Glass working lathe

One of the most important tools for working with glass will be glassworking lathe. I decided to build one by myself, commercial solutions are too expensive or aren’t available.. It will consists of four ball bearings, two dc motors, one linear bearing, several aluminum profiles and some minor parts.. Synchronizing of the chucks will be done manually by setting the slave motor rpm according to master one. I hope it will work I don’t have needed skills to do it by one shaft or something like that..

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High-vacuum stopckocks

After some unsuccessful experiments with common (non-vacuum) stopckocs, valves, etc., I finally decided to use stopcocks designated for high vacuum. I found some on eBay for $25/piece. I applied a vacuum grease, set up an simple vacuum system with hoses and tried it. The stopcock is pretty vacuum tight, but there are still some other leaks, probably somewhere among the hoses 🙁

 

Argon arrived

I’ve finally got an argon bottle, 1.3m³ of pure argon (99.996%) pressed in 8l bottle. It is pretty heavy 😉 The argon was chosen because it is has similar features to neon, but is much cheaper and – the most important – it is available..

File:Paschen Curves.PNG

This image comes from Wikipedia. The argon compared to neon has a little lower voltage needed for discharge, that’s useful..

This bottle + argon cost $100, refill costs $20, argon valve costs $25. Neon nonrefillable bottle with 12 atmospheric litres of neon (compare to 1300 litres of argon..) costs also $100, simple valve without gauges costs $150, evacuable valve costs $250 🙁

The argon discharge is pink-blue, but is much dimmer than orange neon, that is the reason why neon is used in most of dicharge tubes.. I noticed only some bargraph and dekatrons filled with argon.

 

Reduction valve..

My dog 😉 and a bottle with argon at the background..

Reduction valve mounted..

Electronics for pirani gauge

I was working on electronic part of pirani gauge a few weeks, so there were no new posts.. I moved the system from breadboard to the plastic box, added display and microprocessor. Measurement and control of the display is based on arduino.

I am not going to describe the function of pirani gauge, there is a lot of information on the web. All the electronic system is taken from this pages, I only added a pull-up resistor for wheatstone bridge, because after turning it on, the voltage on bridge stayed on 0 – both branches were equal, so now the static branch is slightly (xM ohm resistor) pulled up. I also added a atmega, low-pass filter on voltage reference, display..

Range of the gauge is from 3.3V (maximal voltage, atmospheric pressure) to somewhere around 0V. It is not calibrated yet.

 

Pirani gauge unit, on/off led, switch. The knob on the right is used to balance the output voltage to 3.3V – compensation of temperature and atmospheric pressure differences. The pirani gauge itself is in front of the box.

 

Back view, supply port on the left, pirani sensor port on the right.

inside..

 

I am going to place a PCB and scheme here..

Feel free to contact me.