Cutting gear blanks with laser cutter out of 1045 sheet
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  1. #1
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    Default Cutting gear blanks with laser cutter out of 1045 sheet

    I am designing a gear reducer for a medium duty kind of vehicle that needs to be economically manufactured in volumes of about 1000 units per year. Powder metallurgy is not an option at this moment, the tooling costs are too high. Would prefer to keep process in North America. The accuracy grade of the gear can be fairly low (2015 grade 7) A couple of the gears are pretty thin in comparison to their diameter, lets say 7/16" thick with a diameter of around 6-1/2", one is a ring gear about 1/2" thick by 6-1/2". The module of the gears is in the range of 2.5 (DP about 10).

    In order to keep the cost of the gears low I am considering the possibility of making these gears in the following way:

    -blanks cut from hot rolled 1045 plate by laser
    -blanks hardened to RC30-35
    -blanks blanchard ground
    -center hole machined to size
    -blanks hobbed in stacks

    Does this sound like a viable approach? Anyone have an idea on how to make these gears more economically?

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    If you are serious about 1000 units Per year then contact Tom Shaw At Commercial Gear in Walpole Ma. They can be very competitive and they run a good operation.

    Manufacturer of Gears, Pulleys, Sprockets & Clutches

    Make Chips Boy's

    Ron

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    I would not apply an expensive gear hob/cutter to that surface.

    I didn't see any shotblast/pickle operation.

    Why the BG when you going to stick it in a lathe afterwards ?

    Have the lathe doo the facing and turn the OD.

    That way you save a step, and clean up the OD ready for the gear cutting.

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    Why not use a low carbon steel like 8620, do the machining and then get it carburized? 8620 is pretty stable in size after heat treatment.

    Rc30 isn't very hard for a gear tooth, but if you need the strength elsewhere, then maybe 1045 is ok. Warps all over the place though, due to water quench.

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    The ring gear has a pretty thin section, its going to move during heat treatment, that why I thought it could be hardened before the locating feature and the teeth get done. I figured the HAZ from the laser would be normalized in the heat treat operation. This needs to be cheap like a chain sprocket with hardened teeth.

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    Why laser? just burn them out of plate- if there are no features that would benefit from the laser accuracy why go that route?
    Suggest turning the OD - as well after grinding. Using a hob to top a burned surface is probably not the best choice. Other than that, your process seems very doable.

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    When you say "medium duty vehicle" I automatically think 8620. You know it works, it holds up, everybody does it, why reinvent the wheel ?

    I used to make something similar to this out of 4130 nitrided, similar to what you are thinking, but sort of a pain in the arse. 8620 is easier.

    Yes your ring gears will probaly tweak. Do an intermediate stress relief and square them up again. Ugh but ... at 1000 a year you aren't going to be optimizing the heat treat steps enough to avoid tweakage. It's more expensive to scrap 1000 parts than to do the extra steps ...

    There's a guy in Oakland who might be interested

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    Quote Originally Posted by EmanuelGoldstein View Post
    When you say "medium duty vehicle" I automatically think 8620. You know it works, it holds up, everybody does it, why reinvent the wheel ?

    I used to make something similar to this out of 4130 nitrided, similar to what you are thinking, but sort of a pain in the arse. 8620 is easier.

    Yes your ring gears will probaly tweak. Do an intermediate stress relief and square them up again. Ugh but ... at 1000 a year you aren't going to be optimizing the heat treat steps enough to avoid tweakage. It's more expensive to scrap 1000 parts than to do the extra steps ...

    There's a guy in Oakland who might be interested
    When they make thin 8620 gears (7/16" thick, 6-1/2"diameter) with no hub in volume, do they make them out of plate or out of round bar? 8620 in round bar would cost me about $1.90/lb, a blank cut off in bandsaw would weigh about 5lbs, so $10 in raw material. If plasma cut from 1045 plate the material cost is closer to $7.
    Maybe a $3 in material cost difference is not important for the spur gear but for the ring gear burning out of plate saves a lot of machining time on the blank.

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    Quote Originally Posted by SBAER View Post
    When they make thin 8620 gears (7/16" thick, 6-1/2"diameter) with no hub in volume, do they make them out of plate or out of round bar? 8620 in round bar would cost me about $1.90/lb, a blank cut off in bandsaw would weigh about 5lbs, so $10 in raw material. If plasma cut from 1045 plate the material cost is closer to $7.
    But if you plasma cut from plate you get 1045. If you cut off from bar you get 8620.

    Different steels.

    I used to have things banged into a cavity at the friendly neighborhood forging shop, but I'm not sure you have those anymore ? That way you don't have to use 6 1/2" bar, you can use more readily-available stuff and bam bam bam it. Gives you a stronger part, too. It used to be surprisingly cheap.

    There are places that make rings, too, so you don't have to buy the center section then throw it away.

    You haven't told us what the use is, which makes a lot of difference. But when you say "vehicle" I automatically think of higher stresses than thru-hardened 40 Rockwell gear teeth are going to handle well. Especially if the face width is only 7/16" !

    What are you driving with these things ? That will tell you what material you need to use. Timing gears for a Model A is one thing, a NASCAR V8 something else entirely.


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