How to Make (Almost) Anything | Anders Häggman

WEEK 4 // Large Format Machining

'Architecture beats IDC every time.'

...those were the words that needed to be said for me to redeem scrap pieces of OSB from the Architecture shop. Prior to this I had spent the better part of an hour searching for material to use, until 'James' graciously offered to help me find some material from the Architecture shop. Perhaps foolishly, I had just assumed there would be material for us in the shop. I later found out that there was material elsewhere, I just didn't know to look in the right place. The point still stands however, to make sure you have material, and not assume it'll be available in shop.

The final product that I am making is a rocking chair with a clean modern look, and will look very different from the geometry tester chair I built, which is described below.

Level of previous experience:
Time taken:
Tools used:
SolidWorks // ShopBot PRSalpha // ShopBot V-Carve // Drill Press // Bandsaw // + Various Hand Tools
Got help from:
exArchitect 'James' // Charles Guan // Architecture Shop Staff // Sarah Sedris
Main learnings:
Reserve material early / make sure you have material to work with.
Build in buffer...or be the first one in. Machine schedules will run late.
Zero carefully. Measure carefully.

Although OSB perhaps has a bit of stigma as being the stuff of boarded up homes, the structural properties are pretty terrible, and the surface finish always leaves me afraid of getting splinters, I still like the aesthetic of it. And many people have come up with creative ways to make cool things with OSB. Some examples from dezeen.

Some basic angles and measures that I gathered from reading up on rocking chairs on the web.

The first cut. A lot of work had gone into getting to this point, and it was nice to see something beginning to happen.

The quality of the cut was far from ideal. I initially assumed that my feed or cut rates were off, but I was told the tool that I was using was just worn out. For some of the later cuts I got a new tool to work with. As this is just the first prototype of the rocking chair to test the dimensions, angles and rocker radii, I was not concerned with finish quality at this point.

Oops. Since we had very limited material to work with, the person I was working with and I tried to fit as many of our parts onto the sheet as possible, leaving very little room for error. This was caused by a 'generous' zeroing of the x/y coordinates. Since we had played it safe and left a little margin when zeroing, it came back to bite us when the end mill ran off the edge on the other side. No real harm here, other than the part missing a corner.

The tester chair taking shape.

Another close-up of the cut quality.

Apparently someone had had some issues with the depth settings and ran a little deep. One of the few mistakes I did not personally do.

Changing in a fresh cutting tool.

As the day wore on, the hat slid further and further back.

The assembled tester chair. Notice the several different holes in the testing chair. Both the seat and backrest are adjustable with 5° increments, to find the optimal sitting angle. One can also adjust the seat forward and backward, and the backrest can be adjusted up and down, both with 5cm increments. The 'default' sitting angle and backrest angle that I had designed turned out to be pretty good. Despite all the research I had done on rocking chairs, the rocker radii turned out to be imperfect. The rockers consist of three different radii, one in the middle for the main rocking motion, one at the front end to slow things down and prevent tipping over forward, as well as a stopper angle at the back to prevent the chair from going over backwards. The front radius transition was smooth and pleasant, but unfortunately I had overdone it with the rear radius (being afraid I would tip over backwards), and so the chair rockes nicely backwards, until there is a somewhat sudden reduction in rocking motion, and an abrupt jolt (which almost gives you a little whiplash sensation). The back radius and rockers definitely need to be modified for the final version.

'eka'. Finnish for the first one. This was never meant to be the final chair, but a learning experience. Having built this, I have learned a lot about rocking chair geometry, and would have been very sad had I spent money on fancy plywood to make a nice looking rocking chair with these dimensions. To try out the pocketing cut, I decided to write the 'eka' on the backrest. This was cut with the new end mill into much higher quality plywood, and you can really see the better finish of the cut. I have not done any sanding or other post-treatment for these cuts in this picture.

Lab-mate testing the chair, and finding its 'neutral' position. The basic setup seems good, although the rear end of the rockers needs to be significantly modified. After testing the chair, however, I have a much better sense of what they should be like. Since the final chair will look very different from the tester, another challenge for the next version of the chair will be trying to figure out how the changing center of mass will affect the neutral position and rocking characteristics (if at all).