LED Power Weapon Tutorial

This is my tutorial for LED power weapon effects. The photos show this technique applied to a Space Marine with power sword, but it can equally be applied to any other type of weapon with an energised blade.

I strongly recommend reading through the entire tutorial before starting work, just to make sure you have the necessary skills and tools required and that you’re not going to run into an unexpected barrier halfway through. If you need to know where to buy tools and consumables for this type of project, I have recommendations here.

I have separate tutorials about designing LED circuits, basic LED solderingresin casting and LED eye lenses. This tutorial assumes you’ve either read these, or are familiar with the techniques discussed, especially the eye lens tutorial, which is a starting point this tutorial builds from. Casting skills are essential (although this tutorial does discuss them in detail) as the power weapon effect relies on the availability of a blade cast in resin.

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1. My LED tutorials normally start with the electronics, but as this tutorial requires the  casting of custom components (the resin blades themselves), I’m going to start with that instead.

Next you need to make a ‘sprue’ for your weapon blades. The sprue is the frame that will hold the components during the casting processes. Over the next couple of steps we will be making a rubber mould that makes a negative copy of the sprue, and then filling that rubber mould with casting resin.

Cut your weapon blades from the model, and then construct a frame as shown in the images below. The size of the frame will be limited by the size of the container you are using for casting (see step 3). The sprue frame will form the channels through which the resin will flow when you inject it into the mould, so you don’t want any ‘dead ends’, otherwise you’ll get miscasts with air bubbles.

Power Weapon 01

You will also need to add ‘legs’ to your sprue. These keep the bottom of the objects you are casting from touching the floor of the container (if they are touching, the rubber mould won’t enclose them properly). These legs will also form the injection channels through which you will add resin to the finished mould, and will also allow trapped air to escape; although this is the bottom of your sprue, it will end up as the top of your rubber mould. As you can see I have placed legs at regular intervals on the frame, and at the top point of any raised areas on the flares, as this is where air could potentially collect during casting. Try and ensure the legs are even so the mould sits flat in the container (see step 3).

Although it doesn’t really matter in this case, it’s worth noting that if you’re casting something that has more detail on one side that the other, such as a head or helmet, the detailed side should be facing outwards on the opposite side to the legs. That side will be the bottom of your mould, and has the lowest potential for air bubble miscasts, preserving the details.

Power Weapon 01b

2. Now you need to decide on a container. You want something slightly larger than the sprue, but not much larger as you’ll end up wasting rubber. I use plastic component boxes that are often used for holding different sizes of screw, for example. Coat the inside of the container with Vaseline or similar petroleum jelly. You can buy special mould release agent, but I find Vaseline is cheaper and works just as well. Once you have done that, put a tiny drop of superglue on the bottom of the legs, then press the sprue into the bottom of the container. Wait for the superglue to set, and then to proceed to step 4.

3. Now you need to pour the first half of the rubber mould. If you’re not familiar with mould pouring and casting, then remember you can read my Resin Casting Tutorial. My preferred brand of rubber, I recommend TOMPS Value silicone rubber.

Pour the rubber until it is level with the mid-point of the sprue. This will form the top half of your mould. Once the rubber has set (check the packaging if you are unsure of the cure time), coat the top of the rubber with more Vaseline. This is important as it will help you to separate the two halves of the mould later on. I find you don’t need to put Vaseline on the sprue itself, just the rubber.

Power Weapon 03

4. You can now pour the next half of the mould. This will form the bottom half of your mould. Again, wait for the rubber to set before proceeding to the next step.

MF Tutorial (8)

5. Once it has set, you can remove the rubber from the container. I find a tool that is thin and flat is particularly useful here, something like a small steel ruler. Prize the mould out of the container, and then gently pull the two halves apart. If you’ve used plenty of Vaseline between the two layers this should be fairly easy to do by hand. If there are any bits that are stuck together you can use a scalpel or fine craft knife to tease them apart.

