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Laser cut 6061-T6 ? or use a router ???

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flywheel1935

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Hi Guys just need a basic lead ref cutting sheet 6061-T6 (For a wing spar) is laser cutting or routing the best way or waterjet , as these are the options open to me from local subcontractors ???? spar length a 13 ft long
 
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Hot Wings

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What ever is the cheapest - provided it can get done with a lead time that works for you.

I won't laser cut 4130 but the HAZ on 6061 shouldn't cause you any problems.
 

Dana

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All the water jet cut aluminum parts I've seen have unacceptably rough edges.
 

flywheel1935

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Hi guys, that's the issue I'm trying to resolve, ie rough edges, even considered bandsaw then deburr+polish. but time consuming and the alloy supplier can offer the above cutting options, sheet thickness about 0.060" ( 1.5mm )
 

Norm Langlois

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I cut my project with a carbide on a circular saw. The material was .050 6061-T6
a file and deburr + polish would be reasonable . Most all cutting methods would leave micro groves to a degree. That is your problem even a polish leaves micro groves. the smaller the better. Water jet has very low distortion , If you are going to polish that would polish up fine I would think. The only water jet I dealt with was mild steel . The parts were accurate and easy to work with laser or plasma is a nasty edge, I would avoid,that choice on aluminum. Though aluminum shows little distortion from heat . A burned edge is still changed by the process .
As a industrial fabricator machinist, Machine welder. I have general metal working skill. I always chose to avoid welding aluminum and sparing heat even when needed to form difficult bends to my aluminum Ultra light project. High temp heat changes the composition at the heated zone.
 
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flywheel1935

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I cut my project with a carbide on a circular saw. The material was .050 6061-T6
a file and deburr + polish would be reasonable . Most all cutting methods would leave micro groves to a degree. That is your problem even a polish leaves micro groves. the smaller the better. Water jet has very low distortion , If you are going to polish that would polish up fine I would think. The only water jet I dealt with was mild steel . The parts were accurate and easy to work with laser or plasma is a nasty edge, I would avoid,that choice on aluminum. Though aluminum shows little distortion from heat . A burned edge is still changed by the process .
As a industrial fabricator machinist, Machine welder. I have general metal working skill. I always chose to avoid welding aluminum and sparing heat even when needed to form difficult bends to my aluminum Ultra light project. High temp heat changes the composition at the heated zone.
Saw is an option, got one in the workshop, just change blade ???
 

TFF

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How many are you going to make? Time is relative that a band saw might take technically longer to work, but you can do it now and be weeks ahead of getting in queue for a milling machine. Shear?
 

Jay Kempf

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Laser edges have a pretty significant heat effected zone. Not sure you want to go there for anything critical like a spar. Water jet isn't as bad as people make it out to be a little light sanding/polishing and you have nice parts. No heat effected zone. Cheaper and real easy to program, just a DXF. Router really nice if you have one yourself and you know what you are doing with aluminum takes some experimenting. Harder to learn to program. Probably more expensive than water jet.
 

pictsidhe

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I use a handheld circular saw to cut straight lines in sheet aluminium, with a rigid guide rail clamped on. Look for a fine tooth blade with 0 or negative rake and you can get a pretty nice edge. Screwfix supplied my last one in the UK.

If you want template cut stuff like a rib, a router works surprisingly well. Make sure you up cut and not too deep, or it can get away from you. Keep the speed down, or you'll get aluminium stuck to the bit. I usually spray WD40 or similar on the sheet to help lube a bit. Best to rough it first with a circular or band saw.
 

Pops

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Ribs-- Cut Little oversize with a 4' stomp sear. Mark with my alum pattern with 3/16" dia holes for center of lighting holes and rib locating holes for the wooden form block. After marking outline, trim with shears and file smooth and polish edges with 220. Clamp in form blocks and bend over with a rubber mallet and remove and flute between rivets locations to straighten. Cut out lighting holes. About 25 minutes for a main Bearhawk wing rib including cutting the lighting holes out .
 

flywheel1935

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Ribs-- Cut Little oversize with a 4' stomp sear. Lay my alum pattern with 3/16" dia holes for center of lighting holes and rib locating holes for the wooden form block. Make outline, trim with shears and file smooth and polish edges with 220. Clamp in form blocks and bend over with a rubber mallet and remove and flute between rivets locations to straighten. About 25 minutes for a main Bearhawk wing rib including cutting the lighting holes out .
Have you got any pics ??? looking at a Zenith 701 style wing, with D-Box in alloy, but fabric covered, and internal bracing wires/tubes
 

rv7charlie

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FWIW, I've cut a fair quantity of ~0.050" aluminum on a table saw with a relatively sharp 10" dia 80 tooth carbide blade (finish cut for wood). Carbide wood cutting blades can't tell that they're cutting aluminum. Hardest thing is keeping the aluminum from hanging up under the edge of the rip fence, if there's no backer under the aluminum, and physically guiding it through the saw from one end to the other without letting it move away from the fence at either end. A helper...helps. If the path through the saw is smooth, the finished edge will be ~the same quality as one sheared on a punch shear (referenced to the RV-7 parts I've cleaned up and installed).

