Week 7 - Large Format CNC (Computer Controlled Machining)¶
This Week’s Accomplishments:
Group Assignment:
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Learned about CNC lab safety measures and documented my input along with my classmates.
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Tested runout, alignment, fixturing, speeds, feeds, materials and toolpaths for the machine.
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Investigated different programming languages, compared them, and identified how many can be used to program the same microcontrollers.
Individual Assignment:
- Designed a Fusion 360 chair and cut it using CNC.
Introduction¶
CNC cutting stands for Computer Numerical Control cutting. It’s a process where computers control machines to cut and shape materials like wood, metal, and plastic with extreme precision. Like using a computer to guide tools to carve out designs accurately and efficiently, kind of like a very advanced, automatic version of cutting things by hand.
Our Group Assignment¶
You can access our group assignment of the week at my colleague’s page Batool Ali by clicking Here.
Fusion 360 Chair Designing¶
**Design Parameters:**
The design had to be 12mm in thickness and either using plywood or MDF material, with no screws or glue allowed and only relying on interlocked joints.
1.First I looked up minimalistic chair designs because it is my favorite style along with the Nordic and Japanese styles. I loved these and wanted to create something similar using the only material we had, yet durable.
2.I opened Fusion 360 and created a new project. Sketched the basic outline of the chair on the XY plane. Used the Extrude tool to give the chair dimension. Haitham and Abdulghafoor helped me greatly in this one!
3.I refined the design using tools like Fillet and Chamfer to add details and a bit of beauty. Then exported my design as a .DXF file.
Fusion 360 Slicer¶
Abdulghafoor suggested a software called Slicer for Fusion 360. The Slicer for Fusion 360 is an app that allows you to turn your 3D models into 2D build plans with animated assembly instructions. It’s particularly useful for preparing models for 3D printing or other manufacturing processes so I was encouraged to try it out.
4.After downloading the app, I imported my .DXF design and started getting familiar with each button. I had an issue with the app and asked Haitham for help in which he told me to look it up and get back to him tomorrow; which I appreciated a lot, because it encouraged the sense of dependability in me and to be a source of information on my own by researching. So here’s my design after importing.
A quick guide from what I learned about the functions of the app which were pretty easy:
There was super cool features that turned my simple design into intersect pieces that were already assembled with steps and measurements and all!
5.I noticed that the number of sheets was a lot more than what I had to work with so I fixed my sheet parameters from the left panel.
After choosing a satisfactory shape and size, I ended up with this one which contained 20 jointed parts and two sheets.
There was also a dog bone option which I had no idea what it did.
6.I pressed on the Get plans button at the far end of the right panel and it generated me the required sheets to print where I chose my desired format, again .DXF :)
It even had numbers and labels on each and every part!!
7.The app also detected design flaws and showed them in red color in the right sheet panel. Mine had very small joints that could have been broken, I manipulated the number of parts on each axis until the size was satisfactory.
Preparing for CNC Cutting¶
8.I Exported the design from Slicer for Fusion 360 as a DXF file because it always gives the actual sizes. Then I opened the vCarve software and imported my file. VCarve is a powerful software used for creating toolpaths for CNC machines, allowing us to cut and engrave designs into various materials.
9.To generate a toolpath, I selected the vectors, and chose the type of toolpath (e.g., profile, pocket, drilling) mine was drilling and it was sized 6mm.
10.Then I sat parameters like start depth, cut depth, tool, passes, and tabs.
Tabs¶
Tabs in CNC machining are small pieces of material that you leave uncut to hold the workpiece in place during the cutting process. They prevent the cut parts from shifting or flying off, ensuring everything stays secure until the entire piece is finished. Once the machining is complete, we can easily remove the tabs and finish any remaining cleanup. They’re essential for maintaining the integrity of the cut and avoiding damage to the material or the machine.
11.To add dog bone fillets, I used the filleting tool to create rounded corners that facilitate tight fits between parts for clean and precise joints.
Dog Bones¶
A CNC dog bone (or dog bone fillet) is a design feature used in CNC machining to help fit parts together more easily, so that when you cut out internal corners with a round tool, you’re left with a rounded corner. A dog bone fillet is an intentional overcut into the corner, matching the radius of the tool, so the part can fit tightly with another piece. This technique is especially useful for concealed joints, where we don’t want the rounded corner to be visible. It simplifies assembly and ensures a cleaner, more precise fit.
