Wednesday, December 23, 2015

The Time Transparency Clock

Since the last post I have worked hard in the design and build of the Wood/Plastic clock. I have made a lot of changes in the original design, and I think that the final result is really a very nice clock!

It even has a name thanks to my sister! The time Transparency Clock:

Acrylic is difficult to work in the CNC with small diameter end mill bits. I used a 1/16” 2 Flute carbide end mill for the wheel teeth. After damaging several plastic stock and 2 end mill I learned:
  • Use new and sharp bit or a sharp bit that has been used only in plastic. If you used a bit to cut wood, forget to use it later in plastic.
  • You need to remove very little material each pass :.
  • 24,000 RPM spindle speed and 10 inches/minute feed rate.
  • Keep the bit cool with compressed air.
For the internal cuts I used a 1/8” 1 Flute end mill. You also need a new and sharp bit or a sharp bit that has been used only in plastic but feed and RPM are different: 15,125 RPM, 16.1 Inches/minute feed rate and .004” maximum step down per pass.

With the above settings, and with lots of patient it is possible to get a very nice and clean cut. Below a video showing the internal cut with 1/8” end mill:

The other complicated thing is to bond brass and acrylic. After several test I ended using 2 part transparent epoxy.

Here is a video showing several details of the clock.

I love the action of this clock!

Happy holidays to all!