Timeless tale... cutting aluminum

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kudo

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Before I start going to town using snips to cut out some aluminum ribs, I was wondering what you all determined was the best method to cut thin aluminum in the long run.

water jet/CNC worth the cost/setup?
Good ole snips and scotchbrite?
Patience but covered in aluminum shards from a router?

Which method have you seen that gave the best finish?


All things being equal, what did you all think produced the best edge/part and saved you the most time on sanding ?
 

Victor Bravo

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I have not built an entire aluminum wing, and some of the people here have. But my opinion is that it will depend as much on what you have nearby. I used alocal waterjet shop for an aircraft parts project, and it worked out fairly well, but for a final finish on the edge I still used a belt sander and/or sandpaper to get the water cutting marks smooth. If I had a laser shop nearby I would have used that, and would have resigned myself that I would need sanding for that edge too. A CNC router shop is also something I'd definitely try but I have no experience with that. CNC has the possibility to leave you with the best finished cut edge, which you will "pay for" with slower feed rate.
 

cheapracer

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Laser, well worth it for the accuracy - but that depends on what you are being charged as well, every shop will vary.

6061 for example doesn't manually drill very well, often leaving triangular shape'd holes, laser cures that, but 2024 drills nicely.

The finish depends on the aluminium type, and a bit of elbow grease. I run a flappy disc or fine file down the edges, a slightly bent fine file, with all sharp edges/corners ground well away, over the surface.
 

Pops

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If the ribs of any alum parts are 4 ft or under I use a 4ft stomp shear. For longer, just cut with a good set of hand shears and clean the edges with a flappy disc or a fine file and get real smooth with some fine sandpaper. I live in the middle of nowhere, so no place does waterjeting ,etc. I have make all the aluminum parts for wings for 2 Bearhawks this way. County of 5808 people and no stoplight and Andy was voted out as sheriff and couple years ago.
Important-- Have fun with the build.
 

narfi

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Like pops said a 4ft sheer is very handy.
For curves I like pneumatic snips, mine are just the head I replaced the chuck with on one of my drills. They give a lot cleaner cut than tin snips. There is a bit of a learning curve though. The nature of their 3 teeth is they want to go straight, so I rough cut to less than a bite worth first then the final cut is only cutting on one side and you can carefully follow any curve you want. I have a big single cut vixen file I can clean up the edges with. (And all the prop dressing i have to do)
 

Victor Bravo

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I've never seen a stomp shear that was the shape of an airfoil :)

The Homebuilt Help guys have a great video of using a flush trim router against a wooden form, cutting a whole stack of 701 ribs at one time. Yes this will create a loud roar and it will be snowing aluminum. But you can throw a tarp over the router table and use ear muffs, and save a lot of time.

They also strongly suggest a bench grinder with a Scotchbrite wheel mounted on it to deburr and polish the edge of the aluminim very quickly. That looks like it will work very well, but it is definitely a place for heavy leather gloves and a full face mask. A spinning wheel catching and throwing the edge of aluminum at you is a good way to get thoroughly sliced and diced!
 

proppastie

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Neiko air shear for long cuts (don't buy the Horror Freight)....Wiss hand snips LH, RH, straight cut.....Cut 1/16 over size then cut to size. Table saw with high tooth carbide blade for 1/16 and thicker. Cheap plastic one will work or vintage from Craigslist
 
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BBerson

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My dads old 18" hand shears (looks like 10 pound scissors) cuts across sheets, curves etc. cut to 1/4" from the line then a finish cut as Narfi said.
 

Dana

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My dads old 18" hand shears (looks like 10 pound scissors) cuts across sheets, curves etc. cut to 1/4" from the line then a finish cut as Narfi said.
I've got my Dad's old 18" Wiss shears too... but boy do they take a lot of hand strength (which sadly, with my arthritis, I no longer have...)
 

Aerowerx

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I see that no one has mentioned using a hand held router.

