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torker
12-23-2006, 01:08 AM
Hey guys! Some of you know that I'm about ready to start up my lil' business full time. Been hording cash for several months for start up.
Had a good friend steer me onto a potentially lucrative deal (end result $300,000 a year). I'm being safe here and got the info for $17,000 contract to start with.
I need to cut 1/8" thick 6061 T-6 sheet into perfectly square 11 3/4"X 11 3/4" squares. There are three secondary ops that are no trouble but cutting and squaring the blanks are what buried the last guy. He contracted out the shearing with less than great results.
I'm thinking of buying a good table saw with a sliding table and sawing the works. First job is 34 sheets of 4X8 sheet cut up into ...1000 pieces.
They where going to get them lazer cut but they need to be welded and I'm not sure that the lazer cut parts can be welded without considerable prep work.
I work with lazer cut steel on a regular basis and we have to grind off the carbon on any piece that needs a critical weld. I can't see alu being any different.
I could build a jig and plasma cut them but I'd have the same problem with welding prep.
The table saw,,,with the right blade...no dross...no cleanup....maybe a bit of a round over on the edges...done deal.
I also could rough cut with the plasma then mill at hi speed with alu roughers but the table saw idea looks better. This is a once a year (or so) deal but I'd spring a few grand for a table saw to do it....reason...the remaining part of the contract would require the same kind of cutting but on a much larger scale.
Any thoughts from the real guys...or anyone else :D
Thanks much!
Russ (feelin rich already :D )

J Tiers
12-23-2006, 01:23 AM
Dunno about carbon on teh laser cuts.... I have had quite a bit of prototype stuff made laser cut, and aside from some discoloration, there was no build-up or extraneous stuff.

The discoloration was basically straw to blue heat treat colors..... not mill scale type stuff, and this was often 11 ga steel.

Aluminum I have not had done

bhjones
12-23-2006, 01:24 AM
I've heard from some people that water jet machines can be troublesome if you need to weld the aluminum parts cut in them (the abrasive inbeding into the stock, fouling welds), but with a need to cut that many parts I'd start making calls to reputable water jet operators and find out if this is the case.

If you go the saw route, make sure you use a cross cut box or something that keeps your fingers away from the blade. Cutting that many parts is going to make a guy dopy after a while.

mochinist
12-23-2006, 01:27 AM
Does waterjetting the aluminum cause a problem with welding like the laser does?

I don't know if you have a lot of waterjets in your area, but here in Phx there is quite a few and thier prices aren't bad. The edge when cut isn't shiny though.

mochinist
12-23-2006, 01:27 AM
damn you guys are fast:rolleyes:

torker
12-23-2006, 01:56 AM
Should have mentioned...he doesn't want water jet cutting. Too many problems with coolant cleanup for final powder coating.

lenord
12-23-2006, 02:35 AM
If I had that job, I would do this:
Call my metal man at metal supermarkets.
He has a giant shear, that I know I can learn to use in a few minutes. I've watched being run. Rent the time on the machine, and the shop. Do the work there. Much easier than using a table saw. If not that, sit there and watch the job myself or even just help.

I'd also look into a deal on the sheets. He could get them for me at a discount for sure.

FWIW
Lenord

Mark Hockett
12-23-2006, 02:43 AM
Russ,
What is the tolerance on the squares? I think the table saw is a good idea. You might have to experiment with blades and belt pulley size to get it to cut properly for extended periods, but that shouldn't be too much of a problem. The question is what kind of accuracy and repeatability would the saw have.
I have cut aluminum on a table saw with good results but it wasn't a part that required close tolerances
A good way to do the job would be a very large gantry CNC mill with a vacuum chuck, but you probably don't have that.
I'm not sure what equipment you have in your shop so itís hard to come up with a solution that fits your situation.

