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Movable Bed CNC machine 23

Things are getting exciting now. I know I can use the cnc machine to do many things. While researching on the internet, I stumbled upon lithophane. In case you do not know what a lithophane is, I will try to explain a bit of it here:

plastic scrap for milling

Plastic scrap for milling

In the old days, fine craftsmen used to grind or mold porcelain such that when they were held against back lights, photographs would show through in black and white.

Essentially, thicker portions of the porcelain would be dark because they did not allow as much light through them. Thinner portions, on the other hand would transmit more light through and would show up as brighter areas.

It sure did take tremendous amounts of skill and time to create such pieces of art. But that was a long time ago when tradesmen were highly skilled. Nowadays, with the advent of translucent plastics and machinery such as the cnc mill, it had become relatively easier to produce lithophanes of ones favourite pictures and give them away as presents.

They can last a long time because they are not simply thin photographic films, but are instead carvings on substrates. They make excellent gifts and can be highly personalized especially for that someone special in our lives.

relief picture for parallel cutting

Relief picture for parallel cutting

While they are easier to produce with the right equipment and skill, and they had come a long way from the realm of the highly skilled craftsmen and artists, still they never fail to amaze people who first look at them.

It’s almost magical!

The pictures must be cut in such a way to imitate a photograph – thin portions for light areas and thick portions for dark areas. The shades of grey areas will show in between in various gradients.

Learning how to create a lithophane was a challenge to me but I was able to learn by doing, making mistakes along the way.

My first attempt was a complete failure. The plastic melted onto the tool and quickly became a mess. I broke and lost a milling tool while trying to remove the plastic from it. Also, I had to experiment a bit with the depth of cut, speed, step distances and many other settings. In addition, because the milling took such a long time (4 hours), my computer overheated and gave errors. It missed steps.

milling 3D picture on plastic

Milling 3D picture on plastic

Suspecting that the microprocessor cooling was insufficient, I foolhardily removed the heat sink fan from it with the intention of cleaning it of dusts but had made the situation worse.

When I tried to put it back, I thought that ordinary grease would act as a heat transmission agent but found to my dismay that the contacts were not good enough.

The computer stopped in the middle of a cutting session.

I had to order a bit of CPU heat sink conducting silver compound in order to make it good again. That would take some time to arrive.

Meanwhile, luckily, I had another computer, which I was able to use. This computer was tested for maximum jitter in the latency test for LinuxCNC and was improved upon by specifying one single core to use instead of using the default dual core. In addition, I managed to buy some heat sinks at a local shop for the IC’s of the stepper motor drivers which I then installed to reduce the heat in them. Hopefully, they would not shut off in the middle of a long session of milling later.

Slowly, I had learned from my mistakes. Happy to say, I have successfully made a lithophane as shown below. This was of a larger size, 120 mm x 92 mm, than the previous trial version. I had also reduced the step distance closer so that more details could be seen. However, the whole cutting process took 18 hours. Luckily, the computer did not stop half way during the cut.

Carved lithophane

Carved lithophane

The backlit picture looks much better.

Finished lithophane with back light

Finished lithophane with back light

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