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Open Pour Fluke Mold Part 1 – Design

Open Pour Fluke Mold Part 1 - Design 1

All right guys, today we’re going to make an open pore fluke mold. I’ve been wanting to do an open pore mold for a while because I see a lot of people with 3D printers going the route of 3D printing a master and then making a silicone mold. To me, that’s just a lot of extra time, effort and trouble that you don’t need. So, I’m going to show you how I do it. It’s going to be a one-piece mold open pour from the top, of course, with a hook slot. It’s going to be fluked a little, about 90 millimeters. This is around 3 and a half inches which is perfect for bayou bass. Let’s go.

Define Parameters

Quick review of the parameters that I’m looking at here, the length is 90 millimeters and my max height which is as deep as the lure is going to get is 16 millimeters nose diameter. I used a diameter because I’m going to make a circle for the nose. Now I didn’t talk about this too much in my last video, but I’ve been using this technique a lot to make it easy to scale these lures later. I don’t want to say this is going to be the midpoint, but I call it the midpoint because it’s the part of the lure that’s going to be the tallest point. I set that base on the length of the lure and it’s a percentage so what this says right here is 40% (.4) of the way from the front of the lure is where my max height point is going to be the deepest part of the belly.

parameters in fusion 360

When I come in here and I make my lure, say, 110 millimeters long, all those calculations will be in proportion to the length of the lure and that saves me time. If I set this to a specific length, like you can see here the value is 36 millimeters, if I came in here and I set that to exactly 36 millimeters and then I went in and made the lure 110, my midpoint is still going to be up here at 36 and not adjust accordingly. Then I have to do some adjusting. I change one parameter lure length and it calculates out and I also do that here. We’re going to put a hook slot in this thing and then I want the tail section of my fluke to start 8 millimeters after that hook slot so I have a little bit of meat there after the hook slot and before the tail starts. I’m also doing that here on the max width of the lure which I set off my nose diameter, in this case, is 20 larger so 0.2. My nose is now as wide as it’s going to be so it’s not going to grow that much in width but, again, I drive it off the nose so if I change the nose my width changes in proportion and I do that with the tail.

Make Cross Sections of the Lure

So you’ve seen me build lures this way before, so we’re going to fast forward through this part and when we get the lure all built we’ll start talking about the mold. Sorry, we’re going to jump in a little earlier since I’m doing an open pore mold right now. So the top is going to be completely flat, I try to use this middle red line here as kind of the top of my lure. I can certainly build above that line, but just know that anything you build above that we’re going to chop off to make our open pore cavity. So we’re going to basically be building from this line down rather than from the center like we do. Okay, now we’re going to fast-forward.We divide our max width by 2 because we’re only doing half.

Open Pour Fluke Mold Part 1 - Design 2

So a quick note here, I probably got a little bit of an undercut here, this isn’t perfectly straight but since it’s soft plastic it’s probably not that big of a deal. If you were going to get this CNC, it would be a little bit more of a big deal because it’s hard to machine that undercut. But, we’re 3D printing so we don’t care that much.

All right, so here is the very end of the lure and I’m turning it back into a circle. We’re going to put a tail on the end of this so it’s going to be a little bug longer than the 90 millimeters I had previously talked about. Here’s another way you can use named parameters and put the percentages in the actual drawing itself instead of making other parameters that drives it, just type them in there.

Loft and Mirror to Create the Lure Body

So we’re going to loft this without rails first to see what kind of shape we get and how that looks. It doesn’t look half bad actually so I think I’m going to stick with that for now. I’m going to do a follow-up video to show you how you can add some cool details to the kind of lure but we’re going to keep this one straightforward, simple and clean. Now we just create a mirror, make sure we’re on body as you’ve seen before and then boom, we have this nice little fluke without a tail. Now let’s get to the tail. I’ve been making a lot of flukes lately and I just released 3 different flukes to my Patreon group. If you’re interested in getting molds and hard lures at least once a month, you should join my Patreon through this link HERE.

Open Pour Fluke Mold Part 1 - Design 3

Creating the Tail Shape Using the Form Editor

Now we’re going to do this tail and I’ve been seeing a lot of willow tail kind of things that kind of make the shape of a diamond so we’re going to go for one of those. We’re actually going to use a form editor and I’m not a huge fan of the form editor for making lure bodies because it’s not parametric which means I can’t easily go in and change the dimensions of the lure later on. But, for this tail I think I want to make it more of an organic shape so let’s give it a shot. We click on the form editor and I’m going to start with something called a quad ball and we’re just going to put it on there and back here. We’re going to see how 8 millimeters looks and we’re probably going to mess it up but that’s okay. We’re going to do symmetry mirror and we want length symmetry. Now the whole trick in the form editor is clicking on this modify and then grabbing faces. I’ll link to a couple of people that do really great things with form editor, especially for fishing lures in Fusion 360 HERE. Once you click modify, you can start grabbing and you’ll see this yellow part. Let’s make sure at the top here you’ll see the yellow which means I’m going to move that at the same time. So if I move this out, the other side moves accordingly.

making a lure tale

So once we got something we think we like, we just hit finish form and now we’re back to our lure. We have this arrow and tail and the reason I like flukes is you can have a lot of fun with the tail and we just need to combine those together. I haven’t saved so I should probably go ahead and save as well. I can combine these, or I cannot, in this case I’m probably going to come along and do a bunch of different molds so I leave it uncombined. I can just make new tails and stick them on there and readjusts a few things and it makes it easier to make the mold.

