Category Archives: Wax working

One degree out

Table update: another small section complete! Or at least, almost. I made a small error.

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Spot the error

The alethiometer table has many sections (I’ll get round to posting the designs eventually!), one of which is a ring around the compass rose, inside the ring of symbols, with the full 360 degrees marked. This will be a slight variation on the wax inlay technique, as I’ll be using a gold gilting product called Rub ‘n’ Buff (Gold leaf) in place of the wax. A quick test before I ordered some expensive nearly-black perspex demonstrated that, with the addition of a little ethanol, the excess gold can be wiped off. The added bonus is that the ethanol also clears off the smoky residue left through the cutting process, without visibly scratching the mirror-like surface.

After a disastrous afternoon cutting the sections out on the laser I managed to cut the twelve sections of the ring. After a short chat with the chap who owns the laser cutter and a few minutes playing around with the settings, we identified the problem. The power dial had been replaced the previous evening, so I had completely the wrong settings. This meant that as the laser was cutting through the material the plastic became so hot it was melting behind the laser and sealing the cut. This cost me a full sheet of perspex and a couple of hours of my time, but I learnt an important lesson; perform a practise cut beforehand. At least then I’ll know I have the right settings!

Did you see it? The top three pieces are missing the last degree mark (on the right hand side). How I managed to miss this when I directed the laser to cut I’ll never know. I can’t leave them like that; I’ll have to fix it. Cutting another sheet of perspex is not an option. So I have to accurately place each segment onto the laser bed in order to engrave a single, 5mm line in exactly the right place at exactly the right angle. Now, what I could do is cut the full shape out of a piece of scrap perspex or ply, drop each incorrect segment into the hole and engrave the missing line. This way I can almost exactly place each section and merely direct the laser to engrave the missing line.

I’ll let you know how it goes.

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Completion of symbol tiles

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Thirty-six newly finished tiles!

One section is complete – the production of the symbols! This is probably my favourite part, despite the pitfalls of the process. 36 individual, unique, wax-inlaid perspex tiles, each featuring one of the symbols from the alethiometer.

So how did I do it?

Step one was obviously to find an image of the symbols. There are dozens of images of alethiometers on the internet, but only two were useful. One of them is below (apologies to the person who posted this on the internet – I’ve lost the original link)

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Stock image of the alethiometer symbols

So I separated each symbol and saved them as individual .png files, using Paint. They were then imported into Inkscape and rotated until they were upright and exported as a bitmap (.png again, but if these had just been saved as they were the page background would have been saved as well and I didn’t want that).

Meanwhile, in DraftSight, I created a CAD design of the tiles. Overkill, possibly, but Inkscape wasn’t accurate enough to keep me happy. Using Draftsight I could draw two circles centered on the origin, direct the program to draw a line dissecting both circles, then use Pattern>Circular pattern to replicate the line every 10 degrees around the circles. these could then be cut into individual tiles. One tile was then saved as a .dxf (R13 ASCII).

In the meantime, I ordered some perspex from http://www.plasticstockist.com. Specifically, 3mm thick Silk Opal 040 (51% light transmission). This is a partially transparent, slightly off-white perspex with a matt side. Given that the symbols in the alethiometer illuminate (admittedly only in the film, but it looks awesome!), I want to mount LEDs underneath the perspex in order to create that golden glow. This cost me something in the region of £7, excluding postage.

I had originally sized, aligned and saved the complete tiles in Inkscape and attempted to import both the tile outlines and symbol images as a complete file into the laser software NewlyDraw, but it was having none of it. Using DraftSight, I replicated the tile drawing until I had 36 copies and arranged them as economically as possible. The laser cutter I would be using has a maximum bed size of 200 x 300mm, which restricted me to a maximum of thirteen tiles per cut, in two rows of five (alternating between upright and upside-down) and one row of three, rotated through 90 degrees. Obviously the third cut would only produce ten tiles – this allowed for a practice cut to be made, to ensure that the settings were correct for both cutting and engraving the perspex – I wanted an engrave depth of around 1mm.

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Newly lasered tiles

The practice cut was successful, so I went on to cut the first sheet of thirteen tiles. Not much to look at originally, but that would soon be fixed. Approximately a month before the idea emerged, someone I knew posted this link (http://www.redtorope.com/2011/02/laser-engraved-wax-filled-high-contrast-panels-for-electronics-projects/). Essentially this involves filling the engraved plastic with a contrasting wax. Crayola wax crayons were mentioned, but I didn’t fancy shelling out for an entire pack just for one crayon, and I would probably need three or four to fill all the tiles. A couple of hours scouting around the internet and I came across some furniture repairer’s filling wax, in “Ebony black”, priced at £3.50 for a single stick. Marginally softer than crayola crayons, but ultimately cheaper and without the wasted crayons.

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Melting the wax into the engraved channels using a heat gun 

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Removing the excess wax

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The remaining wax is easily cleaned off using ethanol

The method I eventually settled on (which worked better in a warmer room, given that the workshop was pretty much the same as the outside temperature – somewhere around zero degrees centigrade!) Involved heating the perspex tile with a hand-held heat gun and warming the wax until it was soft, but not runny, then vigorously rubbing over the engraving. Once I was satisfied with the amount of wax laid down, a quick blast with the gun to melt the wax and fill the cracks. Obviously, I had applied an excess, so this was carefully scraped off using the practice tile. Any remaining wax could then be easily cleaned off using a little ethanol and some paper towel.

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The three stages of wax-filling

And that’s it! This job was a little more time-consuming than I originally imagined, as I originally had quite a few problems getting decent images, accurate drawings and persuading Inkscape and the laser-cutter software NewlyDraw to do what I wanted them to do, but the end result is worth it.