| Completed tea pot|
|I like the fact that it changes colour from different viewpoints because the laser cutter scorched the edges of the plywood. |
|I started by painting the original china teapot with black acrylic paint, to cut down reflections, and doing a 3D scan of it. |
This is a screenshot of the result. I was expecting to load it into Rhino, a 3D CAD program, and slice it up to create a slew of sections that I could use to cut plywood, cardboard or other materials using a laser cutter.
It turned out not to be that simple. The 3D scan created a mesh and converting that into a solid in Rhino turned out to be complicated - so complicated I opted for another solution....
|I created a solid teapot in Rhino from scratch, just using the above mesh model to make sure I got the same shape.|
It took quite a lot of time and effort to create this model but I learned a lot about Rhino in the process.
|I sliced the above model at 3.6-mm intervals, the nominal thickness of the plywood. Then I used it to generate about 50 2D sections that I could use in the laser cutter. |
I placed each 2D section within a rectangle with holes at each corner, to make it easier to line things up when it came to gluing together each piece of plywood.
In retrospect, I should have glued together 10 or so pieces of plywood and measured the result, to get a more accurate thickness of the plywood.
As it turned out, the plywood and glue probably added up to slightly more than 3.6-mm so I got a somewhat eliptical teapot in the end. I quite liked it like that, so it wasn't a big deal.
|Laser cutting turned out to be quite laborious. I fitted 50 sections on 7 sheets of ply and each sheet took between 60 and 90 minutes to cut.|
I could have reduced the time a bit if I had butted the sections together rather than cutting each one as a separate entity.
I also ran into problems with the ply not sitting flat in the laser cutter, so the cutter's nib was too far away in some places and too close in others. The result was that I didn't get complete cut-throughs in every case, and had to repeat quite a lot of cutting.
One other observation: I had to export Rhino files in DXF format so they could be read by the laser cutter software. In that process, a couple of oddities occurred - the round holes I'd drawn in each corner of each section became rounded squares and on one of the sections, a curved was straightened. It turned out not to matter too much on my project.
|I decided to make to make not just the teapot but the inside and outside as well, seeing as I had cut all the elements to do this.|
This meant I had a lot of pieces to glue together - 3 on each sheet and a total of about 48 sheets. I decided to use contact adhesive so that I wouldn't have to wait for glue to set.
All the same, it was a laborious business because each piece had to be masked off before I coated it with glue, to make sure I didn't mistakenly glue together the wrong bits.
It took a couple of days to glue together the 3 parts for half a teapot (the teapot itself, the inside and outside).
|The square holes still worked fine for lining up the work.|
I had to be careful that I didn't trap one layer inside another, where there were "undercuts" (such as in the base of the teapot).
|I cut a duplicate centre section in acrylic sheet and engraved the edges of the teapot on it, as shown. I then glued each side of the inside of the plywood teapot to it, and mounted it on a base.|
It would be interesting to make a complete teapot out of acrylic sheet, possibly slicing things horizontally rather than vertically. However, some extra thought would be needed on gluing - the joint would be visible so the glue would need to cover the entire interface. Vacuum might be needed to make this viable.
|My biggest mistake with this teapot?|
I ended up making 2 identical halves so I couldn't make a whole teapot out of them.
It made me feel pretty stupid - and it meant I had to go back and do even more laborious laser cutting.
The plus (sort of) was that I had extra copies of the exterior, pictured, which I really like.