Need a shear for cutting 3" aluminum bar - Page 2
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  1. #21
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    The cast bar is about 30 inches off the floor and the shear will cut the pieces and they will drop onto a chain conveyor and be transferred away from the bar alignment at 90 degrees (angle not temperature) . . .

    The reciprocating carriage is easy, the least of my concerns. I am more concerned about the shear. Needs to be fast, light weight (as in less than 1000 lbs) and dead reliable. (And did I mention cheap?)

    Space around the alignment of the bar can is limited by the floor beneath, and ancillary equipment 3 feet behind, but essentially unlimited above and out in front.

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    Oi! Cheap, fast, reliable, and with a nice pine scent? Dang, you want everything...

    Is the conveyor TBD, or is in place already? Low, to allow space for an enclosed cutting mechanism above it? Wide, or sheetmetal chutes to guide cut parts down to the conveyor?

    The weight shouldn't be a problem, at worst you can have hydraulics for the power source and guided hoses going to a stationary pump. Are you planning on a ballscrew for fly motion, or a chain, or ? What's the number of cuts over the lifetime for this thing?

  3. #23
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    Thinking out loud
    A rolling action Is that possible Like in a packing machine where they seal the bags
    No need for a reciprocating carriage then
    Right now I cannot envision how those rolerblades should look like though
    Perhaps even impossible

    Peter

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    Controlled Automation designs and makes their own shears and punches, they could (likely) get you that cycle time with a servo over hydraulic unit, or their normal mo to go fast - massive hydraulic flow. ( Controlled Automation) tonnage would be minimal, blades really should last a long time (hot AL is super soft).
    Or find a nazel/chambersburg 3 to 4 B with single stroke valving, hard to beat air for shear speed. use exhaust air to cool blades and Al as it is cutting, the shear will get the local area up to the self destruction temperature?

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    Might be a long shot, but have you looked at or researched roll form dies/operations? One job we had two roll form lines that the last die in operation (one pre form, 2 after form) cut the parts to length and pierced 2-4 holes. Might give you some ideas..?

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    Genso's KAJ800/1000 32" hydraulic aligator shear is rated @ 345 tons and will cut 3.0"/3.5" mild steel round.

    They have smaller "probably lower cost" units that would probably work on hot aluminum, I haven't done the math on required tonnage. They're rated in between 1"-2" mild steel round, multiple models. Genso doesn't list prices on these gator shears, can only assume they bring a hefty price tag.

    I seen some relatively low cost bus bar shears that are small, but they only go up to 8" from what they show. Something like that, but bigger could be made to do the job and not take up much space.

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    I would contact Cash... he makes the blades for all manner or shears and might know who makes just the thing. I also have a feeling hydraulics are too slow, but maybe not.

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    Even if you can't get 'in the line' early enough, or it's problematic to cut it while it's hotter/easier, could you install a rod or segmenter to squish it down a bit, leaving the actual cutter a much thinner cross-section of material to cut? Think a rotating hamster wheel with round bar crosspieces spaced every X-inches, pinching the aluminum instead of cutting through. Things can still move in a line as a continuous casting, so no modifications required between 'segmenter' and 'cutter'. Lead ingots are often seen this way...

    If this has been covered above, but referenced by a name I'm not familiar with, I'll be quiet and go back to my Cheerios...

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    I think the weight and speed won't be a problem. My greatest concern would be keeping the oil cool. That is a hot environment and there will be lots of intimate contact between 800F aluminum and the shear blades. If an alligator shear configuration is used, heat transfer back to the cylinder will be significant. Metals for the shear frame and blades can handle 800F easily enough.

    Hydraulic systems that must have a service temperature above about 180F start getting stupid expensive. Typically cylinders have dead headed fluid. I think you will need cylinder valving at the cylinder to allow bypass to the tank and fresh oil each stroke at a minimum.

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    I am in contact with a shear manufacturer now who is working up a quote - they are not concerned about the heat or the size -

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    Quote Originally Posted by motion guru View Post
    I am in contact with a shear manufacturer now who is working up a quote - they are not concerned about the heat or the size -
    Aw shoot !

    We just about had it all designed up here.
    Was going to go with either liquid oxygen, or high explosives...

    Now you done and took all the fun out if it....

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    Quote Originally Posted by digger doug View Post
    Aw shoot !

    We just about had it all designed up here.
    Was going to go with either liquid oxygen, or high explosives...

