23 replies to this topic

[nova]

Vodkaman, on 10 September 2010 - 11:17 AM, said:

If I was to tackle a project like this, I would start with a block of soft clay. Using clay carving tools, remove clay and set the master into the clay. No need for accuracy or setting as low as the parting line, just deep enough that the soft plastic master can be safely retrieved after curing. Build the box and pour the PoP. Remove the master and fully dry the PoP mold half.

Using a belt sander, I would then sand down to what I want as a parting line. Using a drill and a burr, create location bumps, as the mold face is now very flat and will not locate by itself. Re-build the box, replace the master and pour the second half.

The pour hole/funnel can either be molded with clay or cut after completion with a drill and burr.

If I was making an RTV mold of the soft plastic master, I would still make the PoP mold as described above, as far as belt sanding and creating the locator bumps. I would also add a clay pour hole (half). Replace the master and pour the RTV. Once cured, remove plaster (store for future molds), invert and pour the second half of the RTV two piece.

I have made RTV molds of crank bodies using a similar technique to this in the past. More steps involved, but it makes for a very neat mold and a casting with a neat and minimal parting line.

Dave

ps, for injection, I would drill the pour hole after molding, starting small and increasing the drill size gradually. As the drill diameter gets larger, it may be better to turn the drill by hand, as the plaster cuts very easy. Would not want to destroy the mold at the last stage.

Wow. Dave the engineer. lol

Just teasing you Dave..........Nil

www.novalures.com

[GB GONE]

I guess if this was going to be a production mold, I might consider all that Dave but still doubtful. Pop is so forgiving and easy to work with that the perfection of the mold is just not required like that of an aluminum mold. Pop works best with the tiny imperfection as it allows the air to escape well without causing any flashing on the bait.

In addition, I would highly recommend that you mold in the sprue, vents, runners, etc. Drilling them after the fact is very difficult as the drill will wander easily and you will ruin the mold after all your work. Use the sprue from another mold as your sprue. I use coffee straws/stirrers as vents many times as well. Toothpicks work well also. Just wiat to add the tiny vent material until the mold has set up for a minute or 2.

Just finished 5 more molds of a thin paddle tail worm. Will be pouring them tonight after allowing them to dry today in the 95+ degree weather here in South Georgia!

Jim

[GB GONE]

PS AS far as containers to mold you baits in, consider this. Go get an old one-side Plano tackle box and take the lid off.

Use the Plano for your molding box as you can use the spacers to increase or decrease your mold area easily. You can make many mold at one time as well. It is also very easy to clean and remove your pop mold out of.

In addition, the groves in the sides (from the spacer slots) help line up your molds eliminating the alignment pegs.

Jim

[Vodkaman]

nova, on 10 September 2010 - 12:53 PM, said:

Wow. Dave the engineer. lol

And proud of it Nil, proud of it.

Thanks.

Dave