Fabrication: 3D Scanning

I didn’t mean for this little project to get so out of hand, but when there is a will… there is a really long winded way of solving a problem.

Firstly, my fuel injection conversion needed a swirl pot. A swirl pot is an intermediate fuel tank in between your original low pressure fuel tank and the high pressure fuel system. It is not always needed, depending on whether you swapped out your old low pressure fuel pump for an in tank high pressure pump or not. Seeing as I already own a perfectly good Facet lift pump, which is feeding my carburettor, I decided to install a swirl pot. The advantage of using a swirl pot is there is a far lower chance of fuel starvation in corners but at the cost of added complexity and weight.

OLYMPUS DIGITAL CAMERAI bought a shiny aluminium ‘pot a while back for this very task and needed to mount it somewhere in the engine bay. Because I’m putting throttle bodies on the engine I needed to get rid of the battery tray to make space for the trumpets. Having moved the battery and removed the tray I had gained a little space at the back of the bay for the ‘pot. However this area wasn’t exactly flat and true, which made the potential mounting of a flat aluminium tank a bit complicated.

My initial plan was to weld in a little steel support platform, simple right? It would have been a pain and would have required a lot of welding in the bay… and it way too simple a solution.

My girlfriend had been pretty positive about my whole 3d printer fixation and she suggested that there might be a printable solution to my problem. Of course I shrugged this off straightaway.

“It’s not an even surface; it would be an utter pain to measure and get right… I couldn’t guarantee it would fit, blah blah blah, nonsense nonsense, i’m an idiot” –  Josh Ogilvie, 2015

As always she was completely right, there was a printable solution, I just needed a copy of the surface I was working on… time for 3D Scanning!

 

OLYMPUS DIGITAL CAMERAWorking in an F1 team means you’re surrounded by a large number of greatly experienced and talented colleagues who are, more than likely, into the same weird stuff you are. Fortunately Highly-Experience-Engineer-Come-Pro-CAD-Modeller Mark was at hand and he pointed me at an Xbox Kinect style 3D scanner which would allow me to get the point cloud data I was looking for (If you really need to know it was a ASUS XtionPRO Live).

So on one isolated sunny October afternoon I set to work scanning the car. After trying every laptop in the house it was apparent that 3D Scanning is an extremely CPU intensive task (duh!) and that the only machine powerful enough was my PC; so that got dragged out onto the drive. The process was still very slow and I had to be patient not to move the camera too fast or it would lose sync with itself.

FARO_Scenect_3D_ScanI used the free FARO Scenect software to record the point cloud data and I found it very straightforward. It showed me what I had scanned in real time but did not try to do any extra meshing or reduction on top of that, so it was fairly rapid. The data is even in colour so you can tell what you’re looking at. I tried my best to get the panel from as many angles as possible, increasing both the mesh density and its accuracy.

The point cloud data was then exported as an .xyz file for import into MeshLab. I had never used any of this software before so it took me a few evenings of trial and error with different solutions until I found the one I liked. Take it from me, MeshLab rocks. It’s an extremely flexible mesh manipulation tool and has everything you need to turn a point cloud into an STL or equivalent file. In the end I settled on the following straightforward workflow:

  • Save off a copy of your Point Cloud data and hide it so you don’t over right it; you know it makes sense.
  • Import the Point Cloud
    File->Import Mesh->Pick the XYZ File, MeshLab does the rest
  • Delete any unneeded points
  • Orient the Point Cloud
    Do this now or it’ll never be aligned again; trust me. Filters->Normals, Curvatures and Orientation->Transform: Move, Translate, Center
  • Poisson Reduction
    Filters->Sampling->Poisson-disk Sampling
    You will have too many points to sensibly create a mesh out of so you are going to want average them out. This method uses statistical probability to ensure you lose the least amount of LIKELY real points. The hope is you scanned enough data, from enough different angles, that once it is reduced the data will be correct-ish. Remember to enable “Base Mesh Subsampling”.
    MeshLab_SubSampling
  • Calculate the Surface Normals
    Filters->Normals, Curvatures and Orientation->Compute normals for point setsMeshLab_Normals
  • Poisson Mesh Construction
    Filters->Remeshing, Simplification and Reconstruction->Surface Reconstruction: Poisson
    This will build a closed mesh out of your Point Cloud data. It’s important to note that it is CLOSED. If you’re trying to build a surface you’ll need to delete the excess vertices.
    MeshLab_PoissonMesh

