Todd, from my experience of the mechanical shop at my company (some time
ago), where a lot of alu welding was done, a cast alu workpiece must be
heated to at least 200 to 300 degree Celsius before attempting to weld
it with a tungsten arc burner. At such a large piece I guess 4-6 men
with strong torches ar needed to achieve that. You would need 300 to 400
amperes for the arc and, as a guess, a 5 mm electrode with a rounded
tip. The crack must be widened before by grinding it out generously.
Besides, the welder - experienced specialist - will need long arms and a
good heat protection suit, working so close above a mildly glowing plate
that size, if I picture the position of the crack correctly from the
description.
And there is no guarantee that the crack will be healed permanently
after cooling. Obviously there was a lot of tension already in the piece
before, or else it would not have been cracked by the fire. My advice
ist to forget it and try to get a replacement part. Alu has a good price
momentarily at the junk dealers. Sorry!
Peter Blodow
Dipl.-Phys.
Am 28.07.2021 um 19:25 schrieb Todd Zuercher:
We had a bit of a disaster last night. Because of poorly trained, inattentive
machine operators on 3rd shift, we had a pretty bad fire on one of our CNC
routers. The improperly set the depth, then started the machine, turned and
walked away, then evacuated the building when the fire alarm went off, and
never even looked at or stopped the machine. It ran on and burned for more
than 20 min until the FD showed up.
It burned off all the dust-shroud brushes, the dust collector hose, and the
vacuum hose to the table.
Not sure if the wiring for the air cylinder sensors for the dust-shroud doors
will be ok. (They look a little melted) Or if the air cylinders will still
work. The lines to them will have to be replaced
The a 10kw HSK63f router spindle is wrecked (doesn't spin free), we'll send it
out to see if it's rebuildable.
But the biggest problem is that the 5ft by 10ft 1.5inch thick cast aluminum
table cracked! It cracked about 2ft in from the front left corner and runs
about half way across the table in the 5ft direction. The table is supported
from below by 10 linear guide blocks on two rails. The crack runs across
between the 1st and 2nd set of blocks, about 4inches from the 2nd block.
Is there any hope of repairing the table? Are we going to have to replace the whole
table? Could the crack be welded, or is that a bad idea? My main fear is that warpage
issues will cause the linear guides to bind. (The table surface can always be re-milled
flat.) The crack isn't gaping or misaligned, and the table doesn't "look"
warped now that It's cool.
Todd Zuercher
P. Graham Dunn Inc.<http://www.pgrahamdunn.com/index.php>
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
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