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    Default fixturing/clamping thin flat parts

    Hey guys,


    What this stems from is I need to cut this 7.9" x7.9" part. It's 1/8, although I'm thinking of making it 3/16. Material is 6061 t6. and while not typically thing. I wouldn't do this in a vise because of the span of material. Starting off with 8"x 8" rough stock. How would you do something like this?

    I was thinking dowel pins for locating and strap clamp would help clean up the operations but it doesn't look like it.

    Op1 - strap clamp, drill & counter sink the 4 corners.

    Op2 - Remove strap clamp, use 4 counter sunk heads to hold part down, face it (think this will get ugly since nothing is holding it down in the center), Profile, and chamfer

    Op3 - Flip it over and hold it for facing op and chamfer. How to hold it...still working on that.

    Last edited by Djstorm100; 07-10-2018 at 03:42 PM.

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    Quote Originally Posted by Djstorm100 View Post
    What this stems from is I need to cut this 7.9" x7.9" part. It's 1/8, although I'm thinking of making it 3/16. and while not typically thing. I wouldn't do this in a vise because of the span of material. Starting off with 8"x 8" rough stock. How would you do something like this?

    I was thinking dowel pins for locating and strap clamp would help clean up the operations but it doesn't look like it.

    Op1 - strap clamp, drill & counter sink the 4 corners.

    Op2 - Remove strap clamp, use 4 counter sunk heads to hold part down, face it (think this will get ugly since nothing is holding it down in the center), Profile, and chamfer

    Op3 - Flip it over and hold it for facing op and chamfer. How to hold it...still working on that.
    If you need to face it, I think vacuum is the only option. Double-stick tape can work too, but is a right royal PITA if there is any quantity.

    Regards.

    Mike

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    Quote Originally Posted by Djstorm100 View Post
    Hey guys,


    What this stems from is I need to cut this 7.9" x7.9" part. It's 1/8, although I'm thinking of making it 3/16. and while not typically thing. I wouldn't do this in a vise because of the span of material. Starting off with 8"x 8" rough stock. How would you do something like this?

    I was thinking dowel pins for locating and strap clamp would help clean up the operations but it doesn't look like it.

    Op1 - strap clamp, drill & counter sink the 4 corners.

    Op2 - Remove strap clamp, use 4 counter sunk heads to hold part down, face it (think this will get ugly since nothing is holding it down in the center), Profile, and chamfer

    Op3 - Flip it over and hold it for facing op and chamfer. How to hold it...still working on that.

    .
    many people use a big thick aluminum plate with many tapped holes and 1/8" masonite between part and plate. i often just used many clamps and moved the clamps in the way one at a time as needed. Masonite is so can cut through without making a mark on aluminum plate

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    What's wrong with laser cut, and second op the chamfered holes in a drill press ?

    Piloted countersink tool will easily locate from lasered hole.

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    The facing is the issue. If you have to face them to the 1/8" thickness, I would think a vacuum plate, or (for 1-2 off) I would use mitee-bite "mitee-grip" adhesive paper.

    OR

    Plan to face with a down mill path, to force the material against the surface plate, it is mounted too.

    How about a fixture plate (breadboard or tapped holes and some dowel pins?
    1) Mount the blank against dowel stops, and clamp with some strap clamps (or toggles, if you have the qty) and drill / c-sink the holes.
    **Think about clamping just off center of the through hole.**
    2) Mill the through hole, and face/ counterbore to 1/8" thick, @ a diameter that is about 1/4" larger in diameter than the center hole.
    3) Use a flanged bushing, with a through hole and a screw, to hold the center down against the fixture plate.
    4) Install the 4 screw in the corner, then remove the strap / toggle clamps.
    5) Mill the OD, and face the rest of the plate off to 1/8".
    6) Round over / chamfer the OD.
    7) Deburr the back side of the part, while the next part is running.

    My $0.02.

    Doug.

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    you should try solidworks sheetmetal
    .
    you can machine parts out of large sheets of .060" ss using 1/8" end mill and weld the many parts together to form 3 dimensions shapes. sort of like making a canoe or boat out of flat sheets that when ends brought together make curved corners. i often made pans and or small tanks for printing press equipment. cool thing with solidworks you can show part in final shape or in seconds show the sheets flat again.
    .
    usually just have sheetmetal over masonite or plywood so can mill through sheetmetal not cutting into anything like machine table or big fixture plate. just use a lot of clamps so no big deal if one clamp needs to be moved if you got 3 or 6 other clamps on part

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    Quote Originally Posted by digger doug View Post
    What's wrong with laser cut, and second op the chamfered holes in a drill press ?

    Piloted countersink tool will easily locate from lasered hole.
    Both sides are face, chamfer...starting to lean to deburing the bottom edge.

    Don't have a laser

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    Quote Originally Posted by doug925 View Post
    The facing is the issue. If you have to face them to the 1/8" thickness, I would think a vacuum plate, or (for 1-2 off) I would use mitee-bite "mitee-grip" adhesive paper.

    OR

    Plan to face with a down mill path, to force the material against the surface plate, it is mounted too.

    How about a fixture plate (breadboard or tapped holes and some dowel pins?
    1) Mount the blank against dowel stops, and clamp with some strap clamps (or toggles, if you have the qty) and drill / c-sink the holes.
    **Think about clamping just off center of the through hole.**
    2) Mill the through hole, and face/ counterbore to 1/8" thick, @ a diameter that is about 1/4" larger in diameter than the center hole.
    3) Use a flanged bushing, with a through hole and a screw, to hold the center down against the fixture plate.
    4) Install the 4 screw in the corner, then remove the strap / toggle clamps.
    5) Mill the OD, and face the rest of the plate off to 1/8".
    6) Round over / chamfer the OD.
    7) Deburr the back side of the part, while the next part is running.

