Week 5 - 3D Printing and Scanning

In this week of the academy we looked at the diverse range of methods to 3D print and scan objects. Neil told us how 3D printing in the lab is the equivalent of using a microwave in the kitchen. 80% of the time another machine will do a better job; but 20% of the time the 3D printer is the ideal choice. The reason for this is because it can produce objects that could not be made subtractively (this is where the machine removes material to make an object, like the laser cutter does). The 3D printer produces objects additively, as in making up the object from scratch by adding the material. This enables various useful objects to be produced in one job. Classic examples are enclosed ball bearings and bike chains.

This week's assignments:
Design and print a 3D object
Scan a real object to turn it into a 3D image

Aims for this week:
Put more effort into time management!! (started to slack last week... finished the assignment with time to spare but didn't try to work ahead with final project)


 

25th February 2015 - Oh what to 3D print... Ah HA!!

So as soon as we were given the assignment to 3D print an object I thought why not make a bike light housing and all the electronics to go with it. So tonight I am going to design it and hopefully get it printed tomorrow. This is a good opportunity to prototype a potential part of my final project as well as really test my design skills in terms of ability and lack of time.

As I will be stuffing my printed object full of electronics, it was essential that I take measurements of a few components that I would be using. So I took out a pair of vernier calipers and set to work! I took measurements of a 10mm LED, a 9V battery clip and a magnet (could be an interesting way to secure the light!)

I will chug away at rhino and show you guys my progress tomorrow. This is my first change to do some 3D modelling in rhino so it's going to be a big learning curve!


26th February - Modelling complete

After a very late night modelling and not enough sleep, I came up with this design:

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So first we have the clip which will hopefully fit to most bike handle bars on the left. Further along we can see these swooping lines cut into the body of the light. In real life this wouldn't be the most practical as the electronics would be more open to the elements. You're probably thinking why would I put holes the the body?! Well, this is one of the things that means the design cannot be made subtractively, which was one of the requirements for this week's assignment of designing and printing a 3D object. The rest of the design features also make this impossible to be made subtractively. The circular disc hanging out at an angle is a flap connected by a living hinge. The holes in this disc will house 3 10mm LEDs. Inside the body there is a box shape which will house a 9V battery and below that there is a small indentation for a magnet. The idea is that the small magnet will assist in keeping the light secure on the bike.

After presenting the design to the gurus at the lab I was met with disappointment as the type of 3D printers they have in Fablab Amsterdam are unable to deal with areas which overhang by more than around 45 degrees. This is because there is nofacility to support these overhangs sufficiently. It could be done by printing supports to go with the overhang but this would then need a lot of work to tidy up afterwards.

What I then did was develop a second version of my design. I sliced up the object and turned it into a press fit construction kit. In all honesty, this was a real pain to try and do. Rhinoceros started to behave weirdly when trying to merge two objects after being sliced. Random objects would disappear! Eventually I managed to make a mesh of the parts that were playing up. It still isn't perfect so I will try to make some improvements in time for 3D printing.

The other half of our assignment is to scan an object so it can be viewed on the computer. Organic objects are the best thing to scan as they are the hardest things to draw on CAD programs. I chose to scan some sweetcorn on the cob. It has a nicely detailed and complex texture which would be great to scan. I started with a phone app called 123D catch. The app cleverly uses the phone's accelerometer to judge the relative positions of the photos you take of the object and stitch them together. Take a look at the outcome below. Considering its made from just a few pictures taken on a phone, it's pretty good!

There are of course much more accurate and tidy ways of 3D modelling which won't leave the mess that the app tends to leave. Another method is to use the Roland Modela that I used to mill out the circuit board. Except with a different tool which is used to measure the parameters of an object secured on the milling bed. Unfortunately I had to leave it to run overnight and won't see the result until tomorrow (OH the trauma!). In the meantime I am going to work on my bike light design and try to tidy up the press fit version. However, one last note on 3D scanning the sweet corn. I figured it could be possible to use part of the scan as a design for the bike light housing. Imagine, a corn on the cob bike light.. how random but interesting!


27th February 2015 - 3D scan complete!

So this morning I returned to the scanning machine to see how well it recreated the shape of the corn on the cob. It turned out pretty good! But it was going to need some trimming

I trimmed the scan so that I had one piece which I could use to jigsaw many copies of around a cylinder. I used Meshlab to tidy and trim the scan, then I saved it as an stl file and imported it into Rhino to piece together. This process was relatively quick, after less than an hour at the computer I had a design ready for printing.

Click here to download the design file.

I then uploaded it onto the computer used for the 3D printer and began setting it up. There are quite a few settings to consider when 3D printing which all make a huge difference to the quality of your 3D print.

Layer height - A 3D printer has to cut up your design into lots of layers which it then prints out one by one to built up your design. This setting determines the thickness of those layers. It can range from as little as 0.06mm right up to 0.25mm. The thinner the layer, the smoother the finish (but also more time!!). Because it wasn't essential that these experimental designs of mine were printed to the best quality possible, and to save precious time, I opted for 0.25mm.

