Perspex branded acrylic is the best quality. Other brands have additives that make the cutting process significantly slower and smellier on the laser. This adds to production time costs and can decrease operator comfort.
We had to complain about some 8mm white acrylic that was not Perspex branded. We had bought it for a project with a designer who was prototyping a product. When we cut it with the laser, the edges went brown when they should have stayed white, and it was all down to the makeup of the acrylic. We also had to run the machine at a slower speed than we’d expected for the thickness of the material which made the process less profitable for us. Thankfully, the supplier gave us a refund for the material as they agreed that it was of inferior quality to branded Perspex.
We learned something that day, and now we never order acrylic that isn’t Perspex because of these problems.
How is acrylic made?
Acrylic, unlike plywood, is less varied in sheet thickness, but there’s more to it than that. There are two kinds of acrylic, cast and extruded, named after their production processes. Cast acrylic is made by pouring the acrylic into a mould to set. Extruded acrylic is rolled to a set thickness during the production process.
So theoretically, extruded acrylic should be closer to the nominal thickness of the sheet. You won’t see the same thickness differences between cast and extruded acrylic that you’d expect between nominal and actual thicknesses of plywood, where you can expect differences of 0.2 to 0.3mm. The errors are far smaller.
But not all acrylics are equal, and this is the important thing to watch out for. It could affect the look, quality and cost of your product.
You’d assume that 3mm plywood is 3mm thick, wouldn’t you?
Wrong! With plywood, thicknesses are nominal, not actual. This is because plywood is made up of different layers glued together. 3mm usually has 3 layers, and the result is an actual thickness of 3.2-3.3mm. 4mm ply has another layer, and is usually 3.8mm thick.
Potential design disasters
This can create a whole worlds of pain for designers and manufacturers if they want to create products made up of pieces that slot into each other and require a good fit.
If you assume a thickness of 3mm and you design 3mm slots in artwork and then try to fit 3.3mm thick wood in the slot, it’s not going to happen. Or if 4mm ply were used, 3.8mm parts would be too loose.
Imagine making 300 reindeer kits for Christmas, sending the artwork to a maker, and getting back parts that don’t fit?
This could have happened to one of our earliest customers, but we made a prototype, realised the problem and fed it back to the customer. They tweaked the artwork before we performed the production run. This simple check saved our customer – and us too – a lot of time, money and heartache.
Always check that your designer and maker are speaking to each other to avoid disasters like this.
I love these wooden rings! But when Waiata Bespoke Jewellery (nga waiata as they were then) first got in touch and asked if I could engrave the backs of their chunky wooden rings with their logo, I wasn’t sure if I could do it.
Engraving on a curve
First of all, rings are cylindrical. Lasers need a flat surface to engrave. This is to maintain the right focal length for the laser beam for best results.
Secondly, the rings have such knobbly stones on them and nga waiata wanted to supply them made up rather than without the stones. How could we support them securely in the laser so they wouldn’t wobble or fall over during engraving? Any of these scenarios would be disastrous for engraving quality.
It’s amazing what you can do with Blu Tac! I use it all the time to support jobs on the machine. A nice big blob on the engraving bed floor held each ring securely, even although the stones are all different shapes.
My secret weapon
Now for the engraving. The text was small and fine and was to be centred in the middle of each ring back. I used my longest focal length lens which helps maintain focus better over curved surfaces. I also slowed the engraving speed down to maximise precision and minimise any wobble from the machine. This ensured crisply engraved letters, with a nice depth of engraving to give good visual impact in the chunky wood.