Introduction: Home Plastic Injection Molding With an Epoxy Mold.

Picture of Home Plastic Injection Molding With an Epoxy Mold.

I made an epoxy mold of an existing plastic item. Then I was able to make copies of that item using a home plastic injection molding machine.

This process should work for many different types of items or models. Note that the original item must have a parting line without undercuts. That means the model must be able to be separated into two halves from which the new molded part can be easily removed.

Here are the steps:

Step 1: Frame for Holding the Epoxy.

Picture of Frame for Holding the Epoxy.

Epoxy is a two-part liquid that eventually hardens into a solid material. To create a mold from epoxy, you need need a frame to hold the liquid epoxy until it hardens. The mold will consists of two halves, so the frame must also be constructed as two halves that fit together.

This is a pre-made aluminum mold frame that I purchased from LNS Technologies at

I could have tried to make my own frame, but this one was affordable and already had steel alignment pins to align the two halves.

Step 2: Mount the Original Model Into the First Half of the Mold Frame.

Picture of Mount the Original Model Into the First Half of the Mold Frame.

I super-glued a round piece of plastic to the model (a topical fish). This was used to suspend the fish in the cavity of the mold frame. It also forms a channel (called a sprue) that allows the melted plastic to enter into the mold during the final injection step.

Note: this mold frame had cutouts for sprues on all 4 sides, so I had to block the other three cutouts. But, I noticed that the epoxy mold frames on the website now only have a single sprue cutout, so this may no longer be necessary.

Step 3: Mix & Pour the Epoxy for the First Half of the Mold.

Picture of Mix & Pour the Epoxy for the First Half of the Mold.

I purchased a quart of two-part epoxy from Tap Plastics ( It comes in two 8 oz bottles marked Part A & Part B. I mixed equal parts of A & B, being careful not to introduce air bubbles into the mix. Tap also sells colorants that can be added to the epoxy. I added black colorant to better see the mold surface after curing.

Then I carefully poured the epoxy mix into the mold frame to surround 1/2 of the tropical fish. Again, pour slowly to avoid creating air bubbles in the epoxy.

Step 4: Let the First Half of the Epoxy Mold Harden.

Picture of Let the First Half of the Epoxy Mold Harden.

I left the mold frame with the model & epoxy sit undisturbed overnight. By the next day, the epoxy was completely hardened & was able to remove the model to check this first half of the mold.

Before starting on the second half of the epoxy mold, I had to coat the first half with automotive car wax. This prevents the second pouring of liquid epoxy from bonding to the first half. Without this step, I would have ended up with a solid block of epoxy instead of two halves that can be separated!

Then I put the fish model back into the frame & set the second half of the mold frame onto the the first half. The second half of the mold frame has a top removable plate that allowed me to mix another batch of epoxy & then pour it over the first half. (Sorry, I didn't take a photo of this second pouring step)

Step 5: Now I Have the Second Half of the Epoxy Mold.

Picture of Now I Have the Second Half of the Epoxy Mold.

Again. I allowed the epoxy to harden overnight. Then I was able to pry the two frame halves apart (thanks to the automotive wax) and now I had the second half of the mold.

I hope you can see in the photo that the epoxy was able to pick up even the tiny printing details that were on the side of the original item.

Step 6: My Bench Model Plastic Injection Molding Machine.

Picture of My Bench Model Plastic Injection Molding Machine.

I had previously purchased a Model 150A injection molding machine from LNS Technologies. It was affordable & it is easy to use.

I placed the two halves of the epoxy frame mold together. The frame has steel alignment pins, which automatically aligns the two halves. I clamped the mold into the Model 150A & injected some yellow melted plastic into the epoxy mold.

Step 7: A Nice Copy of the Original Item.

Picture of A Nice Copy of the Original Item.

Well, this worked even better than I had expected!

Opening the epoxy mold revealed that the newly molded part was basically identical to the original item (minus the painted stripes, of course).

I have injected several more copies of the fish using this epoxy mold & have not yet noticed any degradation in the details. I don't expect that epoxy molds would be a durable as solid aluminum or steel molds, but it certainly seems like a simple low-cost alternative for making limited number of molded items.


Dominic Bender (author)2014-01-07

I did not know there was such a thing as a desk-based plastic injection system. Thanks for sharing!

