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cnc'd negtive mold in wood/and foammies
19 replies to this topic
Posted 04 January 2008 - 07:54 PM
Just a thought, has any one tried to do a negative cnc'd mold out of wood and brushed epoxy up on it, to seal grain, and wood, added correct mold release and then try'd to pour a fommie within it. I wonder what the end result would be?
Posted 04 January 2008 - 08:14 PM
Whether the mould was made of wood or plaster, it is going to be sealed and then finished, probably with the same top coat epoxy.
Personally, I had problems trying to do foam out of a Plaster of Paris mould. Maybe it was down to the incorrect release agent. I tried several and gave up after four or five binned moulds.
I am affraid the you might end up with a butchered mould with a LOT of program and m/c time invested.
If you want to go this route, I suggest you make some Plaster of Paris moulds and experiment with different release agents, until you get one that really works. Then invest the effort. It should not be wrestling match to remove the foam casting.
If you are going to use foam, I prefer your plan (A), m/c a positive wood master, seal and finish and take an RTV splash off that.
Posted 04 January 2008 - 08:25 PM
Wood master, seal, and finish then make the RTV mold is the way to go for ease of use. I have used bondo, Plaster of Paris, durhams, etc... for the molds and they work fine if as mentioned good release agent used. The trick was to demold early, if the foamie is allowed to expand to its fullest and cure and then it almost locks itself into the mold. Even in cleanly shaped/plain lures, with details (especially undercuts) you can really lock the bait in. RTV is just so easy to demold from that it makes it very easy to just Plaster of Paris the bait right out.
Posted 04 January 2008 - 08:56 PM
I am new to the hole foammie idea, and will try it very soon, if my mold is say a left side negative profile cut into the wood, and I use a release agent down inside the mold designed for 16lb foam , have vent holes in my mold. have a back plate on my mold, which will also have the release agent. and cast one side at a time. Do you all think it would be easier to pull apart one side at a time.
Posted 05 January 2008 - 12:07 AM
You are really stuck on this two halve thing aren't you. I think you are just going to have to do it, to get it out of your system. There is nothing wrong with that, I am like that myself. First I read everything I can on the subject and then wander off and do it my own way. Then I discover why people do it the other way! BUT, not always. Sometimes I find that I prefer MY way.
As for ease of removal. Because the half cast will be flush, it will be more difficult to get to grips with, but if the relese agent works, it should be no big deal.
Travis has made a big point, not letting the foam stay in the mould too long. This could be were I went wrong, also I never found a good release agent before I gave up on the job (to be re-visited).
Posted 05 January 2008 - 02:11 AM
:yawn:HE DID IT HIS WAY!!!! Sorry Vodka reminds me of a song!!! Had to post..
Posted 05 January 2008 - 02:26 AM
If it'll be CNCed why wood??? Metal mold halves be the key.
Posted 05 January 2008 - 05:33 AM
Ya that would be the first time doing a recessed (negative) cnc cut. Always done positive 2d cuts, and was thinking instead of using 6061, trying the wood first just for prototypes and mess ups. But would still want to be rewarded by having a useable bait being casted out of the wood, Other words the motions for the cnc are the same in wood or 6061. Wood is alot less expensive than 6061, for mess ups,and cast offs. I am ready to try it what do ya think?
Posted 05 January 2008 - 05:40 AM
Could you post some close-ups of the negative mould when you've finished. I'd like to see the state of the m/c finish before any tidying up, if you don't mind.
The reason I like the idea of a positive mould is that it would be easier to clean up the surface finish after machining.
This is all good stuff. Go for it and let's see.
Posted 05 January 2008 - 10:11 AM
Before you ruin a mould, make a two part simple test mould, and experiment with release agents and demould time until you get it right, then use your real mould. Too much work to ruin experimenting.
Unrelated question. Why does my spellcheck list demold as the proper spelling, but remould as an alternative?
Posted 05 January 2008 - 10:44 AM
Thanks guys for the inputs, fixing to go down stairs and start a positive mold. I have a cnc'd look alike of a shap Rap #5 but a little bigger I call it a number 6. I will shoot some pics vodka but it will have .125 ball end mill kerfs in it so you can get a idea what kind of sanding a finish shapping is required.Be back in a couple of hours
Posted 05 January 2008 - 11:12 AM
I'm curious to see the Cnc'd mold myself. We have a hobby 3 axis cnc with a digitizer that writes its own programs and has come in very handy in the past. Matter of fact thats what we use to cut our bodies out of in balsa and basswood.
You can program in what sized passes you want to use while digitizing to cut down on the tool marks.........takes a little longer but it sure cuts down on the sanding time.
Posted 05 January 2008 - 11:58 AM
Wouldn't the foam bait get stuck inside a metal mold? If I design a bait that really works it would be nice to have a metal mold that would last forever.
Posted 11 January 2008 - 11:28 AM
Hello to all, back at it. Yes the foam will stick the metal mold, so after much research this past week, came up with, and asked help from alot of TU guys, For sure use the silicone mold system. So I have ordered all my urethane, micro's, RTV silicone, and mold releases. They will be in next week. So far I have made my positive mold and my mold boxes I will post some pics a little latter to show progress.
Posted 11 January 2008 - 12:47 PM
I tried the foamy route a while back. I went through all these negatives and finally got some decent baits. Trouble was then, they never seemed to stop gassing. I let them set for a week, two weeks and still the paint and top coat would blister and bubble. The baits looked like they had warts.
So good luck to you as getting a good looking bait is only half the battle.
Posted 11 January 2008 - 09:27 PM
I would demould cheese and remold my false teeth, come to think of it , I could also demould, my false teeth too. It's probably your spell check set on 'American English' instead of 'Australian English'- sorry VM and Phil, I meant real 'English'. You should see the dramas we have to go through with all of this computer stuff made in USA - color , colour, comes to mind.pete
Posted 12 January 2008 - 03:10 AM
Pete. Yes, it is a problem word for me. I just checked my word thesaurus, no such word as mold (a town in North Wales and Northern Ireland). But, I am going to use the Americanized version from now on, purely because if a search is done, my posts would not register (probably a desirable feature for some!).
So, I do hope you find a solution for your molded, mouldy dentures before the April gathering!
Posted 12 January 2008 - 08:04 AM
Several have had this gassing problem. I haven't observed it execept in a couple of my first two baits and chalked it up to poor preperation, I had pin holes exposed. I try for essentially just to have to cut the fill and vent holes. Minimal flash, usually flakes off with my finger nail. Wipe down with alcohol and then good to go. I have placed foamies out into the sun to try to get them to blister and didn't have any do so. I typically however attempt to mold a stash of baits and set them aside and work with older casts just to be safe due to the experience of some.