3D Printed Bronze

9 11 2011

All photos.

Years ago I looked into Prometal’s 3D metal printing process. The results were impressive but the stainless steel is magnetic:

This disqualified them as magnet holders!

Recently Prometal let me know about an experimental bronze process they are developing. Bronze is totally non-magnetic. BINGO!

Prometal donated a test part to see if I could make an airtight braze with a TIG welder:

The part was to be brazed to a Swagelok VCR fitting like this:

Prometal is still adjusting the process. This test part is a bit oversize so it was difficult to braze, but we got something:

The bronze attaches to the stainless nicely.

I was excited to put it in the chamber like this:

But I screwed up. I welded on the wrong VCR cajon. This one is two short to catch the male thread once the gasket is added.


I had the right part here all along; shown on the left:

So no vaccum check for now. But it looks like the 3D printed bronze parts braze nicely.

I count that as a win. Think of the parts I can make with 3D printed bronze + brazing.

Welding Shields

18 12 2009

In an attempt to protect the fragile coils while welding together the magrid, I’ve designed a magrid with welding shields:

I added code to generate closeups:

The lids have the female side of the welding shield:

Dielectric Test

10 12 2009

I’ve come to a decision on what to build next.

It will be an inexpensive magrid. Not designed to be fully functional, but rather designed to test several immediate concerns:

1) The dielectric varnish between the coils and the magrid chassis. There will be a 30kV+ voltage difference between the coils and their container. The insulating varnish must be evenly applied to the coils. Varnished coils will be stiff and difficult to install. In an attempt to make the coils easier to install, I’m working on an open joint design like this:

2) Test out welding the magrid together. Can we weld this together without destroying the delicate coils inside?

3) Design first iteration of the standoff.

4) Test liquid nitrogen bath.

The machine would have 2 turns of superconducting YBCO and be made using the inexpensive prometal process as before. It will have thick walls to avoid the sagging we got last time.

I’m still working through the details, but this machine should be imminently build-able.

Heat Shield

1 12 2009

The red hot fusor grid reminds me  - I must address thermal issues from plasma, xrays and neutrons for polywell fusion without boiling the superconductor’s liquid nitrogen.

I asked for help with thermal modeling on the polywell talk forum. Good feedback.

Here is a rough draft of the superconducting magrid with a vacuum separated heat shield:

The trick is, the shield must have a gap so that you can weld the lid to the chassis. The welded magrid would have a gap in the shield along the midplane of the torus.

This gap would bring the vacuum between the heat shield and the inner superconductor holder. Well actually it would be  ~10 mToor of ionized deuterium.

This design does not include liquid water cooling. Although it’s easy to add cooling channels with the Arcam process, the real challenge is connecting fluid channels when you weld the lids onto the chassis.

Star Mode

3 11 2009

We got the butterfly value installed and tested out the new grid. Beautiful stable plasmas. Air plasma:


Deuterium plasma in star mode:IMG_4482

No bubbles yet. This video shows the stable air plasma:

Read the rest of this entry »

Arcam EBM fabrication

19 10 2009

I’m exploring the Arcam EBM process for fabricating the magrid.

Our current scale is within their build envelope (250 x 250 x 400 mm and 350 x 350 x 250 mm).

Their process creates a fully solid / fully melted part using Ti6Al4V Titanium Alloy.

Titanium is non magnetic (paramagnetic). GOOD

Titanium has low outgassing (I _assume_). Not seeing good information on this, but I see articles about low outgassing. GOOD

The fully melted part should be vacuum tight. GOOD

Titanium can be welded, but it’s complicated. Gas shielding is required. WORKABLE

Titanium is difficult to machine. It requires specialized tools. It’s tough and springy. Too hot and it reacts chemically. The magrid part is likely too delicate to be secured for machining. We can still lap sand the faces for better mating. BAD/WORKABLE.

Titanium is strong. GOOD

Titanium is beautiful. GOOD

The part would be highly conformal. I do not expect the warping as with the prometal magrid. GOOD

Price. This same part would cost around $2500. Better get it right the first time. WORKABLE

Although it’s a path fraught with peril, it could lead to a fully functional superconducting magrid.

Welding Day

4 08 2009

My shop neighbor Arnie is a talented welder and he got his hands on a MIG welder today.


Arnie, welder extraordinaire

He offered to help us weld up the sled. Sweet. Some pics of the welding:


The finished sled:


My first weld:


It was hard to see the line I was welding.


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