Computer Controlled Machining
This week's individual assignment seems simple: make something big. However this is not as easy as it sounds. After hours of researching something unique but not too difficult to CNC, I found this on a Etsy of all things. It immediately struck my eye because of its unnatural shape, defying gravity. From this images from this design, surely this should be a piece of cake to design, right? Nope.
Making Something Big
Designing
I first started this by opening Fusion 360, a software I would be seeing a lot of. I first started by making some parameters: top_length which was side length of the top octagon, wood_width which was the width of the wood I would use (I set this to 0.7 initially), and tab_length which was the length of the slots that I would design later.
First what I did was create the top of the table. Although I took inspiration from the Etsy design, I was trying to make this my own in some way. So, I started with the hexagon shape and made each of the sides the specific value from the parametric, top_length. Then I started to add the slots for the other piece of wood, making sure to center them on all four large sides of the octagon while applying constraints to ensure no wiggle room.
Then, I moved on to the legs which were a little more complicated (sarcasm). First iteration was great! It had only taken me more than 3 hours to design! Still, after fiddling with the constraints, I had a pretty good sketch.
If you think this is a lot of constraint to keep track of and that I'll probably fail later on because of the sheer amount of constraints and because of the constraints, my constraints will end up costing me a lot of time and because of my constraints, I might have to restarts... you'd be right.
Then, after extruding it to my pre-set wood_width and trying to manually assemble the parts, my friend, Andrew Puky helped me out by explaining how to use the joint tool. That way, I was able to assemble the parts by just connecting each of the faces that would go together in the slots. To create this without needing any drills I would need to create slots that fit together almost perfectly which required a lot of precision. Also, in order to use the joint tool, I needed multiple components. So, I selected each of the parts — the right and left leg and top part — and made each of them different components. That way, the joint tool was able to recognize each component and calculate a way to fit them according to the shapes.
Unfortunately, when I first jointed the two together, I had realized that my constraints were not very good and for some inexplicable reason, some things were not lining up and would not make a closed shape if I changed the value of the wood_width to 0.73 which was the actual width of the wood I was going to use. This was not good. I then spent the next couple hours working on how to fix the constraints by redoing some of the lines and adding the constraints all over. This was not an effective method because instead of fixing things, I ended up making the whole design a lot more complicated.
After some fixing the zooming in on each point to close the open figures, I had been introduced with a new issue: I had a lot of double lines.
I then went through the entire sketch and started clicking on each line and deleting to see if there was a line underneath it. If there was, I would leave it deleted, and if it wasn't, I would just Ctrl+Z to undo the deletion.
I also decided to only work on one of the legs and copy and paste and modify for the second leg.
After a while of doing this, I finally went and copied and pasted and modified. However, this time the joints didn't fit. So, I went to the sketches of both of the legs and changed the position of each of the slots. This took a couple of hours and finally. I was able to finally export into Aspire.
BUT...
Somehow, someway, there was some open vectors found by Aspire's open vector detecting system.
In spite of all this, I decided to restart.
After restarting, making the whole thing from scratch, meticulously adding constraints such as the vertical/horizontal; tangent; and coincidental constraint, I was finally able to make it work.
Testing on Cardboard
Then, after I had successfully assembled it in Fusion 360, I was able to test it out on cardboard using the laser cutter. First, I changed the parametric for my wood_width to 0.5 inches(cardboard measurement I got) and exported the Fusion file as a DXF and then opened it in CorelDraw. The first thing I did in CorelDraw was make sure all the lines were hairline so that it cut on the laser cutter. Then, I went to check the widths of each tab and made sure they were the right size. Finally, I adjusted the print settings as per our lab's pre-adjusted values and sent it to the cutter.
Video:
The assembly after was pretty easy because I gave the wood_width a larger value than the actual cardboard, so it fit pretty easily and it shows that the parameters had worked. Here is what it looked like after I had assembled it.
Aspire
Then, going back to Fusion, I changed the wood_width back to 0.73, imported the file as a DXF into Aspire, selected all of the lines, added dog bone style fillets to all the corners so that the tab corner wasn't too shallow and would end up not fitting, and added the toolpaths with these settings. Also, in general, the dog bone should be half the diameter of the bit so that it takes cuts the minimal amount of wood while still performing the job.
Here is before and after applying the dog bones to the vector.
If you imagine the bit going along the outside of the vector, you can see that that instead of the bit going shy of the actual line I want, it will go deeper and will not be detrimental to the fitting of the slots.
I added the ramp to the toolpath in order to ensure that the bit wouldn't break as per advised by Dr. David Taylor. Since the board had a slight bend after I secured it to the ShopBot's bed, I decided to add a little bit of margin, changing the cut depth from the original 0.73in to 0.735in to make sure it cut all the way through.
Here's how the toolpath turned out. I had also manually added the tabs by pressing "edit tabs" to make sure that it wasn't too close to the tabs. I also just kept the automatic values of the tabs. The dotted line is the original vector and the outer line with the arrow is the toolpath. The small green squares are where the tabs are going to cut out.
Using the ShopBot
Then, because I needed a different piece of plywood than the person that used the ShopBot before me, I was able to change and secure my new 3/4 inch plywood with the help of Zijia Fang. She also accompanied me in the process of milling.
The first thing that we did was secure the board with a Brad gun following our lab's workflow. We then performed an air cut which is meant to let us see where exactly the bit will cut on the board before we actually perform the cut and to see if it got the right bit. It worked, so we were good to go. Here is the workflow to the air cut, using the brad gun, and actually performing the cut.
Here is a video of the CNC machine actually cutting it out.
Video:
Post Processing
After I had fully cut out the wood, I had to remove the tabs using the oscillator. It vibrated a metal piece so fast that it cut through the wood tabs with ease, then I was able to easily remove the large pieces. However, when I had first tried to assemble the table, I ran into the problem of the tabs being too small. At first I thought it was fine and I just had to sand it down a little and it would be able to fit because of the small wood chips that were protruding from the sides.
But, this turned into a couple hours of sanding. After hand sanding for a while, I found that Zijia was also running into the same problem and was using the technique of putting a piece of sanding paper on the oscillator and letting it rub the sandpaper on the wood much quicker. This definitely cut down a lot of time and was able to take off more wood faster.
After a while of doing this, I had finally been able to fit the pieces together. Here is the product and a fun picture of Andrew Puky sitting in the chair he made while next to the table.
Group Work
In this week's group work, I helped design and mill the clearance testers. I also started up the the ShopBot because no one had used it that day yet, and I followed our lab's start of day instructions as per the workflow I mentioned earlier.
Reflection
For this week, I think that it was very beneficial to my understanding of how to use the large ShopBot, and if I were to use the ShopBot again for whatever purpose, I would retain relative fluency in operating it. I also think that I learned that I should always account for the clearance of tabs. I also learned how to use tabs instead of nails to combine things together. This would be helpful because sometimes nails will ruin the wood while only using tabs will use less nails and requires more spacial awareness. In the group work, I think that it helped in situations like mine where the clearance was an issue. By using a clearance checker like the one we made, we can see the best value for connecting a specific piece of wood.