High speed machining aluminum... An open discussion. - Page 2
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  1. #21
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    Quote Originally Posted by DavidScott View Post
    I am doing more and more aluminum plates that have to be machined on all surfaces but I get to put a radius on the top, my design. This allows me to reduce the wasted material to a bare minimum but I only get to hold onto .03" to .05" of the part. I despise any waste and the quantities are in the thousands a year so any savings will add up, my designs so as long as they sell I will be making them. It's been a long time coming but I just made a small batch of steel wedge clamps and stops with teeth .015" apart to use in my fixtures. I have found that I only need to bite into the aluminum about .001"-.002" for it to hold. The difference between a smooth clamping surface and one with teeth is AMAZING!!!! So nice to go from babying the thing for fear the parts will pull out of the fixture to not giving it a thought cause they are not going to move, period!
    How are you holding on .001-.002 of material without launching the parts?

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  3. #22
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    Quote Originally Posted by Shawnrs View Post
    How are you holding on .001-.002 of material without launching the parts?
    That's just the depth of the dents his steel wedges are making.

    Regards.

    Mike

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    Quote Originally Posted by BRIAN.T View Post
    Don't sell yourself short, that's a hell of a chip you're making. Is this cat40?
    Oops, I meant 150ipm, not 300! I do not know where my head was when I wrote that out.

    Yes, BT/Cat 40 machines.

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    I have been making a bunch of fairly large aluminum parts, all 6061 bar stock. Nothing has been kicked out of a vise yet, although I have had a few parts that lifted several hundredths of an inch because I clamped them on the bandsaw cut sides instead of the extruded sides to get more into the machine with my 4 vise layout.

    More recently I have been doing blocky parts, like 6x6x7" and 4x6x8" with lots of material removal and minimal setups for accuracy. I try to do most of the removal with a 3/4-2.25" 3 flute Zrn rougher endmill in a dual contact side lock. 0.2 stepover, 120 ipm, 2.2" DOC seems smooth and quiet, and the long distribution of heat being generated allows dry cuts at high MMR. I am always paranoid of parts lifting since I clamp smooth surfaces in smooth vises. I want to push my machine more but can't risk spindle damage, so I find myself limiting my cuts to around 15 horsepower most of the time.

    It's scary how profiling cuts, like those in HSM, can lift parts so easily. If there is no floor under the cutter, these lifting forces are unopposed and result in a positive feedback loop. If there is a floor under the cutter, the cutter can only pull the part up at a limited rate because the bottom of the endmill can only ramp at an angle equal to the bottom rake.

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  8. #25
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    GD, have you tried dovetailed blanks? I do this for blanks that would bow if I grab them too hard with Talon Grips. .06" deep cut with a Dexi 60* dovetail cutter -- 10o - 60o Dexi-Dovetails | AB Tools, Inc. . Mating jaws are made with the same cutter.

    Blanks thus held cannot lift at all no matter what, even with light vise pressure.

    Regards.

    Mike

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    I've considered putting dovetails into some of my parts specifically for workholding, but since most of my parts are top and bottom 2 operations total, adding a dovetail doesn't make sense for most of them. It would be awesome for 5 axis work though.

    I like the idea of the vise/screw clamping forces forming their own tiny dovetails in a minimal amount of material without adding an extra operation.

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    Here's my go-to figures for ally (6082-T6/2014-T6)
    (Mastercam Trocoidal Optirough HS toolpath)

    BBT30 machine
    MA Ford Series 134 (3flute knuckle form) 14mm diameter 55mm stickout
    S10000 F5000 (@20mm deep & 30% stepover - T/P RADIUS 3mm)
    Toolholder - stubby single screw sidelock (Maritool - 12mm - 50 modified to 14mm as Frank didn't make 14mm at the time (he does now))

    BT40 machine
    MA Ford Series 134 (3flute knuckle form) 14mm diameter 55mm stickout
    S10000 F7500 (@20mm deep & 30% stepover - T/P RADIUS 3mm)

    I standardised in the shop on 14mm as it was the best compromise for the #30 machines - 12mm is a bit small sometimes, and 16mm would sound too "harsh" - the radial gap between each tooth is obviously larger as the diameter of the cutter increases, and on the #30 machines, the 16mm sounds more "hammering" (noisy).

    This cutter will run a lot harder until it breaks - a friend tested on his Makino and here's his results:-
    1/2 Knuckle (MAFord Type 134) 30% stepover 200% LOC 400IPM (10 m/min) (This is a 14kRPM spindle - tool runs at 800IPM but will occasionally break)

    Also workholding - again, we standardised by machining all vice hardjaws 3mm deep x 2mm wide steps and never had any lifting.
    All 4th axis rotaries had Lang vices as standard - with the serrated jaws - and these work exceptionally well.
    We'd even hold stock steel (MS/Stainless) with no pre-stamped serrations, with no issues.

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    As to the post a few above where you get saw cut blanks almost to size.....both shops ive worked at have this mentality. the people cutting the material should spec sizes.

