Wednesday, November 14, 2012

Copper bellows again

I decided I wasn't going to let the peskey bellows defeat me, so I went for it again. My copper bellows MkII are a success! Here's what I did...

As before, I made a wax model on the lathe. This time I stuck to the rules I mentioned in my other copper bellows effort above.
So my recesses are tapered and wider than they are deep.
Wired, dipped in white/mineral spirits, covered with graphite powder. After a bit, burnished with a Qtip with more graphite on it.
Copper plated at very low current.
Below is the bellows just out of the plating solution.
It had two sessions in the plating solution. One to get the form strong enought to survive a bit of handeling and the burn-out. And another to build up a decent thickness of metal. 

Another warning note here: I was calculating on the assumption that the solution was putting down 1 micron every 2.5mins, as I read in the literature.

But even after 6/7 hours I only ended up with 150 microns or so. Measured from the waste I cut out of the top of the form. I'm sure the vertical parts of the cylinder are thicker but the important flexing parts are only that thick, if not less. I would like to have gotten .3mm or even more. As there is serious strength,brittleness and porosity issues with simple electroforming like this.

I realised later that the problem was that even though I had calculated my current density ok, I was using voltage control to achieve it. So my overall power/wattage was less than it should be. Hence the thin deposit.

Friday, July 13, 2012

Very Expencive Beer Mat

I know this is off topic again but...

Just a quick post of a couple of pictures of a thing I cut with my homemade CNC today. This started life as a drawing which I photographed and vectorized. Then CAMed and routed. I'm very happy with the results. Size 120mm dia.

The reason for this piece is partly promotional and also I'm tring to see what my machiene can do!
I'm delighted with how this turned out.

Tuesday, June 26, 2012

Copper Bellows. A lesson for me.

I'm trying to eliminate leaks in my(still not working) laser so I decided to go for copper bellows instead of my current O-ring seal for mirror adjustment.
But I couldn't find any copper bellows, so I decided to give it a shot and see if I could make a pair.
After first considering soldering them up from parts, I decided to electroform.

Here is a picture of my wax mandrel. It is made from injection moulding wax. It turns ok if you don't try to take too much off in one go.
I then cut the recesses or corrugations or what ever you would call it. With the piece still spinning, I hit it with a touch of a gas flame to soften the corners and give me a nice smooth finish.


I parted off and heated a bit of copper wire and stuck it in to the end. Then I was ready for conductive coating.
There are a few options here. Sputter, chemical silver, electroless copper, conductive paint, graphite.
I decided to go with graphite because it was the simplest and I had it at hand.

 So I dipped the wax in "white spirit" for 20 seconds and drained it. Then the surface of the wax was slightly sticky.
Then I bunged it in graphite powder. I made sure it was all covered before the white spirit flashed off.
After a minute I brushed the excess powder off with a makeup brush.
A very important note here is that burnished graphite powder is significantly more conductive than non burnished.
Just rubbing with the bristles of an artist paint brush is enough to burnish it.
I need to reach into the interior ring to burnish the graphite there before it would plate properly.

 Here it is beginning to get its initial copper coating. Nice!

I electroformed for 8 hours giving me 8*24microns so 0.2mm in theory!
 Measuring the bare wire versus the electroformed part confirmed the thickness.
 I drilled and melted out the wax.

I then very carefully annealed the tube, in the process evaporating the remaining carbon. I pickled
and ultrasoniced the remaining crud off.

And then disaster!! The inner rings were so thin that they cracked in the ultrasonic. They came out with some small holes and
crack lines.
I had always planned on re electroforming inside the tube as I thought they would be a little thinner. But they are significantly thinner and quite brittle.

So I placed a copper pipe electrode into my copper plating solution and began plating from the inside.
After another 4 hours...
 I ran the ends on the belt sander to clean them up...
 And tin/lead soldered it together. Ta da, one flexible mirror mount!

In retrospect I would do this differently. I had a huge problem with the shape of the mandrel causing different plating thickness
I bet anyone with plating experience could have seen that coming. So for the next electroformed copper bellows I will follow these guides:
  • Interior corrugations must be wider than they are deep.
  • Returns must be angled to face the electrode for copper plating reasons.

