Outdoorartist Posted December 22, 2014 Report Share Posted December 22, 2014 Hello everyone, I am brand spanking new to this hobby and site and have already figure out it could get expensive and addicting in a hurry! I am making POP molds of all my favorite lures and some needed to be two part molds. I read that you need an injector to get good results from tails and small parts. All the injectors that I could find were way expensive for me to buy just to see if I like the hobby and plan to continue. SOO, I have built my injector into my mold. I made a cavity in my mold using a dowel that I plan to pour the plastic into then reuse the dowel to PUSH the plastic down into the mold. I cant seem to find any information for anyone doing this. I know I will have to be extra careful and make sure I have all the proper PPE. Has anyone done this? Does it work with decent results? What are some things that I should watch out for? I also read that POP molds do not seal that great so there will be alot of flash but having vent holes isnt as big of an issue as with the rtv, silicone type molds. Any thoughts on this? Thank you for any responses! Merry Christmas! Quote Link to comment Share on other sites More sharing options...
Travis Posted December 22, 2014 Report Share Posted December 22, 2014 It will work but the longevity is not the greatest. On some grubs (two piece) I did as you did and used a large plunger from a plastic syringe to push plastic. Goofing around I messed with vacuum, compressed air, and spun some also to push or pull plastic in and it worked fine but took a lot of clean up with all the vents I had put in the molds. A properly made mold will not have flashing. Quote Link to comment Share on other sites More sharing options...
Outdoorartist Posted December 22, 2014 Author Report Share Posted December 22, 2014 The 2pc molds I have made so far are only single bait molds. I am just trying to get a feel for it. I feel like the quality of the mold is pretty good. I do not have air bubbles in them and my cavities are picking up great detail of the baits, I can even see who made them after sealing with elmers and water. I got a piece of copper tubing to place inside of the port that I made and plan to sand the dowel down to fit it. I am not looking for a long term solution, as I will probably get an injector if I continue, but just a way to get a couple bags of baits to try out against their originals. If I feel like they are good I plan on maybe designing my own versions and things. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 22, 2014 Report Share Posted December 22, 2014 A novel idea, I have never read anyone trying this before. The first thing that leaps off the page, is the danger factor. I certainly would try it, BUT, suitable gloves, protective clothing and a full face mask, as we cannot predict with any certainty what is going to happen. The two halves of the mold will certainly have to be clamped. This likely eliminates RTV as a possibility for this method, due to the bore closing in on the piston, but you might get away with it, but always check the piston movement before pouring. I think aluminium round bar would be favorite for this experiment. You may have to doctor the bore to get the piston free enough to slide. This could be done with a second bar, scuffed up with emery, starting off with fine grade. It will take some trial and error to get the balance right. If the hole gets too sloppy, you could get plastic squirting back, especially if you get an unexpected blockage. I say again, safety is the number one concern here. I think a reasonable lead in for the piston would be preferable, rather than filling up to the top, at least an inch I would say, and don't get skimpy with the mold wall thickness around the piston, plaster is not good in tension. Another solution would be an aluminium sleeve, if you can find a bar and sleeve material that is a good fit. If the initial trials are successful, I would build a simple pouring box with a hinged lid. Pour the plastic, close the lid, insert the plunger and inject. DAve Quote Link to comment Share on other sites More sharing options...
Cami Posted December 22, 2014 Report Share Posted December 22, 2014 (edited) Here you are an Italian Tutorial to realize a multi cavity silicone mould with a incorporated injecting room: http://xoomer.virgilio.it/cjbur/a_stampoMulti.htm The two valves are reinforced with two flat pieces of wood, the piston has been obtained by the shank of a bolt. Master has been worked by turning a wooden rod, after that a single cavity silicone mould has been created to obtain parts in resin. Even if it is written in Italian language, I think that the pictures are enough clear to be understood. There is also a video that shows how to inject. The trick is given by the quite open window on the mould top. NB: it is not an idea of mine, but Save76 is the Engineer of this method adopted by a lot of us. Bye Cami Edited December 22, 2014 by Cami Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 22, 2014 Report Share Posted December 22, 2014 Here are a few links to a vacuum injection method that I developed back in 2007. I called it vacuventing. I am sure there are more posts on the subject out there, if you try a search: http://www.tackleunderground.com/community/topic/10718-hairy-worm/?hl=%2Bhairy+%2Bworm http://www.tackleunderground.com/community/topic/10957-3d-legs/?hl=vacu-venting#entry75522 All the images that I ever posted on this site have been lost, so I searched back through my records and found these. DAve Quote Link to comment Share on other sites More sharing options...
Outdoorartist Posted December 22, 2014 Author Report Share Posted December 22, 2014 Cami, the link you posted is basically exactly what I have done. The only difference is that mine are plaster and my injection and bait are in-line so I am pushing straight down toward my bait. Vodkaman, I have been looking for good information about the vacuum method. The first mold that I made I scraped air canals to all of the little pieces and then connected them to a vent hole. But I did not like the look of it so I scraped it. I am hoping this works. Also, I made my plaster molds extra thick to compensate for any pressure. Both halves are close to 2" thick. I know that it will require extreme attention to safety for sure, I will prolly make an aluminum foil shield around my dowel to minimize any splatter that may shoot out of the injection port if an air bubble tried to come back up or if it squirted under pressure. I am glad to see that in all my tinkering I may not have wasted my time! I bought some Silicone today to try to make a silicone open pour mold just for fun, I am excited about this hobby! Quote Link to comment Share on other sites More sharing options...
Travis Posted December 22, 2014 Report Share Posted December 22, 2014 Just cut a few 1/4 ply blanks to work as cauls on the mold. RTV can be clamped this way and POP if needed. As far as safety you aren't exerting any major forces so no real issues. Common sense would tell you if you put 2x the amount of plastic needed and mash it down bad things are going to happen. It takes very little pressure to fill these. Use a glove if needed on the plunger and let the clamps work as the stand (glove hand if you want to hold the mold also). Many of the molds I made would fill on their own with just a reservoir. The plastic doesn't cool nearly as fast as it does with aluminum so you get better flow and need very little pressure to fill small appendages. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 23, 2014 Report Share Posted December 23, 2014 Sounds like you were very close with the vacuum method, shudda percevered. Good points on the safety issue by Travis. I was perhaps being over cautious. I am coming at this from a theoretical point of view and so need to be over cautious, for your sake. Lots of good posts above and very quick response too, people obviously enthused by this idea. Dave Quote Link to comment Share on other sites More sharing options...
Outdoorartist Posted December 23, 2014 Author Report Share Posted December 23, 2014 Well, made my first couple pours tonight into open molds. The learning curve is quick! Right off the bat I realized that I should have sanded down the lip where the bait ends and plaster starts! First pour I didn't heat the plastic long enough. The small legs broke in every pour I made, I really don't know why yet.... But I still managed to make baits that could easily be fished with! Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 23, 2014 Report Share Posted December 23, 2014 I did a mold layout for a piston mold, using a bait that I had on file. It is important to know the volume of your bait, so that you can calculate the volume of the piston. For this particular bait, the mold required two pistons; 1" dia piston x 152mm plastic length, to produce 5 baits. This gives the possibility of two color baits. Not sure how that would work out, but an interesting variation. The easiest way to accurately calculate the volume of the lure, is using the Archimedes dunk test method. Dave Quote Link to comment Share on other sites More sharing options...
