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Old 07-19-2014, 10:24 AM
tennsmith tennsmith is offline
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Default Deformation due to welding

Seeking advice/recommendations on how to recover from welding a panel into a dashboard with resulting deformation. Here is what I did. I wanted to replace the "instrument cluster area" on a '36 Ford dashboard. I cut out a precise rectangle in the dash which removed the original instrument mounting location and fabricated an equivalent rectangle of identical sheetmetal thickness to ocntain the new instrument layout. Next, I probably screwed up, but at this point, that is water over the dam. Not wanting to fret with the use of a holesaw to cut the openings for the new instruments, I cut them out on my milling machine, using a rotary table and a small diameter milling cutter. The resulting panel was "more holes than metal." This panel was then filed/fitted to the rectangle in the dash with considerable precision such that no gaps in excess of about .005" existed. Next, the panel was randomly "tacked" into the dash at about 2" intervals around the perimeter using a TIG torch. Then, a repeat tacking exercise, filling in between the 2" spacing such that I had the panel tacked every 1" around its perimeter. At this point in time, all was well and the insert was properly "in plane" and it looked like it was originally "made that way" with the exception of the areas still to be welded. Then the perimeter welding was accomplished, using a TIG torch, in 1-2" sections, randomly picked about the perimeter such as not to create intense heat in any one area. When the job was finished.....I had a mess!! The insert panel is now deformed "inward" away from the driver, as if it grew in size and was too big for the hole into which it was welded. I've noticed that my bottom weld seam is "angled", that meaning the two pieces are not in a plane, but rather, at an angle of maybe 5-8 degrees to each other. The resulting angle is in the direction such as to promote/cause the insert to be deformed inward. So the question is: Can I recover in some way from this, or would the best solution simply be to remove the panel, replace it with a solid panel and worry later about how to get the instrument mounting holes cutout? My thoughts of things to try were: (1) maybe straighten the aforementioned angle by using a press; (2) perhaps reheat the entire perimeter with the hope that some of the stresses would be distributed; (3) localized "shrinking", perhaps of the insert panel. (4) Re-install a new cutout panel using MIG and a stitching or dotting technique to minimize heat. Any ideas/suggestions would be welcome.
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Old 07-19-2014, 10:38 AM
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Marty Comstock Marty Comstock is offline
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you never stretched any of your welds. You weld something so thin and small, it will warp, badly. Solution, stretch the HAZ, enough so that it comes back out straight, but not so much so that you over stretch.

simpler solution before the water went over the dam would be to stretch as you go before it become a mess, so with each weld, you return to your datum line before you begin another weld.

Pics would be of value here, too.

Marty
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Old 07-19-2014, 11:20 AM
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Steve Hamilton Steve Hamilton is offline
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Default Correcting weld zone distortion

Hi Bob

Marty is right, every time a weld is made, with any method, the metal will shrink in surface area.

To correct that the metal must be stretched, but only the metal that has changed in color. Where the color has gone to blue, purple, straw etc. is called the Heat affected zone (HAZ). The stretching is usually performed by hammer on dolly contact. or with an air powered planishing hammer.

Caution!!!!!!
Do not work on the areas that are still bare metal color, they will go back into shape when the HAZ has been stretched the correct amount.

Go Slow and keep checking to see that the metal is moving back to the shape it was in before you started tack welding.

You may be surprised at how much time is required to get the metal stretched back out. A rule of thumb is 1 to 1.5 Hrs per foot of weld zone.


Steve
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Old 07-19-2014, 01:23 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Steve Hamilton View Post
Hi Bob

Marty is right, every time a weld is made, with any method, the metal will shrink in surface area.

To correct that the metal must be stretched, but only the metal that has changed in color. Where the color has gone to blue, purple, straw etc. is called the Heat affected zone (HAZ). The stretching is usually performed by hammer on dolly contact. or with an air powered planishing hammer.

Caution!!!!!!
Do not work on the areas that are still bare metal color, they will go back into shape when the HAZ has been stretched the correct amount.

Go Slow and keep checking to see that the metal is moving back to the shape it was in before you started tack welding.

Steve
Bob, Marty and Steve are correct about your welds having reduced the metal area, and weld engineers call this "negative weld volume."

You always have to stretch the HAZ after welding, just as they are saying.
Now, get to it.
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Old 07-19-2014, 04:42 PM
David Gardiner David Gardiner is offline
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The fix is never as simple as that. The welding will have caused more shrinking in some areas than others. To confirm this just look at the HAZ. If it is uneven the shrinkage is uneven and distortion is inevitable.

You do need to stretch the weld but you also have to understand what is happening to the panel as you do or you will end up with an overstretched panel.

The normal way of finding where to hit is to use your hands and eyes as well as a file to show where to hit. You will probably find you need to move some areas of panel up and some down using on dolly and off dolly techniques especially as you get the panel closest to the correct shape.

I hope this helps.

David
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Old 07-19-2014, 06:00 PM
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David,
What you noted above is called Metalshaping !!!
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Old 07-19-2014, 08:27 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by tennsmith View Post
Seeking advice/recommendations on how to recover from welding a panel into a dashboard with resulting deformation.

The insert panel is now deformed "inward" away from the driver, as if it grew in size and was too big for the hole into which it was welded. I've noticed that my bottom weld seam is "angled", that meaning the two pieces are not in a plane, but rather, at an angle of maybe 5-8 degrees to each other. The resulting angle is in the direction such as to promote/cause the insert to be deformed inward.
Back up the angle with a good track dolly, and lift/push hard on it when you smack the weld with your hammer.

Choose a body hammer that has a mostly-flat face of about 1.25'' dia. The weight should enable you to swat the peak down easily, and also stretch the weld seam a bit.

Keep your straightedge handy so you know what is coming up and what is going down, and also if you are keeping the overall length in plane.

Work the out-of-position areas towards being in proper plane, and check often with the ruler (truth-stick), as you will then know when you are going too far.

It may be interesting to learn that as you resolve the weld-shrinkage by hammering the discolored areas only, that you will reach the "zero point" and then - if you keep going - the surface deflects the other way, past zero. Now, this is not hard and fast, because other contributing factors can make the panel flex against your efforts, but at least you can Begin to learn the relationship between shrunk, hammer-relieved, and over-stretched.

Hope this helps make the puzzle solution a bit clearer ...
(we're cheering for you)
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Last edited by crystallographic; 07-19-2014 at 08:30 PM. Reason: speling
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Old 07-20-2014, 08:33 AM
tennsmith tennsmith is offline
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Thanks guys, I think I understand what I need to do....now I need to just do it. I do have a followup question...... at the current time, the panel is exactly as it was welded with the weld seam still proud to the surface as it has not been ground off. I assume, based on comments received, that this seam should be ground flush with the surface before the stretching process begins in order to allow hammer contact with the entire HAZ. Would it be prudent to hammer a bit on the weld seam before grinding it flush in order to stretch this localized area?
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Last edited by tennsmith; 07-20-2014 at 08:41 AM. Reason: a follow up question was asked.
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