Fabrication: From CAD, to 3D Print, to Fibreglass

To trackday a car it needs a reasonable level of illumination, to communicate your intensions and make yourself more visible in low light conditions. Indicating left, pass me on the right. Hazards flashing, I’ve had a bad day. This is something the Locost has not needed until now, as it has only ever been driven on closed courses with only one car competing at a time.

I already own a set of rear light clusters that I bought almost six years ago when I was initially stockpiling parts. I decided to go with these “hamburger” style rear lights as they mirror the round headlights at the front of the car, that I am also yet to install, and also I could get them with clear LED’s which would keep the car aesthetically pleasing. It also helps that they weren’t cut-off-your-left-leg-and-right-arm expensive.

The easiest and quickest place to mount rear lights on a seven is directly to the rear bodywork. While this could have been done on a Saturday afternoon, with time for a few cups of tea in-between, it would have been almost irreversible and completely illegal for road use if I ever felt like going that way (lights must be a maximum of 100mm from the outer most bodywork). So this left me with only one option which was to mount them on the rear wings. Never one to turn away the opportunity to do something the hardway I decided this would be a great opportunity to make my own light pods, in my own asthetic style- fire up the 3d printer!

CAD

First of all, my printers build volume is a measly 150*150*150mm, and would have never been able to print an entire light pod in one go. Also, PLA plastic would have never been a good choice for components like this, given that they will sit in the sun for extended periods of time (damn you 60degC glass transition temperature). These would have had to have been printed in ABS. Printing thin walled ABS shapes is pretty much a no-go without some major warping, so this left me with only one option… a 3d printed mould.

I grew up around fibreglass in all its forms. Quick shabby make-a-mould-out-of-Tupperware fibreglass, and top quality a-thousand-layers-of-wax-and-lots-of-polish fibreglass; this was going to be something in the middle. Because of my limited build volume I opted to design the mould to split into four separate parts. This also meant that releasing the strangely shaped light pod would be relatively straightforward as long as everything was unbolted and persuaded a little; so it was win/win.

After measuring the curvature of the rear arches and the geometry of the lights I frew the mould itself and split it in the X and Y axis. This is a female representation of the lightpod, with the reverse being the actual “male” final piece. Getting a clean striation-free mould surfce was going to be unlikely, and comes with the territory when 3d printing, so I knew I was going to have to sand and polish the final mouldings after they were produced.

Light Pod Mould

3D Print

I believe these components took between 16 and 19 hours each to print in PLA, which goes to show how awesome my Printrbot Simple Metal is. I’m very happy with my printer setup at the moment, as it’s hugely reliable over a long period of time. Hold on, where’s your RepRap gone Josh? That’s a story for enough time…

Light Pod Complete Mould

The mould was sanded with 200 grit sand paper and given 5 layers of wax. The wax helped to fill in the crevasses between the separate mould pieces and massively helped the release after moulding. In short, this stuff rocks.

simonizwax

Fibreglass Mouldings

Once the mould itself was ready to use the mouldings were made in a fairly simple way. Firstly a layer of White Gel Coat was applied to the mould with a brush. Gel Coat is essentially resin with pigment in, which gives the moulding an outer layer which can be sanded and painted to achieve a nice finish. If the mould is of a high quality the Gel Coat can simply be left as is. I would eventually be painting these moulds so I wasn’t too bothered about the initial surface finish.

Light Pod Gel Coat

Once this had adequately hardened polyester resin was brushed into the back of the Gel Coat and 450gram fibreglass rolled into that (I gave it approximately 4 hours at 10degC, with a 3% mass fraction of catalyst to kick things into gear). The rolling process is important as it helps to remove air bubbles from the structural fibreglass and improves the strength of the composite. It also helps reduce the amount of resin you have to use, as the fibres are pushed tight against the Gel Coat and the resin soaked through. If the whole lot was just brushed on then it would have likely had a higher resin content and been heavier.

Light Pod Laid Up

This was left for two days to harden and then extracted from the mould. I’m very happy with the final product and its far lighter than I expected it to be. The ‘pods will be glued into the back of the arches and then faired in with filler. The whole lot will then be smoothed and painted; probably glossy battleship grey.

Light Pod A

Light Pod B

Light Pod C

Have you ever tried any Fibreglass work? If not, give it a go! Its actually ver y rewarding and if you take your time with each step you can achieve great results.

Aluminium Printer Chassis 2

3D Printer: Upgrades 1/3

The current trend towards cheap and accessible home CNC machines is fantastic. I wouldn’t have a 3D printer if it wasn’t for the slow and steady reduction in component prices due to the high demand of an expanding hobbyist market. Also, China has made manufacturing a tenth the price it used to be.

While this has lead to the component parts, and ultimately the overall machine costs, becoming more affordable to the home-maker there are some short comings to this: 99% of hobbyists do not demand or need industrial level quality. If you want to print a bobble head of yourself to show your friends then usually you can live with middling quality, poor tolerancing and materials that only stay in shape at room temperature, and so 99% of the machines you can buy are built to that standard.

Now my 3D Printer was cheap and a somewhat early-days experimental product; the company that made it has already gone under (link). I wanted a “quick-way-in” to 3D Printing, hoping to make the odd part here and there for my numerous car projects, however I have quickly come to realize that it’s now a fundamental tool in my workshop, it just needs more capability. I need it to print accurately and repeatedly in higher temperature plastics. To ensure my machine could do this it needed two key upgrades.

