JRammit Posted April 11, 2015 Report Share Posted April 11, 2015 If im not the 1st person to do this, feel free to tell me.. But if i am, your welcome! I learned how to make 2 piece plaster molds on YouTube, and all the ones i saw were injected in one side and vented out the other... After a little trial and alot of error i learned if vent holes are too big, too much plastic escapes and baits are left with hollow spots.. If holes are too small, too much pressure builds up and plastic blows out in the mold leaving a ton of flashing to tear off...... So... Tried an experiment and it worked great! Drill a 1/4 inch hole through the top of the mold (starting from bait side) near the end of the bait and connect hole to specified point on bait via dremel (i use an engraving bit).. Flip the mold over and enlarge your hole (i use a 5/8" spade bit) only drilling about 1/2 way through to create a reservoir... Plastic should be injected from same side of the mold as the vent (i also saved $60 on an injector by watching a guy on YouTube use a copper pipe, works great but this method will work with an injector too) Since liquid always levels itself, as long as your injection point and vent are higher than the cavity, it will always be full.... Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 12, 2015 Author Report Share Posted April 12, 2015 Tip: the mold in the picture actually gives me problems with bubbles in the middle cavity... I drilled another vent, didnt help....... Previous molds only had one vent connected to all the cavities, worked much better! Not 1 single bad bait out of those molds yet! Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted April 12, 2015 Report Share Posted April 12, 2015 It certainly looks like it needs a vent. Dave Quote Link to comment Share on other sites More sharing options...
Travis Posted April 12, 2015 Report Share Posted April 12, 2015 With the shape of that bait I would rework how you are making the mold. Inject from the top not the side that way any bubbles will raise into the sprue. The current design any bubbles will naturally want to collect in the high point of the lure body unless you flush them out with plastic. Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 12, 2015 Author Report Share Posted April 12, 2015 Thats kinda the idea behind the reservoirs, i try to push enough plastic through to evacuate any bubbles, and any hollow spot or shrinkage gets back filled by plastic in reservoirs and pipe Heres the 1st mold i did using this method... 1 shot, 4 perfect baits every time Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 12, 2015 Author Report Share Posted April 12, 2015 Same with this single cavity, perfect worm every shot........ Maybe i just got lucky on these molds... Thought i was onto somthin! Quote Link to comment Share on other sites More sharing options...
Travis Posted April 12, 2015 Report Share Posted April 12, 2015 Pushing plastic through a mold to remove the bubble is fine but wastes a lot of plastic and doesn't make sense in my book as a mold redesign removes the issue. I understand the reservoir mentality but that won't make up for trapped air bubble unless you are really passing a lot plastic through. Most likely depending on plastic temp that area is "dead" rather quickly with plastic just pushing past those slower areas (sort of like an eddy). As you have mentioned you can add other vents to those trouble areas but once again ok to fix a mold already made but remolding can remove the issue. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted April 12, 2015 Report Share Posted April 12, 2015 I understand the flushing concept and I like it - a lot. But, you are not flushing that middle cavity. The molds that worked, the lures look a lot thinner and they are all connected to a flushing vent. Perhaps the flushing reservoir(s) need to be increased, by extending with another pipe. You can then extend the flushing until you get it right. Finally trim the pipe to the length that works, so it acts as a guide. Something else to consider; the plastic takes the route of least resistance. You need to give the plastic a reason to flow through that middle cavity. The point of your thread was to share your method, which I don't recall seeing before, so well done for coming up with an original idea and putting it into practice, and good on you for sharing. But, if you show a problem, we all want to help you fix it Dave 1 Quote Link to comment Share on other sites More sharing options...
