homemade injection molding machines

[glycerine]

I posted a few weeks ago with some questions about injection molding. After that I got to looking around online doing a little research. I saw a homemade injection machine online that used pnuematic hydraulic bottle jacks, so it was capable of producing quite a bit of pressure. Basically the same concept as a shop press. Anybody ever built anything like this???

 

[Russianwolf]

I was watching "How it's made" the other day and they were doing some casting. Some of the pressure requirements are based on the mold types. A Stainless Steel molds can hold up to a lot of pressure, but some molds are rubber because removing the parts from a SS mold would be too difficult. The rubber molds use less pressure as they would deform (and fail) at high pressures.

Now, I'm not sure if you can use plastics with the rubber molds or if they are wax only.

But one of the other advantages of the rubber molds.... you can make them yourself easier than the SS molds. If it'll work for you.

 

[dogcatcher]

I asked a neighbor that is retired from a manufacturing outfit. His simple answer was that injection molding is too dangerous to mess with. He said that a mistake with high pressure and melted plastic can kill you. According to him to make good molds it takes a good tool and die maker to make them. The melted plastic is injected under high pressure, take the combination of the mold, and high pressure they have to be perfect, or you can get hit with melted plastic.

 

[studioso]

I doubt that you can build a decent, safe injection machine for less than the cost of a used one.
Used Injection molding machines are sold everywhere: look up bidspotter, used dealers and more.
I think you will find that what is shockingly expensive is buying the mold.
If you are savvy, you can get them made in china.

 

[workinforwood]

I bet Mr Bic built his first one and look where he stands on the mountain now! I am not any expert, but every injection molding machine I ever saw did not use liquid plastic, they used plastic pellets that where blasted into a steel mold and then quickly heated up and fused together. Over the years, I've been to a ton of factories like this. Maybe there is ones that use liquid plastic too, but the pellets do make more sense because you don't have a bunch of hoses getting trashed out by liquids, especially if using liquids that would be mixed together before being in the mold..they risk curing in the lines. I seen them make their own pellets too. They mix huge vats of liquid resins and add colors, if that's what they need and then the sheets they pour are ground up like a pepper grinder. A lot of the used ones, well I've been on that end many times too..picking up plastic pallets and plastic drums from places like Coca Cola, and there's guys with these machines, they go up a conveyer and into a huge grinder to become the pellets for plastic injecting.

 

[sbell111]

I don't think that they were referring to plastic that started out as a liquid. Rather, I think they were referring to hard plastic in the form of pellets that is hested by the machine to a point where it becomes liquid and is injected into the mold.

I have had two experiences with injection molding in my life. The first was at the NY state fair some forty years ago. They were making small screwdrivers and giving them away. Watching them make that screwdriver and then being allowed to take it with me made quite an impression on a young Steve Bell. That experience, I believe, is responsible for several of the crafty things that I have taken on over the years. The other experience was in working at a plastics molding company for a summer while in high school. Both the state fair screwdriver and the car parts that I made in high school started out as plastic pellets, got melted to a liquid, and were injected into a mold.