Mold making question

[guiley]

Since I have given up on getting a custom aluminum mold made for reasons that have been covered by other posts here, I am working on making an RTV mold. It is basically a 6" worm mold (see www.guileyworm.com for pictures) and I would like to have 6-8 cavities. I will need to have the master machined since I don't have an exact bait to use as a master. I am looking for some advice from those of you who have made molds before. First of all, what is the best material to use if you are machining or carving a master? I am considering aluminum or delrin. Secondly, should I machine 6-8 masters, or machine 1, make a mold of it, and pour the 6-8 masters in that mold. I am wondering if I will loose a lot of the sharpness of the original master if I mold the new masters from it. Any pointers or advice would be appreciated.

Brian

[sloegoe]

That's a uniquely shaped bait and I assume it is round (two sided) I've made many two sided urathane molds but the pour is going to be very hard with all those turns. You might have to move the mold around as you pour. If you have more than one cavity you will mess up the other worms. If you want to make a one sided mold this is a slamdunk. -sloegoe.

[guiley]

sloegoe,

I am planning on a one-sided mold, but using a master that is round with a flat on it just big enough to get the bait out of the cavity. If the worm is 1/4" in diameter, the mold cavity would be about 3/16" deep and a cross-section of the mold would look like a circle with a flat top. I've heard this called a 3/4 round mold. In order to cast the mold, the mold material or the master has to be soft enough so you can get the master out.

I think RTV is soft enough to get a solid master out of the cavity. But this is my first attempt at mold making and I am looking for advice. Thanks!

Brian

[redg8r]

Using RTV, youre gonna be able to do your "3/4" type mold.

I traded for some stick worms from TU member "fireball lures" that only had maybe 3/16 wide flat belly, meaning the mold was nearly enclosed.

RTV will give you the ability to pour baits with a good undercut & still retrieve the master (prototype)

Id recommend making one master lure using polymer clay or wood, then make one small rtv mold to pull 6 castings from it.

you can use alot of materials to cast the duplicates, resin, plaster, wax, water putty, even plastisol. if you use plaster or putty, seal the castings with spray laquer or acrylic.

Then Id make a single 6 cavity mold from those castings.

After you have the 6 cavity mold, you can use it to cast a "positive" mold from. theres a good demonstration in here from "dtrs5kprs" search for "mother mold"

Using that process you can pull multiple 6 cavity molds from that one & youre in business.

[redg8r]

Also shoulda mentioned, if youre using polymer clay, go ahead & give that a clearcoat of spray acrylic or laquer too.

the better the gloss, the better the gloss on the resulting pours.

below is a pic of one of my "positive" molds. These have what you'd call a "3/4" undercut with a small footprint or "flat belly".

All I do is cast polyester resin into this RTV mold & pull a usable 5 cavity mold everytime.

its also a good idea to protect this mold from heat & light & store in a safe place. used right, you can get hundreds of molds from this one.

[sloegoe]

I totally second redg8r advice and I would recommend using clay for your master like sculpey then coat it to gloss the finish. With an RTV you are looking at even more resiliense than the actual plastic worm so you will have no problem getting it out. -sloegoe

[guiley]

Thanks for the advice and pictures sloegoe and redg8r. Do you usually do any carving of that final polymer clay 6 cavity master to sharpen up any of the details before you coat it?

Brian

[sloegoe]

I'm having a hard time keeping the mold, master and relief all straight. You're going to make a master out of clay then cast over it with let's say a plaster of some kind, then take the clay out of the plaster (durahms) and coat it with laquer or the like.( you can and I do make slight adjustments to the mold with a dremel before you coat.) Then we can make multiple copies of that master with this mold. You can use Rtv or plastic worm material for this. Take these "6" copies and glue them to a peice of glass and build a dam around them. Then cast them out of whatever material you want. You're done.

Ithink redg8r was then saying you can make a relief of your 6 worm mold by building a dam around your mold and casting that out of RTV so you can easily make new 6 worm molds. any quick Q's (sloegoe@sbcglobal.net)