BobF51 (author)Dominic Bender2016-03-31

The process scales down nicely - depends on what you want to do. There are folks who actually do injection molding with hot glue guns.

ahmed.hamad.984991 (author)2015-04-09

Hey everybody, please check this out

foxconnmold (author)2014-12-18

Thanks for sharing!very good!

rayleb (author)2014-01-08

Did you have to grease or wax the original before pouring the epoxy?

finnr (author)rayleb2014-01-08

techkits (author) in reply to makenai3 days ago
Yes, I coated the fish model with automotive wax to keep the epoxy from adhering to it. I've heard that non-stick cooking spray may also work.

makenai (author)2014-01-05

Did you have to coat the fish with anything to prevent sticking?

techkits (author)makenai2014-01-05

Yes, I coated the fish model with automotive wax to keep the epoxy from adhering to it. I've heard that non-stick cooking spray may also work.

bazingaaaaah (author)2017-11-28

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

dstroyr46 (author)2015-09-16

What is the name of the marine epoxy you used? There are 4 different ones at tapplastics. The side A does not come in 8 Oz per website.

techkits (author)dstroyr462017-10-22

I was mistaken when I wrote "Marine". I used the General Purpose epoxy:

But I have been told that Devcon 10710 works well also:.

gulnar (author)2014-01-08

Great instructible! Have you tried this for something not made of plastic? I'm afraid it might get stuck in the epoxy, but maybe you have other experiences :) I might try that for jewelry making, though silicone compounds may be better for metals and waxes.

techkits (author)gulnar2014-01-08

I've tried two different thermoplastic materials with the epoxy mold (polypropylene & polyethylene), but have not yet tried non-plastic materials. If sticking to the epoxy was a concern, I would at least try spraying the mold with a non-stick coating beforehand.

One nice thing I discovered about the aluminum mold frame is that I can remove the epoxy mold & inject plastic directly into it without the frame. Then the frame can be re-used to make other epoxy molds.

scottmayer (author)techkits2017-05-09

Thanks for the very clear instructions.

I have two question:

1) do you think Model 150A injection molding machine would work using an epoxy mold to cast objects out of a light polyester thermoplastic such as 'InstaMorph'?

2) If so, do you think that this plastics' extremely low melting point of 130 degree F might significantly extend the useful life of that epoxy mold?

techkits (author)scottmayer2017-10-22

I have not tried using InstaMorph, but ANY thermoplastic materials with low melting points should definitely extend the life of the epoxy mold.

griffster22 (author)2017-05-07

Does anyone know if I can just buy the casting frame and fill the mold without the press?

techkits (author)griffster222017-10-22

LNS Technologies also sells the aluminum mold frames in 2 sizes:

RichardG148 (author)2016-04-03

Did you have any further issues with the general purpose epoxy resin? As the Devcon ones are extremely expensive here (over $100 for 500g tub).

techkits (author)RichardG1482017-10-22

Users have notified me that Devcon 10710 Aluminum Filled Pourable Epoxy works well.

biochris1801 (author)2015-12-08

Have you tried making molds using a 3d printer? I understand a PLA extrusion printer would not work but using a casting resin like 3DM-Cast?

Just wondering if anyone has tried and if any SLA resins would hold up to the temperature and pressure required.

techkits (author)biochris18012017-10-22

If the SLA resin mold was allowed to cool between each injection, it could likely work OK. I tested using the LNS Model 150A to inject into an ABS 3D printed mold & it worked OK.

larsim (author)biochris18012016-09-01

Or maybe you could make the fish with the 3d printer and create the mold with the epoxy resin?

Manoj VO (author)2015-04-02

i use steel mold for my desk top injection molding so far. my molds are made by die maker in CNC machines which is expansive. can you please which type of epoxy is ideal? is it durable to withstand high pressure and temperature. is it possible to make complicated help.

techkits made it! (author)Manoj VO2017-10-22

Users have notified me that DEVCON 10710 Aluminum Filled Pourable Epoxy works well.

Dustin Rogers (author)2016-12-29

I'm curious what type of thermoplastic was used to make the fish? At what temp does that plastic melt?

