Following the successful 2 sided CNC test, the only thing remaining to work out was how to get the model the right thickness. After much consideration we worked out the the simple alteration in Artcam to fix this problem;
- You still divide the difference between the model thickness and material thickness by two to put the model in the centre of the material bock. However, you must then set up the material slightly differently by putting that offset at the top of the material block rather than the bottom. What this does is it tell the machine to start cutting deeper down by however much the model height and material thickness differ meaning the model sits in the middle of the block and gives the correct thickness. Below you can see that the offset is at the top of the material, whereas before we had been putting it at the bottom. The material Z zero is at the bottom.
So having sorted out this issue I was ready to start full production. A method that I attempted to use to minimise the thickness of the material I was using was to rotate the pieces until the Z height was small enough to fit inside a smaller block of blue foam. However, what happened was due the slightly rotated model, what was usually a perfect circular model became a model with curved edges, so when you rotate this by 180 degrees the edges overlapped. Initially I thought this would be okay because you flip the model in real life which should match the edges, but it offset the model on each side creating a edge on the form with was not cutout. See below.
Below is a video of the tests on the CNC. At the start of the video you can see the CNC cutting out the material blocks out of a sheet of blue foam from which all the forms will be made, once I have successfully generated the toolpaths for each form using the method I have now established. At the end of the video you can also see the CNC begin cutting in the wrong place due to the model offset in the material which is when I realised somthing was wrong.
I also realised that the model had to be in the exact centre of the material block, so when you flip the side the pieces remains in the same centre and the machine cuts exactly on the back of form. So this is another lesson learned and I am now confident that I have the correct method to produce the 3D forms.