Milling a large 6061 plate FLAT - Page 2
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  1. #21
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    ^ forget what it is in the mic - 6 but after alkaline etch the surface is smutty, hence you then acid etch it to get rid of that (magnesium??) and rinse then anodize, so long as the part is kept wet bettwen etch and acid etch your fine, don't let it dry, just etch, rinse acid desmutt and anodize, if you desmut with sulpheric, you only need a quick rinse prior to anodize.

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    Quote Originally Posted by scadvice View Post
    Ask the engineer for a material change to Mic-6 aluminum. Here’s one link to spec’s ect… It's already to your needed spec's
    Product Catalog: Mic 6(R) Aluminum Cast Plate | Arconic

    Optimist says the glass is half full
    Pessimist says glass is half empty
    Engineer says glass is wrong size

    In the current situation, the Internet says “use MIC-6 tooling plate”

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  4. #23
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    Quote Originally Posted by HuFlungDung View Post
    Serious question: I've got no such service nearby, but have wondered who on earth would want to grind aluminum? Maybe it grinds well when wet, does it?
    The material supplier can usually have it done for you. As far as Blanchard grinding aluminum? It is done everyday without a problem.

  5. #24
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    can the end customer inspect to that? If they can't, make it work and sell them some sunshine on the cert for the job. On some jobs it will matter- on some you'll put enough extra weight with the rest of your stuff on it to bend it more than 0.005 inches in 48....and I have seen a lot of jobs that size where even 0.035 is workable function, but your customer pays the bill.

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    A vendor used to advertise double disk grinding, both sides at the same time. Don't remember who it was though. Seem like that would be the best way.

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    Somebody's sig sums this up, "You can't win, and there's a penalty for trying"

    Call in sick

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  9. #27
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    You are being told by multiple people here with more than a few years experience that you are going to have a heck of a time keeping that thing flat to even double what the gods are asking for. Mic-6 or other cast jig plate is your best bet of meeting their requirements. As soon as you touch the surface of that plate, its going to start to move and you will chase the curl until you're out of tolerance on the thickness. Then you can try it on a 2nd piece hoping to get lucky this time. How much is the material worth ? Just because you have it in stock, is a poor reason to proceed.

    Perhaps after you have scrapped two pieces of material the gods will reconsider their foolishness. Good luck!

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  11. #28
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    I milled a 14 x 30" x 1.25" T6061 plate to within a couple of thou of parallel. I did not have any major curl of the plate, but I didn't have any actual thickness spec to hit. The biggest headache with milling large plates near the limits of machine travel is getting the cutter clear of the work on exit so there is no back side cutter shaving going on, which results in a permanent ledge.

    Extruded brass has to be the worst thing ever: cut the skin off and it bows back and forth like crazy.

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    Quote Originally Posted by SteveBausch View Post
    Optimist says the glass is half full
    Pessimist says glass is half empty
    Engineer says glass is wrong size
    In my experience the engineer almost always specifies a glass size and/or style that is not available as a stock item...

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    I would try double-sided tape. We have had good results with that. I do not know the brand but it is blue, pretty thin tape - may be Scotch brand. It will take a lot of careful cleaning and stoning and re-cleaning, but that's what I would try. Use a good free-cutting tool and no coolant, a light spray of WD 40 without hitting the tape... Go fer it.

    I will add this - if this plate has holes for bolts (or can be added if this is an in-house deal), like others have said, bolt it to another plate or the table through those holes and face it flat while bolted down. Then when it is bolted down to wherever it goes, it will be in approximately the same state - unless what it bolts to ain't flat...

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    Quote Originally Posted by Larry Dickman View Post
    send it out to be Blanchard ground. It's not worth screwing with.
    Exactly.
    Better yet buy some mic6 tooling plate.
    It's what that material is for.

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    I run a seismic test lab and use similar 6061 T6 plates as sacrificial adapter - drilled and counterbored to match my servo-hydraulic shake table mounting pattern, then drilled/tapped and threaded inserts for whatever I need to bolt down (7ft tall 3500lb telecom battery racks and such). The adapter plates must be very flat, since the shaker table is on oil film bearings with only .010 clearance (4x6 slip table). Twisting the table by bolting down a warped plate can/will cause bearing drag/damage and ruin my day.

    I finally came up with an easy and inexpensive method that doesn't require machining or grinding. I level the plate supported on jackscrews, run masking tape around the edge to make a dam and pour ~3/16" deep thin epoxy (bar top coating seems to work very well). Let gravity level it and it's flatness ends up matching the curvature of the earth.

    You might talk to your customer and see if they'd be willing to accept something similar if the application can tolerate it.

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    Quote Originally Posted by Bellinghamster View Post
    I run a seismic test lab and use similar 6061 T6 plates as sacrificial adapter - drilled and counterbored to match my servo-hydraulic shake table mounting pattern, then drilled/tapped and threaded inserts for whatever I need to bolt down (7ft tall 3500lb telecom battery racks and such). The adapter plates must be very flat, since the shaker table is on oil film bearings with only .010 clearance (4x6 slip table). Twisting the table by bolting down a warped plate can/will cause bearing drag/damage and ruin my day.

    I finally came up with an easy and inexpensive method that doesn't require machining or grinding. I level the plate supported on jackscrews, run masking tape around the edge to make a dam and pour ~3/16" deep thin epoxy (bar top coating seems to work very well). Let gravity level it and it's flatness ends up matching the curvature of the earth.

    You might talk to your customer and see if they'd be willing to accept something similar if the application can tolerate it.
    We had good luck doing similar. We used 605 resin for the filler as I recall. Clean the materials with acetone, etc and use a release agent on both pieces to make getting the material off the sacrificial plate easier and easier to clean the 605 off the sacrificial plate for the second side if you have to flip more than once.

    Tooling plate is the way you want to go, if you can.

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    epoxy is a good idea. but i would spray release agent deliberately on and let it level. sikafloor 156 is cheap and does the job, you dont need any fancy, uv stabilised epoxy. then clamp it to the table and true it up on the other side. peel the epoxy off and done.

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    Well I finished the plate and got it within .003" flat and parallel. It was 1.5" thick 6061 t6 aluminum that I cut roughly .05" a side flipping it 4 times. I roughed out the 8 larger holes. Then on my last two passes I faced .012", drilled, tapped and holemilled dowel holes, flipped, finished the larger holes, then faced the last .012"

    You can see my setup in the pictures. Made counterbore holes so I can bolt the part down to three points. I used 3 jack screws to dampen the part.

    So my final thoughts, yea it took me longer then a Blanchard grinder but I was able to do it. I think it wouldve been much easy if I could've used T0 or the MIC-6 Aluminium.

    Sent from my SM-G950U using Tapatalk

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    glad to see it worked out. Where did you get the jacks? Home made?

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    Quote Originally Posted by Larry Dickman View Post
    glad to see it worked out. Where did you get the jacks? Home made?
    No they are eBay scores, would be a good home project though

    Sent from my SM-G950U using Tapatalk

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    Next time, order it already flat from these guys.
    TCI Precision Metals - Machine-Ready Blanks and Contract Machining
    I used to buy some aluminum from them- it was always right.

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  24. #39
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    Quote Originally Posted by garyhlucas View Post
    A vendor used to advertise double disk grinding, both sides at the same time. Don't remember who it was though. Seem like that would be the best way.
    I have never seen or heard of a DD grinder that would handle a 24 x 40 plate. Blanchard is the way to do it and it can usually be handled by the supplier. As far as Mic 6 plate (or equivalant)it is not structurally close to 6061 T6. It is very soft and gummy. YMMV

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