One of the hardest things to do is to manufacture a part that is intended to fit an existing structure, particularly if that structure has compound curves in the X, Y, and Z axis or Three Dimensionally. In this article I’ll show you how I used 3 photographs to identify the shapes I needed to construct baffles for my big 40% Pitts Challenger. Cooling the big Desert Aircraft 120CC motor isn’t a problem in December, but come July, I’ll be wishing I baffled the air entering the cowl straight through the fins of the heads on that big powerplant.
I started by taking 3 pictures of the cowling. One from the front. One from the top, and one from the side. I purposely took pictures with clutter in them to demonstrate that you don’t need amazing photographs to do this technique.
Take One Measurement and Scale Everything from it:
When I import the image into Autodesk Fusion 360 I’m going to need to be able to scale the image (A Canvas in Fusion terminology) so that it is the exact size in model space. So I used my calipers to measure the width of the hole in the front of the cowling. In this case, the width of the hole was about 66mm wide.
Import your pictures into AutoDesk Fusion 360 with the Insert Canvas Function and Model!
Your going to want to paste your front view on the front plane and the top view on the top plane. You’ll use each of these planes to set the curvature of your models and their respective sizes.
Trace your contours using the Spline tool.
I used the spline tool to draw an almost perfect outline of the hole. I then offset the spline with the thickness of 3 passes on the 3D printer for a 0.4mm nozzle. So I am making the shell 1.2mm thick for strength.
Begin Converting your 2D views into 3D space with the Fusion modeling tools.
I want the shell to curve slightly in toward the crankcase of the engine so I drew a slight curve from above and used the Sweep tool to “Extrude” the spline into a 3D object. I’ll mirror this object since both holes are identical in the face of the cowling.
The shell we created is flat on the front but the cowling is curved on its face so I setup what I am calling “Clipping Masks” to get the edges curved to the contour of the cowling. The image below shows how I used the spline tool to accurately follow the contour of the top of the cowling. This is going to be used to “Trim” or “Clip” the face to the right curvature and the correct length. Remember, I am not making any measurements here. I’m using the photo for all my “Shapes”. The left head on the engine is farther back (60mm) than the right head (25mm) so I drew the clipping boxes to trim the model to its proper shape.
The image below shows how the blue boxes above are “Extruded” or “Press/Pulled” to a thickness and how they are used to cut the existing baffle models to not just shape but length.
The final models are shown below with all the canvases, sketches, clipping masks, etc hidden.
I then export the models into .STL files that the 3D printer “Slicer” can read. The Slicer will take the models and generate the G-Code to control the Prusa Mk3S 3D Printer to print the cowling baffles. I used PETG filament since it is more heat resistant than typical PLA.
The models are then exported to the 3D printer where they are turned from the electronic world to the physical world! I love this part! Fire it up, drink a bourbon until you trust that things are going well, and go to bed. The next morning is like Christmas and your are presented with the following gifts! Notice that I printed a fairly wide 5mm “Skirt” at the bottom edge of the parts. I didn’t want to risk them coming loose from the build plate in the middle of the night!
I dropped the finished parts into the cowling and they were a perfect fit on the first try using this technique. If I had to measure everything there is no way I could have obtained this accurate of a fit without a TON of sanding and re-fitting etc. I epoxied the baffles into the cowling using West Systems Resin and Hardener reinforced with fiberglass and 24 hours later I had a very solid baffle system that fit perfectly on the front of the Pitts!
Its incredible what is possible!
Obviously what I have shown here is a fairly advanced technique. It took me about an hour to take the pictures, model the parts, slice them, and get them exported to the 3D printer. The print took about 3 hours and 20 minutes to complete. It took about 20min to epoxy the parts into the cowling not including the 24 hour cure time.
I have used this photogrammetry technique on at least a dozen projects and have yet to not nail it on the first try with a perfectly fitting part. The custom turtle deck below was modeled in Fusion for the Pitts from the picture of the cheesy cardboard one that came with it. The Pitts Logo and my Signature were both traced using the spline tool and extruded onto the custom part in a single model. I just requested a color change in the slicer so the Prusa would prompt me to change to yellow when it was time.
As you can see, just about anything is possible!
See you at the field!