Seams With 2-Part Molds

[charger24]

I have been working on custom lures for a while now, and have come to the point where I am ready to make molds of my lures. Recently, I picked up some silicone mold (alumilte HS3) and began making 2-part (horizontal) molds for the lures. After pouring plastic and letting it set; I took the lure from the mold & noticed a horizontal seam that ran across the lure. I made another 2-part (vertical) mold, and after pouring plastic and letting it set... again, I had a seam that ran down the back and belly of my lure. Am I not separating the molds correctly, or will I have to use a 1-part mold?

The reason for me not wanting a seam is because I have scales that run all around the lures, and if I sand the seam it will remove the scale pattern. And the reason for me trying to use a horizontal 2-part mold is to be able to add the correct layers of plastic (with the correct mix with micro balloons) to get the lures to swim correctly.

I watched a Solarfall video of how to make a 1-part mold, but think it would be harded to add the right layers. Is this the only way to not have seams?

Thanks for the help!

[dlaery]

I have vowed to have the words "It should work" from my vocabulary!

 

Seams With 2-Part Molds

I think that goes together like Bread and Butter.

 

I would use lots of guides or pins to line the 2 halves up.I like a pin to be cone shaped and not cylinder shape. Don't put them too close to the cavity of your part that you are copying.

When pouring you plastic, don't use too much clamping pressure, might cause distortion at the parting line.

You didn't say how you make your mold but if you are using a clay base to make the 1st half to pour the silicone over, I would make it as flat and smooth as possible. I would use a mold release that is dry to keep the 2 halves from sticking. I had tried Vaseline to coat the half to keep from sticking, but I don't think it leaves a smooth surface on the cured mold/mold cavity.Good luck, maybe others with have some suggestions. 

[Travis]

I don't think with the methods we are using you can avoid these seams.  You can do things to make them less of an issue but you are going to have them.  Definitely have the seam on the vertical as sanding or scraping the area ends up having less effect on the bait.   Have you painted and cleared a bait yet?  You will loose scales in a heartbeat if you don't have them over exaggerated (in my opinion), nice scales will end up looking like very weak raised areas otherwise.  For me going scaleless was the better option for the over look of the bait.

[A-Mac]

I make a 1 side split mold to help alleviate seem problems.  The two methods I like best include a solo cup mold and a pvc pipe mold.  The solo cup mold works great because the conical shape holds the mold tight without any clamps.  The only downfall is the longer the lure, the more silcon that is wasted.  On my small cranks, the solo cup is the way to go.  Also, having only one split down the side makes for only 1 seam.  In addition, the mold keeps itself in line (along with the cup contours) since it is still only a 50% split.  My suggestion on making the split is to only cut as little as necessary to remove the lure, your mold will last longer and you will have a minimal seem line.

The pvc pipe method is great for long lures in order to avoid using so much silicon.  I'm using 1.5" pipe that is cut on opposite sides.  I leave enough pvc in place to keep the circular structure, but trim enough to flex it when I need to slip the mold in or out.  I still use the 1 side split mold technique and have had good results.  I'll never go back to a 2 part mold.

[mark poulson]

If you want to keep a 2 part mold together with minimum seams, try making matching open faced plywood boxes, with 1X perimeters, and putting 8D finish nails in the 1X as locators.  I make my mold boxes with 1/4" plywood, and drill my locator holes before I make the actual mold, so the two halves line up perfectly.  I hold the two mold halves together with small bar clamps.  If I need more pressure, I add a loose piece of 3/4" plywood to each side before I clamp.  With the 3/4" ply reinforcement, I can put as many clamps as I want without deforming the mold.

With all the trouble we go through to make masters and molds, a little more time and effort to make a reinforced mold box is a small price to pay for better baits.