Injection Moulding, small scale.

Discussion in 'General' started by Joules, Jun 7, 2015.

  1. Joules

    Joules Member

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    Just wondered if this had crossed anyone elses mind. I have been toying with the idea of an injection moulder based around the V6 or Volcano head. I know pressure will be low, but since cycle time isn't so much an issue I can heat and chill the mould as needed. I figured something using a Ramps board so the machine can pretty much cycle itself. For my application I am looking at components of a couple of grams or less. I have an old Austin Allen Gnat injection moulder that has sat idle in the workshop for a good while. It is both too big and too small. In that I mean it's too big for micro moulding and too small having a capacity of 12 gram per shot. Thats alot of waste plastic if you have to clear the head each shot to avoid the plasic degrading. 12 gram for larger objects is still quite small once you factor in sprues etc.

    Some nice examples of desktop micro moulding machines on the net got me thinking. I would be looking to mould in PLA, moulds made in JB Weld high tempreature epoxy, should handle ABS as well.

    I do alot of prototype work, and in some cases the items are clips or disposable components and it would seem PLA would be an ideal material for those applications.

    Any thought's ?


    Joules
     
  2. Sanjay

    Sanjay Administrator
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    I've also considered this!

    The readily available suite of materials in a convenient filament form factor makes it really compelling vs a pellet and auger drive. There's no good way to make a really tiny auger for a tiny IM machine, but using basically a reprap extruder and something like a volcano you should get a workable shot size and a huge increase in ease of use.

    You'd be surprise how much pressure you can actually generate with a geared extruder with 1.75mm filament, the filament is a tiny little piston so generates a good deal of pressure. It's no hydraulic ram, but I think it would work admirably.

    You could get a larger shot size with 3mm filament. You can also chain together multiple volcano blocks if you're feeling fancy, just couple them in series - you'll need something M6 threaded with a hole in the middle to take the place of the nozzle in the first block. I know of one person doing something like this, and are using 3mm, so another 3mm heatbreak can be used to couple the two volcano blocks together.

    I'd definitely look at using some off the shelf reprap electronics too, RAMPS is a good shout.

    All that really remains thereafter is to create a mould actuation system, which could even be done by hand.

    The hard part, as is always the case with IM, would be mould creation. It might even be feasible to print moulds. I'm imagining a nylon mould with water cooling channels printed into it, probably ludicrous but I'd like to try.
     
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  3. Joules

    Joules Member

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    Thanks Sanjay, I will stick with 1.75mm as that is what I use on the printers so it keeps things simple. On feeding the hot end I had thought along the lines of a larger splined wheel and really getting the filament pressed in to spread the load. However my prefered is precut filament loaded via a magazine and a screwjack pushes the filament in (bit like the tiny auger), that way I can make use of odd bits too. I had a batch of filament that was all broken and trying to work out how best to make use of it than just throw it away. Easy to have adjustable stop on the leadscrew for different shot values and feedback if the stepper stalls for any reason.

    One concern I did have was the heat break wall. I wonder if for this application it is probably better double thickness as I am uncertain of the load on the nozzle when pressed against the mould. The intention is to close the mould with a motorized toggle clamp as per fullsize practice, the toggle will also push the mould against the nozzle.

    Its mostly still early CAD stage, but trying to anticipate problems and solutions before cutting metal. :geek:

    On mould making, I have used alloy frames with Devcon epoxy (JB Weld works too) poured over a wax master to make the moulds. I also use electro etching in steel for really thin stuff.
     
  4. jhon

    jhon Member

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    I am interested in starting a small fishing lure business out of my shop at home with the hope that it takes off and then moving to a full production facility. I have the contacts to market the product and the knowledge to design it however I lack the knowledge to manufacture the product...Are there affordable machines out there to get started without spending a fortune? Where is a good place to learn the pitfalls of injection molding..Would I be better off just designing the products and having them molded by someone else?
     
  5. Dr Jeep

    Dr Jeep Well-Known Member

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    I think It's the moulds more than anything, There are a few options for lower volume injection moulding but none of them are cheap as there is a lot of design work beyond the base CAD model for anything reasonably complicated.

    Pretty much the order of things is silicon moulds which are good for prototyping but produce the worst quality fit and finish ( and don't last for very many shots ) then you have aluminium moulds which are good when your order quantity is in the 100s rather than 1000s then finally steel moulds which will bankrupt you unless you can sell units in the 1000s or 10's of thousands.

    I like Sanjay's idea of nylon though for prototyping. I'd try that or even SLA printing if FDM like the bigbox won't do and really nail your product and check it is marketable before going anywhere near aluminium or Steel moulds for injection moulding.
     