Do wear long sleeves, gloves, a cap, and eye protection. And make sure the rip fence is *perfectly* parallel to the blade (adjustable on any quality saw).

The spars are only a few cuts. If I were spending money on commercial processing, it would be for CNC routed (or other process) ribs. Recover some of the labor cost through less aluminum waste.
 

Pops

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Have you got any pics ??? looking at a Zenith 701 style wing, with D-Box in alloy, but fabric covered, and internal bracing wires/tubes
Picture one one 4 seat Bearhawk wing kit that I built, I built two wing kits.



DSCF0019 (2).JPG
 

GeeZee

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I cut a Sonex horizontal stabilizer spar with my router using a 1/2” carbide bit. The “spar“ is a pretty hefty (I think) 2” 6061-T6 angle that’s probably an eighth inch thick. I needed to cut one leg off (Leaving a center portion that was still the full angle) It did a great job. I made two passes with the same setup. The second pass left almost a mirror smooth surface. It’s been a few years but I think I cut it close, within about a quarter inch then used the router.
 

ScaleBirdsScott

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Good quality CNC router table with carbide running high RPM will give an absolutely awesome edge. A home-shop maker-grade CNC router like I run still will give an edge that is quite nice, but there can be some chatter marks, which come out with a file and/or a 3M abrasive wheel, but basically puts you in the same boat as waterjet.

I feel like regardless of process, there are basic machines and high end machines and a high end machine of any process is likely to give better results than the low end of any other process. As in, a really good laser will give so little of a HAZ that it's basically negligable; while a low quality "budget" laser cutter (that still cost the shop probably 125k USD) probably leaves the edges a little more brown and crispy. A really really nice waterjet designed to cut detail parts out of thin sheet would give just amazing results I'm sure, while a heavy duty industrial waterjet will probably give a finish on par with most plasma cutters (except for the burning) and also ruin any finish on your sheet you'd hoped to preserve with the backblast.

So it all depends. My logical thinking says, bet towards CNC router methods as a good commercial grade router table is a lot cheaper than the good commercial grade lasers and waterjets out there, so it's more likely that you'll find someone with a good-enough router, than it is you'll find vendors rocking the best lasers or water tables that could hope to get better results.

Or do it by hand with a saw and some fixtures and setup? I guess that works too if you have some way to, say, rivet/cleco a fence to the aluminum outside of where you plan to cut. There's no room for freehanding this stuff so if you don't have a dead-nuts guide and you aren't so good with the saw that it was just the obvious choice to make already, I wouldn't try the saw for a 12 foot long straight edge.
 

flywheel1935

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Thanks guys, still amazed at the skills that are still out there, Pops love the pic, Plan is to develop the LMA into a Kitfox type STOL kit, will be making an alloy wing, then later a CrMo Airframe, so bits can be swapped around, Found some guys on YT recently fitting Cessna 172 wings onto Super Cubs, they fly really well apparently !!! Hope to start cutting metal over the winter, when it's too cold to bond the current airframe.
 

Jay Kempf

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When I said Heat Affected Zone I didn't mean cosmetics. Aluminum is funny in that it will harden like crazy or fully anneal depending on the heat applied. Embrittlement is a big issue if forms as it can cause cracking upon any strain and then propagation. You really want to make sure you don't have any of that going on around highly loaded edges. Can be dealt with but laser would not be my choice for anything my life depended on that was going to have the potential for cracks starting from edges and heading toward holes. Have used all kinds of laser cut parts over the years in all kinds of materials. Have never used a laser part for an airplane. I am sure there are people who have. Lasers used to be so much more expensive than punch presses. Now not so much. Water jet is always the lowest quote when I do prototype work for customers. Being able to lay a whole sheet out and they can just cut it without the engineering and programming charges always wins.
 

flywheel1935

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When I said Heat Affected Zone I didn't mean cosmetics. Aluminum is funny in that it will harden like crazy or fully anneal depending on the heat applied. Embrittlement is a big issue if forms as it can cause cracking upon any strain and then propagation. You really want to make sure you don't have any of that going on around highly loaded edges. Can be dealt with but laser would not be my choice for anything my life depended on that was going to have the potential for cracks starting from edges and heading toward holes. Have used all kinds of laser cut parts over the years in all kinds of materials. Have never used a laser part for an airplane. I am sure there are people who have. Lasers used to be so much more expensive than punch presses. Now not so much. Water jet is always the lowest quote when I do prototype work for customers. Being able to lay a whole sheet out and they can just cut it without the engineering and programming charges always wins.
Ive dismissed laser because of HAZ, its more about trimming a 13ft x 4ft sheet into the spar shear webs, top and bottom caps will be riveted and bonded alloy angle.
 
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