    My $0.02.

    Doug.

    Doug, how are you going to face the backside of it?


    Thanks everyone, loving the help and suggestions.

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    You don’t spec the material… If it’s steel or could be tool steel NO WAY am I facing that when you can buy Starrett or Precision in 8”x??” sheets and saw to the 8” length plus it’ll be +/-.001”.

    Good luck,
    Matt

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    Quote Originally Posted by Djstorm100 View Post
    Doug, how are you going to face the backside of it?


    Thanks everyone, loving the help and suggestions.
    I was not planning on it, as I didn't know that was mandated. (I assumed there was nothing on the bottom to machine.)
    Why would you want to face the backside? Are you required to machine both sides, or is it just cosmetic?
    If cosmetic, then forget about the 2nd operation altogether!

    Just FYI, "I" would look for a way to purchase 1/8" thick material, and not face them at all.
    Facing 1/8 x 8 x 8 is not a job I would consider, unless I had a vacuum table.
    Just my $.02

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    Quote Originally Posted by doug925 View Post
    I was not planning on it, as I didn't know that was mandated. (I assumed there was nothing on the bottom to machine.)
    Why would you want to face the backside? Are you required to machine both sides, or is it just cosmetic?
    If cosmetic, then forget about the 2nd operation altogether!

    Just FYI, "I" would look for a way to purchase 1/8" thick material, and not face them at all.
    Facing 1/8 x 8 x 8 is not a job I would consider, unless I had a vacuum table.
    Just my $.02
    My apologizes, you are right. I thought I had put that in the OP.

    Cosmetically yes as it will be bare alum. fixture vacuum plate seems to be the best way but cost. I'm jump in the deep end, taking classes at night and bought my own little cnc machine to do personal projects at home. Looking for Fadals and 2010+ Haas. Don't want a older controller to go out and have to retro fit a old machine with new 15k controller.

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    Quote Originally Posted by Matt_Maguire View Post
    You don’t spec the material… If it’s steel or could be tool steel NO WAY am I facing that when you can buy Starrett or Precision in 8”x??” sheets and saw to the 8” length plus it’ll be +/-.001”.

    Good luck,
    Matt
    6061 t6...good catch. Updated post.

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    Default fixturing/clamping thin flat parts

    Quote Originally Posted by Djstorm100 View Post
    6061 t6...good catch. Updated post.
    It looks like you are trying to make some kind of cover.

    McMaster-Carr

    Find the mirror-like 6061 sheets...

    I understand trying to do it all yourself but if there is no need for facing both sides... then don’t. And if you’re looking for a good finish on 1 side... buy it already like that.

    If you are doing a small amount of these maybe try the superglue and painters tape like NYC CNC (on youtube) likes to do. Would be much cheaper than investing in a vacuum fixture.

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    Consider using MIC6 tooling plate. I've made stuff like this before and I can tell you that 6061-T6 will​ warp significantly after facing. MIC6 is cast plate so the residual stresses from rolling are not present.

    We made fixture plates and vacuum plates by bolting a piece of 1/2 x 10 x 10 plate to a 1.5 x 2 x 6 bar that we then clamped in the vice. Vacuum chucks are great if you have more than about 5 parts to make. Otherwise double sided tape and prayers. Oh, and no coolant with tape.

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    This isn't much of a question to ask on a professional machinist forum. Sorry if I'm being blunt, but buy some 1/8" material and knock 5 holes in it Done. You are gonna struggle facing 1/16 off that plate.
    If I have oversize 1/8 plate I mill the perimeter leaving small tabs to sand off.

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    Quote Originally Posted by Rstewart View Post
    This isn't much of a question to ask on a professional machinist forum. Sorry if I'm being blunt, but buy some 1/8" material and knock 5 holes in it Done. You are gonna struggle facing 1/16 off that plate.
    If I have oversize 1/8 plate I mill the perimeter leaving small tabs to sand off.
    Sooo my question bother you. However in my location there are no schools that teach actual machining...they teaching push button machining.

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    Mag chucks work well for onesie twosie steel parts but this is aluminum. My shop’s first choice would be double sided tape, second choice vacuum depending on quantity. For the people calling double sided tape a pain chances are they’re using the wrong tape. We use some sold by sabic polymer and it releases with a spray of isopropyl.

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    many machinist use a 12" by 12" by 1.5" thick aluminum fixture plate that goes in a mill vise. there is room to clamp a thin part and 1/8" masonite or plywood to the fixture plate with kant twist clamps, if you use 4 clamps you can move one clamp at a time that gets in the way.
    .
    i have made many parts this way. many machinist got the aluminum fixture plate machined to go in the mill vise in 2 seconds. it also has many 1/4-20 holes if needed for edge stops to align part if needed.
    .
    i have had fixture plates near mill for decades. once you see one used and or used one your self you quickly never not want to have one around in shop ever again

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    Quote Originally Posted by Hazzert View Post
    Mag chucks work well for onesie twosie steel parts but this is aluminum. My shop’s first choice would be double sided tape, second choice vacuum depending on quantity. For the people calling double sided tape a pain chances are they’re using the wrong tape. We use some sold by sabic polymer and it releases with a spray of isopropyl.
    This could turn in to a production item. I am beating my self up over this. The tolerance for thickness is not critical at all just flat.

    There are 4 legs, rectangle with a tapped hole in one end and slot 7" down the 8" leg. Pallet design should be easy with this Will be 4 or 5 ops (facing all 4 sides, thread the end)

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    Quote Originally Posted by Djstorm100 View Post
    This could turn in to a production item. I am beating my self up over this.
    Vacuum fixture then .

    They are not that hard to make, and work well.

    Regards.

    Mike

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