Robo welder is rotating. Not welding yet but soon.
It amazes me that tiny motor and gear box is all you need.

Here is a movie to prove it.

Just because something you are building is small does not mean it does not take a lot of time.

I tried the rubber tubing coupler but it did no rotate smoothly.
It would wind up and then would release.
This is a special coupling nut with a 4-40 set screw.

Paul Lamar


I am getting a degree in robo welder design.

I have discovered several things. Don't use caster wheels that are the least bit soft. It is best to make your own rollers out of metal.

The grounding of the tube resting on the stop doesn't work very well. I found some 4 gage wire in  an automobile hi fi audio shop that is very flexible. A zillion tiny copper wires.
I stripped the insulation off but not entirely necessary.
The insulation is soft and flexible as well.
About 2 bucks a foot.


I will attach that to the tube with
a hose clamp and wrap several turns around the tube to be unwrapped as the tube turns and is welded.

I found a 110 Volt synchronous motor at MaMaster Carr that rotates at exactly 1 RPM no matter what. It has enough torque to twist your wrist off.

It takes the speed of welding out of the equation. All you need set is the welding current and the distance of the tungsten to the metal.
The gas flow can be near the bottom of the recommended scale to conserver that expensive consumable.

Paul Lamar


A bit of advice from someone who has thousands of hours experience with
welding wire in a physicly dynamic environment. First, properly size the
wire for the current load. #2 for 100A give or take depending on the
insulation(bumping 1 or 2 guages here won't kill you). You always want to
size on the high side because.. it's expensive to replace. Welding wire has
many fine conductors, composed of alloys that resist fatigue and heat
crystalizing. Welding wire, is quite properly more expensive because it
handles abuse and motion.
If your robowelder only needs 360/380 degrees of rotation, get enough length
so you can perform the rotation without too much twist per inch of wire, but
always turn it back to a start index.
C. Smith



tig does not use wire. Filler rod sometimes but not needed here.
This is basically an over lapped joint.
Here is a picture of the part that is welded on to the end of the
4130 .049" wall one inch OD tube. The turned down part goes inside the
end of the tube.

Paul Lamar

I believe C.Smith is talking about the ground wire. Being an electrical
engineer, he is right, #2 copper is the right size for 100 amps.

H.Lunt

Thanks.

BTW everybody please set your editors to send plain text to me.

html does strange things to email programs.

We are getting email from different OS's XP, Wind 7, Wind 8
etc., etc.. Mac, cell phones etc., etc., etc. Apparently they send
messages in different ways.

Paul Lamar

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