ARFF79
12-23-2006, 03:30 AM
Why from sheet stock? Was it supplied by the customer, or was this what was specified? If it was my job, I would order it in 12" wide strips to start with(easier to handle), and cut it to length with an autofeed saw(bundled of course). A cold saw being the prefered method, bandsaw 2nd. this will give you 2 square edges to start with, if your saw is set up properly. Next slap them in a vise and mill the other 2 edges to size. Finally, break the edges unless the call out prevents this, clean and send them off to the next opereation or the customer.

As to buying a new toy for the job...For modest to large lot production, an autofeed saw with clamping would be a better investment than a table saw with a sliding table in my opinion. It would be more versitle(1-2 pieces as well as hundreds), freeing up your time to do other work while it runs thru the stock and may open up more opportunities for other work that you might nomally pass as too labor intensive. the sliding table saw would only iterest me if I was going to be doing a lot of Al plate and could not get it cut from my supplier.

Evan
12-23-2006, 03:31 AM
That's a job for a power shear. If somebody else didn't do a good job shearing them they either didn't have the right equipment or didn't know what they were doing. There is no reason at all that you couldn't hold .010" tolerances or better with a good shear.

Since you don't have a power shear you are going to be forced to use a method that is either less accurate or much slower (read expensive) or both. That size and thickness of plate is just too much for a stomp shear so that won't do it and that is probably what the other guy tried to use.

As for the use of a saw that all depends on the tolerances and edge finish required. It won't come close to a good job of shearing though.

As for carbon on aluminum that is laser cut, where would it come from? You will have oxide on the cut but then aluminum has oxide on all surfaces. Aluminum doesn't make slag like steel does.

winchman
12-23-2006, 03:47 AM
Cutting aluminum with a plasma machine that uses compressed air is bound to produce some oxide, but what about doing it with inert gas?

Roger

tattoomike68
12-23-2006, 03:47 AM
A good iron worker would shear them up easy. If you dont have an ironworker you need one.

They pay for themselves quick, if you get one in the 100+ ton range you can punch holes up to 1" in steel plate too.

A piranha p90 is a good one.

darryl
12-23-2006, 05:39 AM
I cut aluminum sheet and plate on my table saw all the time. I get a nice, square edge that doesn't have the 'squished' look that a shear gives. (any shearing job that I've seen anyway) I use a skid, which prevents the material being cut from having to drag across the table surface. The skid has a fence which is carefully aligned at 90 degrees to the blade, and a stop which can be clamped to the fence for repeatable cuts. The skid would be used for cross cutting longer pieces to size, and subsequently squaring them. You'd likely be starting by ripping a 4x8 into strips just slightly wider than you want. The skid takes over from there.

It's easy for me to get a cut that's within about 3 thou of being perfectly square over about 10 inches or so, and that's repeatable. I can resize a cut by using a shim of paper between the stop and the material, and that small amount of trim is also repeatable. In other words, I'm saying that the table saw is plenty accuate enough for precision cutting to size and square- this is a 30 year old 8 inch rockwell table saw, not anything expensive.

For me, the table saw is where I cut aluminum (or any other sheet material0 when I need it to be accurate, especially where more than one piece is needed of the same size. A few things I've done to help this- I spent enough time truing the metal guide strip so it fits the tables slots very well without slop- I placed the guide in a table slot, then carefully drilled through the skid into the guide, tapped through both, then placed a screw (countersunk) and lightly tightened. Then did another one, then another, etc. Then the final tightening. The end result is that the guide remains free to slide without binding, since it didn't get off centered at any one fastening point, and actually has no way of going off at any point. There's no play where each countersunk bolt goes. Another thing I did was to spend enough time aligning the fence on the skid so that it cuts square. I went through the same process of drilling, tapping, and countersinking one fastener at a time so that I didn't disturb the alignment of the fence as I attached it. The actual alignment was done using paper shims at one end, and because this fence is about 30 inches long, that gave me the chance to adjust by about 1 thou per foot to get squareness.

The blade was raised through the skid to cut the kerf where it wanted to be, and this kerf goes through the fence as well. It's easy to measure from the side of this cut line when placing the stop. I put extra mounting bolts in the fence on either side of this cut line for added resistance to mis-alignment.

