Advice on metal selection for plasmacam

Metal Shop
#1

I plan to make a few custom signs similar to the one below. The idea is a shape or two with some words that are overlaid on corrugated metal. The corrugated metal will be a simple oval, rectangle, etc. I’ve had success with thicker metals like 10ga on the plasmacam, but I suspect that is too thick for this use because it will ultimately be too heavy. I have new fine cut consumables for the plasmacam so I should be able to cut thinner metals . I could really use some advice in selecting the gauge of the steel for the shapes and words. Anyone have experience with signs like this?

Second, I know we don’t have a working Z-height control on the plasmacam so I’m sure I can’t cut the corrugated steel on there. Any ideas how I could cut that steel? These signs are as large as 4’ x 4’.

BTW, I’m quite handy with electricity and electronics. I recall seeing that Tim already tried to get the z-height voltage divider working. I’d be happy to look at it again if someone thinks its possible to be successful with another pass at it.

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#2

My 2 thoughts, of the tools available @ DMS are:
Handheld plasma
Right angle grinder with cutoff wheel

not sure if either will meet your needs/desires, but that’s what strikes me.

Also, depending on thickness, handheld shear (I don’t know if there are any @ DMS or not, but there sometimes appear to be some “tin snips”…

@Trent_T seems to have gotten the best results for cutting thin material, as far as I know, with the cutting of the fairy wings. I wonder if he’d have any insight…

#3

So most corrugated is galvanized, and thus not eligible to be plasma cut at the space. But I’ve never found a good way to cut it either.

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#4

ah. galvanized… of course. freehand with the angle grinder might be the ticket.

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#5

I wouldn’t mind trying some settings on the Z-height if you don’t mind using some of your stock. @Chris_Wischkowsky & I had some settings that seemed to work. I need to get them from him the give it a shot. The other issue we may have is the actual amount of travel or lack there of. I will tell you this, you can cut a pattern on the laser out of wood. Then use that as a template. I have created a template before out of Masonite and used it as a guide. You have to remember to offset the center of the cut to get it the right size. I did not do this at the space but at home with my scroll saw.

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#6

Only if you have good air respirator on.

#7

I’ll look for some other way to put a quality cut on hot-dip corrugated metal. For the signage though, maybe i could ask a slightly different question. What is the thinnest gauge hot rolled sheet metal you think I can cut, with a fine cut tip, that will not warp so much it snags on the torch? Consider a cursive word that is ~3’ long.

#8

You can use virtually any method, but those which do not heat up are obviously preferred when it comes to keeping the galvanizing in tact, rather than making the zinc turn to vapor.

If you use a grinding or fast cutting method (you can use a circular saw, for example, or a reciprocating saw with the right blade you will still make the zinc airborn, though with less harmful effects.
And finally, the method I will advocate because it reduces that particular concern to nearly nill, is the shear method. You can use nibblers or shears or even no tools (more realistic depiction)…

I prefer the shear method, but obviously, you’ll need a good shear.
The Metal Shop has both an electric shear and a nibbler, but I don’t know if they’re in working condition or if what you want to cut is within their scope. They are (as far as I recall) both Harbor Freight specials, for whatever that brings to the table.

I think we should refer you to the operator’s manual for the Duramax Retrofit Torch. On page 3-40 (PDF page 76/98) is the chart for “low speed fine cut unshielded mild steel”. It bottoms out at 26 gauge, so I recon that’s the thinnest material the manufacturer thinks is reasonable. I imagine you should buy 2x what you think you need, and plan to practice quite a few cuts before making your final run. Plan to lose some consumables, too. Hopefully it’ll work like a charm and you’ll have bought extra for that next project…

#9

I tried some 24ga and it warped enough for the torch to snag and drag it around. I might just get some more of that and experiment a bit.

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#10

I’ll suggest paying special attention to the torch-to-work distance. 0.06" is pretty darn close (about the width of a penny, eh? :wink: ) .
It might be good to find a “clean” place on the table, where the stanchions haven’t been buggered, to help ensure the work lies flat (or maybe when the flip happens, hopefully on/around July 15, it’ll work better for this type of cut).

Note there are “fine cut” vs. “low speed fine cut”. The low speed is 1/2 the feedrate of the regular, so you might want to be certain of which consumable and settings you are employing.

Also, if you’re able, use a “edge start” technique, rather than a piercing cut in. Piercing is simply harder on everything, as you have to dump a lot of heat to get started, relative to the amount of heat needed to keep the cut going.

That’s all I can think of at the moment. Hopefully one of our other folks will chime in with your silver bullet. :thumbsup:

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#11

I’ve been cutting 16 ga hot rolled steel plate with fine tip. 35 Amps and 140 speed or so. Just do the pause before each cut so cut pieces don’t flip up and hit the head. I get some warp and I’ve had success using a 1/8- 3/16 inch torch height

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#12

Wouldn’t a water-jet cutter work for this? Maybe not due to hills & valleys involved…anyhoo @chadb posted a YouTube video regarding a DIY version a few weeks ago: https://talk.dallasmakerspace.org/t/hobby-waterjet-cutter/22059