lasercut test bend

Practical project step 3 – Initial prototyping

The project included a few aspects that could prove tricky – a curved wooden box, moving parts, electronics, and repurposed materials. All of these required some degree of prototyping. I started by prototyping the physical box – the cabinet my data monitor would sit in – and looked at laser cutting techniques for creating it.

What material to use?

plywoodI had decided to make the cabinet out of plywood, because it is cheap, easy to work with, and suitable for use with our Trotec laser cutter. As I wanted to create a Steampunk look, I needed a material that could be stained or painted to give it an old style weathered look. However, I also wanted to make sure it was a sustainable resource, as one of my project objectives was to minimise waste.

Plywood is made by sandwiching thin layers of wood, with each layer rotated to increase strength (see Woodguide). Its environmental credentials depend on the type of wood used and the glue that binds the layers together. The plywood supplied by the university is Hoop Pine Ply, which according to Austral Plywoods is made from Hoop Pine grown in NSW and Queensland and certified following the Responsible Wood system.

Another way to reduce waste is to use off-cuts of plywood or acrylics from other students’ projects, and to leave any remaining material in the workshop for other students to use.

Laser cutting a bend in plywood

My design was for a cabinet with rounded corners (to give it a friendly retro look), so I researched laser cutting techniques for creating bends in wood. I found some useful resources, including:

  • Cutting techniques for material flexibility: a guide to adding curves and flexibility to rigid sheet materials using a Trotec laser cutter, plus some sample cutting patterns. The article mentioned 4 key considerations:
    • Material properties
    • Direction of the grain
    • Distances of the cuts
    • Material thickness
  • Curved Laser Bent Wood: a really useful article by Aaron Porterfield on Instructables.com. The article demonstrated and discussed different patterns that can be used to achieve a bending effect in wood. It even included drawing files you could download and test yourself.

Based on the above articles and discussion with our lecturer Paul (who showed some samples of tests other students had done), I decided the ‘wave lattice’ was likely to be the most suitable. I downloaded the file as reference, then recreated the pattern in Illustrator to achieve the desired effect for the size I needed. Here’s a close-up of what the pattern looked like:

AI artwork for lasercut bend test

The next step was to do a small laser cut test of the pattern with the actual plywood I would be using. Here’s the result:

Cardboard prototyping

Pleased by the success of the bent wood test, I then created artwork for the box panels, using Adobe Illustrator. This was so I could create a cardboard prototype, and test it would fit together as envisaged.

The top and sides of the box were designed as one long piece, curved at the corners. To calculate the length of that piece, I used some basic maths to figure out the circumference of the radius corners.

  • Corner radius = 50mm
  • Total circumference = 2∏r = 2 x 3.142 x 50mm = 314mm
  • Radius length = 1/4 of circumference = 78.5mm
  • Total length of side/top piece = height of left side (250mm) – radius (50mm)+ left corner radius length (78.5mm) + top width (330mm) – left+right radius (100mm) + right corner radius length (78.5mm) + height of right side (250mm) – radius (50mm) = 787mm

Now I knew that to make it in one piece I’d need a piece of plywood at least 800mm long. Here’ are my rough sketches showing those calculations:

I double-checked lengths of paths In Illustrator. Here’s what the artwork file looked like:

Artwork for laser cutting the box panels

I also created artwork for the acrylic covers for the dial cases, and the dial pointers. You can see the cardboard prototypes below. I made a few minor adjustments as a result of these, including making the ‘eyes’ slightly bigger (so it would be less fiddly to fit the dial motor, but still leave room to mount the fixings). The slots in the dial faces needed a bit of adjustment to align with the screws in the brass cases. This is one of the issues with using found objects like the lamp bases for the dial cases – they are not made with technical precision! I discovered the 3 screws were not equally spaced at 120 degree intervals.

After creating and adjusting these prototypes, I moved on to the build stage. I knew there would likely be a few issues – not only because I was new to using these tools and techniques, but also because I was trying to make something work that included a mix of found objects and custom parts. I figured there may be a need to come up with some workarounds here and there, but was determined to do it as well as I could to achieve my original vision.

Next >> Practical project step 4: Building the cabinet


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Step 2: Design and preparation
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