Saturday, March 31, 2012

Cheap grease

Look, its non silicone high vacuum grease that doesn't cost alot like Apiezon does! I got this over the phone from a lab suppliers in the UK.

Water Cooled Magnetron. A go go.

I decided to try a water cooled magnetron. My Oil Burner Ignition Transformer is rated 8000v at 34mA so thats.....8, 3s are 24.... 250watts or so. Enough to get hot in a vacuum I would think. So I made an inner brass cylinder to fit around my deep pot magnet from .5mm sheet and silver soldered it. I then made two rings of 4mm dia wire, these fit over the inner cylinder. Then an outer cylinder, brass silver soldered. I then soldered it together. The lovely copper pipe to get the water in, came from Halfords. I'm not sure why they sell it but I suspect something on the break line of cars.
So I flared the ends and drilled 4mm holes in the sleeve and soldered the pipe in place. Fingers crossed its water tight...

The seal around the inlets on the belljar is just an o-ring Wilson Seal style. Its a standard plumbing fitting altered a bit on the lathe. It is necessary to remove the first 3mm or so of thread on the 'body' of the fitting in order to allow the 'nut' to pinch the o-ring enough. I also recut the inner bevel of the body of the fitting to 45 degrees or so. It seems to work well. Plus grease of course.

The anode here is a similar setup. The loop is iron wire, well no, its a welding rod so it's probably steel !

Bell Jars, a rural approach!

I have been working on my new set up for a while now. I've been a bit busy on other projects but I'm gonna try detail some of the bits I've finished.
The first thing is the bell jar. Its made from a 'recorder jar' from a milking parlor.(Thanks again to Mr Hart!) I picked three up at local farmers auction. Cheap too!
As far as I know they were used to keep track of how much milk was being sucked out of the poor cows. We like them because they are made for vacuum use.
This is how they look in their original state. Closed at the top and bottom. An amazing piece of glass.

I went to Ireland's only scientific glass blower(details below) and got him to cut the bottom off one. It was borosilicate, the others seem to be nonpyrex glass. I'm not sure what they are made of.
The good news was that the boroglass one had two openings at the top. Perfect for the sputtering setup I was hoping for. I wanted to isolate the baseplate from the sputtering power supply.(Note: the pump and therefore the baseplate is earthed and that is the same potential as the magnetron, so this makes it not really isolated from the sputtering power supply. I don't know what else to do!)
I believe finger prints can be an issue in high vacuum, I wonder if foot prints are an issue too?!

The name of the scientific glass blowing company is Lab Glass Services. They are in The Grange, Oldtown, North County Dublin. Talk to Colm a very helpful chap! 01 8433442

Saturday, January 14, 2012

BL Neon!

I was lucky enough to visit a fantastic neon sign company this week. Bernard, the owner of the company BLneon was kind enough to give me an in depth and fascinating lesson in many aspects of neon work.

Below is a picture of a piece of neon he made for me there and then as he explained the process of how a neon sign is made.
My first contact with BLneon was a cold call a couple of weeks ago. I was looking for a used 15kv NST as a laser power supply. (I'm trying to eliminate possible problems with my currently non-functional laser.)
I explained what I was up to and Bernard was bemused but interested in what I was badly describing over the phone. Without hesitation he offered me a visit his workshop in Celbridge and I jumped at the chance!
This is a shaky shot of Bernard and his son Keith with the freshly made neon tube!

Visit BLneons Website:

Ciaran looks after the digital end so don't forget they do normal signs too!

I was very touched by the generosity and openness of the whole family on my visit. Unfortunately a lot of companies in Ireland have become very paranoid and secretive over the last while, fearing I assume litigation or thievery from everyone who isn't a straightforward customer.
My visit to BLneon rekindled my faith in Irish companies. Perhaps when the focus is on quality and craftsmanship instead of money, there is far less to fear.

Many thanks to Bernard, Keith and Ciaran!