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    Roughing 7000 series with 25mm dia ripper with 40mm loc 3 flute endmill from Walter
    HSK80F 33,000 rpm
    1.1" deep at 594 ipm
    full slot
    Working holding is very rigid and plenty of horsepower 174.

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    Quote Originally Posted by jowens909 View Post
    Roughing 7000 series with 25mm dia ripper with 40mm loc 3 flute endmill from Walter
    HSK80F 33,000 rpm
    1.1" deep at 594 ipm
    full slot
    Working holding is very rigid and plenty of horsepower 174.
    I'll try that on my Speedio this afternoon .

    That's moving right along. You are moving 1 CF of material every 3 minutes.

    Regards.

    Mike

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    I know the Speedio wouldn't run those parameters. But you would be surprised how well the Walter ripper tools cut with lower rpm machines.

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    I'll add to the workholding side being the limiting factor in my experience. Probably 95% of my work is first op in either Talon Grips or 5th axis vise with the serrated jaws. Mitee bite seems to hold pretty well, but I've launched quite a few parts from the 5th axis vise even with it torqued to the max rating. In almost every case it's been using a HSM adaptive path and it's happened as the tool rounded a corner. The way it calculates engagement it digs deeper as it comes around the corner and I've found that if there's any question in the workholding it will bite and rip it out. Also has usually been with slightly taller parts so there's more moment arm. It wasn't with particularly aggressive parameters after reading what folks are running here, generally 1/2" powder metal rougher, 2xD depth and 10-15% radial, can't recall the exact speed and feed right now but they were on the mellower side. I've been thinking about making jaws for the 5th axis that have a little more bite.

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    The only time I try to find the limit is when I'm doing production work.

    You can run 100% faster and it saves what? 2 minutes? Sure, it looks cool but why risk tossing a part or breaking a tool?

    Your initial numbers don't look so bad.

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  20. #34
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    I've also noticed these HSM path don't deal with corners very well. Most stock you would put in a vise has 90 degree corners, and HSM paths round them out too hard on the first pass, it seems like the path will briefly double the load and cutter engagement. To avoid this I sometimes have to use a separate tool path to round the corners before the HSM path, which is annoying and wastes time.

    And damn, that jowens guy above is plowing almost 11 cubic inches per second with whatever machine that is. That's a 3d metal eraser.

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    Quote Originally Posted by Generic Default View Post
    I've also noticed these HSM path don't deal with corners very well. Most stock you would put in a vise has 90 degree corners, and HSM paths round them out too hard on the first pass, it seems like the path will briefly double the load and cutter engagement. To avoid this I sometimes have to use a separate tool path to round the corners before the HSM path, which is annoying and wastes time.

    And damn, that jowens guy above is plowing almost 11 cubic inches per second with whatever machine that is. That's a 3d metal eraser.
    Early mastercam wasn't very smart when optirough was introduced.
    So the trick was to offset the tool an amount where the path would cut air around the part but cut/clip the corners.
    Or hand edit the NC code putting in a slower feed for 1st cut.
    Later versions handle this much better now to the extent that the problem has gone.
    Use a stockmodel as 1st op then the toolpath is stock aware.

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    I'm still exploring the boundaries with my new Brother. I know about tool pullout now 🙄. So far, work holding has been ok. I have mighty bite jaws but made my own "teeth" because i got tired of fiddling with the individual ones, and they want $$ for extras. I made one continuous tooth that spans the full length of the 8" jaw. Now I'm not constantly moving the little teeth around to fit the stock. I made the full length from a scrap piece of SS. I only do aluminum though. sure is nice to not have to fiddle with the little screws.

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    We did the opposite added material to accommodate location/hold bolts/pins. Bolted it down to a patterned hole grid plate machined on the machine itself. Only pick up the zeros after a PM, twice a year is done to the machine. This is all modeled in a post CAM which programs the machine tool. This allows the parts to be moved from machine to machine, provided the work envelope is proper and parts are secured until they are de-tabbed. I've designated a commonly used core tools in some of the tool sockets and have done 350 imp at 10K rpm before. Yet the idea of high speed machining is lost sometimes?

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    haas dm2 - aluminum
    1/2" 3 flute yg1
    15k rpm
    1.25 doc
    20% step over
    405 ipm feed
    using a shunk hydraulic holder

    haas dm2 - 4140 steel (annealed)
    3/8" 4 flute Niagara variable helix (.02 radius)
    8967 rpm
    1.25 doc
    5% step over
    249 ipm feed
    using a shunk hydraulic holder


    most common roughing speeds/feeds used in the shop, if the doc is less, we typically leave the feedrate the same anyways.

  25. #39
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    Quote Originally Posted by Finegrain View Post
    That's just the depth of the dents his steel wedges are making.

    Regards.

    Mike
    That doesn't seem like you are holding out much. we use mitee bite pitbulls knife edge and there have been times we have moved a part out of a fixture. This could be an issues with undersize parts or the operator didn't tighten the part enough.

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    I drive my clamp screws down with a torque controlled pneumatic screwdriver. Real fast and dead repeatable.

    How much clamping range do the different Pitbulls have?


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