Re(Calibrator) Phase10

Two possible methods to produce the desired geometry in glass remained slumping and casting.
Both require kiln or furnace and a pre fabricated shapes or mould to work with.
With the slumping, it is essentially quite simple, all that is required is a shape to slump the glass on it. In this case, the mould is made of either firing clay or plaster with silica mixture or any other suitable fireproof material.

a glass placed on top of the mould before firing

In this case a simple window glass is used and it is cut to size of the sculptural clay mould (page 224, The Complete Book of Creative Glass Art). The piece is then fired in a kiln to an appropriate temperature.

fired glass takes the shape of the mould

Here the edges of the end product are deformed in unpredictable pattern, or at least in this example it is difficult to say where the glass would go, so it is a slightly improvised technique.

Alternatively, we can bend the glass into the mould, which gives us more control over the end geometry. (page 54, Techniques of kiln-formed glass)

Bending glass into mould

Or in some cases, it is beneficial to bend the glass over the mould.

Bending glass over the mould

Most other techniques are more or less similar to those ones.

And another option is casting, which is really an ancient technique that has first been used by Egyptians. The molten solid glass, or frit, or any other crushed glass is heated and as it solidifies, it takes the shape of the mould.

Casting by crushed glass and topping up during firing

There are millions of ways of making a cast glass, in the example above, a crushed glass is filled in the reservoir and more of it is added during the firing. This gives an opportunity for creating unprecedented combinations if desired, but more care must be taken in return. (page 82, Techniques of kiln-formed glass)   

All these techniques have one thing in common, the necessity of having an initial moulds to work with. To be able to manufacturing these moulds, it was time to start  experimenting with real materials and fabricate some full size mould pieces. As a test, I started with a fraction of the geometry, by cropping the piece in 3Ds Max.

Cutting the mould piece in 3Ds Max

I wanted to produce this mould with the help of the three dimensional 3 axis CNC(computer numerical control) router. The router uses a software of its own, called MasterCAM. This program allows to create a G Code for the Pacer 3D router, which is a universal language for CNC programming and is widely used in the industry.  MasterCAM is a complex and sophisticated piece of software that also enables so called cutting simulations to take place, so that the chosen cutter can be tested and monitored. 

Milling simulation in MasterCAM

MasterCAM is a significant software in its direct relation with CNC milling machine. The setup is not extremely complex, but it requires  a thorough understanding of the process, of how the Router works. I started by preparing my tools and adjusting the parameters and running few simulations on screen, to check  the approximate surfaces achieved.

Cutting simulation completed

There are number of different cutting combination and vast amount of cutters, with which I experimented quite a lot.

Library of straight cutter

And each cutter in its turn, has various parameters to be altered and adjusted in accordance to the particular material stock and depth of the cutting.

Cutter Parameters

Apart from choosing the right cutter,it is important to set up the most time effective cutting method for first roughing and then finishing. Same cutting can take much longer if more complex technique is selected, for example in the same simulation for the same cavity a radial cutting  mode is almost 10 times slower than the parallel cutting (the image of the first simulation), although the result is a slightly smoother surface with the radial cutting.

Radial cutting simulation (takes 10 times more time)

Once the setup is complete, the MasterCam produces the G Code, for the Pacer. This code is then  transfered to another software which works directly with  the Router and  in the  image below we can see this  relationship.

Pacer router performing the milling action

On this above image, what we see on the screen is the setup and positioning of the extruded polystyrene (or most commonly referred as blue foam stock on the machine bed. Below is the close up of what is on the computer screen.

The material representation on the cutting bed

Now  that the code has been implemented and the  job has been uploaded, the cutters have been all set up, the router starts cutting. The big bed of the machine is vacuumed, to secure those materials on the bed safely and the extractor  is working  with the cutters.

The milling of the polystyrene

As programmed, the pacer performs the first rouging, afterwards it carefully places down the first cutter and picks up the second, in this case finishing tool, and resumes the work. On the image below, we can see the rough cut area being reworked with a smaller cutter for finishing on M80 Sika block. 

Router performing the finishing with the smaller ball cutter

Consequently, depending on the cutters and cutting techniques, a wide range of outcomes can be achieved.

different cutter and techniques

1. 12mm straight cutter roughing with 6mm staight cutter roughing again with 45 degree angel.
2. 6mm ball cutter  finishing at 90 degree  angel.
3. 6mm straight cutter used for finishing at 0 degree angel.
4. 6mm ball cutter tested at 45 degree angel.

The radial roughing or finishing has not been shown here,since it  was proven to  be unnecessarliy time consuming and perhaps only suitable for rear cases,when the other  methods fail.
After generating these moulds I am ready to go into experimenting  with  various materials.
The 3D router experience is indeed very valuable, in terms of understanding  how the  computer works with  a code,  very similar to how we humans read a book.
When observing  the  machine  work on a delicate piece of geometry  with the smallest of the cutter, I felt a certain admiration and wonder. It is incredible how this big  mechanism of  several tons,works in such a subtle manner, almost like a jeweller. This had a prrofound  effect on me and I found  myself more and more often  drawn to  this machine, experimenting and observing its work.
Until now, the idea  of a code  was an alien concept to me, however,I started studying the G code, very curious to "understand" the machine. The endless pages of numbers and letters started to speak  to me, I found out that when the machine reads G31, it knows that now its time to skip a function, and most importantly I realised that I am the one who told the machine to skip the function in  the first place. In his "The pattern on the stone" William Daniel Hillis, the great American  inventor  describes "I etch a pattern of geometric shapes onto a stone. To the uninitiated, the shapes look mysterious and complex, but I  know that when arranged correctly they will give the stone  a special power, enabling it to respond to incantations in a language no human being has ever spoken." (preface, The Pattern on the stone: The simple ideas that make computers work, 1998). This is a magnificent description of a computer  programming and human-machine "conversation".