15. Wildcard Week¶
For this week we had to:
Design and produce something with a digital fabrication process (incorporating computer-aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it.
This week we visited the factory of former Fab Academy student Ashot Margaryan At his factory, there were many machines for metal processing. But the most important thing for me was the acquaintance with plasma cutting, which provides fast metal cutting, including the ability to work with thick materials. Its feature is work without contact with metal, which eliminates problems with tool breakage.
Finding a Design Solution¶
As a job on the plasma cutter, I decided to cut the legs for my final project. The final project is a clock made from plywood using a CNC router, with its own gear system. The legs will be one of the important components of the project, which will ensure its stability and aesthetic appearance.
The watch dimensions are as follows:
| Name | Size |
|---|---|
| Length | 1 122 mm |
| Height | 732 mm |
| Thickness | 93.6 mm |
At the beginning, I decided to search the Internet for what metal legs for furniture are. Here are some examples I found on ebay.co:
Let’s see another example from etsy.com:
But for me, it would be more acceptable to use the following construction, which I found on the site [pinterest.com] (https://www.pinterest.com/pin/665899494886353569/):
If we compare with the previous examples, then in the last example there are slots at the places of the upcoming bend. Since we do not have a special tool for precise bending of metal, and we plan to use a vise and a hammer for bending, having cuts at the bends has several advantages. Firstly, the slots will allow us to bend the part with less effort, making the process easier. Secondly, they will serve as fold markers, helping us pinpoint where the fold is.
Using all of the above examples involves using four separate pieces for one piece of furniture at its four corners. However, since my watch is 93.6mm wide, this makes using four feet unreasonable. Therefore, a more reasonable solution would be to use two bent parts at two ends, each of which has two legs. Such a solution requires a custom design to meet my requirements.
Part design¶
I decided to draw a drawing of a part for cutting on a plasma cutter in the program Fusion 360. The choice of the program was also the fact that it has the ability to generate G-code.
Let’s start drawing.
First you need to create New Design, then the drawing needs to be done in Sketch.
The width of the watch case is 93.6 mm, and I want to make the height for the watch legs 90 mm. Based on this, using the Line tool, you should draw two side lines 90 mm long and an upper horizontal line 92 mm long. As a result, after bending, if we take into account that the thickness of the metal used will be 2 mm, then, accordingly, the width of the legs will become approximately 96 mm, and the height will be 94 mm.
The Line tool is very convenient to use, immediately when drawing a line it is possible to specify the length and angle of rotation, and there is also a binding to draw a line horizontally, vertically and with appropriate settings at a multiple of 15°. In addition, the program provides the ability to use various snapping tools, such as snapping to the center, end or intersection of other objects, which allows you to accurately place and orient lines.
I want to make the width of the frame for the design 9 mm. To do this, let’s draw two horizontal lines 9 mm long from the bottom points inwards.
Then you need to mark the contour lines and use the tool Offset
You need to specify the direction inward and the size offset 9 mm
The result is a frame with a thickness of 9 mm with an open bottom
I want the legs for my watch to look like a truss.
Let’s draw auxiliary lines and draw lines from the bottom points by 60°. And after using the tool Trim, cut off unnecessary lines.
And now, using the Offset tool, set the thickness to 9 mm, and after using the Trim tool, remove unnecessary lines.
Using similar operations, let’s create a similar system for the upper part.
The middle part is already done. Now let’s select the whole drawing, copy (Ctrl + C then Ctrl + V) and move it 94mm to the right. The strip for bending in the case of using a 2 mm steel plate is desirable to make 2 mm thick. For this reason, moving the copied part by 94 mm, we get a 2 mm strip for bending.
For this part, it is desirable to have a cantilever part. Using the Trim and Line tools, we will trim and draw lines and get the following:
Let’s do the same operations for the left side. The result will be the following:
This was perhaps the most irrational way to design the left side of the part. There is a very good Mirror tool that would do the same with much more ease. And when using this tool, if you change something in the original, then everything would automatically change in the mirror image.
And now let’s create slots at the junctions. To do this, connect two vertical lines of two surfaces with lines (Line tool), then select the two extreme points of these two lines using the Sketch Dimension tool to set the distance between the lines. Then copy these lines and move them between two other vertical lines of the surfaces and remove (Trim tool) the extra lines.
The sides of the part are done, and now it’s time to create the substrate on which the clock will be insulated. To do this, let’s draw a bend strip. And then for the middle part we will draw two lines under 45° before the intersection.
Then draw a horizontal line from the point of contact, and from the right corner of the upper part of the left side of the part, at an angle of 45° draw a line to the intersection. After that, from the upper left part of the left side of the part, draw a vertical line to the intersection.
After cutting out all unnecessary lines and doing the same for the right side of the part, we get the result.
I want to slightly change the design of the left and right sides of the part, namely to make them sharper. Let’s do this using the Extend tool (extends a line to the intersection with another line), Line and Trim.