I like the fact that the smaller blade, 8 inch in this case, is stiffer than a larger one would be. I also use a pair of stiffeners with it. It's nice to be able to make a cut, then shave off a couple thou if need be, and see that come off nicely. If I felt to, I would purchase a suitable blade for aluminum, but the results I get with the carbide tipped combination blade are easily good enough to satisfy me, and I'm fairly picky. A suitable blade can only make things better.

For some of the fixturing I made some time ago I drilled holes and pressed pins in, for the 'ultimate' in avoiding misalignment. I haven't done so for this skid, but it wouldn't be a bad idea, especially for the fence. These I would put near to the kerf line, as that is where the fence sees the highest impact forces.

Safety is obviously important. Aluminum can get hot during the cut, so be aware that you might get the urge to let go of a piece while cutting it. Bad news. Also remember that the swarf is nasty. This is probably a case where wearing gloves is better than not.

Sorry for the long post, but one more thing. You'll be making some burrs, especially at the corners, when cutting. For that many pieces, it might be handy to make some grooves in the fence where these burrs can nest and not interfere with the placement of the pieces against the fence. I keep a file handy and knock these off when I need to, but that's an extra step (or two or three) to take for each piece being cut. I would want to just get the cutting over, then de-bur later.

Tin Falcon
12-23-2006, 07:18 AM
Torker:
I second evans opinion. Power shear it will make a 4 ft long cut straight as an arrow quick as a wink. table saw will give more of a Machined finish.
powere shears are a wnderfull thing. It would probly pay you to get pre cut squares ie have the supplier do the cutting.
Tin

DocZ
12-23-2006, 09:31 AM
Being a wood butcher by nature I would third the opinion of a power shear. But if you do wish to use the table saw route I would opt for a different path. The suggestions of Darryl using a cross cut sled are great but for production work on 4x8 panel goods we usually go a different route.
First the panels are loaded into a vertical panel saw (read small footprint small price and easy material handling) The 4x8 sheets would be x cut into 11 3/4 x 4' strips. These would be taken to a miter/radial arm saw newt and be cross cut into the 11 3/4 blanks you require. Yes two machines but less expensive than a great tablesaw and far less in terms of labour and removes the inherent inacuracy and recutting of large sheet goods on a less than production oriented "table saw". You will need to tune both the machines from runout square etc but this is the case with any op. Get a very good non ferrous blade and use a blade stiffner with it.
I still like the power shear idea better
Just my one cent worth
Cheers
Z

bob308
12-23-2006, 09:35 AM
i would go with the 12" bar idea . would be easier to handle and only one cut per part.

WJHartson
12-23-2006, 10:14 AM
Russ, in the aluminum rolling mill where I worked we sheared all sheet and sawed all plate, .250" and thicker, that want to customers. The saw swarf can be a problem when you saw aluminum and you should use a flood coolent system if you are going to do any volume of cuts. Our saws traveled over the plate on a rail system and the plate was held down by vacuum. The blades were carbide tipped.

Joe

QSIMDO
12-23-2006, 10:20 AM
How about a punch press?
With good dies you'd whack those plates out in no time with no secondary ops (again-good dies) and then be flexible enough to bid the next blanking job.
http://cgi.ebay.com/NICE-ROUSSELLE-10-TON-OBI-PUNCH-PRESS-A1_W0QQitemZ130061488089QQihZ003QQcategoryZ31372QQ rdZ1QQcmdZViewItem
Make some money back on scrap too.

john hobdeclipe
12-23-2006, 10:33 AM
What kind of tolerances do you need to hold?

Your Old Dog
12-23-2006, 10:59 AM
Any thoughts from the real guys...or anyone else :D
(feelin rich already :D )

Torker, put me down in the "or anyone else" category.