    Now you done and took all the fun out if it....
    Yeah, I followed some of the links and those gave me better search key words which led me to a shear manufacturer that looked like they did customs and I contacted them. All good . . . the best link was to the sloppy forklift driver spilling molten aluminum which had a chain reaction of dumping the whole furnace on the floor. You can’t make this stuff up.

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    Quote Originally Posted by motion guru View Post
    Yeah, I followed some of the links and those gave me better search key words which led me to a shear manufacturer that looked like they did customs and I contacted them. All good . . . the best link was to the sloppy forklift driver spilling molten aluminum which had a chain reaction of dumping the whole furnace on the floor. You can’t make this stuff up.
    Mr. Murphy was playing at the top of his game on that one.

  15. #34
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    Quote Originally Posted by Peter from Holland View Post
    Thinking out loud
    A rolling action Is that possible Like in a packing machine where they seal the bags
    No need for a reciprocating carriage then
    Right now I cannot envision how those rolerblades should look like though
    Perhaps even impossible

    Peter
    Keep it simple.
    A upper and lower spinning drum above and bellow the conveyor. They are running at a surface speed slightly faster than the conveyor. The lower drum acts as a anvil. The upper drum has a 3" long tungsten carbide insert blade which pinches the extrusion. The slightly higher drum speed is needed to compensate for the drum slowdown when the blade pinches the bar and to prevent the extrusion from being pushed backward by the displaced material as the blade enters the bar. The drums are geared together and driven by a single servo motor. There is a large flywheel on the upper drum to store energy for the bar pinch and minimize the drum slowdown. The drum and flywheel spin back up to speed during the portion of the cycle when the blade is clear.
    The cut bar length determines the drum diameter. If the cut bar will be too long for a realistic drum diameter, the single blade can be replaced with two or more blades installed on the drum.
    The drum may also have a left and right side guide to funnel the extrusion into the center of the drum.

    The power requirements for the pinch can be reduced by using 1 1/2" projecting blades on both the upper and lower drums. There is less material volume being displaced.

    An alternative to the above operation would be to use the same two drums each with a cutoff blade but have the blade synchronization offset by a few degrees and have the blades slightly longer so that they overlap when meshing. This would be closer to a shearing process rather than a open die forging process.
    Last edited by Robert R; 08-16-2019 at 10:21 AM.

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    There is a simple valving arrangement that applies full pressure to both sides of the cylinder at once to rapidly extend it. I would configure two synchronized cylinders to pull an upper shear blade down into the metal. Valving is super simple, since you only need to valve one side of the cylinders rather than both. Basically on the retract it acts like a regular cylinder but on the extend it behaves like a cylinder with a bore diameter equal to that of the shaft. It can get some crazy high speeds at lower forces.

    But I know a lot more about hydraulics than I do about shears.

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    Default Impact cutoff shear

    The old school method is to use a impact cutoff machine. This consists, in this instance, of a pair of die blocks with a 3" X 3" opening which act as shears. The die blocks are forced to shear by two rotating cam wheels spinning at constant speed. The cutoff is engaged by two wedges which are pushed between the cam wheels and the die blocks by a pneumatic cylinder. The wedges fill the gap between the cams and the blocks. Operating speeds are up to 300 cuts/minute The machine produces square edges without burrs.

    I am unable to upload the machine diagram. However you can see the original diagram in volume 14 page 719 , 9'th edition of the Metals Handbook "FORMING AND
    FORGING".

    The impact shear would be mounted on the flying cutoff carriage and would need electrical cables for the two cam wheel motors,a pneumatic line for the wedge piston, a interlock signal cable and maybe a lubrication line. The machine will be more compact than a conventional shear.

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  19. #37
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    Quote Originally Posted by Robert R View Post
    The old school method is to use a impact cutoff machine. This consists, in this instance, of a pair of die blocks with a 3" X 3" opening which act as shears. The die blocks are forced to shear by two rotating cam wheels spinning at constant speed. The cutoff is engaged by two wedges which are pushed between the cam wheels and the die blocks by a pneumatic cylinder. The wedges fill the gap between the cams and the blocks. Operating speeds are up to 300 cuts/minute The machine produces square edges without burrs.

    I am unable to upload the machine diagram. However you can see the original diagram in volume 14 page 719 , 9'th edition of the Metals Handbook "FORMING AND FORGING".
    Sounds like the linked company I posted, they only show tube though.


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