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« on: October 04, 2011, 06:53:11 AM »
It all started out as a laser project but…….
This is one of the first (proof of concept) of a number of different signs which are to be placed adjacent to the related plants at a special garden event in 2012. The intention is that partially sighted / blind people who can read Grade 2 Braille can, at their own pace, associate a smell / aroma with the relevant type of plant / flower.
The material I have finally used is a PVC based engraving laminate, I have not yet been told the actual colours that are be used but this piece of white / red was handy.
The Braille characters have been formed using the well established process of drilling a series of holes, just over half the depth of the diameter, then pressing in (interference fit) spherical balls, in this case they are 440c stainless.
Try as I may with the laserable (acrylic) laminate I have just not been able to get the hole depth consistent between the different colour samples – it seems that the pigment of the colour affects the laser penetration so each colour sample has a different setting and obviously the depth has to be maintained quite accurately - also, with the laser, it is a raster process and not a vector one as I would prefer.
The advantage of spindle drilling the holes (vector process) is that the same GCode toolpath can be used, with offset, when automatically inserting the balls. The disadvantage is that the engraving process is a lot slower with a spindle than it is with a laser. Anyway I decided it was “swings and roundabouts”, I would use the PVC laminate and it would be an all spindle process with two tool changes. Engraving point first, endmill second and ball insertion device third.
As you can probably guess by now, the process of placing balls in holes to form Braille characters has been patented (there are many related patents in fact) and I have just had a teeny little bit of disagreement with the main patent holders, who would have me (and others wishing to produce ADA compliant signage) believe that the extent of their patents are far greater than they really are. Also they are asking $2000 USD for a license (which I have severe doubts has any validity) to use their process, tools and consumables.
However, thanks to some international co-operation and an opinion by the UK Intellectual Property Office, I am now confident that this ‘$2000 licence’ is totally unnecessary and is little more than just a ‘pitfall for the unwary’. If I am wrong – well, we will just have to wait and see.
Tweakie.
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