Travis Posted April 13, 2015 Report Share Posted April 13, 2015 Horizontal injection has been used for some time as many hand pour guys used the single sided molds with a top plate and similar injection port. Naturally some started trying to make two piece molds and do the same but encountered the same issues as the OP. Vertical just a lot easier to get better results. Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 13, 2015 Author Report Share Posted April 13, 2015 Perhaps the flushing reservoir(s) need to be increased, by extending with another pipe. You can then extend the flushing until you get it right. Finally trim the pipe to the length that works, so it acts as a guide. Dave Beat me to the punch!... That was my next trouble shoot........ But i didnt think about the other molds being of slimmer baits, makes since And i remelt all my scraps, so nothing wasted.. And i now have a convenient reservoir to catch it all rather than peeling it off my desk Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 13, 2015 Author Report Share Posted April 13, 2015 The point of your thread was to share your method, which I don't recall seeing before, so well done for coming up with an original idea and putting it into practice, and good on you for sharing. But, if you show a problem, we all want to help you fix it Dave Thats why im here!... I just should have actually tested that 3rd mold before i started bragging about it (ha ha!)... I love any and all input!... This site is great!!! Im half way between new and experienced, and ive received ALOT of good advice here, so wanted to contribute something back Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 21, 2015 Author Report Share Posted April 21, 2015 Pushing plastic through a mold to remove the bubble is fine but wastes a lot of plastic and doesn't make sense in my book as a mold redesign removes the issue. I understand the reservoir mentality but that won't make up for trapped air bubble unless you are really passing a lot plastic through. Most likely depending on plastic temp that area is "dead" rather quickly with plastic just pushing past those slower areas (sort of like an eddy). As you have mentioned you can add other vents to those trouble areas but once again ok to fix a mold already made but remolding can remove the issue. Ok Travis, ive tinkered and tinkered with this mold and im almost ready to accept defeat... I could redo my whole set up, but i have one more idea, wanted to run it by someone before i scrap the mold.... My initial problem was the assumption that the 2 plaster pieces would not seal together air tight like a machined aluminum mold would... I figured all my hollow spot problems in my older molds resulted from shrinkage or plastic leveling itself inside the mold....... What if i drilled tiny pin holes in the "problem areas" of the cavity itself??.. Can i make holes small enough that plastic won't enter? Or will i end up plucking tiny plastic hairs off my baits?.... I see your point, and eventually ill need to move on to vertical molding, but in the mean time ive got fish to catch! Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted April 21, 2015 Report Share Posted April 21, 2015 Yes, start off small and gradually open them up until it works. Once you are away from the cavity you can cut a deeper slot to the edge using a Dremel cutting wheel, but there are lots of other ways of achieving this. Dave Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 21, 2015 Author Report Share Posted April 21, 2015 My thought was to actually drill out of the mold, through the top so any trapped air can escape... The holes would be oriented on the flat side of the cavity rather than the edge... I wory if i started hacking away at the edge i might jeopardise the "seal" and cause blowouts... Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted April 21, 2015 Report Share Posted April 21, 2015 I thought about going out that way, my concern was blockages requiring fiddly poking with a piece of wire. Dave Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 21, 2015 Author Report Share Posted April 21, 2015 This bait began in a single cavity RTV mold with severely improper venting.. Only about 1 out of every 3 shoots came out a keeper.. Now im shooting 3 at a time with 2 keepers every shoot... If i get that middle one right, ive nintoupled (if thats a word) my productivity... A little wire poking won't set me back much Quote Link to comment Share on other sites More sharing options...
Travis Posted April 21, 2015 Report Share Posted April 21, 2015 I am with Vodka I would hate to have to poke little blockages out but if you are ok with it all good. I have had it work on some molds and not fill just leave a very small nib. So small not enough to even cut. Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 22, 2015 Author Report Share Posted April 22, 2015 Ill give it a try, better than time spent redoing an old project when i have so many new ones to move onto! Quote Link to comment Share on other sites More sharing options...
JRammit Posted April 28, 2015 Author Report Share Posted April 28, 2015 New design... Vertical for thicker bodies... Only got one bait before it cracked (was down to my last bit of plaster, ended up too thin) but it was bubble free!... Thanks Travis! Quote Link to comment Share on other sites More sharing options...
JRammit Posted March 12, 2016 Author Report Share Posted March 12, 2016 Thought i would re-visit this old thread to show the method became a success By turning the mold vertical and shooting from the bottom im getting consistent results The horizontal set up still works great every time for thin baits, but the vertical set up forces any and all air out of the mold.. Supplies some plastic to draw in for shrinkage.. And the reservoir on top is a great indicator for when the mold is full Two examples so far http://www.tackleunderground.com/community/gallery/image/15604-the-clubber-craw-2-green-pumpkin-green/ http://www.tackleunderground.com/community/gallery/image/15605-the-mud-worm-motor-oil/ 1 Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted March 12, 2016 Report Share Posted March 12, 2016 Those look terrific, good job. Dave 1 Quote Link to comment Share on other sites More sharing options...
JRammit Posted March 12, 2016 Author Report Share Posted March 12, 2016 Thanks Dave! I really wanted to get the vacuum working, but you were right, its just not necessary for simple designs like these This method has far fewer "moving parts", there for less to screw up (ha ha!) Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted March 12, 2016 Report Share Posted March 12, 2016 Is that a built in injector I see there - looks like that really worked well too. Dave Quote Link to comment Share on other sites More sharing options...
JRammit Posted March 12, 2016 Author Report Share Posted March 12, 2016 Its an insert for the copper pipe... I tried molding an injector in, but the plaster cracked under pressure (as expected) The tube does work great, im custom cutting a pipe for each mold to cut down on re-melts 1 Quote Link to comment Share on other sites More sharing options...
JRammit Posted March 13, 2016 Author Report Share Posted March 13, 2016 Now that i think about it... I guess it is a built in injector Quote Link to comment Share on other sites More sharing options...