Power Weapon 05

Now you need to remove the sprue from the top half of the mould. Make sure you get all the legs out too, as these can sometimes snap off! I tend to archive the sprues for future use, just in case I ever need to re-make the mould. Homemade moulds like this will generally be good for somewhere between 10-20 casts before bit of rubber wear off and they start to lose detail. So depending on what you’re casting, you may wish to remake them again at a later date.

6. If you turn over the top of the mould, you should see holes where the legs of the sprue were glued to the bottom of the container. If any of the holes have not formed properly – for example, certain individual legs were too short and did not reach the bottom of the container – then you can cut the holes with a scalpel. Remember, you need these holes for allowing air to escape and for injecting the resin. If you’re having trouble seeing where the holes should be, hold that half of the mould up to a bright light and you should be able to see them.

MF Tutorial (11)

7. To hold my moulds together and keep them level, I tend to cut out a base of thin plastic card and use elastic bands to hold the two halves firmly together, as seen in the image below. Just make sure the bands are squeezing too tight, as you don’t want to deform the mould.

MF Tutorial (12)

Now mix and inject the resin into the holes in the top of the mould. I like to use TOMPS Polyurethane Fast Cast Resin. I tend to use 5ml disposable plastic syringes for the injection process. These are readily available online from retailers such as Amazon. I find it best to inject in several different different holes to ensure that the resin fills all parts of the sprue. Just be careful when withdrawing the syringe that you don’t accidentally pull apart the two halves of the mould. Keep going until there is resin coming out of all the holes. At that point the mould is full.

Resin casting is messy and smelly. Never cast in an enclosed space, or if you do, make sure you leave the space immediately after injecting all the resin to allow the fumes time to disperse. I like to use a foil covered plastic tray to hold my moulds. This helps to catch any excess resin run-off that might otherwise damage tables or workbenches.

Wait for the resin to set (consult the packaging for the cure time) and then proceed to step 8.

MF Tutorial (13)

8. Remove the elastic bands and separate the two halves of the mould. You should see your cast sprue, as shown in the image below. Now carefully remove the cast from the mould. If it does not come out smoothly, you may need to strategically snip the resin sprue frame with clippers. If you need to cast more weapon blades, clean any leftover resin out of the mould with a brush or tweezers, and then return to step 8. Otherwise, proceed to step 10.

9. Now it’s on to the miniature itself, starting with the base. First, complete step 1 – 5 of my LED eye lens tutorial to assemble the base and battery holder, then proceed to step 11 of this tutorial.

10. Now you need to prepare the LED. For this model I used two of the Blue Ultra Nano SMD Chip LED (3V) from the website Small Scale Lights. As an aside, I really like this supplier – they have a good range of products and excellent customer service. You will need to prepare the LED so it looks like the one in the image below. This is fairly simple – just unsolder the red and black insulated connecting wires, leaving yourself with only the enamel coated wires shown below. This is done because the enamel wires are easier to work with as they are significantly thinner than the insulated wires. Just make sure you note which wire was positive (red) and which was negative (black)!

Power Weapon 10

11. Now we need to drill two holes into the resin blades. Remove the one you want to use from the cast sprue, if you haven’t already, and clean off any excess resin. The idea is to drill two holes side by side that travel the length of the blade to the point where you want the nano LED to rest. In this case, I made them line up with the two ‘power nodes’ on the blade. The drill bit used in the image below is a 1mm drill bit. As the nano LEDs are 0.9mm wide they should fit into the 1mm holes. Be very careful at the drilling stage! If you accidentally break the blade or drill through the surface then you’ll have to throw it away, grab another one from the sprue and start drilling again. Only dry fit the LED at this stage to test it, don’t glue it into position.

Power Weapon 11

Power Weapon 11b

12. Now drill holes through the sword hilt, hand, arm and torso of the model. I used a 1.6mm and 2mm drill bit for this, just to make it easier to pass the wire through. If you have right angles that you need to drill through (like the elbow joint below), I find it useful to drill in from opposite ends of the component and meet in the middle. Alternatively you could cut the arm in more places to allow easier drilling.

