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Aluminium Mold To Cast Custom Lures

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I must have missed this video, first time I have seen it. The video highlights a few problems for the CAD designer in that you have to be aware of the milling process and the tool radii required. You can start with a very pretty CAD model, but after the machining process you end up with an unrecognizable mush.

It would be a lot more interesting to see a video of the complete CAD design process that people use with the different CAD systems.

Dave

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Great lures. I also had some experiences with cnc molding but didn't go as far as aluminum. ( that's maybe why the lures got stuck into the mold regularly although I used release agent )

The Urethane foams are regularly setting pretty quick. What kind do you use to have time to fill all the cavities and close the mold in time?

I've played with Altropol Neukadur PU RF 150 but the results where half rewarding and didn't managed to do more than 2 cavities at a time.

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On 3/1/2021 at 11:41 AM, Vodkaman said:

I must have missed this video, first time I have seen it. The video highlights a few problems for the CAD designer in that you have to be aware of the milling process and the tool radii required. You can start with a very pretty CAD model, but after the machining process you end up with an unrecognizable mush.

It would be a lot more interesting to see a video of the complete CAD design process that people use with the different CAD systems.

Dave

I am in the trial and error stages of digital crankbait making. This may be my first post on here, but your contributions to this site have provided answers to most of the questions I’ve had preventing the need to ask a bunch of questions. As far as I can tell, no one has documented the end to end process of building a lure with a CNC machine.  I picked up a micro mill CNC off Craigslist last fall that was built in the late 90’s for very little cost. Using information from the internet, I have been able to get the machine, a cnc’d sherline mill operational on modern software.  It’s stunningly precise in its movements for something like this  

I plan to make the attached crankbait on the attached CNC micro mill from the attached photo of the CAD design.  I almost had the 1/8 inch thick aluminum lip cut last night but The depth of cut and feed rate was too aggressive and the bit started chattering and messed it up. The OP was running a very powerful, very rigid higher end CNC in my opinion.  Probably a machine costing 10k+. if you’re truly interested, I’ll document the process and post on YouTube. This is going to be hard maple hollowed such that it floats with center of gravity in lower front third of the lure.  

The ‘software stack’ I have chosen is Fusion 360 for CAD, vCarve Desktop for 2d CAD/CAM and CAM of 3d profiles designed in Fusion 360 and Mach3 for machine control.

I see the following benefits to building lures digitally:

1) Ability to control where the center of gravity is without trial and error.

2) Ability to make exact fit airbrush templates on 3d printer

3) Consistency.  Once I have the basics down, I’ll be able to replicate the design and develop trolling depth charts for the lure  (I’m a troller)

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DGFidler - good project.

The CAD model of the flat sided body is as simple and uncomplicated as it gets. I only see one issue with the design and that is the eye socket. If you intend to use a ball-end cutter or a cutter with a radius then this result is not possible.

Secondly, be careful regarding the calculation of the COG using the CAD software. The COG only takes into account the downward forces of the body material, the ballast, hooks, lip and other hardware. The buoyancy forces are not considered, and for a lure that actually floats, the center of buoyancy (COB), the sum of the upward forces is actually greater than the COG which is the sum of the downward forces. The COF or Center Of Forces will be about half way between the COG and COB.

This is a complex idea that is going to hurt a lot of heads and burst some balloons regarding understanding COG. This detail will likely not be important to your bait, but when the lure is static in the water, the center of forces, the sum of the upward AND downward forces is not the same as the COG. The problem arises if the two forces are too close together, again most unlikely otherwise this would have been discussed before.

The beauty of knowing the COG and the COB is that you can then accurately predict the float angle, the attitude that the lure sits in the water, be it nose up, nose down or level. It is then possible to alter the position of the hooks and ballast at the CAD design stage to control the float angle.

I will write in more detail about this one day and try to make it clearer. But, the information is only of advantage to CAD designers, manual designers will have to use the 'suck it and see' method.

Dave

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The software I use to generate the tool paths allow you to pick a ‘vector’, in this case the circle defining the eye socket, and choose the tool. I’ll use a flat bottomed end mill. The whole thing is much more manual than I thought it’d be when I first started reading about it. I expected the software to allow me to tell it what tools are available and it’d figure out the optimal way to mill it. Maybe that’s the next generation of CAM. The reality is you have to decide what tools to use and the software will generate tool paths to remove the most material given your choice. 
My educational background was computer science which included basic physics classes. Much of that coursework revolved around ‘mass’, however the effect of the air (or in this case water and air) were mostly ignored. Maybe some limited study of coefficient of friction and the fact that friction on a moving object through the air is exponential, etc. Anyway, the concept of buoyancy was not covered and I completely overlooked it. I’d guess it’s related to the material’s relative density as compared to water. It does kind of ‘bust my bubble’ that COG is not the end all measure. I’m sure there is some software that would incorporate this concept, but certainly not for free!  
 

In software development, when you start working with a new language, the first project is customarily a simple process to output the words ‘hello world’ on the screen, printed page, in the file, or whatever the output medium is. This is my ‘hello world’ project. It starts at the level I had moderate success in my own lure making. Once I started trying to do more complex shapes, my lack of carving skills and left hand/right hand bias created lures that were asymmetric; they float at odd angles, dive to the right, dive to the left. Once I have worked out the workflow and build process in this simple design, I intend to make crankbaits that I actually fish with.  One of the main ‘problems’ I hope to solve is during the summer, we take off the shelf floating deep diving crankbaits and troll them behind 300 feet of monel wire to get them to run at 50 feet down. I hate the wire. My kids backlash the reels, it kinks; in general it takes the fun out of our fishing, but it’s highly effective so we do it. Some people believe the wire gives a unique vertical presentation, but I hope to design and build a box of crankbaits that dive to 50 feet with 10lb mono line with 300 feet or less of line out. My first experiments will be to determine whether it’s possible to build a ‘heavy’, non floating deep diver.  Why do we need a floating lure if our intention is to fish it 50 down?  I think we don’t, but that’s what they sell. This is what motivates me to build my own lures - to obtain something that’s not for sale.  Even if it’s still trial and error, the machines will let me experiment with test lures having less variance. The worst type of variance is variance you’re not aware of; carving the left side less than the right because you’re right handed for example. 

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You have made a solid start. Plainly, you understand the eye socket issue, and you will be applying these cutter thoughts to your future designs.

As for the 2nd part, the buoyancy thing, I can see your line of thought because I went down that line myself, but wrong. The upward buoyancy forces are all about Archimedes, volume displacement of water. The total external volume of the lure generates an upward force of 1 gram for every cm³ of volume. The CAD COG of this uniform density volume will give you the COB.

Dave

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On 8/20/2013 at 1:45 PM, ArdentAngler said:

Very nice, I asked a machine shop who specializes in making lure molds....they told me $2000-$6000 for a two piece lure mold! Guess it takes many hours to draw up a lure on the computer that's what drives the price.

I bet print-a-lure (facebook) could do that for you for a fraction. He does custom soft-plastic moldes for a coupld hundred $

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