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    Default Die set dimensions?

    I am new to forming using a die set, and have been googleing to try to figure out the answers, but came up short.

    I am bending 16 gauge mild steel sheets approx. 20 x 24. I would like to form 1/2" ribs throughout the 24" length to strengthen it. The easiest way for me to do this would be to make my own die set using 1/2" 4140 HT rod embedded in the top press die.

    The bottom die would be machined with a round nose endmill.

    My question is, what size round nose endmill should I be using for the correct clearance?

    Is it as simple as adding the thickness of the metal being stamped to the bottom die?

    Thanks
    Chris

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    The problem is far more fundamental than the size of the pocket. When you form ribs like that in an open die, material is going to drawn into the form. If the form die is longer than the sheet of material, the width will shorten by the amount of of material drawn into each form. The sheet will look like and accordion. If the form die is shorter than the sheet, the end result will look like crumpled paper. To avoid these issues require a die that is far more complex than two platens. Secondly, you are going to need a big press and I am guessing about 25-35 tons of force. This can all be calculated, there are tables for this.

    Tom

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    How about if I only did 3 ribs? One toward each side and one in the middle and adjusted the width to accommodate the shrinkage?

    thanks

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    Quote Originally Posted by Caspian View Post
    How about if I only did 3 ribs? One toward each side and one in the middle and adjusted the width to accommodate the shrinkage?

    thanks
    If the ribs are very shallow- Say .030" I think you may get away with a simple top and bottom tool. If you want more rib than that I think it's not happening if you're asking the questions you're asking about forming. There's just no way to do it without moving parts or multiple operations.

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    I was planning on moving the metal three times, once for each rib. I apologize for not mentioning that in the beginning.
    Based on that, think its doable?

    Thanks
    Chris

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    The answer to question of end mill size is rib radius plus max material thickness. Are doing this in a press break? If you want the sheet to come out reasonable flat you will probably have to over bend the material or put in a stiffening rib around the radius you want. It would look like a half donut around the rib.

    Tom

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    Quote Originally Posted by Caspian View Post
    I am new to forming using a die set, and have been googleing to try to figure out the answers, but came up short.

    I am bending 16 gauge mild steel sheets approx. 20 x 24. I would like to form 1/2" ribs throughout the 24" length to strengthen it. The easiest way for me to do this would be to make my own die set using 1/2" 4140 HT rod embedded in the top press die.

    The bottom die would be machined with a round nose endmill.

    My question is, what size round nose endmill should I be using for the correct clearance?

    Is it as simple as adding the thickness of the metal being stamped to the bottom die?

    Thanks
    Chris
    It is as simple as adding the Material Thickness. But you do not have to use a Ball End Mill. You just need clearance for the material to flow over the Punch Radius.

    Tonnage wise I would hit it hard enough to keep the part flat after forming.
    Attached Thumbnails Attached Thumbnails pm-002-rib-tool.jpg  

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    If you are "coining" the metal then you only add material thickness. If you are truly forming/drawing the rib, you'll need to add about 10% to 12% of T to it. Also the "pocket" as you call it is really a form negative, and will require a radius around the outside so the metal can flow.

    As Tom said, if you're not forming/drawing under pressure the result is going to be very unsightly. You will have uncontrolled flow for the operation resulting in wrinkles. There isn't a way around this.

    As Garwood said, if the ribs are very small, what my shop would call an emboss, you might can get away with simply punching it. It still won't look as good as doing it under pressure.

    There's a reason tooling is expensive and TND Makers do things the way we do them.

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    Thumbs up

    I really appreciate your time and sharing of knowledge. In hindsight, I should have laid out the set up I was planning.

    I have a Di-arco 48" press (no model or tonnage listed) that I am hoping will handle 24" or 14 or 16 gauge sheet metal rib forming.

    I have 2" x 1.5" D2 steel to make the die set and 1/2" 4140 rod to make the rounded male die.

    I am (obviously) a nubie to this. For the time being, I want to make a prototype of my project. If it turns out to be something people want, I will invest in professionally made dies.

    That being said, would the best results come from squared off endmill female die or round nose? Since I will have to buy one to fit the need, i am ok with buying an round nose.

    The key purpose is to add strength to the sheet metal, how deep to draw it?

    Thanks again,
    Chris
    Attached Thumbnails Attached Thumbnails 20180419_203535_resized.jpg  


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