Machining Thin Wall SS Component (0.004", 100 micron wall) - Page 2
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  1. #21
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    Quote Originally Posted by adama View Post
    might be worth contacting Implex (sp) who is a member here and makes all sorts of weird bits but this might be too big for him.
    Thought this too, so I sent him a PM.

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    The thing to remember is that when dealing with really novel flight hardware, how to make it can be a research project in and of itself. There are NASA research programs specifically devoted to hardware development, for example the APRA programs in the Science Mission Directorate. Just because it has never been done before is only a minor inconvenience.

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    The way i calculate it (max stress = pressure x radius/ thickness), you've got about 10ksi of stress. Nominally, 316 at 750°F has about 30ksi of short-term yield strength. So your nominal design has only a 3x safety factor. Coldworking (that is, machining) greatly reduces SS strength. I don't think you've enough meat in the walls to hold pressure in a part that you've machined.

    https://www.nickelinstitute.org/~/Me...teel_9004_.pdf

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    1. Ruf the Out side leaving 2 mm per side stock ,yes 2 mm per side

    2 ruf and finish inside
    3.make 2 precision mandrels thar have 60 centers
    4. Install mandrells and finish outside between centers on a WIRE EDM THAT HAS A SPIN FIXTURE..
    5 Fire the drawer of this thing and get your money back.The person that drew this part is NOT A DESIGNER.
    A Anybody can draw a part that might be made 20 years from now,A designer must know what can be manufactured today.If you can make this ,you must handle this only with foam rubber tweezers. All of your tolerances and roundness are going to disappear when you heat it up to 700 f. Edwin Dirnbeck
    Last edited by edwin dirnbeck; 09-12-2018 at 06:57 AM.

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    You all believe in moon and mars landing? I can only say:

    No television, no moon landing; no personal computer, no mars imagery.

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    Quote Originally Posted by litlerob1 View Post
    An experienced guy with a Wire machine will be able to burn the ID out. (Maybe)

    is.

    R
    Am I missing some thing? This part has 2 flat bottomed blind holes .How are you going to wire edm the I.D. ? Edwin Dirnbeck

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    a bit OT, but, looking at the design, I see that the thin wall section is so thin to max out heat exchange rate (if I'm right about the placement of the part in the engine), but then some sort of a radiator, heat exchanger will have to be fitted around it, which will most likely be aluminum, so why not make the heat exchanger with a bore and either hard anodize for wear resistance or plate something like Ni coating on it to serve the purpose of this part, the design just makes no sense at all to me, and being public, I doubt there is some secret new know-how that requires this exact shape of the part

    I sometimes see these "impossible" parts form people that employ kids fresh out of college to do the design part, and those kids have nearly zero knowledge about manufacturing in general and absolute zero in regards to machinability of certain materials

    on topic, like people suggested, machine ID features to finish, close fit a plug for shallow hole and a mandrel for deep one, glue them in with something like cyanoacrylate glue, finish turning the od, leave something on the thin wall section, grind that to size, gentle heat to soften the glue and remove the plug and the mandrel, nowhere I see a need for any sort of EDM to make this, but a very good reconsideration on the design of the assembly should be done before you make it, because if it does work out and you'll start to get orders for multiples, there won't be any time (or reason from the view point of management types) to redesign it so it actually makes sense

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    Quote Originally Posted by edwin dirnbeck View Post
    Am I missing some thing? This part has 2 flat bottomed blind holes .How are you going to wire edm the I.D. ? Edwin Dirnbeck
    You cut out the rest of my post, I recommended an assembly.

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    Quote Originally Posted by bosleyjr View Post
    The way i calculate it (max stress = pressure x radius/ thickness), you've got about 10ksi of stress. Nominally, 316 at 750°F has about 30ksi of short-term yield strength. So your nominal design has only a 3x safety factor. Coldworking (that is, machining) greatly reduces SS strength. I don't think you've enough meat in the walls to hold pressure in a part that you've machined.

    https://www.nickelinstitute.org/~/Me...teel_9004_.pdf
    Thanks. The same contractor that drew this is doing the structural analysis. We'll have to investigate if there some additional derating of the material required based on the manufacturing method. Might have to have a tapered wall that's thicker at the hot end than the cold end.

