3D Printer: Upgrades 2/3

It’s taken me almost two months to get around to writing part 2 of this series, opps! However this is because I have actually been using the printer, and working on a project for a friends rally car (watch this space).

Now where were we… ah yes, the heated bed. In the previous article I explained why a heated bed is a good upgrade for a 3D Printer, especially one that uses high temperature plastics such as ABS. Installing one is easy straightforward, however my little machine required a few modifications along the way.

To convert your printer to use a heated bed first you’re going to need, you guessed it, a heater to heat the bed.

1. Sourcing a Bed Heater

A simple flat Silicone Heated Bed. Easy to install... and ORANGE.

A simple flat Silicone Heated Bed. Easy to install… and ORANGE.

I chose to use a 12V Silicone Bed Heater. These are easy to get from China and come in an array of different sizes to suit your needs. As I write this, doing an ebay search brings up 47 of them from a range of manufacturers.

Truth be told I took this route because its what everyone else does, however there are some major benefits to this style of heater. Firstly they are simple to wire (4 wires, with feedback), they are relatively thin and they can be driven straight from most standard firmware.

 

Most common printer PCB’s have the ability to drive a 12 or 24 volt heated bed directly, however I opted to use an external power supply. My heater is rated at 350 watts, so at 12 volts it can draw up to 350/12 = 29.1 amps! I was not willing to push that through a thin PCB, no matter how much the manufacturer says its marginally spec’d to that ampage.

An all purpose 12v DC Power Supply. 240v to 12v made easy.

An all purpose 12v DC Power Supply. 240v AC to 12v DC made easy.

In hindsight I probably should have gone for a higher voltage heater and then wouldn’t have had to flow as many amps to achieve my desired bed temperature; especially given the fact my power supply has to drop down from 240 volts! A smaller step would have been more efficient. In fact 110V heated beds are available, their just less common.

 

 

2. Wiring the Heater

The heater has four wires, one pair is power/ground for the heater itself and the other pair are attached to a thermister embedded in the heater. The thermister wires were attached directly to the control PCB and this allowed the software to measure the temperature of the bed while printing. The power wires went to the external power supply via an automotive relay (12v 40amp). The relay was switched using the heated bed control off the PCB, which is usually used for driving the bed directly. This giving a lovely 12v output to charge the relay coil and switch on the bed.

Power Supply

IMG_20160525_190955

 

 

 

 

I ran the power switch and thermister lines through the case via some two pin connected. Initially I wired theconnectors straight to the aluminium printer chassis but soon realized one of the pins ground through the outer thread! This mean’t I had to print some little top hats to make sure the signals didn’t ground. Printing parts for the printer; it’s 2016.

Case ConnectorsExternal Connections

Working Temperature Feedback

 

 

 

 

Once this was all wired together surprisingly it worked straight away (well once the above earthing issues were fixed). This gave me closed loop temperature control of the bed, ensure a nice consistent temperature.

3. Fitting the bed

It wasn’t all straightforward. The Chinese manufacturer neglected to give any dimensions when listing the heater, so I had no idea how thick it was going to be. I had a feeling it was likely going to cause issues with the self leveling system, as this requires the bed to bottom out when being installed to get under the sensing probes.

Low and behold once I installed the heater the aluminium bed no longer fit. Fortunately I had my non-heated bed on hand and I used it to print taller probe mounts. Magic.

Raised Probe Towers

 

 

 

 

So that’s it for this installment. In part 3 i’ll go through building an enclosure and the tricks I’ve learn’t when printing ABS.

 

A closing thought and something to consider before getting one of these machines. The more I have used the printer, the more I have come to realize that it is as much a piece of workshop machinery as a lathe, mill or welder. It requires maintenance, care and cleaning to remain consistent and usable. In my experience, few people have the patients for this.

 

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.

Analysis: A good case for Cold Air Intakes

I have been writing a series for the website covering street tuning of ignition maps. I believe I have come up with a dyno-free method that may or may not work; you’ll have to wait to find out.

The process requires a series of 3rd gear pulls at Wide Open Throttle (WOT) with varying offsets of ignition advance. I was expecting to see a strong correlation between power and ignition angle, with more advance giving more power; as the map that is currently in there is highly conservative.

The baseline was repeated to check consistency, but ultimately the consistency was poor. After a crawl through the data it became very obvious that the variation in engine inlet temperature had a great effect on engine power. See below.

Air Temperature Effect - 1.6 Pinto on a DGAV Carburetor , K&N Filter

Air Temperature Effect – 1.6 Pinto on a DGAV Carburetor , K&N Filter

I think this is a good argument for using a cold air feed! Which I had completely neglected. As the engine is now switching over to fuel injection I’m going to repeat the tests and hopefully yield a better result

A cold air feed will be present and accounted for; watch this space.

 

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!