Goal
The goal of this week assignment is to make something big. In Fab Lab Barcelona we have an extra challenge. Unlike the rest of the World, we cannot use a brand new shiny board to make our assignment. We must find something old that people is trashing, save it from destruction and give it a second opportunity.
Last week MIT lecture review
Last week I forgot about the summer time difference and I was late, so I could not attend the assignments showcase. But I saw them later in the recorded video and I learned some useful things from it. The showcase is a great way of learning things from others errors and successes.
Finding something to mill
This section will cover everything I did to get something to mill. You can skip to the end if you are not interested. But I can tell you that this was by far one of the most funniest weeks because of this extra challenge. We had a lot of joking in our Facebook group before we started sweating because we had nothing to mill. In Barcelona, there is a day once a week that the City Hall names Disposal of Junk and old funiture when you leave those things you want to get rid of and they will pick them up for free. The thing is that they will pick those things between 8 pm and 10 pm, but before that, several informal recyclers will try to find something valuable. So if you want to obtain wood you will have to arrive before the informal recyclers come. You are doing this for educational purposes. They are doing this because it is their way of living. Believe me, you do not want to compete with them.
In Sitges (my town) it works different. 20.000 inhabitants is not
enough to have a fixed day for picking old furniture so you call
them every time you want them to pick something old.
The Search
I went to the local disposal centre of my town and I didn't find anything. First of all, most modern furniture is made out of conglomerate wood. This kind of wood is pretty useless for milling because it is made out of sawdust and wood leftovers (which may sound good because of the recycling) but they use products which contains added urea formaldehyde (forbidden in LEED certification among several other Green Certification Systems) as a binding material. Urea formaldehyde irritates skin and lungs and it is a potential cancer source for long exposures. Anyway I did not even find conglomerate panels because in the disposal centre they crush all the furniture they receive so it was all unusable.
Next I asked to my Facebook friends if someone had something they wanted to trash and I received a message from a friend who wanted to trash an old small desktop. I picked it and it was really small, about 50 x 100 cm working area, but it was made of solid wood. Not a high quality wood, just pine wood, sort of soft and fragile wood with a lot of knots and imperfections that made it not very suitable for milling either. Anyway I accepted the risk and I decided that I would use it for my assignment.
Pre-processing the wood
As I said before, this kind of wood has multiple imperfections and hidden cracks. In my first attempt to disassemble it (brute force with my nude hands) the wood cracked as you can see in the picture below.
So I started using some tools to fully disassemble it with care. I had to saw, carefully removing all and every nail (I don't want to break the bit or the machine, or even worse, killing one of my mates with a flying nail), fill the holes and finally sand the surface. Below you can find a set of pictures of the whole process. It took me all Saturday and minor scars scattered over all my body.
Finally what I obtained was some parts of usable wood. A 3 cm thick piece of 50 x 100 cm, two pieces of 38 x 69 cm (2 cm thick) and several pieces of about 30 x 10 cm (1 cm thick).
Designing something big. First attempt
From now on, I am in the same conditions as my Fab Academy
colleagues. Well, sort of, they have a whole 120 cm by 240 cm board
and I have some scattered small pieces of wood. The only
question remains is how am I going to make something big from
something so small?
I am thinking of a Kids Wooden House. I always wanted to have one when I was a kid. And I am pretty sure my kids will enjoy it so much. But it cannot be a traditional wooden house because I don't have enough wood. So my idea is making something structural like a Geodesic Dome made out of trusses and connectors. The dome should be no more than 70 cm height so it can pass through doors when it is fully mounted.
I started reading about Geodesic domes and it seems to be an entire universe around it. There are several kinds of this domes. The one I will use is based in the icosahedron. The most important decision to take is the frequency of the dome. It can be 1V, 2V, 3V, 4V... and so on. Every level of frequency raises the number of trusses and connectors and it resembles more and more a sphere. I want it to be as simple as possible, but a 1V dome doesn't even look like a dome, it looks like a virus without legs to me. So I will choose a 2V dome because looks like a nice North Pole Station and it uses a relatively small number of pieces. A 2V dome requires 65 trusses (2 different kinds) and 36 connectors (three different kinds). For a 60 cm dome trusses measure about 38 cm.
I am using Vectric Cut2D software to make my toolpaths. This software is pretty same the one used in Partworks that comes with the Shopbot. I believe that Partworks is a branded version of Cut2D, and Partworks 3D is a branded version of Cut3D. Cut2d allows you to make three kind of toolpaths: drilling, cutting and pockets.
