October 2008

The toolpath for the router was not quite right and the result was a rough surface that was not usable (Wasteful. I will try to use the remaining material or give it to someone else to use). I am going to use the pieces that I cut out last week instead and sand them a bit to make a nicer surface. The pieces remaining to be cut will use a better toolpath thereby minimizing, or removing all together, the need to sand afterward.

I shopped hardware for my chair at McMaster-Carr today. Based on the hardware measurements, I added correct holes into the pieces of the chair where the hardware will fit. They are stainless steel have a very high tensile strength (80,000 psi). One of the things that I realized from my quarter scale model was that the seat would rub against the hardware that connects the legs to the armrests/seatback piece. So I changed the design of the seat slightly to clear the hardware when it is flipped up. I also changed the way that the seat is connected to the back legs. Making these changes however means that the seat no longer flips up without hitting the seat back. So I am going back to the use of neodymium magnets (purchased here) to make the chair hold together when it is folded up and keep the seat upright but prevent it from flipping back to far. Below I’ve highlighted the areas where the magnets will be placed (red arrows) and where little metal slugs will be placed (blue arrows). The illustration does not show the holes that will have to be drilled for metal pieces to be inserted into the seat bottom.

I’ve made sure that the magnets are strong enough to hold a connection to metal through a 1″ thick piece of MDF to approximate the connection stength when I use the BioFiber Wheat Board. The connection is not too strong where separating the pieces will be hard. The seat bottom when flipped up will be pulled evenly from both sides and appear to float. Hopefully this all makes sense.

I have finalized my chair design.

To give the chair more character and to make a material connection with the table, I have added plastic components from the left over ecoresin of the table to the chair. Handles in both arms as well as one at the front edge of the seat will be emphasized with inlayed ecoresin. They are both decorative and bring attention to the places that have been designed for grabbing (be sure to click on the image to see it in a larger scale).

I made a quarter scale model with the rapid prototype machine ($89). I am glad that I did this as it shows that the connections will work where I have them and that the seat will flip up and stop before hitting the backrest but at an angle where it can be carried and not flop around.

My man James at North Star Surfaces has secured some sheets of Biofiber Wheat for me at a nice discount ($90 for two sheets that are 3′x 4′). Normally one 4′ x 8′ sheet cost twice that. Thanks James! I had wanted to use Plyboo for the drawer of my desk but he had no left over material in the thickness that I want. A new sheet of 1/4″ Plyboo is $250. Too much especially when I need to spend money on labor to have the drawer made. I am going to look into FSC certified wood instead.

The table legs are being made by David Hill. I expect it to be done any time now. I hope to be able to take a few pictures of his shop. It is definitely worth a picture or two.

BTW- if you are getting this in e-mail form, know that there is a link to the blog itself at the bottom of the email.
More to come.

I will print out the mold tomorrow which will mean that we can get rolling with this very soon. I am anxious to have some physical objects in hand!

I headed over to Discount Steel from there to look at and feel the different gauges of steel and aluminum. Going up from 3/8″x2″ is too heavy using steel bar. I don’t think that I could get the radii for the the bottom bends with aluminum. So a little redesign is in order.

I would like some feedback on the following:

On a side note, powder coating is in the running because it a leaves no waste as any left over powder is recovered and the process releases very little VOC’s into the air. So once I do get the legs made, they are going to look nice after a powder coating. I have used Midland Powder Coating in the past and will probably use them again. I hope to get some photos of that place. It is very creepy!

The chair design is coming along. Here is where I am at with it.

As is typical with many design processes, the form belies it complexity. Jeff is confident that we will be able to create the form that I am after, but it will require a fairly complex combination of mold-making and hand-crafting finesse to get it just right. Fortunately, the material as well as the mold will allow for inexpensive multiples. We will create a small batch of them. They may use different types of Porcelain or finishes. The ones that make it through the process without defects will be keepers. Jeff will of course get one as a memento of our collaboration. So let’s hope that there are at least two that come out okay.

After our meeting, I came up with the following mold concept:

We had thought initially that the porcelain would be poured into the mold and then the interior piece would be removed after the clay hardened somewhat. Since sending this to Jeff, he seems to think that using this mold in this way would risk cracking the clay. So he is recommending that we lay in sheets of clay and press the interior mold into it.

We’re going to head over to Continental Clay soon and once I know the properties of our material, then I will render and print the final mold in the RP machine.

Ah, the chair. I am having a bit harder time figuring out exactly what I am doing with this. I want to create a folding chair. This seems simple enough. But I would like to use as little hardware as possible and have it fold up nicely and look good. I think I am getting close to having the mechanics of it worked out (this sort of thinking always keeps me up at night, argh.). It is hard to give the legs character, i.e. not flat and straight, and have them fold up flush to one another. I have been keeping BioFiber Wheat in mind as a likely material candidate. I may need to go back to Northstar Surfaces and look at the material again. I cannot remember if it is perfectly smooth or slightly rough. I am thinking about color and would not want to paint the chair if the surface is pock marked.

Here are a few preliminary sketches:

I’d like to get the design nailed down this weekend.

A student at MCAD mentioned the following website to me: ecolect

It is a repository of green building materials that is added to by designers. There are many more options out there than I would have guessed.