Vulnerable parts of a design
Three of the stag’s legs and its antlers are long and thin. This makes them vulnerable to breakage. After making a prototype, I knew that the legs would be ok, but the antlers were still too fragile. The design worked in print, but when cut from plywood, they were too fine.
I advised Jessica had to beef up the antlers and it made a big difference to the look of the decorations. She agreed that we should make the decoration a bit bigger than the bear and seahorse as it was less chunky. That helped a bit too.
What can go wrong?
Lots of things can go wrong when cutting fragile shapes, especially when the edges are made up of lots of straight lines as Jessica’s decorations are.
When the laser cuts, it accelerates away from corners and decelerates towards them in preparation for the turn. When you’re cutting circles, there are no corners, and the laser head sweeps round at the same speed. When there are lots of angles and the laser slows down for each one.
The general rule of thumb with laser cutting is that you cut as fast as possible at as low a power setting as possible for a clean cut through. Even if the laser power is perfect when the machine speed is constant, it can be overpowering for the same material at a slower speed. As a result, there can be burning on the backs of the items as there’s enough time for the material to catch fire!
This meant that I had to fine tune the machine settings very carefully. I used a few sheets to complete the order. As different sheets of plywood vary in thickness, I had to tweak the machine settings for each sheet. Slightly thinner or marginally thicker sheets had to be cut slightly faster or slower respectively to compensate. It was a fine balance, but necessary to achieve a high product quality.
Balancing the decorations
Jessica wanted the stag to hang in a ‘prancing‘ position rather than sitting horizontally. After making several prototypes, I found the sweet spot. Moving the hole slightly to the left or right affected the angle significantly.
Geo Festive was the most difficult of Jessica’s decorations to find the balance point for the hole for. The bear and seahorse have more obvious centres of gravity and tweaks to hole location had a less dramatic impact.