I saw in another comment that you used the TAP plastics general purpose epoxy which is a clear/yellowish color. Why is your epoxy black?

techkits (author)Dustin Rogers2016-12-29

The Model 150A injection machine works with any thermoplastic material up to 490 deg.F. So you can use common plastics like Polypropylene, Polyethylene, Polystyrene, ABS, etc.

Tap plastics also sells color additives for the epoxy. I mixed in some black coloring to be able to better see the mold surface.

Dustin Rogers (author)techkits2016-12-29

I'm familiar with what plastics can be used. I was wanting to know which type was used in this instructable. What is that yellow fish made out of?

techkits (author)Dustin Rogers2017-10-22

Sorry, I don't remember the specific yellow plastic that was injected at that time. It might have been polypropylene...

techkits (author)Dustin Rogers2017-03-12

I added Tap Plastics Super Pigment so I could better see the surface.

swarner414 made it! (author)2017-08-14

Great instructable, thank you. I tried making an epoxy mold, but will change to the epoxy you used. This is the item I'm trying to mold. The surface that is laying on the table is the surface that is most seen. I'm wondering how you would set this up. I was thinking to put the main plastic in one side, then the small tabs that stick up in the other half. Would love your insight, thanks

dznodes (author)2017-06-26

What was the specific product ID that you purchased from to generate this black epoxy mold?

techkits (author)dznodes2017-06-26

thugzbaby (author)2017-06-09

do you know of any suppliers of eva foam for injection molding?

tommyoke (author)2015-06-23

Would an epoxy mold be able to withstand an injection pressure of ~10,000psi without any deformation?

techkits (author)tommyoke2017-03-12

No, that would be too much pressure for epoxy molds. However, epoxy molds can work with the Model 150A from because it generates about 1000 psi pressure.

techkits (author)tommyoke2015-06-24

No sorry, I don't think an epoxy mold could handle that much pressure.

friendorfoo (author)2016-02-21

Once you make an epoxy mold like this, can you use the aluminum frame again for something else? or is it stuck being a fish mold.?

techkits (author)friendorfoo2017-03-12

You can remove the epoxy inserts and reuse the frame with a different epoxy mold.

friendorfoo (author)2016-02-21

Can you remove the epoxy inserts and reuse the frame as a different epoxy mold? or is it stuck being a fish mold after this?

techkits (author)friendorfoo2017-03-12


BrandonW152 (author)2017-02-19

About how many pieces can this mould make until its no longer useable? Love the instructable!

techkits (author)BrandonW1522017-02-19

Using an epoxy mold is not for high volume production. The heat from the repeated injection of hot plastic can eventually soften the epoxy and you can lose details.
If you allow the epoxy to cool between injections, you should be able to get a few dozen pieces.

prashantu6 (author)2017-02-19

Sir can i use silicon rubber instead of epoxy

HackDaBox (author)2016-10-10

Any idea on how we can produce a large cup? i have the cup that I wanna replicate but I have contacted quite a few places and some stated that it would cost a $100K to make the mold.

Surender sharma (author)2016-04-27

Where we buy this Epoxy Matterial

jcoulson (author)2016-03-30

What an awesome instructable - it was exactly what I needed!

Cambenora (author)2015-05-05

Cool instructable. *Favorites*

Do you have to use epoxy? Could silicone be used instead? Or latex?

Saifuddinm (author)2014-12-07

i want make a plastic heater for home injection plastic machine. do anyone can give me a suggestion how to do it. this is my college project.

rippa700 (author)2014-01-08

This is great and I have something I want to make. How strong in the plastic that gets injected? Could you make neat door knobs from it? Also, do you need the injector? Could you keep one of the other holes open and pour i molten plastic? I've not seen these DIY injectors but they look fun. Thanks

techkits (author)rippa7002014-08-12

Thanks for your interest. Thermoplastics like ABS or Polystyrene can make very strong parts. Some automobiles are composed of up to 20% injection molded plastic parts. Molten thermoplastics are very thick and will not pour into a mold. The molten plastic must be forced into the mold under high pressure (often several tons).

The Model 150A injector shown can create over 1,000 lbs per sq. inch (PSI) of injection pressure.

There are some 2-part liquid polyester casting resins from (tapplastics) that can be poured into a mold.

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