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MIG JIG
Introduction.

The immediate problem is that I need to do some MIG welding, in order to construct some simple machines, but as far as I know, whatever I have learned in the past, has long gone !.  I do have a MIG welder and I do understand the basics, but that is all.  Now rather than facing a  painful learning curve I want to automate my welding, so that I can get consistent results.  I think that simply boils down to a sort of simple welding jig that can produce perfect spot welds.  Unfortunately  when I am ‘designing’ anything I always over do it , but I have scrapped all of my first complicated  ideas and have tried to come up with something simple.

Two problems.

The first is setting up the welder, which includes  getting the wire feed right, the current setting right and the right inert gas flow  Problem number one is that I cannot hear the gas  and my welder has no gas flow indicator., So I am going to have to do something about that. I also had problems getting the welding wire to feed through the nozzle, because I was using the wrong size nozzle !.   Current and wire feed speed is something I will have to learn by practice. I also have a full pub type CO2 gas bottle, so rather than use the expensive small ones, I will make up an adapter for that too.
The other problem boils down to my lack of skill in applying the welder to the pieces to be joined. I have an automatic welding mask, but still have problems seeing what I am doing once the arc has struck.  Specifically I cannot see how close I am to the work and that causes all sorts of problems for me.  I also have problems welding in corners, because I lose the angle of the gun, in trying to concentrate on everything else, like my trousers being on fire etc.
The solution I see is to make an aid that will always ensure the gun nozzle is at the optimum distance and at the correct angle.  The other factor is the speed that you weld, for example to get a decent deep penetrating sot weld the nozzle must be in position for about two seconds and then moved at a rate to move the weld puddle along the run for optimum weld strength … and this requires a degree of skill !.  I think the simple way around the latter problem is to avoid doing runs !.  Simply make a series of spot welds.  Now a Dutch friend of mine  always told me that you could hang five tons onto a spot weld, which is greatly in excess of what I need !,  All I need now is something to hold the gun in the correct position and angle and I have it cracked !.

Thinking forward.

I  can see that providing I live long enough, I will probably be making several machines and to simplify life I have decided that they will all be fabricated from 20.0 mm square steel tube . Now this automatically decides the correct height of the nozzle above the work. All I need is some sort of fixture to hold the gun in that position. If I need to make many welds, I simply move the work around under the gun nozzle.  It would help if I did this using a spring loaded arm, that will move the gun away from the work to aid positioning the work for the next weld.
I scrapped my initial idea for motorised run welding, keep it simple !.
It did occur to me that I might also want to weld larger tubes or assemblies, so it made sense to make the nozzle height adjustable. Also since I know I also want to use, it to weld forks, I need to make sure that the various welding jigs can just drop into place on this  aid and be perfectly aligned.  















For example, this is the welding jig for the steel frame slingshot. The welding nozzle will be automatically positioned dead above the joint and at the correct height above it, so it you press the button on the gun handle for two seconds, you should end up with a perfect weld (it says here !).  Then simply turn the assembly upside down and do the same to that side.

Construction.

I will start  making this device perhaps tomorrow and will post the progress here on this page.



10th September 2102.

Busy day, but did manage to get some of the parts made and drilled.










Top left is a part of the gun angle adjustment thing. Top right, these hold the two bottom items vertical on the base and the  four  part arm swings between them. The smaller holes give  height adjustment. This plus two other feature give infinite adjustment over the range.
I decided to move the goal posts a little and  allow the welding  torch to be held vertically, or set to 45 degree’s for corner welds. It also seemed logical to provision for straight welding  welding runs, but not at the expense of the simplicity of the jig, so I will be making a separate sliding work tale at a later date.
I still have to make up the arm swing stop adjustment devices, gun clamp and make up a  base etc.

11th September 2012.

The height setting works in 20.0mm increments from about zero to  80.0mm.  Using the swinging arm arrangement to hold the gun means that the arm describes an arc, however over a 20.0mm height difference there is little deviation of the actual welding spot on the work.  Now I had to have aa positive sop on the arms lowered position, so I decided to make it variable, giving me infinite adjustment between  0 and 80.0mm. There is a wing nut on the back to make adjustments. This device also sets the height of the arm when it is pivoted upwards to clear the work, or move it.

















The next photo shows some of the component  temporarily assembled.  It can be seen that the arm is divided into two pieces and the part that the welding gun will be clamped to, is set to give a weld perpendicular to the base plate. It is secured in this position by a 5.0mm steel pin (with a knob on it). It this pin is removed the end piece can rotate  +45 degree’s or minus 45 degree’s for doing corner welds. The head of the arm is secured in these positions by the same 5.0mm pin.












In the next photograph the pin has been removed, the head of the arm set to 45 degrees for doing a left hand corner weld.












I am quite pleased with what I have done so far, as the image in the mind does not always successfully translate into reality.
I think the next step is to make up a  fire proof base to fit it all on and the gun clamp.

12th September 2012.

I have cut out the base plate from 9.0mm thick aluminium plate and cleaned it all up.  Last night I decided that  the stop for the low arm position could be improved on, so I have decided to make another one of those. With a fine adjustment knob, it is a bit over the  top really, but that’s me !.
I am just about ready to mount what you saw yesterday onto the base, so in preparation I turned up a spacer to make sure the top of the vertical tubes are parallel when mounted, as I do not want much play on the arm. Still have to make the gun clamp but, I will get the jig mounted on the base plate first. It progresses.

13th September 2012.

Determined to get things mounted onto the base today and make the new adjustable arm stop.












The  components are now assembled on the 9.0mm base and that worked out fine.  I also made a pin for the 20.0mm  adjustment holes. Under the arm you can see the new arm stop I made today, with fine adjustment and locking wing nut.  All that is left to do now is  make up my mind how I am going to clamp the welding torch to the end of the arm. The original plan was to clamp it onto the side of the arm, so I will have to wait and see what appears tomorrow !.

14th September 2012.

Made up and fitted the welding gun clamp. That is the basic welding jig completed.  In use, specific purpose jigs will ‘plug in’ to this table to speed up jig change. The small jig for welding the forks onto the shafts will be the first.  The  only other thing I could do, is fit a spring to the arm to automatically hold it in the ‘up’ position.













Project completed.