Actually I'd do as Lenord suggest and farm it out "BUT" I would find out from the customer what the accuracy has to be and then make that a specification. Anything that don't meat spec you don't pay for. You might advise your customer that the more critical he gets on spec's the more expensive it cost to do. Extreme accuracy should have a great bearing on price.

fishfrnzy
12-23-2006, 12:12 PM
At the metal supply house I worked at 10 years ago we used a precision aluminum plate saw to cut to tols of +/- .005 for L, W and square was stanard and done in large prodution work. Worked out to about .20 per lb in a competive market. This would be .35 - .40 per piece if the place that supplys your sheet can do it. Blade and motor are above the metal.

You could saw on table saw yourself and there are several good sugggestions above on set up but the saw will throw chips in every direction about 10 feet. Gotta protect the motor as well as any others in the area from the chips. The hottest ones like to find their way into your gloves and clothing. Make sure you secure the work for saftey.

We also sheared alot of material at this place, but it would be better to find out if the customers objection was the sheared edge as it has the break marks and the pinched ends typical of steel. Pinches top of sheet on the first cut and bottom of sheet on second cut. Shear tends to cut hafway though material and tear through the rest. Should be able to get to +/- .010 with the right equipment.

Laser cutting aluminum fairly new but I have several customers that do it. It is usually done with nitrogen so the cut edge should not be oxidized but it will leave a fuzz burr on the bottom about .010-.020 in height that will have to be removed. I think one of my custs said that their 4000 watt laser would cut at about 200 IPM but the hourly rate on lasers like this is high as it is a
$ 600,000 dollar machine.

Punch press to do whole part with other operations done at same time is also good idea but initial tool will be a little expensive but will make one part with one hit, gets cheap in production. Would be best to get sheets sheared to 11.75 first and cut to length and do holes with press.

torker
12-23-2006, 12:18 PM
I use a 12' power shear at work all the time. It's the best machine in the country...not saying a whole lot. It all depends on how much they beat it up the day before.
We shear a lot of 1/2" thick mild steel plate on it and it can get out of adjustment after that.
I've sheared alu on it and I don't like the squished and snapped off look.
I'm going to look at a table saw with a big honkin sliding table on it today.
I've cut thousands on cupboard doors on these and they are very accurate.
I'll cut a few samples with my plasma cutter and show you the dross it leaves.
Russ

torker
12-23-2006, 12:29 PM
One more thing...the alu plate needs to have the sticky paper backing on it...both sides, throughout the whole operation. I'm thinkin it'd be a melted mess using a plasma cutter.

Rustybolt
12-23-2006, 12:35 PM
I agree with the table saw idea as far as accuracy goes. Another method would be to mill them out on a router table.

Mcgyver
12-23-2006, 01:07 PM
what is perfectly square? is there a tolerance? I haven't cut AL with a table saw, but lots do - interesting some to the problems guys have posted about. A good sliding table would work to a couple of thou, at least the good ones, have you a sliding table saw? a good one (ind or high amateur like a Felder) might end up being the most expensive piece of equipment in the shop. still a shear sounds so much faster, less mess. maybe rough them out then with a shear setup with stops and a very accurate guide finish cut?

for that much metal, go up stream in the supply chain. Metal supermarkets is more MRO, and they don't have the margins. you will probably meet minimum volumes to order from samual and sons or Russel metals etc. those are billion dollar distributors operating all over NA but there are many more. for sure shop around and get quotes. tell them your annual expected volumes. I've done work in the service centre industry and it is bizarre how pricing is done. priced based on who you talk to, what kind of month they are having, what they paid for it, current market and what your zodiac sign is. do shop around a lot, there is huge variance.

also, when quantities get really big, remember sheet stock comes in coils and the service centre cuts it into 4x8 sheets. if you need enough they'll just slit a coil to width, ie 12". for that matter the service centre would deliver slightly over sized squares, then with shear accurately set up and jigged, you do the final cut - probably how I'd go at it.

BadDog
12-23-2006, 02:26 PM
Obviously some great ideas, and I didn't read it all, but something that just occurred to me if you do have to size them in house. Depending on tolerance, some variation of this might work out?

Get them rough cut somewhere (or in house) at some reasonable oversize in both dimensions. Maybe 0.050 or so? Maybe less if depending on variance?

