Introduction: Home Injection Molding

Picture of Home Injection Molding

This Instructable explains how to make real injection molded plastic parts using a simple hand-operated machine. I realize most of you reading this don't have one of these machines, but I decided to post here anyway just to let all the garage inventors out there know that such a cool tool even exists.

More details about the machine can also be found at


Step 1: Machine Set Up

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a) Plug in the machine. b) Turn on the power switch. c) Adjust the thermostat to the desired temperature.

Step 2: Insert the Mold

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a) Place a mold in the machine. b) Make sure the sprue hole on top of the mold lines up exactly with the injection nozzle. c) Clamp the mold in place by turning the vise handle clockwise.

Inexpensive homemade molds can be made using an epoxy or urethane resin. Or, by machining a desired cavity into an aluminum block using a benchtop CNC machine.

Step 3: Pour in Some Plastic Pellets

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Pour some plastic pellets into the injection tube. Wait until they melt (1-2 minutes).

Step 4: Pull Down Handle to Inject Plastic

Picture of Pull Down Handle to Inject Plastic

Pull down on the handle with a quick, but steady motion. You will feel a solid resistance when the mold cavity is full. Hold the handle there for a few seconds, and then lift it back up until it locks place.

The downward force on the handle causes the injection nozzle to press down tightly against the top of the mold, allowing the molten plastic to flow directly into the sprue hole.

The time it takes to pull down the handle will vary, depending on how much plastic you are injecting. A small part (1-2 grams) may only take about 2-3 seconds to inject (plus a few seconds holding time). A larger part (5-10 grams) may take 10-15 seconds or longer to inject (plus a few seconds holding time).

Step 5: Unclamp and Remove the Mold

Picture of Unclamp and Remove the Mold

Wait for the molten plastic to cool in the mold for a short while (usually 5-30 seconds depending on size and shape of part). Then, unclamp the mold and remove it from the machine. Then, separate the two mold halves from each other.

Step 6: Remove the Part From the Mold

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a) Remove the part from the mold. b) Cut off the sprue, and trim away any excess plastic (i.e. flash) there may be around the edges of your part.

That's it, you're done!!

NOTE: If you think this instructable is "book worthy", please click on VOTE NOW button at the top of the page. Thanks.


bazingaaaaah (author)2017-11-28

How does the air escape from the mold while injecting the molten plastic?

aküçük (author)2017-11-04

How mach price?

MikeH85 (author)2016-06-19

Guy on YouTube shows how to make one and how to sort recycle plastics.

Mlybarger (author)2014-04-27

This is really interesting stuff, but where do you get or how do you make the metal molds that would be used with something like this?

danwsmith7 (author)2014-03-11

Can you tell me about the owl mold?

tokuta (author)2014-01-08

can i use this to make my own bey parts?

rgarrido09 (author)2013-08-01

Nice machine and simple!!! What material is used for the molds?

Junk_Wizard (author)rgarrido092013-10-19

Cast iron was the original material many years ago. Common molds of today are steel or aluminum (depending on use, the steel molds will make many copies before degrading compared to aluminum) many at-home injection molders will use an epoxy cast.

HarveyH44 (author)2008-07-20

Nice machine, would have been better if you gave some info or links to who makes or sells them. Wonder if you could use recycled plastic, just need to shred it up. I work in a plastic factory for 5 years, the machines are huge. I've been making pewter figurines for years, have dozens of molds, pretty sure the melt temp is about the same as PET (470 degrees F).

GrfxGawd (author)HarveyH442013-07-05

Now, I've done neither pewter work nor plastic molding, but if you have, the main difference is loading the hopper, and using pressure to get material into the mold. I suspect HarveyH44 you'd obtain excellent results in short order.

E=MC2 (author)HarveyH442008-07-20

Sorry, I didn't know if commercial link was permitted in instructable, so I did not include.

website is:

There's a lot more details about machine on the website.

bfk (author)2013-05-02

In researching my instructable, I came across this. There are more possible injection molders out there than you may think:)

lfiore (author)2012-06-29

Here is another larger home size benchtop injection molding machine. You can use it to make small and large parts for prototypes or short runs.