1. Heated Bed

A Rare ABS Print Success

ABS can be printed in a warm room in your house, however you will soon become a lonely single man due to the smelly fumes.

My little fisher delta was very much limited to printing PLA (Polylactic Acid) due to not having a heated bed. PLA has a melting point of 150-160 degC and a glass transition point of 60-65 degC, so it’s easily extruded at 100 degC when it’s malleable and workable. If you’re printing at 25 degC room temperature then there is approximately 35 degC delta between its set temperature and the glass transition temperature, and that’s fine.

However I’m printing in a cold garage which is usually at 10 degC or less giving a Temperature Delta (TD from now onwards) of ~50 degC, this is still fine but you start to get into shrinkage issues on big prints due to the thermal stresses across the part.

I really wanted to print in ABS (Acrylonitrile Butadiene Styrene), or as I like to call it, “The Good Stuff”. ABS has a glass transition temperature of ~105 degC (much more like it!) and has no true melting point as it becomes amorphous (Wikipedia is awesome). It’s very tough, impact resistant, acid resistant and heat resistant, which makes it far more suitable for automotive applications.

However the glass transition temperature of ABS causes print problems as you have to extrude it at higher temperatures (I use 130 degC). This mean’s the TD across the part is far higher than if your printing with PLA and warping and cracking becomes a real problem. What you need to do is ensure the print is kept warm while printing to reduce the TD and it’s common to achieve this by using a heated bed.

2. Aluminium Chassis

Broken Printer Chassis

Acrylic really is a terrible structural material

Now simply heating the standard acrylic print bed was not an option as it was liable to flex all over the place and therefore I wanted to at-least use an Aluminium or Glass print bed. Aluminium has a thermal conductivity of 205 W/m.K which means it will heat up slowly and maintain a fairly uniform temperature distribution (Acrylic has a thermal conductivity of 0.2 W/m.K).

On the Fisher Delta the geometry of the print bed is important, as it has a three point self leveling system and these three points need to be accurately positioned. Because of this I opted to get the bed laser cut at a local company, along with the rest of the machine. The acrylic parts were all starting to bend and warp and it made me question how accurate it was anymore; I had only been using it for three months.

Aluminium Printer Chassis

Much improved frame with increased accuracy

So once I got my parts from the laser cutters I pulled my machine apart and rebuilt it to be far more durable and long lasting beast. She also looks pretty nifty in Matt Aluminium.

 

In Part 2 I’ll cover the wiring of the printed bed and the modifications I had to make to fit it into the Fisher Delta frame.

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!

Fabrication: My First Proper 3D Print

You can’t avoid CNC these days. I’ve managed to produce some pretty complex components with an angle grinder, welder and a spare afternoon but, if you want to produce a top quality part, you have to go CNC.

It’s been my plan to build a CNC plasma cutter for some time now but, the truth is, I don’t have any real experience with the electronics and mechanics involved; yet. There are many articles out there of people who have taken the plunge and just learnt as they went along but I have so many projects there is little time left for another big build.

As a halfway house I decided to buy and build a 3D Printer kit. The printer includes a lot of the same components the plasma cutter will need (stepper motors, drivers etc.) giving me the opportunity to learn some machine design, and I also get a 3D Printer at the end of it.

I put the machine together in my evenings over a busy October and managed to successfully print the test model. However the next big step was to design something I actually needed, build the appropriate tool chain, and successfully print it .

The Fuel Pump Bracket

I’m converting my 80’s daily wagon over to fuel injection for a bit of fun and added fuel economy. The high pressure fuel pump for the system needs to be mounted in the bay along where the ignition coil used go; this required a custom fuel pump bracket. While I would usually fold something up out of thin steel or thick aluminium, I have a 3D Printer now and I’m going to make use of it.

FuelPumpBracket_Design_1To begin with I took the measurements I needed from the fuel pump (60mm diameter) and the mounting holes on the car and roughly drew my plan in my notebook. Then I used <insert generic 3d CAD software> to model it. One of the many great things about 3D printing is that you can easily add the space for captive nuts and counter sunk bolts into your design, at the cost of little-to-no extra manufacturing time. My fuel pump bracket uses three M4 bolts to tighten onto the pump and these are neatly sunken into surface.

Using a “Slicer” program I turned the STL model file into G-Code for the machine to understand (Slic3r). You can set your material density, resolution and supporting material with this software, and I found it to be very flexible.

OLYMPUS DIGITAL CAMERAI received 100m of white filament with the machine so this is what I have been using for my prints. Black would look a bit nicer but until I have some more experience I’ll stick with the standard stuff. This turned out to be a good idea as my first try at printing failed after 10 minutes. If you look at the pictures on the left you can see that I didn’t specify enough infill density, so the internal structure was too open; this lead to warping and separation from the print bed.

OLYMPUS DIGITAL CAMERAFor round two I went up on the internal density and used a 10mm brim on my print to make sure it would stick to the bed. This greatly improved the quality of the print and ultimately it was successful. However it was soon clear that I had gone overboard on the resolution settings, and material density, leading to a print time of over 9 hours! I left the machine working over night while I dreamt of future plastic parts.

The final component is gorgeous, but completely overkill. I could have halved the material density and removed a lot of excess material from the design. That said, I am confident it will do its job for many thousands of miles. With a splash of Matt Black paint I reckon it will look like a production part.

OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA

Next job: A 3D printed throttle cable bracket.