  6. Joules

    Joules Member

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    For a simple setup, this is about as cheap as you get new, unless you fancy buying my old Austin Allen Gnat.

    http://hindleys.com/machinery/plast...ection-moulding/injection-moulder-mod-25.html

    Moulds for short runs can be cast in Devcon or JB Weld high temperature epoxy. You still need an alloy billet to surround the epoxy to stop it cracking under injection pressure, but at least the alloy shell is reusable.
     
  7. TstarkEngineering

    TstarkEngineering Well-Known Member

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    This post caught my attention and is very interesting. I deal with injection molding on a daily bases for a medical device company, and of course I enjoy 3d printing but never really thought about doing something like this.
    The idea is possible but may not be ideal. I think the idea behind creating a tiny press is possible, but all comes down to mold design(or as UK people say mould :p). You would ideally need to bring the mold up to a certain temperature so you might have to have some sort of heater blocks in the mold itself if the mold were 3d printed and I am not quite sure how this would react. Also, who knows how your flow into your cavity would be, and you would probably need some sort of runner system or gating system as well. Drying of the material may also become a more critical factor. Lots of factors that would be really cool to see.

    I have seen a few companies make inserts out of plastic to run a few shots, but I have never personally seen an entire mold, but I am sure someone has tried it.

    Ideally if you could 3d print a mold then have a mini press(cheap enough for a consumer) to be able to pop out 100 parts within a few hours. Like a babyplast (if anyones ever heard of that)That would be a game changer for 3d printing.
     
  8. TstarkEngineering

    TstarkEngineering Well-Known Member

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  9. Joules

    Joules Member

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    Hi guy's, I have an old injection moulder I no longer use and wonder if anyone would like to buy it for :-

    A: Potential Kickstarter enabler
    B: Re-use your old PLA models after shredding them.
    C: Conversion from analogue electrics to new RPi or Arduino control for timing and pneumatic control.


    Austin Allen 250 PRT Injection Moulder

    If I remember rightly it has a shot capacity of 12gm. That's total including the sprue.

    It needs 1kw single phase (240vac) for the heater and electrics. @80psi, air consumption is 7.8cfm for a 10 second cycle, but on single shots you can get by with a 4cfm compressor (just). On auto the cycle time can be adjusted from 3-50 seconds.

    The lock pressure is 7.5 tons @ 100psi and 9 tons @ 120psi

    Maximum mould (billet size) 7.5" x 8" x 4" (x2 as they are mould halves) the mould can then open upto 4" for part ejection.

    Machine foot print 32" x 15" and it's 66" tall, can be broken down into two or more parts for transport. I got it home in an estate vehicle, the machine is over 200kgs in total weight.

    I don't have any pellets left as they are long gone, last used with nylon some years back. I am looking for £600, buyer collect I'm afraid from South Yorkshire, it has the original operating and service manual.


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    Any further questions just ask.
     
  10. TstarkEngineering

    TstarkEngineering Well-Known Member

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    I wonder how much it would cost to get to the US
     
  11. Joules

    Joules Member

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    You could probably pick one up over there with less hassle :cool:
     
  12. TstarkEngineering

    TstarkEngineering Well-Known Member

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    ya I imagine so. I was tempted to purchase a allforge(kickstarter type project) recently. But I kept thinking Why not just by like a baby plast instead..
     
  13. Joules

    Joules Member

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    I've never come across a Baby plast here I could afford, looked for years but nothing. That was one reason I started looking at designing a desktop moulder using 3D printer parts.
     
  14. Joules

    Joules Member

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    Have you seen this one. It really got me thinking about desktop production.



    A jewel of a machine.
     
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  15. Thomas Kamsker

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    Hi,
    to do the moulds is quite easy (if you have the equipment ) so if there is interest we can do a kind of service where the people send down the file and get back 2 alu pieces as mold for that file.
    i do CNC milling machines and have build an Machine inspired by http://www.amazon.com/Secrets-Building-Plastic-Injection-Molding/dp/1878087193

    so if we set this up as an service it might be handy for people who want kind of mass production of small pieces

    i personally don't think that it makes sense to do that in 3d printable materials but i am no "PLASTIC cientist"

    best reg
    thomas
     
  16. Joules

    Joules Member

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    PRICE DROP on moulder. It's buyer collect, so UK only unless you fancy a long drive

    And now SOLD
     
    #16 Joules, Jun 6, 2016
    Last edited: Sep 8, 2016
  17. Cedric_K

    Cedric_K Member

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    Injection moulding with a reprap stepper, some filament and a volcano nozzle... is it a joke ? I deal with IM for 10 years, honestly I can't see any reprap way to make something looking like that.

    You need so high pressures to fill a cavity, if you were able to build this pressure inside a volcano nozzle, its own threads could be ripped ;)
     

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