Wood working tools (allegedly---never actually tried it myself) work fine on aluminum.

You will need two templates the shape of your airfoil blank, including the flange. Clamp the aluminum between the two and run around the edge with the router and straight bit with pilot roller.

Edit: http://woodroutercenter.com/guide-on-use-of-wood-router-and-router-bits-on-aluminum/
 
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BBerson

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Nobody's mentioned a bandsaw?
Bandsaw has limited throat. A sawzall might work for you. Cuts up old 1/16" aluminum ladders in seconds.
Thin sheet might need a light temporary contact cemented to cheap hardboard to keep from chatter. Hardboard (3/16" 4x8) is $9 at Home Depot.
 

Kyle Boatright

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I've used a tablesaw, a bandsaw, a router, and a jigsaw to cut aluminum. My preferred deburring tool for sheet edges is a good file or a scotchbrite wheel on a grinder.

They all work fine. Just use a fine toothed blade on the bandsaw and jigsaw. The rule of thumb is the tooth pitch should be fine enough that you have 1.5 teeth engaged on average. That makes it tough to use a toothed blade on thin material. Personally, if I was doing multiple ribs, I'd make a wooden template and use a router. The only thing you need to watch out for is (are?) the shavings from the aluminum. They can get inside the router and cause problems.
 

ScaleBirdsScott

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My CNC router makes some really nice parts and it's hardly the fanciest or most expensive.

For just one set of ribs, I'd make some kind of 2D templates and use a basic hand router table and accept that there will be a one-time brief shower of aluminum chips which must be disposed of. But If it's a constant airfoil/chord then you only have a few templates to make. And ultimately the cut quality will be as good as you could really expect, and the overall investment is minimal.

If you plan to do a full-blown set of tapered ribs and a bunch of other parts, and have access to original CAD data, considering a CNC router at home as probably becoming on the verge of practical. I've used one to make pretty-much every piece of an all-aluminum plane, and it quickly was worth the cost/setup time just in the one design (There was a lot of making parts for samples, and making stuff for other projects, so it certainly has done more than just the parts for one plane).

Shipping the parts out to a local shop that can do it with a waterjet or router can be done. I think I paid about $120/sheet back in the day for waterjet. Figure out how many times you'll have to do that and roughly what your costs would be for that work. IF it's even 30% of the cost to just buy a CNC router table and you have any hidden desires for your own machine that need an excuse to pull the trigger, it's all the excuse you need.

Waterjet will need some filing/sanding/deburring along the edge, it definitely leaves a grainy crusty edge. Also make absolutely sure they use the right aluminum and that it has plastic or some kind of protective film on, if it doesn't your aluminum will get essentially sandblasted.

Laser parts come out cleeeeean but there can be a latent little toasted edge in places depending on how it's all setup. I've seen parts come back brown almost black along the edges and others with no visible way to tell it was laser-cut at all. Pretty sure it comes down to the exact machine, material, and settings, and so YMMV.

CNC router cut parts will come out sharp but mostly clean. A quick skim along the crisp edges with a 3M abrasive wheel, or a pass or two with a file, or a run along the edge with a deburring tool, or some combo of those, makes what looks like a perfect, hard, machine razor edge into a sort-of sad, underwhelmingly soft edge. But the latter is more what you want for final product.

I've been able to take stuff right off the router and it has a clean enough edge that I can form and work the parts without any deburring at all. Certainly before final fit up and riveting I'd skim the edges, but while crisp, and occasionally quite sharp, the edges are not jagged or rough or generally full of 'getchas' so they can be worked with. Especially with the plastic film on.

But if your part gets loose and rides the bit up, vibrates, or the endmill is not crisp; now you're gonna have some flashing on the edge of your cut if not some straight up jaggy rough edges. Thankfully these nasty cuts are quickly cleaned with the aforementioned tools as if they never happened. Sometimes if the machine is a bit rickety (like mine) you'll end up with the actual edge showing a wavy sort of pattern. That's when you definitely want to run a file or sander across those edges to clean it all down to a single surface.