You know, one day I came to the Iaac and I found that the biggest, key and central piece of wood had disappeared. Vanished. I asked everybody and no one knew. Perhaps it is now a cuckoo clock, perhaps a kinetic sculpture, perhaps it was used as firewood in a BBQ, who knows. The only thing I know is that all what I did till then was useless. A piece of advice for those coming to Fab Academy 2014 in Barcelona: "never put off till tomorrow what you can do today" because nothing lasts too long in the Iaac.
Designing something big. Second attempt
One day my mother-in-law was about to trash a cabinet with a woodworm plague, and I could save a shelf from destruction. A piece of marine plywood about 35x85 cm. The woodworms do not like this wood because all was full of holes except this shelf. I put a warning sign this time.
The sign proved to be effective because during the weeks I spent thinking what to do no one touched my piece of plywood. Unfortunately I could not imagine anything big that I could make with this little piece of wood.
Designing something big. Third attempt
Friday 2nd of august was the last day the lab was open. They close for summer recess. That day I was in the laser cutter room looking for shafts for the machine design assignment. I was trying to digest my failure to design something big, but when all seemed lost, I walked past the door and found hope.
The Iaac students left these remains of chipwood boards from their assignments. I asked Alex, one of the lab operators, if he would give me one piece. He accepted only if I was going make something nice and valuable. That sentence raised my blood pressure but I grabbed one, took measures and started thinking.
Me and my older son enjoy watching American Chopper in Discovery Channel. I thought that I could make a Bobber Motorbike balance bike for him. I took the following design decisions:
- Distance between wheels: 1 meter
- Frame angle 30º. Suspension angle 60º
- Hardtail bike with 90º angle between frame and front suspension
- Solo saddle seat with adjustable height
- Beach bar handlebar
- No light, rear mirrors or fenders like the real old school Bobber bikes
And that led me to this balance bike (I used Rhino). As you can see, not even a single foot of wood was unused. It looked like this piece of chipwood was made for the bike actually.
Milling the board
The next step was joining all the curves to closed polylines and export the design to DXF format so that I could import it in Partworks (aka Vectric Cut2D). The material exterior size was 125 x 250 x 1 cm and my bit was a 6 mm diameter flat end. So I created 3 toolpaths in partworks, all of them @12.000rpm spindle speed and a feed rate of 30 mm/s:
- A profile toolpath for cutting the holes.
- A drill toolpath for the 6 mm holes
- A profile toolpath for the cutout of the pieces.
Actually I had to create a fourth toolpath because Partworks did not want to mill the front suspension. It kept saying: ERROR. No toolpath generated for current parameters. Check tool can fit into selected vectors at machining depth. And there was no way to override this message and force milling the part. I hate when this happens a few hours before the lab is about to close for one month. So as I said I had to create a fourth toolpath with the bit passing ON the vector, and not OUTSIDE the vector. That changed by 6 mm the size of the front suspension, but it was that or nothing.
The Shopbot was another little nightmare. Paul Giron helped me in setting it up correctly and zeroing XYZ axis. Only God knows why, but there was no way to connect with the Shopbot. Only after a random combination of computer reboots, try again the same port, scan all ports, restarting the Shopbot program, pressing all buttons we found, changing the USB cable, yelling at the computer and hitting the machine... then the Shopbot connected and Paul told me: Don't touch anything now! So did I.
Remember to place the screws that hold the wood at places that you are certain the machine won't reach. You don't want to break the bit or loosing an eye with flying shrapnel.
Post-Processing and final result
After the milling process i removed the tabs with a hammer and a chisel. Well, actually soon after the photo was taken, and pushed by the clock, I started using my hands and brute force to do the job.
The finish was quite good but I sanded all the edges and started assembling the bike.
In the end, Fran (my son) liked it very much. But now I have another problem because both kids want the bike now. They always want the same thing at the same time. But guys, dad is not in the mood of milling another for, say, 400 days in a row. So share, sharing is good.
What I learned
This has been the assignment that took me the longest time to complete in all Fab Academy. Actually I finished it at 10 pm on the last day, at the very exact moment the lab was closing for summer recess. Don't get me wrong, it doesn't mean it was the most difficult assignment, actually it is one of the easiest. You just don't follow my schedule. Try to finish things ASAP, because when you keep something unfinished for such a long time, you end up hating it. Start something and finish it, take all the time you need but finish it. Really.
Download files
You can download all the files related to this week here.