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Making a corner in sheetmetal for a dust tight box

Making a corner in sheetmetal for a dust tight box

Making a corner in sheetmetal for a dust tight box

(OP)
We're working on packaging an industrial product where we will have to meet UL Type 12 and IP54. I've seen some products where they have made the enclosure out of gasketed sheet-metal without welding. One place we have trouble with is getting the corners to seal up without resorting to welding.

Something we've seen uses a feature like this:



The small web of material formed provides a gasket sealing surface at the corner. Does anyone have experience at making a feature like this? I'm suspecting that it could be done on a press brake with a special tooth that has a recess to form the web around the corner.

Thanks in advance,
Matthew

RE: Making a corner in sheetmetal for a dust tight box

MatthewDB,

Why can you not weld it?

IP54 requires you to stop "splashed" water. If you have accurate seams, I do not think you need a gasket.

Could you design a corner bracket to be used in each and every sealed corner? Look into this carefully. If you do this right, someone with a CNC mill can make a bunch of them for you.

Can you fill seams with something like RTV?

--
JHG

RE: Making a corner in sheetmetal for a dust tight box

(OP)
"Why can you not weld it?"

This is for a high volume product that is cost sensitive. We want to use galvanized metal for an interior heatsink airflow path. If we weld we have not only the costs of welding, but then we need post weld finishing.

"IP54 requires you to stop "splashed" water. If you have accurate seams, I do not think you need a gasket."

The 4 in IP54 requires testing with a low pressure spray from all angles. That alone would probably mean a gasket. Not only that, the 5 in the IP54 requires that you pass a talcum powder ingress test. UL Type 12 requires a test with cement dust.

The corner bracket idea has merit, as long as we could control the cost.

"Can you fill seams with something like RTV?"

I've always been hesitant to rely on a sealant in production. It's messy, and I don't think it would be consistent enough.

RE: Making a corner in sheetmetal for a dust tight box

Seems like you had enough material before this step to fill in the cutout, but I don't see how you guarantee that the two seams get adequately sealed.

TTFN
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RE: Making a corner in sheetmetal for a dust tight box

MatthewDB,

If your system is high volume, you can afford the tooling for castings.

Your heat sink comments make little sense to me. If your enclosure is sealed, you cannot have airflow in and out of the enclosure. You can have circulating airflow inside the enclosure!

Your final heat conduit is the enclosure itself. Your cross sectional area is the surface area of the enclosure, which should be quite large. The length of your conduit will be your wall thickness. It should be very efficient, even if you use a low conductivity material like plastic.

--
JHG

RE: Making a corner in sheetmetal for a dust tight box

(OP)
The box is "sealed" in the sense that there is a heatsink inside with outside air moving through it. The channel that the air flows through the blower and then heatsink will be dust tight. The heatsink will be part of the dust tight boundary. The power devices will be in the clean side and the fins are on the dirty side. The blower itself is rated IP54.

We're dissipating over 9kW, there is no way that much heat goes through the walls of the box. We're having to push 1,200 m^3/h of air through.

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