Design and Prototype - Lesson Five

This week has been about making my jigs on the laser cutter, and also has been a massive set back. I began by using 6mm MDF which I laser cut my jigs onto, and then layered them up in two halves and glued together:

Part of jig glued together

Once they were glued together I used the disk and bobbin sander to smooth them down:

Sanding on the bobbin sander

However after I did this it meant that it had some flat spots which I couldn't remove, which I decided to solve by using some of my spare bendy ply and gluing it to the jig. This was really effective and removed all the flat spots.

Bendy Ply gluing to jig

 I then was ready to start gluing my framework together, so I glued 6 strips together using PVA glue for both the leg and frame, and clamped them to the jig.

Frame strips gluing together

However once the frame and leg were glued together it was clear that they were not going to be strong enough, and would snap under very little weight, so I decided to try some glue that another student was using, called Titebond:

Stronger Glue

 I was hopeful that this would solve the structural issues that I faced, as it was a much stronger glue. Initially I believed it had solved the problem, but after some testing it failed, with a clean snap through the grain, meaning that it wasn't the glue hat wasn't strong enough but the material itself.

Initial test with strengthening piece

Failed testing

This then meant I started to panic, as the only way I could see being able to solve this issue was to make it out of construction veneers, a slower and much more expensive way. However after much discussion I decided to see if 4mm normal plywood would bend o my jig without snapping. I was rather dubious at first, but soon I had fixed it around the jig with less problems then the bendy plywood.  

Two strips of 4mm Plywood bent around jig

This meant that all my dimensions have been changed and my design altered slightly to make the whole chair stronger. I first remodeled the chair in 3D, as shown below, which includes a new "U" shaped piece:

Chair Remodeled

This means that next week I will be making the legs and the slats, as the 4mm plywood board that I require has to be ordered due to the grain direction on the boards. This means I have been set back quite a lot, but I will just have to do other things such as making the jig for the new piece which has been added to the bottom of the chair.