Building the Mold Body

So now we have this done and one thing that we can do with open pour molds that we don’t really have the ability to do with an injection mold is we can make it fit the lure body perfectly. With a injection mold, I think I do 16.4 millimeters for the opening of the hand injector that I use and that kind of drives the overall diameters of the thickness of the mold because I have to have at least 8.2 millimeters that are going to be eaten up by the hole. In an open pour mold, we’re just going to print a solid chunk of resin and so we can make it fairly tight to the lure body itself with not a lot of extra beef.

lure mold body in fusion 360

So let’s make our mold body, it’s pretty simple I’m just going to do it from the side here and just do a rectangle. I’m going to give myself a little bit of space in the front, you do need a little bit of extra so you can’t make it razor thin because a scope resin is a high temperature resin but it does need a little bit of thickness in order to maintain its shape under the heat. Then we just hit E for extrude and look at the top here and make this symmetrical. We’re going to come out just past that width of the body and you can see this is the stuff we’re going to chop off. Chopping this off, we’re going to lose a little bit of the top and this tail section back here. So now we can turn on the opacity control to about 70 and we can see through this thing here now. One thing you’ll notice here is we’re going to have an undercut on this tail so we’re going to have resin going over the top of that. Again, open pore mold 3D printed so this isn’t something we really care about it’s going to be easy to pop that tail out of there no problem. If you were designing this to do CNC, you wouldn’t be able to do that at least in a single block mold so we would have to split this mold in half from the top down.

Cut Out the Lure Cavity

So now we’re going to combine. We’re going to my target body which is my mold and then use my tool body and open port and cut my tail out. We’ll go ahead and keep those tools around and we’ll cut them. All right, I’m going to go ahead and cut this but you can see that we also have some parts that are not going to go away. Let’s click ok and let’s take those tails and these and you can see we didn’t really get all the way through there. Now I can hack these out if I wanted to, but let’s just fix it so it’s correct. Now what we’re going to do here is we’re going to come back to our sketch 5 and I’m going to go ahead and rename this to old sketch. Let’s edit it so we can just offset this a touch and we’re going to drag it with the dimension and make it .5. Then we should go ahead and dimension all of these bad boys here and make that 103 and this 19.2. Again, I’m going to constrain this front edge to the center, pop it up and let’s just make that 2.8 to get a fully constraint. All right, so now I just click finish sketch, it goes and now I have a nice opening.

lure cavity in fusion 360

Let’s turn the opacity back to 100 and se what’s going on in here. This is looking good considering it was looking a little weird earlier, but it looks fine now, the overhangs might get me there but it looks pretty cool. We’re going to roll with it for now, it might be completely wired but who knows. Okay, so now we’re going to add chamfers to the outside edges to save a minuscule amount of resin, but it also help to make it easier to get off the build plate. I’m going to select the edges here instead of all the faces because I don’t want to chamfer on this top edge.

Create the Hook Slot

Now let’s do the hook slot. Hook slots are straightforward, I’m going to come in at the top here and do a new sketch on the top plane. We’re going to take a line, make sure it’s centered and we get the hook slot length and there’s my hook slot. Now for the start point you just need a little bit of beef up front in the nose so we just need to add this dimension from the center line to here. It’s 4.8 now and that’s probably about where it needs to be depending on how you rig your flukes. Since we’re just using this for ourselves, we’ll go ahead and make it 5. The more meat you have on the front there, the better if you’re going to nose rig it with a wacky wig or put a screw eye in, but we’ll leave it like that for now. Let’s finish that sketch and now we’re going to use the thin extrude command and we’re going to click on this guy then extrude, click that line. Here’s a fun trick, I’m going to do 2 sides, so my wall thickness is my slot width. Then, I’m going to drag this guy down and let’s take a look at it from the side. We want to drag it down and we can drag it down as far as we need it to go but we need to go all the way through the lower body. Now, when you do 2 sides, a lot of people think that it’s going to go out but you can actually go in on 1 side or a negative number. So if I grab this top, I can come down and this is going to be how much beef I have on the top. So let’s do a negative number, 5 is fine, and it looks like a decent hook slot. We want to do, for now, a new body and we do a new body here because I’m going to come in and I’m going to add a chamfer to that edge.

adding a hook slot tp lure in fusion 360

Print Considerations

So let me point something out to you, you already need to be thinking about how you’re going to print this. This is the fastest way to print this, probably, would be to put this face here flat to the build plate but what’s going to happen if you do that is it’s not going to work right because that hook slot is going to go out into space you’re printing within layers and is going to get ripped apart unless you had a million supports in there. You don’t want to do that because that’s a mess. We could come in and split this mold in half a do a different kind of slide design, but we don’t want to do that either because we could print it from the nose first but then you end up with a similar problem. So if you want to print from the nose first because you have some other detail in the lure that prevents you from printing it from the tail first, you need to come in here and add a fillet to that edge and you need to fillet it basically all the way which, again, is not great either. If you do this, you need to leave as little hanging off here as possible, you can bring it back down here and maybe make it work but you still have about half of it hanging off.

So in this case, the way to print it is going to be relatively obvious, if we look at the back here you can see that this hook slot piece comes straight out of the tail and there’s no overhang. It’s not going to work perfectly, it’s part of the mold and if I pour that tail it’s pretty narrow and I suck at hand pouring. This is a pretty big chunk of resin here, but I think we are ready to give it a print.

Alright guys, I hope you like that design overview. I’m going to go print some of these and in the next video you’re going to see me print them, pour them, and go fish with them.


Take care- Tight lines