Plastic is compressed from the top with a hydraulic ram instead of a manual handle. There is also a digitally controlled temperature controller, and internal plasticizer for quick color changes. At the bottom it uses a hydraulic clamp for more force to hold the mold closed, instead of a manual vice.

The machine can make really finely detailed parts and also use harder materials, such as ABS and Polycarbonate.

Levon Fiore @ Medium Machinery, LLC see our
Small Manual Benchtop Plastic Injection Molding Machine

nerd12 (author)2011-12-09

if you ran out of plastic and had a million scratched CDs, you could scrape the shiny surface off and cut the cd into chips for melting.

Jack Scott (author)2010-12-17


How much and how do you buy this machine?
How do you make plastic modes?

I would like to buy one of these but I need more information.

email me at

dannyboy75 (author)2010-06-19

Thanks for this instructable. I don't really like instructables that have a 'commercial break' feel about them but I have been looking for one of these (and by the way I also have the book mentioned in some of the other comments-very good too-worth the money) as I don't want the hassle of getting a small industrial unit. So many thanks

wyeastpapa (author)2008-11-12

Check out linsay books. fo google dave gingery how to make your own injection molder.

Culturedropout (author)2008-09-10

There's a book out by Vince Gingery about making your own injection-molding setup. Most of the complexity is in making the frame, lever, etc. strong and accurate enough for the purpose. He later came out with another book that uses a drill press (with the power off!) to supply the up-down motion with the necessary accuracy and force. With the second method, it looks like there's just an aluminum block with a fairly precisely drilled or milled hole in it to fit a piston made from a length of steel rod, and another hole in the block to take some kind of (apparently readily-available) cylindrical heating element. Add a thermostatic temperature control (or just a rheostat and a candy thermometer?) and a mold, and have at it. He uses strips cut from soda bottles, milk jugs, etc. as raw material.

Thanks for posting the info on the Vince Gingery book. Ken

killerjackalope (author)2008-07-20

I'm pretty sure I could make one of these, I have most of the bits here, just need to give it a try I guess... What temperature ranges do they operate at?

Was you able to make one of these thanks

Not yet but it's getting there, I've had to look hard for substitution bits...

are you going to sell these or just for your own use thanks

If I can make it work reliably and well then I'd consider selling them...

E=MC2 (author)killerjackalope2008-07-20

Max thermostat temp is 550F +/- 5%

killerjackalope (author)E=MC22008-07-20

Cool, I think I could find something to operate about that...

8bit (author)killerjackalope2008-07-22

where would you get the piston?

killerjackalope (author)8bit2008-07-22

Possibly machine it or use some piece of junk I have kicking about, I have a few ideas...

8bit (author)killerjackalope2008-07-22

What ideas? I'm looking for ideas. Went to the hardware store but couldn't find two pipes that fit nicely. BTW, a good tip: use some sheet metal to prevent splatter when injecting. That way, you won't get burned if something fails.

killerjackalope (author)8bit2008-07-22

Well, I'll have a look see what I can dig up, my rig may be a tad more industrial looking than commercial ones...

trapper23 (author)2008-08-03

hi can you tell me where i can acquire this machine i have uses for it in making prototype units rgards trapper23

E=MC2 (author)trapper232008-08-03

Website for machine is I updated instructable to include URL.

8bit (author)2008-07-22

where do you get pistons like that? I was thinking abt making a machine like this.

John Smith (author)2008-07-20

thats pretty cool but theres no way in hell that i am spending 1500 on an injection molding machine.... i mean, i'm a week or three away from goin all out and buying a $975 mill with $500 bucks of tooling, (its around $1400 total), but... man thats alot. i guess if you do production work, its easily justified. but you could build one. Dave Gingery has a book on making one. There's several out there... ...

LeumasYrrep (author)2008-07-20

Nice Machine. Too bad about the price thought =P. I have seen a home made version in The Home Shop Machinist. Plastic Injection Molding Machine Volume 10 Issue 3, May 1991. Like HarveyH44 suggested it used recycled plastic. Tops of milk jugs and such.

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