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TIG welding tubing and flanges with an automated fixture

Posted: Wed May 23, 2018 12:43 pm
by Andrew Seltzman
I have recently built a welding lathe for automated tube welding for an upgrade to my fusor. The lathe holds a TIG torch at a fixed distance from the tube or flange and rotates the part at a constant speed. A current path is provided through the chuck drawbar which is insulated from the gearbox. The gearbox is driven by a variable speed stepper motor. An additional fitting on the tail stock feeds argon into the inside of the tube for internal gas shielding.

Calculations used for the but weld onto the valve were adapted from:
http://www.pro-fusiononline.com/welding ... rbital.htm
For a ~0.1" wall tube of 3/8 diameter, the welder settings were:
Electrode tip ground to a 90 deg angle
Rotation rate of 4.1RPM => ~5inch/min surface speed
Electrode to tube gap = 0.05"
Pulsed TIG on
3:1 peak to avg current
5 pulse per second pulse rate
35% pulse width
HF continuous
Peak I = 80A
current was decreased to ~80 of starting value manually via TIG pedal during the weld process

Welding lathe
lathe1.jpg
lathe2.jpg
lathe3.jpg
But welded welded tubing to valve
valve.jpg
Welded flange
valve2.jpg

Re: TIG welding tubing and flanges with an automated fixture

Posted: Wed May 23, 2018 5:04 pm
by Rich Feldman
Nice work, Andrew. Thanks for sharing it.
It's great that your electrical connection to the chuck is just a flexible wire, since the rotation is bounded.

How many practice joints did you make, before the real job?

Re: TIG welding tubing and flanges with an automated fixture

Posted: Wed May 23, 2018 7:51 pm
by Rex Allers
Small detail question:
What was the source for that fancy clamp you are using for the torch?

Re: TIG welding tubing and flanges with an automated fixture

Posted: Wed May 23, 2018 9:14 pm
by Bruce Meagher
Very nice orbital welder! I’ve hope to stumble across an Orbitalum, Swagelok, or the like for cheap, but I think they are too rare and too desirable to show up secondhand at an affordable price. Are you using a little Arduino to control and drive the stepper motor?

Re: TIG welding tubing and flanges with an automated fixture

Posted: Wed May 23, 2018 9:49 pm
by Andrew Seltzman
The chuck is capable of continuous rotation, the wire on the jaw connects to the chuck body so weld current dosen't flow through the jaw ways or scroll. The current then flows down the drawbar (a 1/4-20 bolt) which is insulated from the gearbox so current doesn't flow through the worm gear or bearings. The current is grounded by a spring loaded copper brush that is presses against the back of the drawbar. I did one practice test on a tube of the same wall thickness to ensure it would not melt or be damaged before welding the valve.

The stepper controller is a Pololu TIC T825
https://www.pololu.com/product/3130

The gearbox is:
https://www.ebay.com/itm/VEXTA-RHINO-DR ... Swdytaro92

The clamp for the TIG tourch is a handlebar clamp for a gopro
https://www.ebay.com/itm/Bicycle-Bike-M ... SwKWRZ3h0h

Re: TIG welding tubing and flanges with an automated fixture

Posted: Sat May 26, 2018 5:27 pm
by Mark Kimball
The link you included in your OP indicates that the base metals are joined with no filler metal. I didn't recognize any facility in your setup for feeding in filler metal. Am I correct in concluding that you are NOT doing so?

Mark

Re: TIG welding tubing and flanges with an automated fixture

Posted: Sat May 26, 2018 11:40 pm
by Jerry Biehler
A good chunk if not most of vacuum welding is done without filler. All fusion welds.

Re: TIG welding tubing and flanges with an automated fixture

Posted: Sun May 27, 2018 7:48 pm
by Richard Hull
Jerry is correct. If the metal is thick enough, the weld current controlled intelligently and the work held fast, most vacuum welding is possible without filler rod. For 1/4" thick ++ flanges a machined grove around the inside of the flange hole will supply all the filler material for a pipe to be welded. there are many tricks in TIG vacuum system welding where filler rod is just not needed. Typically, if possible, filler rod is avoided in vacuum system welding.

When done professionally, almost all TIG vacuum welding is special jig welded. In most cases, only a few custom constructed jigs for the most common joints are needed. In the largest and most complex systems and chamber construction CNC welding can be used to good effect. Still, in some rare situations, only a pro with electrode in hand and filler rod will do. A good professional, specialized in the vacuum welding business, is always cheaper than building a new "one off jig" or CNC welding.

In the end, most vacuum systems are "Erector set" bolt together affairs using standard fittings and plumbing. A lot of repetitive 360 degree weldments are needed to make the "pieces-parts" of the Erector set components and, as such, are typically all jig welded.

Richard Hull

Re: TIG welding tubing and flanges with an automated fixture

Posted: Sun May 27, 2018 7:55 pm
by Mark Kimball
That's good to know. The education continues....