I feel like my limited experience with a hand router and templates gave very similar sort of results.

Using an auto-nibbler can do quick work. But I would be a bit loathe to do a whole set of ribs that way. A few skin panels cut to shape? Sure. And those shavings are absolutely the worst ones. Give me a mountain of router chips before I deal with the half-crescent moons from the nibbler.
 

cheapracer

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Nobody's mentioned a bandsaw?

Thinking about it, I'm surprised no one has mentioned a plasma cutter.

My tiny plasma, and also tiny dirt cheap compressor, I can pick both up with one hand, well they are just awesome.

The trick is to making templates such as various radius curves, straight edges, and my nest trick, various sized washers with small handles welded on the cut holes with. Just need to first understand the distance from the edge where the cut actually is, and size accordingly. 4mm in my case. You want a 25mm hole, then you need a washer with a 33mm hole in the middle, not rocket science.
 

TFF

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Maule uses a hand router to cut their ribs. Economy of scale. Still cheaper to pay someone to do it manually at the volume they build at. A new method for them would require FAA approval. Certified plane.

Any method comes down to time and money. How fast you want the part made and how much money you have to make it. I have seen people need parts yesterday and are willing to pay. I have seen people spend more in a static jig than building their own CNC machine. I have also seen hand tools and a wood stump. Made correctly, the airplane does not care how. It’s about the fun of building.
 

Monty

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Plasma can work, but the heat affected zone can cause problems. Can also be fiddly to get the kerf to behave. Best to use CNC plasma if you are going to try. One mistake people make all the time is thinking using CNC will save time. It won't. Unless you use the machine, and cad all day every day, you will spend more time trying to learn the software, debug the program, and waste a lot of material in the process....Only makes sense if you are making a lot of parts.

The one exception that no one to my knowledge has exploited is a laser cutter. Not a metal laser-too expensive. Just an inexpensive laser that will cut MDF and masonite. There will be a wood shop or somebody in your community that has one, unless you live out in the middle of nowhere. Even if you do, you can use somebody like Big Blue Saw.

This works more like a printer. Does not require the kind of knowledge most CNC programming/operating requires.

Imagine having all of your rib and bulkhead templates already cut out and shipped to you in a box. You can even engrave the FS and BL station or part number on each piece, and which side is up. Then you just blank out the ribs and bulkheads with a shear or bandsaw, clamp between the laser cut parts, and cut them out using a router table with a flush cut bit. You could also use a hand router, but I prefer the stability and precision of a table. The aluminum parts now are all exact, with no HAZ or other issues.

You can use the router to round off the edge of the laser cut form blocks and hammer the flanges. done.

In my experience making the form blocks is as much or more work than the actual ribs, so this would save an enormous amount of time. The resulting precision would make assembly much easier too.
 

Aerowerx

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I did read one comment about cutting ribs with a hand held router.

You may be tempted to stack several blanks together and do them all at once. But you will then not be able to separate the individual ribs.

I don't know if they actually get welded (seems unlikely to me), but it is more likely to be burs on the edge locking them together.

The cure for this (so I have read) is to put a thin sheet of some other material between the aluminum sheets. Like heavy paper maybe?
 

MadRocketScientist

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I did read one comment about cutting ribs with a hand held router.

You may be tempted to stack several blanks together and do them all at once. But you will then not be able to separate the individual ribs.

I don't know if they actually get welded (seems unlikely to me), but it is more likely to be burs on the edge locking them together.

The cure for this (so I have read) is to put a thin sheet of some other material between the aluminum sheets. Like heavy paper maybe?
If the cutter is really sharp the burr will be minimal, paper tends to be really abrasive on cutters. They might not stick if the PVC sheet mask is left in place until after cutting them?
 
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