12.After I created toolpaths for each part of the chair and added a dog bone on each corner, I simulated the toolpaths to ensure everything was correct and there were no collisions.
BUT.. Cutting and assembling didn’t go correctly…
Cutting the Chair with CNC¶
MDF (Medium-Density Fiberboard) vs Plywood¶
MDF and Plywood are two of the most commonly used materials in woodworking, each with its own unique advantages. MDF is made from compressed wood fibers and resin, resulting in a dense, smooth surface that is easy to cut and shape. It’s ideal for indoor projects like furniture and decorative items because of its uniformity and excellent paintability. However, MDF is not very strong and can sag under heavy weight, making it less suitable for structural applications. On the other hand, Plywood is constructed from thin layers of wood veneer glued together, with the grain of each layer oriented at right angles to the next. This gives plywood superior strength and durability, making it great for construction and outdoor projects. It’s more resistant to moisture compared to MDF, especially exterior-grade plywood. Despite being slightly harder to work with due to its layered structure, plywood offers better performance where strength and resilience are required. MDF is typically cheaper, but the choice between the two ultimately depends on the specific needs of your project. So I chose plywood because I wanted it to be durable and water resistant since I tend to always have drinks with me lol.
13.I vacuum cleaned the dust from the previous wood material then with the help of my instructor Faisal and my fellow classmates.
14.Then I secured the plywood sheet to the CNC machine bed with screws on the side while leaving a 2cm margin to put these screws nicely in place.
15.Inserted the appropriate cutting tool into the CNC spindle (6 mm).
16.Zeroed the machine to the starting point of the material, and started the CNC machine and monitored the cutting process.
17.Not all pieces were cut to the end unfortunately. I removed the pieces from the CNC machine once cutting was complete. They were patchy and torn.
Big Issue Assembling the Chair¶
18.I sanded the edges of the cut pieces to remove any rough spots, which took a long time because of the type of the material (plywood).
19.Assembled the chair with the help of Abdulghafoor and Faisal. The joint spaces were too tight, the machine must not have cut it properly and on top of that I sat the thickness of each piece to 11.6mm instead of 12mm based on Haitham’s suggestion to get an optimal cut, but things did not go accordingly sadly and I had to use a hammer and DW40 to easy insertion of pieces together.
The chair eventually broke from too much pressure trying to fit pieces together especially with the many intersections it had. The end product was smaller than what I anticipated as well so it was going to be perfect for my one year old niece if it had not been broken :(
Starting From Scratch¶
Not losing hope, I sat with Faisal and he inspired me to design a new chair, with little to no time until the CNC week comes to and end, and with work hours about to finish, I rapidly came up with a chair design that included a desk to place my laptop and notebook on and a side bin tray on the left of the chair, since my room doesn’t have any proper place to study, I decided to make it a studying chair while sitting on the floor and crossing my legs comfortably. Faisal took the measurements of my legs while they were crossed and we designed the chair based on that.
I followed the same steps of CNC manufacturing as before but this time increased the drilling depth to over 12mm to be sure of it cutting properly. I also changed my material to MDF wood because it was the only one left available to use so I was risking the durability and water protection of the chair so I made it with three combined circular discs and joined to perform as the legs of the chair, so 12 mm x 3 pieces giving me a 36mm thickness leg on each side plus one in the middle for extra support.
I cut the chair, assembled it, and put a pillow inside it for some back support. It wasn’t as creative as I hoped it would be, I wish to have new opportunities to create more and more chairs that are successful.
Here are all the downloadable chairs I designed
My Week in a Summary¶
This week, I got more into 2D design for CNC production and mapped out the workflows involved. I documented the design process of my big project and detailed how I created the CAM-toolpath. Plus, I shared the whole journey of making a large object, from setting up the machine to testing joints and adjusting settings. I also noted any hiccups and how I fixed them, and included my design files, both editable CAD files and final versions.
Reflecting on the week, assembling the chair was the hardest part ever. I had so many issues with my plywood piece that it ended up breaking off because it did not fit well so I had to shift to MDF. I found it super interesting to learn about the details of 2D design for CNC production and how precise workflows can make a big difference. The experience with creating a large object was tiring but fun, especially understanding the importance of machine setup and material properties after I suffered to join my pieces together anf failing multiple times. This week was a fantastic mix of learning and doing, both educational and fun!