Shell thickness - This determines the thickness of the walls of your design. The 3D printer doesn't print out shapes as a solid block of plastic, instead, a shell is made of the design which is filled with a mesh design. This saves material and time with negligible sacrifice to strength. Mine have been set to 0.8mm.

Fill density - This determines the density of the mesh that fills the shell. I set mine to 20%. This is adequate in normal situations but if the design has to withstand significant force, values of up to 80% would be more appropriate. This would have a big influence on job time.

Travel speed - This is the speed at which the nozzle travels around the printer bed. I set it to 150 mm/s. This can be further altered once sent to the 3D printer so that the speed changes for different parts of the design. For example, outer and inner shells want a speed set to 90% of that value. That gives a better surface finish. It also means you have room to make the filler inside the shell print even faster. This can be set to 120%.

Once the job is sent to the printer a separate window pops up showing the temperature of the filament, manual controls and speed controls. The ideal temperature for most filaments for this machine is 230 degrees celsius. Normally the user of a 3D printer such as the one we use will want to change the filament that is currently in ot. So when the user wants to use their filament, they will need to flush out the old filament by running their chosen filament until it is only printing with the desired filament. To film this weeks time lapse video I used a clamp to attach my phone to the 3D printer.

First I printed my digital corn on the cob, it took a whopping 4 hours to print! I even stopped the printing an hour early. That was partly to save time but also so I had a neat cross-section of the print so you can see how the machine structures it. It isn't a perfect print but you can at least see the individual corn pieces. I will need to do a redesign and reduce the layer height next time.

I then set off to print the parts of my bike light design. I developed a third version which has no clip but just a magnet housing so that it could still stick to metal surfaces. I started with the smaller parts, the LED and battery housing and as time was limited. These turned out pretty well, the LEDs fitted nicely and the battery fitted nicely but I still needed to test the push-fit parts of the design. Also, check out the printing process on my latest and greatest time-lapse video yet!

After seeing these printed I understood why people find the 3D printer rather overrated as a method of prototyping let alone a method of production. The surface finish on all of these parts were really bad and to improve it would add even more printing time. But still I pressed on with printing my own bike light and went to print the bigger piece. I learned a valuable lesson from this to not make walls which are too thin otherwise they rip off! You can see the carnage created below. But you can also see that my press fit design worked a treat! (Well.... the battery housing at least)

That concludes my antics for today but I will work on my bike light design over the weekend and try to optimise it further.


2nd March - Second round of printing my light

Over the weekend I redesigned the body of the light so that the walls were 5mm instead of a measly and ambitious 2mm. I then sent it to the 3D printer and hoped for the best. Below you can see a time-lapse of the printer doing it's thing.

I am delighted to say that not only was the printing a success, but also the rest of the light! The push-fit LED housing fitted perfectly,the magnet housing was just right, and there was no need for the battery housing as the magnet held it nice and steady. Take a look at it below!!

That concludes my assignment of designing and printing an object which cannot be produced subtractively. I am very happy with the outcome as I have managed to produce a functional item. It does need some development like all prototypes but it could be very useful when developing my final project. With a few improvements I could prototype my initial idea of making a bike light, not just a light.

Click here to download the design file.


3rd March 2015 - Unexpected disaster!

Last night I was checking out how strong the magnet in my light was. It was so strong it ruined the hard drive in my laptop! I put the light down on the laptop where the hard drive is housed without thinking twice about it until it was too late. I was left without a laptop and all my write up from the previous day lost. So instead of trying to develop my digital sweetcorn, I spend most of the day repairing my laptop. Thankfully I did a back up over the weekend so I hardly lost any work. Please learn from my mistake!! Here is me operating on my beloved laptop below.

After this fiasco was resolved, there wasn't enough time to run a 3D print job so instead I worked towards my final project somewhat my dismantling a hub dynamo. This would give me the chance to note and document the mastery behind it. This with my understanding of the principle behind electromagnetic induction will help me figure out a way of maybe incorporating it in the final project. I will document all the main features of the dynamo from inside-out.

Right inside the item we have a coil wrapped around a plastic collar/roll object. Slits in the walls of the collar enable the ends of the coil to stick out perpendicular to the rest of the coil. A similar collar could be either 3D printed or even made from the laser cutter using a press fit design.

There is then a very elegant laminate core which is designed to sit in between the magnets and the coil to improve efficiency. It is also important to to note that fact that the layers of laminate lie perpendicular to the layers of coil. A similar feature could be produced in the lab.

An axle sits in the center of this coil. One end of the coil is soldered to a washer which enables the axle itself to become one of the terminals of the dynamo. The other terminal is at the other end of the coil which sits nicely in a slot in the axle so that it can be housed up the length of it while sitting flush with the axle surface.

The inside of the hub casing is lined with magnets. When the coil and axle are placed inside and rotated, a current is generated.

You can see photos relating to each point below:

My next step could be to calculate the number of coils used to get an idea of how many I will need and see if there is a way to manipulate the positions of the elements into a more convenient arrangement that would be easy to instal on any bike.