Monday, September 12, 2011

Epoxy Resin Cast Blaster Parts - Build Guide!

Wouldn't it be useful to be able to easily replicate and make your own replacement blaster parts? or perhaps even custom make parts too?

The common method to make replacement parts amongst modders usually involves cutting shapes out of polycarbonate sheets, but that requires a fair amount of work with special tools, along with lots of polycarbonate dust flying everywhere.

The other method is to contract a custom parts fabrication company to do it, but that requires dealing with minimum order quantities and higher monetary expenditures, not really cost efficient for simple blaster parts.

Therefore i was looking at an easier (and cost effective) method to make detailed parts as and when required.

With this objective in mind, i looked into a technique that is commonly used in many scale model hobbies to make replicated parts = Epoxy Resin Casting.

I've seen modders use epoxy resin to reinforce joints or to fill up empty spaces in blaster casings, but i've not yet seen anyone actually make working detailed blaster parts using epoxy resin.

So i tested out the epoxy resin cast method and it works!

Here is the build process...

- Make the Casting Mold -

In my example, i use EasyMold Silicone Putty to make the casting mold, so my process will be based on this particular product.

Once a silicone mold is made, the same mold can be used repeatedly for casting many parts.

There are other similar silicone mold brands that can also be used too, just follow the instructions specific to those products.

Step 1:

Mix 2 equal parts of the silicone putty components. Knead the mixture until the color is uniform.

You will need to work fast as the EasyMold Silicone Putty compound has a very short working time.

Step 2:

For this example, i will be casting a PAS trigger.

Press the original plastic PAS trigger into the prepared silicone compound, make sure it sits completely in the putty and creates a detailed impression.

Note thats this is a one part mold. For functionality and simplicity, i only needed to replicate the right side of the trigger as thats the side that requires part detail for the catch spring to mount on.

For more detailed molds, 2 part molds can also be made by creating the mold in 2 stages with enclosed mold pieces.

Step 3:

After 20+ minutes, the silicone mold will cure enough that you can remove the original part.

Leave the silicone mold to cure further for a minimum 24 hours... then its ready for usage.

- Make the Epoxy Resin Cast Part -

For the casting material, i used high strength 2-part epoxy resin. The epoxy resin does not adhere to the silicone mold so its suitable as a casting material.

I've tested various epoxy resin and they all vary in strength depending on the intended application. Since the part i intend to make undergoes high mechanical stress loads, i found that Devcon "Plastic Steel" Epoxy worked well, as it has good tensile and shear strength.

Step 1:

Mix the 2-part epoxy resin and hardener until it has a uniform color, then apply the mixture into the silicone mold in layers until it is completely filled.

Make sure to fill up the mold completely so that there are no unfilled spaces or air bubbles trapped inside.

Let the epoxy resin cure for 6-8 hours (cure time will depend on environmental conditions).

Step 2:

After the epoxy resin cast part has cured, remove it from the mold. Just flex the silicone mold slightly and the part will pop out.

Trim off any mold lines or excess epoxy resin material with a hobby knife or sanding file.

Here is a comparison of the epoxy resin cast trigger versus the original plastic trigger.

If the cast part comes out with lots of holes (looking like swiss cheese), then it's probably due to too many gaps and air bubbles introduced during the mold filling process.

Just mix a small amount of epoxy resin again to fill in those holes and let it cure further.

Step 3:

Fit the epoxy resin cast part to the blaster, it should have a perfect fitment.

Do any further trimming or adjustments as required, then you can start using it.

Since you can re-use the silicone mold many times, just cast a new part anytime as and when needed! :)

Application Demo Video:


So far, i've tested the epoxy resin cast PAS triggers and they were able to handle up to 20+ kg load main springs. The catches worked perfectly over hundreds of shots, so it looks like they can be suitable and durable replacements for other load bearing parts too.

Yes... its indeed possible to make epoxy resin cast blaster parts! :)


  1. Where'd you get the silicone putty from?

  2. VersatileChicken,

    I got the EasyMold Silicone Putty from Art Friend shops.

  3. Hi,
    Sry,my question abit out of the topic,may I ask wat PETG material u use for the sliding breech u use on your pas YouTube vid above,and also where 2 get them??
    Thnx & hav a nice day:D

  4. some people have had problems with the end of their plunger tube breaking in modified recons if they dont use plunger padding-would this be strong enough to replace the plunger tube?

  5. greendra1000,

    For my slide barrel breech, the outside tube is 1/2" SCH40 Clear PVC pipe, while the inside tube is 0.528" ID PETG tube (same ones most Nerf modders commonly use as PETG barrels).

  6. dbmeed,

    Its possible, but the process will need a very precise two part mold being made and the part will have to be cast in exact dimensions 'cos it has to seal perfectly with the bolt.

    Imho, its probably much easier just to find suitable sized PVC or PETG tubes with matching end caps and make replacement plunger tubes from those materials instead. :)

  7. Could we use play-doh or a water/flour mixture instead of silicon putty? Thanks!

    1. 16kuokhc1,

      Its possible to use those alternative materials to make molds too... though they might be abit weak in maintaining their form, so you'll just have to make sure they are stable enough to retain the mold impression for the epoxy resin to cure into shape properly.

  8. I was wondering if this could work with stampede gears?

  9. Yes, Epoxy resin is multiple useable chemical.

  10. could we cast polyethylene instead of epoxy using a silicon mold?

    1. Anonymous,

      Not sure about... though if the polyethylene doesn't require high temperatures to cast, i guess it could work.