the tool diameter and material-specific surface speed (SFM).
Feed rate (IPM or mm/min) determines how quickly the tool moves through the material and depends on chip load, tool flutes, and RPM.
Material can play a role in the best setting to use. Harder materials like steel require lower speeds and higher torque, while softer materials like aluminum allow for higher speeds. Small tools typically need higher RPM, unlike larger tools which operate at lower speeds to manage heat buildup.
Reflection¶
I would not necessarily call this week difficult, but some parts were definitely overwhelming. I had to try several different designs, but ultimatly, I think if I were to CNC again, I could do essentially the entire process (designing, laser cutting, setting up Aspire, setting up the CNC machine) in around an hour. I learned a lot this week because I had never used Aspire before, and I did not have a lot of previous CNC experience. This week was also stressful because I did not want to get behind, and basically everyone was around ready to CNC at the same time. This week was not the most enjoyable because I did not really have a big need for something large, so I was not really as excited to make something, but I learned a lot. The group project for this week was not very difficult and also not very interesting. The pieces my group milled to test the widths of wood are also definitely going to come in handy in the future.
Useful Links¶
I looked at several previous Fab Academy documentations for ideas on what to 3D print, but I did not end up following any of them. I wanted to create something a little more unique.
AI Help¶
Here are all my ChatGPT searches from Week 7: PDF
Files¶
Plant Table Ready to Mill crv3d File (with Andrew’s chair as well)