Monday, November 27, 2017

It's all about information

The year is 1850.  Suppose you are a reputable country watchmaker. In your shop window you have a large dial clock and all day long your customers and passers-by would stop in front of your shop to set their pocket watches against your master clock. The question is: How would YOU know what is the correct time?  Obviously this information would have to come from somewhere!  The solution was simple.  Every week or two you would take your best pocket watch, buy a newspaper, hop on the train, travel to London - and there you would set your pocket watch against the clock on display at the most reputable London clockmaker, who himself would have got 'his time' from Greenwich.  And there, at the observatory, clocks were set and regulated by astronomers, mathematicians and scientists who were really the 'true time keepers' because they knew how to calibrate their clocks against the movement of the stars.  Indeed, for a country watchmaker weekly trips to London were often the highlights of the week. 

Of course, with the invention of radio, everyone with a wireless could have direct access to accurate time. Bip, bip, bip - the time is 8 o’clock. 

Nowadays, we no longer need radio signals nor any effort on our behalf in order to 'know' the time. Thanks to GPS and the internet, our mobile phones and commuters are 'synchronised' countless times per day - and the time itself comes directly from the network of atomic clocks located all over the planet.  In just 100 or so years we have come a long way!

However, when it comes to the 'dissemination' of some other types of information we are still facing some serious issues with accuracy.

For example, suppose that you live in Germany and you've engineered and built two superbly precise machines. One stays in Germany, while the other is disassembled and shipped to Australia. The question is once that Australian machine is reassembled how are you going to calibrate it so it will machine metal as accurately as it did before, as the one on the different side of planet?

As clever as it is, the machine itself cannot calibrate itself.  As accurate as your watch may be, it will not tell you the time, unless you FIRST tell your watch what the time is! In both cases, the information has to come from an external, super accurate source.

I will not bore you with the details - but in the case of our five axes nano precision Kern mill, this outside information comes in the form of a small metal object which 'contains' crucial information. This object is machined in Germany to extremely tight tolerances, measured in a number of points, then shipped to us to be used as calibration 'etalon'. Without it, our machine could not be set.

While the geometry of 'etalon' is simple, thanks to the extreme precision with which it was machined and measured, it contains a number of crucial information. It will help us to establish the centre point of the table, work holding position, the eccentricity of the spindle, the relationship between the three main axes - and much more. 

Due to the fact that it had to be mounted on the tool holder, it was manufactured not by Kern, but by Erowa, a German 'tool holding' specialist.  However, after Erowa measured its dimensions, Kern re-measured it and re-certified it again, with even more accuracy. Each dimension was measured a number of times to 1/10 of  1 micron. Yes, we are talking nano!

The photos below are attached for your enjoyment. If you wonder what the cost is of this tiny piece of metal, then let me just answer this question in an indirect way: the etalon is kept in a safe and I am the only person allowed to handle it.

As you would imagine, we are now very anxious to get our mill assembled, calibrated and running.  However, we still don't know when the German engineers will be able to travel to Sydney to assemble it. Christmas/New year and endless European holidays are not working for us.  Patience, patience!


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