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viewer challenge: a benchtop injection molding machine

Former Member

Hi Ben,

 

So, I've seen a few youtube videos of people converting the Harbor Freight mini-mill to be CNC and I've seen the maker bot plastic extrusion 3D printer, now let's connect the dots and create a plastic injection molder.  With the HF CNC mill, one could, in theory, mill metal molds for an injection molding machine.  The maker bot guys figured out how to control the melting of plastic for their extruder.  If you put those things together, you get the basic parts of an injection molding machine.  The only thing left is a hopper fed piston type arrangement that can soften/melt the plastic and push it into the mold.

 

To me, the injection molding machine is the last unconquered territory of the homemade fabrication machines.  CNC has been done.  Circuit board reflow has been done.  Picking and placing of electronic parts has been done.  3D printing is a work in progress.  However, injection molding plastic parts is still beyond the capabilities of the average DIY'er.  To have a plastic part injection molded by a company costs a couple thousand dollars minimum.  If I had a benchtop molding machine and a CNC metal mill that could crank out molds for me, I'd be in plastic molding heaving.

 

Imagine if you could mold the shells of your game machine laptops instead of gluing/stacking/screwing CNC'd plastic parts.

 

Thanks,

Dave

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  • While i agree that this could a worthwhile project, I would like to add some thoughts from my own work on my makerbot. On the makerbot the plastic is run through a very small heater section, and it has gone through a number of changes due to inconsistancies and difficulty of long term operation The current design is now quite stable and i've been running it for many hours without any problems to speak of. To scale the heater design up from one of those may prove quite difficult to get consistant quality. But mechanically according to the baisc picture of an injection molder on wikipedia, it seems simple to create, all you need is a motor attached to a wormscrew that moves the plastic pieces into the heater and the pressure from the incoming material forces the molten plastic out an oriface into the mold.

     

    I think what makes this project unfeasable for most people is that you basically have to make every object you'd like to produce 2 times, which takes that much longer. So unless you are going to be doing a medium or large scale production of items its probably not worth the extra time to make a mold and then cast the part over just maching the part. Also you have to have the design right the first time as its much harder to make changes to a metal mold than to adjust a machined part through an additive or subtractive process. Again i think its a great idea and it be great for someone looking to make and sell their project on a larger scale, but for a hobbyist making a prototype or custom project, not as useful. But hey that's just my opinion.

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  • While i agree that this could a worthwhile project, I would like to add some thoughts from my own work on my makerbot. On the makerbot the plastic is run through a very small heater section, and it has gone through a number of changes due to inconsistancies and difficulty of long term operation The current design is now quite stable and i've been running it for many hours without any problems to speak of. To scale the heater design up from one of those may prove quite difficult to get consistant quality. But mechanically according to the baisc picture of an injection molder on wikipedia, it seems simple to create, all you need is a motor attached to a wormscrew that moves the plastic pieces into the heater and the pressure from the incoming material forces the molten plastic out an oriface into the mold.

     

    I think what makes this project unfeasable for most people is that you basically have to make every object you'd like to produce 2 times, which takes that much longer. So unless you are going to be doing a medium or large scale production of items its probably not worth the extra time to make a mold and then cast the part over just maching the part. Also you have to have the design right the first time as its much harder to make changes to a metal mold than to adjust a machined part through an additive or subtractive process. Again i think its a great idea and it be great for someone looking to make and sell their project on a larger scale, but for a hobbyist making a prototype or custom project, not as useful. But hey that's just my opinion.

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