Learning 3D – modelling & printing

A “real life” situation

When learning something new, I find it very useful to have an actual application to which the learning applies. I had previously made a couple of attempts at learning 3D modelling using Blender but with essentially nothing to show for it, due to a few reasons, one of which was that I didn’t have a compelling reason to get something working.

This time it was different.

Earlier this year some severe weather left us without power for a few days, and the power restoration prediction was not looking good. In the face of that we decided to buy a generator, eventually deciding on a petrol driven 3KW model. As is typical, after the first 10 hours or running the first oil change for the engine became due, and whilst doing that I discovered that the space between the oil sump drain hole and the frame on which the generator is mounted leaves very little room for a container into which the old oil could drain.

The (yellow) frame is only 13mm below the bottom of the engine.

Having learned that my son recently bought a 3D printer, the idea formed that a good application for the printer would be to create a funnel to channel the oil to where an appropriately sized container can be placed which can hold all the sump oil being drained.

3D modelling

After creating a rough sketch on paper I decided it was the right time to learn how to create a 3D model of the funnel, and for that I decided to learn FreeCad. I found it was reasonably easy to get a basic design created – and FreeCad’s parametric modelling (i.e. it’s “Part Design” workbench) is intuitive to use. After some iteration and tweaking I came up with a design I felt was worth printing.

The first funnel design

Part of the process of producing the design also involved sharing it with my son, and for that I also started learning Blender (for real this time!). Initially it was just so I could import the model from FreeCad, set up the camera, background & lights and render an static image. However, I also found Blender easier to pick up (which was likely, in part at least, due to the version I’m using – 2.83), so I found myself learning more of the modelling and animation aspects as well.

3D printing

It turns out that when you’re learning 3D modelling and printing, the printing part is also an iterative process! Here we were learning about the limitations of the printer’s ability to produce overhangs and discovered that the design I envisaged with the sloping exit chute made printing a bit of a challenge. (An overhang in this context is a part of the model that had nothing under it to support the soft filament as it exits the printer nozzle.)

Needless to say, some tweaking during the printing process resulted in a funnel that was not exactly the same as the FreeCad model.

The finished funnel still in the printer
The post-print test

When I received the printed funnel and placed it into position under the engine, I realised there was a potential flaw in the design I’d originally envisioned, namely that there is a real possibility for the oil to overflow the funnel as it flows out of the sump hole.

The funnel in situ


Taking the things we learned so far it seemed worthwhile to redesign the funnel. Two main factors drove the direction of the redesign, namely:

This resulted in a flat part (i.e. no downward sloping exit ramp) that was wider and had higher sides to better contain the oil.

The new design – funnel Mk2, rendered in Blender

The other refinement was that in the meantime, I have learned how to model / simulate fluid flow in Blender, so it is possible to use Blender to check the functionality of the design. Using the viscosity of the engine oil and (admittedly a guess) the velocity of the oil exiting the sump hole I could build a simulation to ensure there would be no oil overflow.

With confidence the model would perform well, we could now print with confidence, and also eliminate any print side adjustments since this flat model could be printed easily.

Funnel Mk2 printed.
The new funnel in situ.

It’ll be exciting to find out how this performs when it’s time for the generator’s next oil change!

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