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    Quote Originally Posted by jz79 View Post
    a bit OT, but, looking at the design, I see that the thin wall section is so thin to max out heat exchange rate (if I'm right about the placement of the part in the engine), but then some sort of a radiator, heat exchanger will have to be fitted around it, which will most likely be aluminum, so why not make the heat exchanger with a bore and either hard anodize for wear resistance or plate something like Ni coating on it to serve the purpose of this part, the design just makes no sense at all to me, and being public, I doubt there is some secret new know-how that requires this exact shape of the part

    I sometimes see these "impossible" parts form people that employ kids fresh out of college to do the design part, and those kids have nearly zero knowledge about manufacturing in general and absolute zero in regards to machinability of certain materials

    on topic, like people suggested, machine ID features to finish, close fit a plug for shallow hole and a mandrel for deep one, glue them in with something like cyanoacrylate glue, finish turning the od, leave something on the thin wall section, grind that to size, gentle heat to soften the glue and remove the plug and the mandrel, nowhere I see a need for any sort of EDM to make this, but a very good reconsideration on the design of the assembly should be done before you make it, because if it does work out and you'll start to get orders for multiples, there won't be any time (or reason from the view point of management types) to redesign it so it actually makes sense
    Here's a link to a cross section. The thin will is to minimize the heat conducted along the length. If the heat is going down the length of the wall rather than heating (and expanding) the gas in the hot end then it is not going through the gas inside of the engine and is therefore lost.

    I think the guy that drew this is a young guy. I think drawing this up is one of his first jobs.

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    Quote Originally Posted by bosleyjr View Post
    The way i calculate it (max stress = pressure x radius/ thickness), you've got about 10ksi of stress. Nominally, 316 at 750°F has about 30ksi of short-term yield strength. So your nominal design has only a 3x safety factor. Coldworking (that is, machining) greatly reduces SS strength. I don't think you've enough meat in the walls to hold pressure in a part that you've machined.

    https://www.nickelinstitute.org/~/Me...teel_9004_.pdf
    Thanks, I'll ask whether or not we will have to take into account manufacturing method and derate the material strength even more. I think the the person who designed this only took into account the strength loss due to the temperature. They might have to thicken the wall a little. I bet they'll try to make it thicker in the hot area and taper it down to the cold area, just to make this even more difficult.

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    Quote Originally Posted by litlerob1 View Post
    You cut out the rest of my post, I recommended an assembly.
    YES,I missed the last sentence in your post.You are correct .my mistake Edwin Dirnbeck

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    I might be able to make it as an assy.
    Perhaps as a unit.

    Using one of 2-3 options I can think of on how to do it for the long, thin, straight wall.
    If You are open to an NRE / test, PM me for quantities required, desired timescale, target price.

    I would make a "lookalike" first, testing the various approaches.
    As in not caring about the radii, etc. just getting the hard parts right.

    I would expect to spend about 1 week at it for 2-3 tries.

    Then on your possible acceptance of method/quality per samples You get, we could maybe agree on details.
    I am not stating I can do it.
    I am commenting that I make somewhat related stuff and can think of how to do it.

    I´m from Helsinki, but my shop is in Barcelona, Spain.

    If You need a US supplier, I could maybe make the 1-2 samples and then sell a "how-to" package for qty x.

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    Quote Originally Posted by hanermo View Post
    I would expect to spend about 1 week at it for 2-3 tries.

    1 Week for 2-3 tries? This parts sub 4" long and circa 5/8" diameter?

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    Have you considered Deep Drawing?
    Deep Drawn Tubes | National Die Company

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    Quote Originally Posted by adama View Post
    1 Week for 2-3 tries? This parts sub 4" long and circa 5/8" diameter?
    that was a "subtle" hint at the expected payment range

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    +1 on laser welding an assembly. A place like New England Small Tube or Eagle Stainless can probably draw the tube to exactly your dimensions. The big advantage of that is the tube will be work hardened by the drawing so quite a bit stronger than if it was machined. Also those shops will cut all your parts to length so you can get a big bag of them at not terrible cost. Further, if this is to minimize conductivity it must be surrounded by air so maybe there's some flexibility in the tube dimensions and thus you could use a standard size?


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