Custom Baits - Forum
General => General Discussion => Topic started by: JOHN62 on 02/06/13 19:32 UTC
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of the box?!? Call me crazy! I'm a guppy at this!! My first try at injecting into a tube mold was a failure! Part of the tail/skirt came up short. 2/3 of the material set up in the syringe. I've been casting dental gold and other dental alloys for 51 yrs. Yea, I'm older than dirt! We would NEVER think of casting into a cold mold. The modern day dental semi-precious alloys melt at about 2,100 degrees. And we cast into a mold that is 1,700 degrees.
My question is, has anyone tried preheating the mold and syringe? This would/may prevent super heating the plastic. I'm only talking about preheating to maybe 125 or 150 degrees. My hot tub is 104. My garage is heated to about 55 degrees. So I'm sucking hot plastic into a 55 degree syringe and injecting into a 55 degree mold. That's expecting a lot!! I live in Colorado so I am in the winter season. BUT, you guys are having success. So maybe I'm over thinking this.
My wife say I over think everything.
I'm anxious to hear what you have to say!!!
Sincerely, Older than dirt, John, a PROUD VETERAN!!
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When I used to have all my pouring supplies in a cold shop, I bought a griddle to preheat all my molds and injectors so they were warm to the touch or almost hot. Now I shoot all my baits in the basement where it's around 65-70 and I haven't had any problems. I hope I helped.
Josh
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Hey John, Welcome to the club. I live near Buffalo, NY and my pour room is in the attic of my house. It's about 40 degrees up there. I use a griddle set on about 200 degrees to prewarm my molds and injectors. Nothing extreme just enough to get the chill out of them. When the plastic comes out of the microwave I place the Pyrex in the same griddle and turn it up to about 360. After the first shot the molds and injectors retain their heat so no additional heating (warming ) is required. Hope this helps. John
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I preheat mine in the winter, even though my man cave is heated. It isn't real warm in there, but I don't want things to freeze. When I head out to pour, I set my molds that I'm gonna use on a box in front of my heater to warm up. Its one of those infrared heaters. By the time I get things in order and ready to shoot, they are warm. Some molds with small appendages, such as your tube, need to be fairly warm or the plastic cools before it can fill. Some fellers shoot some scrap plastic in first to heat the mold. Once it is warm, hold a little pressure, ten count or so, to fill the mold. Hope this helps, Joey.
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You got your answer so all I need to say is, THANK YOU FOR YOUR SERVICE! Hoo-Rah!
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We're working under cold conditions here in Iowa too. At the Do-It shop we will occasionally use a heat gun on the injector and the molds to "take the edge off" (especially on the first go-a-round) and at home I'll set them infront of the heater for a few seconds before clamping them up. A hair dryer works too, but it takes a little longer. I usually tend to heat the plastic a little hotter than what I'm actually shooting for just to counteract the cooling from the cold injector and molds.
and a BIG Amen to the "Thanks for Your Service".
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For me personally i dont preheat my molds at all but im not working to really cold weather.. usually 40's at night here in socal, sometimes we get below freezing but not often..
I will heat my plastic to 360(i use a thermometer and keep very close watch) and will shoot the first round. I will leave the first round in the mold for a good minutes and half to two minutes to get the heat transfer, and i wont empty my injector. This usually gets my mold and injector up to temp pretty well.
Remember when shooting alot of the same mold heat is not our friend. It will require you to keep the mold closed longer to let the plastic harden. This in turn will allow the plastic in your pyrex to cool down which will mean more reheats in the long run..
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I keep my stuff in the house in winter and bring out what I'll be using. Also it doesn't hurt to suck up some plastic and then empty it back into the cup a few times. Also you'll learn that different molds behave differently. The tail not filling completely is probably due to the cold mold, but I have a grub mold with small appendages and I found I have to have the plastic fairly hot and I have to shoot it pretty fast. If you continue having problems even with a warm mold, something to think about.
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Try keeping a cup of junk plastic around to heat up to 360 for the purpose of pre-heating the gear. A couple quick injections and you're good to go.
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I live next door in the even colder state of Utah. My work room is in a small secret room that is back in the rafters of my house. It is in the low 40s in there right now. I have been using a hot plate (which I use for small batches of plastic for hand pours) just barely on to warm up my molds and injectors before shooting. It definitely helps. If I don't, I sometimes have problems with clogged injectors and dents in my baits.
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You can definitely shoot the mold a few times to warm it up and that will get things running smooth, but as mentioned, keep some scrap plastic that will be used only for preheating. This preheating plastic will turn darker over time (don't waste Your stabilizer in this plastic!). If I were shooting a Tube Mold (I don't have a Tube Mold), I'd use 2 Pyrex cups...1 for melting the preheating plastic, 1 empty cup for receiving the molten plastic as You heat the insert...
Disclaimer- This is just ME, if You do this, be very careful!!!
Melt the plastic in 1 cup, hold the insert/spline over the empty cup, pour the hot plastic onto the insert/spline...coat the insert completely. Set the coated insert aside. Using the same plastic, draw Your injector full and shoot the Tube Mold (without the insert). Give these parts time to cool then remove the cooled plastic, assemble the mold. Now Your injector and mold is warm.
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I use a small hotplate to initially warm my molds or run a few cycles of scrap plastic through them to warm them up...and keep my injectors up against my work lights to keep them warm. If I have a window open for increased input area (ventilation)...I cover my molds with a kitchen towel after I take the baits out to keep them warm.
Being the safety nut that I am...I put my lights and my heating units on the same power strip...so if the lights are off...so are my heating devices!
Andy
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Your Signature gets me every time, Andy Sir!
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Ditto re Tom and the junk plastic. I also use the forced air heater to heat the molds if I'm also heating the garage.
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I also use junk plastic for reheating my injectors and molds. Y can heat it to 360+ without really worring about ruining it since it junk anyways. I would also take the time to Thank a proud Veteran. With out the sacrifices of so many what we do for our hobbies or business would never be possible. Thanks again
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ive been shooting in 30 degree weather, i have a mini space heater that ill warm my molds up infront of while the plastic is cooking. they dont need to be hot, but warm to the touch.
the real trick for me is heating my injector in a griddle while the plastic is in the microwave. i like to get it as hot as possible, you know its hot when you can feel it through the gloves!
in the cold weather, preheating an injector with scrap plastic wont last, it'll cool real fast. so i just toss the injector into the griddle right before i heat my plastic, only takes a few minutes to heat up.