Power Weapon 12

Designer’s Notes: Incorporating LED Heads

Although I haven’t done it with this model, if you’d like LED eye lenses in your model in addition to the LED power weapon, then this is the stage to think about inserting the LED into the helmet. This is covered in detail in steps 11 – 14 of my LED Eye Lens Tutorial, so I won’t go over it again here. 

If you’re using the same LED as the ones in your power weapon blade then you can simply connect the helmet LED in parallel with the blade LEDs. But if using two different types or colours of LED then one of them will probably need a resistor in the circuit to balance the current draw – different LEDs will have different current draws. If you’re not sure how to determine what type of resistor you need then that is covered in my designing LED circuits tutorial

13. Now drill a hole through the legs and pass the wire down through the hand, arms torso and out of the bottom of the legs, pulling any slack through. If you accidentally drill any extra holes in the legs then don’t worry, these can be filled with modelling putty later.

It can be useful to mark which wire is which before you feed them through – if you haven’t already – so you know which wires are connected to the positive side of the battery, which are connected to the negative side, and which is the one connected to the resistor (if you are using one). You can mark near the ends of the insulation with a tiny dot of paint, or similar, as a reminder. If you’re not sure which wire is which, hold a battery between them with your fingers to test the polarity, or use the diode test setting on your multi-meter.

Power Weapon 13

14. The next stage is to solder the wires onto the battery holder. Connect the negative  side of both LEDs to the negative terminal. I normally solder my switch onto the positive battery terminal, which means the positive sides of the LEDs should be connected to the unused terminal of the switch.

Power Weapon 14

Once you have made the connections, test the circuit by turning on the switch! If the LEDs illuminate, excellent work, you may now proceed to step 15. If it doesn’t work, this is the point to back-track and start fault finding. Double check all connections that you have soldered so far and that the polarity is definitely correct. A digital multi-meter with probes is handy for this.

15. Now you need to glue the model together, if you haven’t already. Now attach the finished model to the base. I find the best way to do this is to put two small balls of modelling putty under the model’s feet, press it into the putty so it’s standing up, then wait for the putty to cure and harden before proceeding further. This helps to make sure the model is attached to the base in the correct pose and position before going on to hide the rest of the wires and connections. Any slack in the connecting wire should be curled up under the model on the base.

Power Weapon 15

Test the circuit again at this stage, just to make sure you haven’t accidentally damaged any of the connections.

16. Now cover the rest of base in putty to hide all the wires and connections. Just make sure you leave the moving parts of the switch accessible. The battery itself should also remain accessible from underneath. This is also your opportunity to fill in any holes you may have accidentally drilled, e.g. in the legs.

Power Weapon 16

17. Now it’s time to glue the blade into place. Put a tiny dab of PVA glue onto the nano LEDs and use tweezers to feed the LEDs into the blade. Remember we’re aiming to get the LEDs to line up with the ‘power nodes’. This stage is quite fiddly! Once you’re happy with the position of the LEDs, glue the blade onto the sword hilt with a small amount of superglue. Once the glue is dried, you can use modelling putty to fill any gaps around the base of the blade and reconstruct the hilt if necessary. I also added texture to the base at this stage.

Power Weapon 17

Now you need to prepare the model for the undercoating process. Use blu-tack (or similar) to cover the blade in the areas where you want the LED light to shine through. This is extremely important, otherwise you could ruin all your hard work so far!

18. Once the undercoat spray has been applied and it has dried, carefully remove the blu-tack from the blade.

Power Weapon 18

19. Now paint the model! To achieve the ‘lighting’ effect around the ‘power nodes’ I simply left paint off the parts of the blade where I wanted the light to shine through. If you put too much paint on I found it was easy to scrape it gently off the resin blade with the sharp point of a sculpting tool. This can be used to make fine lines to enhance the lightning pattern. So there we have it, one finished model with LED power weapon!


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