Laser and Plasma cutters/engravers.

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Chlomo

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I've seen a video on Youtube that describes a wing manufacturing process utilizing a 'cnc punch turret'.


However something tells me that gizmo is not the weapon of choice for most of us homebuilders; one might consider going laser or plasma.
That being said there are a lot of 50~60W laser engravers that can work 600mm * 400mm and cost somewhere around $5K. As for the plasma gadget I remember seeing frequent ads on Popular Mechanics a few years ago.
But before we talk about whether or not to buy one of those there seem to be some pros and cons to weigh regarding the technical aspects of those machines.

Accuracy: Laser is very accurate. Plasma maybe not as precise but we are not building F-22 planes here.
Cost: Obviously laser costs a lot more to cut(unless you own the machine) I've seen quotes of a few $s a minute for simple cuts.
Speed: Of negligible importance considering total build time

DOES PLASMA RUIN THE TEMPER OF ALUMINUM???
 
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Aesquire

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Plasma will erase the heat treating but only in a narrow band. I'd want to have a shop do a test piece for me to make Sure it's not an issue.

More important is the slag. My experience with plasma cutters is mostly in 316 stainless and mild steel. It leaves a jagged slag edge that needs cleanup before the next operation. What it leaves on 6061? Have a test part cut.

Also the CNC machines should give a better edge than the hand held version.

My buddy quit using his manual cutter because..... well to be honest.... new toy so used it a Lot. Then got a $300 electric bill. ( we do have the highest rates locally )

Others will know better but that's my snap judgement.
 

Head in the clouds

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DOES PLASMA RUIN THE TEMPER OF ALUMINUM???
Yes, it does, so does laser. However the heating is very localised i.e. close to the edge of the cut and in most cases that annealing of the edge has the advantage that it makes the edge less prone to cracking. Since most cracks propagate from the edge of a part that can be quite a useful benefit.

Laser and/or plasma cutting of CRMO Chromoly sheet has quite the opposite effect leaving the edge very hard and relatively brittle. Re-drilling burnt holes to size can be a challenge and it's a benefit if you can re-sharpen your own drills with a reduced rake angle. For larger holes, say 3/8" and up, I prefer to burn the holes very close to size and then ream them to size rather than drilling them. Critical laser/plasma cut components need to be heat treated to return them to the Normalised Condition, or hardened/tempered, as appropriate for the specific part.
 

Chlomo

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Yes, it does, so does laser. However the heating is very localised i.e. close to the edge of the cut and in most cases that annealing of the edge has the advantage that it makes the edge less prone to cracking. Since most cracks propagate from the edge of a part that can be quite a useful benefit.

Laser and/or plasma cutting of CRMO Chromoly sheet has quite the opposite effect leaving the edge very hard and relatively brittle. Re-drilling burnt holes to size can be a challenge and it's a benefit if you can re-sharpen your own drills with a reduced rake angle. For larger holes, say 3/8" and up, I prefer to burn the holes very close to size and then ream them to size rather than drilling them. Critical laser/plasma cut components need to be heat treated to return them to the Normalised Condition, or hardened/tempered, as appropriate for the specific part.

Hmmmnn pleasantly surprised! That is very comforting to hear!
 

Chlomo

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Plasma will erase the heat treating but only in a narrow band. I'd want to have a shop do a test piece for me to make Sure it's not an issue.

More important is the slag. My experience with plasma cutters is mostly in 316 stainless and mild steel. It leaves a jagged slag edge that needs cleanup before the next operation. What it leaves on 6061? Have a test part cut.

Also the CNC machines should give a better edge than the hand held version.

My buddy quit using his manual cutter because..... well to be honest.... new toy so used it a Lot. Then got a $300 electric bill. ( we do have the highest rates locally )

Others will know better but that's my snap judgement.
Thanks, Hopefully when cutting out rib blanks I can most certainly dedicate a few minutes per part to clean the edge! Still much better than trying to cut them with hand tools.
 

cheapracer

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Still much better than trying to cut them with hand tools.
Spend just one day making a range of quick templates and life is a breeze with a hand held plasma.

Big washers with flat handles tacked on that can be clamped are ideal for holes for example, just do a test hole cut and figure the cutting radius the inner washer edge difference and go from there, I have about 10 different size washers like this and a couple I turned up in a lathe for larger holes.

Of course a variety of straight edges, various angles made from 2 pieces of 25mm x 2mm flat and some random curves as well, all pretty easy stuff.

I had a picture of them somewhere, I'll have a look ...
 

Chlomo

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Spend just one day making a range of quick templates and life is a breeze with a hand held plasma.

Big washers with flat handles tacked on that can be clamped are ideal for holes for example, just do a test hole cut and figure the cutting radius the inner washer edge difference and go from there, I have about 10 different size washers like this and a couple I turned up in a lathe for larger holes.

Of course a variety of straight edges, various angles made from 2 pieces of 25mm x 2mm flat and some random curves as well, all pretty easy stuff.

I had a picture of them somewhere, I'll have a look ...
Excuse me but I don't have any knowledge in handheld plasmas they sure sound attractive but wouldn't the plasma melt/burn the template? (I may be missing something here)
 

akwrencher

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Excuse me but I don't have any knowledge in handheld plasmas they sure sound attractive but wouldn't the plasma melt/burn the template? (I may be missing something here)
There needs to be an offset anyway to compensate for the radius of the tip, so the plasma "flame" isn't all that close to the template. Works very well. The other day I had to cut a piece of steel bar stock in half lengthwise. I just clamped a straight piece of 1"x3" steel tube I had laying around and made a nice straight cut. Actually, I think I used the O/A torch for that one......too thick for my little plasma, but it works the same way.
 
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