It’s time to create platforms for the legs. The pads must have a bend line. Let’s use the Line, Circle, Sketch Dimension and Trim tools and draw them:
Now let’s draw the places where the legs are attached to the clock. Since the thickness of the plywood is 10 mm, the holes should be made in places so that they pass through the middle of the vertically lying plywood. Based on this, let’s draw a horizontal line, the location of which is 5 mm relative to the edge. And then mark the line and make it constructive.
Then, having built holes for fastening with screws on this line, the final form of the part will take the following form:
The work in Sketch is finished. Click on Finish Sketch. Then Select the Extrude tool, move the mouse cursor over and select the area of the part and set its thickness to 2 mm.
My part design is complete.
Cutting settings (G-code)¶
When the part design is finished, you can go to the MANUFACTURE section. Since the part needs to be cut on a plasma cutter, you need to go to the FABRICATION section.
First of all, go to Setup and set the zero coordinate. For me, the lower left point of the rectangle that bounds my part will be characteristic.
Then you need to create NEW TOOL. To do this, click on CUTTING, a pop-up window opens on the right side. In the Tool section, click on Select. A pop-up window opens, in which, if you click on the ”+” sign at the top, you can create a new tool. From the Cutting section select Plasma cutter.
Then we set the geometric parameters. In my case, set Nozzle diameter to 1.7mm and Kerf width to 2mm.
Then you need to set the nozzle movement speed, in my case I set it to 1800 mm / min.
Then, in the Geometry section, select the contour along which we want to cut. To begin with, we will select only the outer contour. The red arrow shows the direction of the tool movement relative to this contour and which side the cut will be made on.
If you click on the red arrow, the direction of movement of the tool will change, and the cut will be made along the inside of the contour. Working with a plasma cutter is very similar to working with a CNC machine. A contour or line can be cut in three ways: along the line, along the outside, and along the inside.
Then I create a duplicate operation.
Then I change the contour, as a result of which the cutting of another contour continues.
I decided to create different operations for cutting, because at the initial stage, when I wanted to do this by selecting all the contours at once, the small contours were ignored. And for cutting small contours, an open contour cutting was chosen as an operation, which is a line.
After cutting operations are selected for all contours, we can select all operations and save the G-code for our machine.
It is important to choose the right post. In this example, to save the G-code, I opened the file on Ashot’s computer, since his computer had the settings for this plasma cutter.
Cutting parts¶
The CNC plasma cutter is a modern industrial device used to cut metal materials with a plasma arc.
The working area of the plasma cutter on which we worked is 6 meters by 3 meters.
It is equipped with a computer and software that allows you to control the cutting process with high precision and repeatability.
G-code can be loaded into it via a USB flash drive. And by selecting the appropriate file, you can see the trajectory of the head movement on the screen.
By using the appropriate buttons on the computer, you can move the head. Zero coordinates are set according to the location of the material to be cut and according to the location of the workpiece to be cut.
Let’s start cutting. Cutting speed (1800 mm/sec) and distance to the part (4 mm), but there is one more cutting parameter that comes out of the computer a lot, this is voltage (in my case 119 Volts).
Everything you need is done, now you can start the machine:
Handmade¶
Since slag is generated around the cut during the cutting process on a plasma cutter, slag treatment is required.
Before deciding on a possible project this week, I was looking into projects that could be made with a plasma cutter. In these projects, there were parts that are intended for subsequent bending. Therefore, I decided not to limit myself to obtaining flat parts or volumetric parts assembled using welding, connecting elements or bolts and nuts.
As part of my project, the part must be bent manually mechanically.
Primary slag removal¶
To remove the slag that appeared from the plasma cutter from cutting, I first of all used pliers. Since slag is not part of the metal, it can be easily removed when subjected to force.
And to remove the rest of the slag, I used a hammer.
Part bending¶
For bending the part, I used the vise that was present at the factory. Fortunately, I had the opportunity to test the bending of the part, because the first time I made a mistake in the order of work. As a result, this led to the impossibility of continuing the process.
And to solve this issue, I needed to return the part with the help of a hammer to its original state, but I did not achieve ideal smoothness, but I was able to identify the sequence of actions.
In order not to get confused in the order of bending, I made a special drawing, which demonstrates the order of bending.
I want to note that bends 1, 2 and 3 are made by placing the part between the vise and hammer blows. And 4 and 5 bend only with a hammer.
A badly bent part helped me figure out the sequence of the bending process. And fortunately Ashot was kind and allowed to print two more such details.
Here are some steps in the bending process:
And here is the final view after bending:
Conclusion¶
I liked this week because we got the opportunity to work with an industrial device. Although we did not have enough time to fully immerse ourselves in the details of working with the machine, it was a very valuable experience that allowed us to appreciate how our knowledge and experience gained at the Fab Academy is applied in practice with new machines. If we have the opportunity to work with this type of machine in the future, I hope that our practice will help us to start working on a plasma cutter from a more professional point of view.