Then you can export the results for use in your CAD package of choice. For instance, I couldn’t use the resultant STL data straight away as it had to be further post processed to become a surface object. I put my new surface patch into an assembling along with a model of my Swirl Pot and the rest was fairly straightforward. I drafted two extruded bases from the ‘pot down to the surface to fill the gap.

To my surprise it all actually fit together once printed and after a quick splash of Matt Black I was ready to bolt it all in. I’ll take some more photo’s once everything is finally mounted in the car and painted.

I want to use this same method build a CFD model of my little red car later next year; wish me luck.

 

OLYMPUS DIGITAL CAMERA

OLYMPUS DIGITAL CAMERA

Fabrication: 3D Printer Round Two

OLYMPUS DIGITAL CAMERA Before I begin I would like to state that I did not leave the fuel pump bracket in plain old boring white, but painted it in a stealthy matt black colour (see right). Needless to say I’m bloody happy with how this turned out, especially for my first 3D printed design. However this was a very simple print, with minimal overhangs and most of the printing motion was through the z-axis. Although I think it’s gorgeous it doesn’t push the envelope of what my printer is able to do. Moving on…

I needed a throttle cable bracket for the throttle bodies going on my daily driver. The cable itself will mount at the centre of the bodies and it is required to point at the rocker at around 45 degree’s from horizontal. The cable sheath has a plastic rectangle on the end which sits within a rectangular hole 18mm by 22mm in size; all very straightforward.

However the only place this bracket could mount was two M8 studs which hold the bodies onto the manifold, therefore the bracket needed to be strong enough to withstand the vibration it will see over its lifetime from the engine, be at a direct 45 degree angle to the printing plane as the main mounts would make the main print base and have a severe overhang at the top of the bracket because of the massive rectangular hole the for cable sheath.

OLYMPUS DIGITAL CAMERAOverhangs cause issues. You can’t print hot plastics into thin air, they have a tendency to not sit right or sit at all, so you need to use support structure when printing. Fortunately Slic3r can do this automatically for you (its so awesome). If you look at the completed print on the left you can see a small tower leading up to the overhang. Although very low density this tower gave enough support to stop the initial edge of the top of the bracket from falling into oblivion while being laid down. Voila! One bracket. It required a little filing to remove some excess material but it’s hardly back breaking work.

OLYMPUS DIGITAL CAMERAOnce the print was complete I noticed one clear issue: it was backwards. Now this is a simple lesson for anyone who wants to tread in my footsteps.

“The X-Axis in Slic3r, when modelling for a delta style printer, is backwards. I should know.” Josh Ogilvie, 2015

I didn’t realise this when printing the fuel pump bracket as its symmetrical along the z-axis, but when printing the throttle bracket it meant the final piece was useless (…for anything but a  sweet looking desk ornament). After this it took me two minutes to flip in software world and then I set it off printing again.

OLYMPUS DIGITAL CAMERAI’m extremely happy with the final print and I’m just touching the surface of what a 3D Printer can do. It’s very clear to me that without decent, modern, open-source software this whole process would have been a lot harder; I have the makers of Slic3r to thank for that. I think I will be donating some of my hard-earned pennies to their project.

The curves, gussets and fillets you can put into a CAD design are not easily reproduced when working with aluminium or steel by hand. But it’s clear to me that 3D Printed plastics somewhat fill the gap between hand made parts and billet CNC machined components. They don’t solve every problem but the ones which they solve, they solve in style.

Cool? I think so.

OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA

 

 

 

 

p.s. Yes, I will put lock-tight on those nuts!