I have been experimenting with 3D printing in the office. I wanted to create a wing with a flap which can be 3D printed in one go. Using the desktop 3D printer and materials we have in the office.
This post describes my experiments in printing just the wing and flap. My goal is to get the basic design and printing process right before moving on. At a later stage, I will look at putting servo to control the movement, but the first thing is to see that the printer can do.
Now there is nothing new here. There has been various other projects printing whole of or parts of aircraft. However, they all require some assembly. If can print the flap and wing in one go, it is one less part that needs assembling.
3D printing builds up layers of material to create a part. It is sometimes known as additive manufacture. There are various different techniques and materials that can be used. It is also one of the technologies usering in Industry 4.0.
The technique I used is called Fused Filament Fabrication. A computer model of the part is loaded into the printer. Then a plastic filament is fed through to a heated nozzle. The nozzle extrudes a thin line of plastic to create a layer, then moved on to the next layer until the print is finished.
The 3D Printer in the Office
The printer we have in the office is a Wanhao Duplicator 5S. The plastic I used to print was PLA (polylactic acid), because we had some open. PLA degrades over time so this spool needed using up. PLA does not need a heated bed (like some other plastics), which is good because the one for this printer is a little temperamental.
The First Attempt
Making the Digita Model
The first step was to create the digital model used to create to be sent to the 3D printer. I decided to use a NACA 0012 airfoil. It’s a symmetrical airfoil with a maximum thickness of 12% of the chord, which was 150 mm. I set the gap between the two parts to 0.3 mm. The wingspan was 300 mm. I used Solidworks to create the model.
Slicing the Model
The Duplicator 5S uses its own software for slicing in the STL file into layers. I went for its standard setting with an 8% infill.
The estimated print time for this model was 13 hours, 58 minutes and 19 seconds. Using 122.1 g of plastic.
The First Print
Unfortunately, the filament broke. This happens sometimes when 3D printing – the plastic had become brittle, due to it being a little old (and absorbing moisture). However, some lessons were learnt.
You can see the inside of the wing here. The wing also felt a little fragile, so the 8% infill, although light, would not make a strong enough wing. Also, you can see the axle of flap fused with the hole it would have sat in.
Again, looking at the bottom of the print, you can see where the flap and the main part of the wing have fused during the print. Even if the filament had not snapped part way though it would not have been able to move.
The Second Attempt
I made a few tweaks to the computer model:
- Made the wingspan smaller, from 300 mm to 100 mm
- Increased the gap to 1 mm
- Increased the infill amount to 20%
- Reduced the layer high, from 0.2 mm to 0.1 mm
- Finally, increased the height of base-plate.
The estimated print time for this model was 14 hours, 14 minutes and 30 seconds. Using 92.5 g of plastic.
Why would this print take longer? Because of the increased infill and reduced layers. There are twice as many layers per millimetre and the printer is not moving any faster, as well as there being more lines in the infill.
The Second Print
First, to make the plastic less brittle I gave it a blast with a heat gun and let it cool. This softened it up making it more bendable.
However, it’s not perfect. There is a little warping with at the base of the wing (you can see it clearly on the left corner). This does not effet the flap but could be a problem if I was planning to use it on something. Also, increasing the gap between to two part to 1 mm does give the flap a lot of play. I would need to do some more testing to see if the 1 mm gap can be reduced without the parts fusing like in the first print with the 0.3 mm gap.
I have a few options on where to take this next. I could try to refine the process of working with the printer in the office. Or I could try with other 3D printers in the university. There are some which allow two materials to be printed at a time, one of which would be a support material.
Another option would be to optimise the internal structure of the wing model. Right now the slicer software determines the thickness of the outer edges and infill amount and grid.
Also, I could try different airfoil and flap designs. I have plenty more airfoil designs that could be used. Generally speaking, the airfoil is chosen with the purpose of the aircraft in mind. Which is why I chose a simple one for this test, no need to complicate things. Additionally, there are many other flap designs which could be tried. As well as leading-edge devices.
The above two would require more CAD work, as well as some simulation to make sure they do what they are designed to. If you have any ideas of what you think I should go next with my 3D printing of wings let me know.