Home Plastic Injection Molding With an Epoxy Mold.

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Introduction: 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:

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Step 1: 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 - https://www.techkits.com/

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.

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 www.techkits.comwebsite 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.

I purchased a quart of two-part epoxy from Tap Plastics (www.tapplastics.com). 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.

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.

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.

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.

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.

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101 Discussions

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

0
BobF51
BobF51

Reply 3 years ago

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

0
rayleb
rayleb

6 years ago on Step 7

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

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finnr
finnr

Reply 6 years ago on Introduction

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.

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makenai
makenai

6 years ago on Introduction

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

0
techkits
techkits

Reply 6 years ago on Introduction

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.

1
TomerL4
TomerL4

2 years ago

How many cycles of injections does to epoxy mold last?

Do you have to cool it between injections?

I was thinking of doing the same but with clay to create the mold.

0
techkits
techkits

Reply 11 months ago

Yes, you should allowed the epoxy mold to cool between injections to avoid heat build-up that could eventually degrade the epoxy.
It is difficult to estimate the life of the epoxy. I will likely vary depending upon the type of epoxy used, but I think Devcon 10710 would be best because it contains micro particles of aluminum that will help absorb heat during injection. That should make the epoxy mold last longer.

Devcon 10710.JPG
0
tanaychoure
tanaychoure

Reply 4 months ago

But still can you please put a number or atleast a rough range on it, considering average scenario and use of recommended epoxy? e.g 5-10, 50-100, 500-1000

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22635
22635

2 years ago

do you have or know of anywhere that has a bigger mold frame that can make something 5 inches x 2.5 inches?

0
techkits
techkits

Reply 11 months ago

Sorry, I'm not aware of anyone other than LNS Technologies that sells these types of epoxy mold frames

Epoxy Frame.JPG
0
AliceS70
AliceS70

Question 1 year ago on Step 3

can magic-glos be used in a plastic mold.

0
techkits
techkits

Reply 11 months ago

Not sure, since I am not familiar with "magic-glos".

0
DavidH1095
DavidH1095

Question 1 year ago

nice job. did you have to degas your epoxy at all? what injection temperature were you injecting at?

0
techkits
techkits

Reply 11 months ago

I did not have the ability to de-gas at that time, but it would certainly help eliminate tiny bubbles in the epoxy.
The yellow plastic material in the instructable was injected @ 360 deg.F, but I allowed the epoxy mold to cool between injections to avoid heat build-up that could eventually degrade the epoxy.

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techkits
techkits

Reply 1 year ago

I did not, but I highly recommend it because I did get a few tiny surface bubbles on the epoxy mold.
Injection temperature was around 400 deg.F.

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MohamedM58
MohamedM58

11 months ago

can i use other type of epoxy ?!