Then setup to do 2 ops at once on a mill. Set 2 fixtures side by side. The first that locates the back wall and one side square with front to back dim at something like +0.025. The second fixture is the same but with the back fence at final size. The follow a machining pattern, 2 ops at a pass on the power feed, that roughly follows the block squaring process in 2D.

Again, depending on how much flexibility and tooling you have, you could maybe gang mill it. Either stacking several as above on a vertical mill, or stack them and cut both parallel sides at the same time on a horizontal mill. Horizontal would knock them out pretty fast with a nice fixture to make setup of maybe 10 at a time go quickly, and then locate 90* for the second pass.

Being as I barely rank "newbie HSM" status, I didn't reply sooner, but this is what occured to me...

Your Old Dog
12-23-2006, 04:20 PM
Obviously some great ideas, and I didn't read it all, but something that just occurred to me if you do have to size them in house. Depending on tolerance, some variation of this might work out?

Get them rough cut somewhere (or in house) at some reasonable oversize in both dimensions. Maybe 0.050 or so? Maybe less if depending on variance?

Then setup to do 2 ops at once on a mill. Set 2 fixtures side by side. The first that locates the back wall and one side square with front to back dim at something like +0.025. The second fixture is the same but with the back fence at final size. The follow a machining pattern, 2 ops at a pass on the power feed, that roughly follows the block squaring process in 2D.

Again, depending on how much flexibility and tooling you have, you could maybe gang mill it. Either stacking several as above on a vertical mill, or stack them and cut both parallel sides at the same time on a horizontal mill. Horizontal would knock them out pretty fast with a nice fixture to make setup of maybe 10 at a time go quickly, and then locate 90* for the second pass.

Being as I barely rank "newbie HSM" status, I didn't reply sooner, but this is what occured to me...

He can do that pretty easily as he's going to have a ton of scrap. With an 1/8" curf times all that cutting he ain't gonna come out even so scrap won't be in short supply. I think the press is still his best bet. He may have to explain the situation to the client and see how he wants to proceed. Each 4x8 sheet will only net him 24 squares of 12" square if he does not sheer instead of the 32 pieces anticipated.

But, as they say, that's just me talkin :D

sandman2234
12-23-2006, 06:31 PM
I can see it now, "Aluminum Drops from a friends shop"...Shipped to your door from the frozen north.
I will be waiting, and wondering.
David from jax

DR
12-23-2006, 08:58 PM
Before you get too far into this, call one of the larger suppliers of aluminum. They have plate saws that'll hold .005"+/-. Your order is big enough to get their attention.

Shearing is another option if the customer will allow it. Shared plate tends to have a rolled edge which is very seldom exactly square.

A number of times I've ordered pre-cut pieces of aluminum. In a couple of instances the pre-cut parts were less than I was quoted for the raw material, I know that doesn't seem to make any sense, but that's the way they billed me.

torker
12-23-2006, 10:02 PM
He can do that pretty easily as he's going to have a ton of scrap. With an 1/8" curf times all that cutting he ain't gonna come out even so scrap won't be in short supply. I think the press is still his best bet. He may have to explain the situation to the client and see how he wants to proceed. Each 4x8 sheet will only net him 24 squares of 12" square if he does not sheer instead of the 32 pieces anticipated.

But, as they say, that's just me talkin :D
YOD...you didn't read my initial post huh? The squares are 11 3/4" X 11 3/4".
I'd still get 32 pieces out of a sheet.
Some good ideas here...as usual! I'm going to shop around some more to see if someone can supply the squares to the right tolerance.
BTW...these don't have to "perfect" Just a whole lot better than he has been getting. These are doors that have to fit into a box...so they have to look square and they don't have a "right side up"....meaning that they can go in either of two ways. The holes for the screws have to line up no matter if it upside down or right side up...lol!
Russ

madman
12-23-2006, 11:09 PM
A cnc equipped backstop shear. Set it up and measure the first part and stay ther and measure every 10 or so then 25 or so . If concistent tell the shear guy see yeah later and theres a little xtra foir you (case beer) if you do me anice job.