Gallery, Projects and General > How do I??

Plastic injection molding ( moulding?)

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John Rudd:
I'm thinking of building a small injection machine to make some plastic fans that I need.

One fundamental question is how large a heater do I need?
The temperature will be controlled at around 230 C so any excess heat capability of the heater is really redundant...if you get what I mean?
I was thinking 2 x 150 Watt heater bands around an extruding chamber 45 mm diameter with an internal bore and lentgh yet to be determined...

If anyone has experience in this field, feel free to educate me....

charadam:
John,

Wouldn't 3D printing be a better method?

Lew_Merrick_PE:
Hi John  --  My approach is (admittedly) somewhat weird in that my set-up allows me to Die Cast as well as injection mold.  I use a pair of 1000W heaters along with a "bang-bang thermocouple temperature controller to manage my molding temperature (a friend of mine made one for me for about USD5.00 back in 2002).  --  Lew

John Rudd:
@ charadam,
Firstly I dont have a 3d printer.... :Doh:, 2nd, I dont have access to a 3d scanner or other means of providing an stl (?) file for printing one, 3rd, I dont know anyone with a printer... :scratch: and 4th, not sure if a printed fan would endure the motor speeds....in excess of 4000 rpm... :scratch:
The fan(s) is (are) for a vintage electric drill that I'm refurbishing, the fan once removed cannot be replaced as it is destroyed in order to remove it...,( crap design I know... :doh:) but there you have it...
Also the plastic fan has a metal centre boss where it fits onto the motor shaft....

I've molded some fans in resin using a silicone mold, but havent tried them to see if they stand up to the speed....but the original fans are probably molded in the first place..,

Lew, thanks for your approach, sounds like there's an excess of available heat at 2kw..... :zap:,
I'm going to use a PID temp controller to control the heaters....

I'll post up a picture of the type of fan I'm on about....

ddmckee54:
I've got my doubts that that a silicon mold would stand up to the pressure of injection molding.  As far as a 3D printed fan surviving the motor speed, there are versions of 3D printed model airplanes with 3D printed props and 3D printed fans for a ducted fan.  Both of these would be running at higher RPM's than a drill motor runs at.

You don't need a 3D scanner to create the STL file, you use a 3D CAD package to design the 3D model and then export the model to an STL format.  You DO still need a 3D printer though, know anybody that's got one?  There's a lot of us on here that have one, and a fan for a drill wouldn't take that long to print - probably only an hour or two.  The other thing is that because you are molding the part at an elevated temperature, you need to allow for shrinkage if you need a dimensionally accurate part.  Since this is supposed to fit on a shaft dimensionally accurate is probably a good idea.

Don

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