If you want to make more than one unit of any given prop replica, it is inevitable to make molds of all the parts you need. This way you’ll be able to make multiple resin casts of each piece. For the Neutrino Probe, this presented a few unique challenges I had to tackle along the way due to the special nature of the body, its prototype parts and the fact that I wanted to put electronics in there. In this blog post I’ll show you exactly what I thought would work, what did’t work and – most importantly – what I ended up doing.

If you remember, the main body of the Neutrino Probe (minus the emitter) consists of five pieces – some of them big and some of them rather small.

Let’s begin with the main piece, which was the trickiest to mold. Why was it so tricky?

Well, for one it had to be hollow for me to be able to install the electronics later. To do that I needed enough room inside to fit the circuit in. However, due to the large grooves on the outside it was difficult to estimate how much I could hollow out without risking to break through one of the grooves. Therefore everything had to be measured exactly.

The other aspect was that the master model for the main part obviously was round since I turned it from wood. The actual prop part however needed to have one flat side where the display panel would go. How should I approach this? Cut off the unwanted piece before molding? No. Being out of wood, the material could easily have ripped thus ruining the entire thing. Also, being round it would’ve been difficult to get a grip on it and make a clean cut. Lastly, it would have been too final a solution for my taste. Had I cut off too much of it, I would’ve had no way to correct that mistake. So, I decided to solve the problem by molding only as much of the prototype as I needed and not one millimeter more. I’ll explain below.

To be able to do precise work, the first thing I did was to mark a line on the prototype where I wanted the flat side to be:

My first idea was to suspend the piece in silicone rubber by hanging it from wires (that’s what the small holes in the picture above are for) and pouring rubber in the mold below, until the pencil line was reached. What I didn’t take into consideration however, was that wood actually floats, not only on water but also on silicone rubber. Duh! So when I poured the silicone inside the mold and it reached the master model, it slowly began to move upwards, sinking my plan (pun intended ;)) millimeter by millimeter.

So, I needed a new plan. And one was quickly found. It was slightly more elaborate, but worked perfectly. Here’s what I did:

Since molding only part of the master model didn’t work, I decided to do a full-blown two-part mold with a lid that I could later take off. And that lid should be exactly where the pencil line was. The first step to accomplish this was to use a scrap piece of cured silicone from the first try and use it as the “floor” for the new mold box. Yes, you can saw cured rubber quite well. On top of that I built the box walls using LEGO as I always do. Around that I put some plasticine to seal the box and fix it in place.

Having everything absolutely level is important if you don’t want to produce crooked castings. That’s why I always check using a water level before molding.

Next I placed the prototype part inside the mold box and secured it using two strips of tape. Any type will do. I arranged it in such a way that the pencil line on the body was parallel to the “floor” of the mold box.

I then poured a little bit of silicone in the box, just enough so that the master model was covered up to the pencil line.

And this is how the silicone looked like when it was cured. This was gonna be my lid.

In order to continue, I then had to clean up the lid a little in an effort to make it as flat as possible. So I removed the excess rubber using scissors…

… as well as cutting pliers.

As preparation for the next step I then applied (quite a lot of) vaseline on the exposed area of the silicone as a releasing agent.

In this next image you can clearly see the applied vaseline and the brush strokes on it.

Then I reinserted the master model inside the mold…

… and secured it again using tape to prevent it from floating up as it did before.

Then I poured in silicone once more.

Note that I only covered the piece by about half. Why? Well, I couldn’t leave the tape in there to keep the prototype in place, so I needed something else. That’s what this intermediate layer of silicone was for.

When it cured it acted as a grip to keep the part where it was supposed to be and I could extend the box walls (the white LEGO pieces in the next picture) and fill up the mold. Without any vaseline in between, the silicone became one piece in the end, which is exactly what I wanted.

After demolding I was able to seperate the two pieces of the mold without any problems.

Getting the master model out of the mold was a little tricky, since so much of its round form was inside the mold, but thanks to the flexible nature of silicone rubber that became no serious problem.

After a little cleanup I was very happy with the result:

Now on to the next challenge: Making the casting hollow. Since my “resin displacement”-technique worked so well with the ODN Scanner, I didn’t think twice to use this method again here. The idea is to manufacture a rubber displacer piece on a stick that can be lowered down into the mold before filling it with resin. Afterwards it can be removed, making the final piece hollow.

To create this rubber displacer, I prepared a wooden beam with three screws, only partially screwed into the handle. This is where the rubber would stick to the grip. Inside the mold I used some of the clay that I use to prevent mold boxes from leaking to form a temporary mold for the displacer. The tricky thing here was to estimate how thick the walls and how big the displacer should be. I ended up making the mold rather large, thinking that I could always remove some of the cured silicone from the displacer piece to make it smaller. No correction would have been possible in the other direction.

(By the way, that’s what I ended up doing – shaping and correcting the cured rubber by cutting and sanding away material until it was just right.)

This is how the displacer grip looks like lowered down into the mold.

In this shot you can clearly see the screws that will dip into the silicone and attach the displacer to the wooden stick.

All filled up with some RTV rubber:

And this is how the complete mold looks like after demolding and cleaning up:

A perfect fit!

Now, if you have paid attention, then you know that the very first sentence of this post after the break actually isn’t correct. The main body of the Neutrino Probe (minus the emitter) isn’t made up of five, but of six pieces. The sixth very important piece is the display panel, which closes the main body and houses the 7-segment-LEDs for the readout. I built it from three layers of sheet styrene, glued together and filed to shape.

Slightly thicker than the LED component I’m using. Why that is? You’ll see… in the next blog post.

Three layers of sheet styrene glued together.

The usual game: File, putty, sand, prime, sand, prime, and so on…

And here’s the finished panel. So why didn’t I build this piece earlier? Well, simple: I didn’t know the exact dimensions I needed before molding the main body element of the probe where this part needed to fit on. So, logically, I couldn’t build it until the mold for the main body part was done.

Molding-wise this piece was very easy. I attached it to a board, built the usual mold box around it, and filled it with rubber.

And the finished mold:

Now if you’re thinking “Wait a minute, aren’t those LED digits supposed to be installed into that element? Don’t you need a hole in there for them?”, then you’re thinking right. I’m going to show you how I’m doing that in the next blog post!

The next piece to mold with an interesting story is the emitter. As you might remember from this blog post, I built one using styrene, putty and primer way back after I did the main parts of the probe. It consisted of two very small pieces and looked like this:

And here it is together with the rest of the business end:

It looked very nice and I was quite happy with my work considering that these pieces are so tiny.

However, I came to realize that they were not precise enough and more importantly not smooth enough. Because here’s the deal: Of course the emitter had to be cast in clear resin so that it could be illuminated from the back. For the casting to be absolutely transparent and clear, two conditions had to be met: The casting had to be bubble-free (more on that in the next blog post) and the surface of the prototype had to be absolutely, 100% smooth. If it hadn’t, the silicone would’ve translated all the irregularity, texture and roughness – as subtle as it might have been – into the mold which would’ve produced castings with a milky, frosted surface and not a glass-like bright finish.

So I reached out to fellow prop-builder Myron Stapleton who has both the experience and the equipment to turn parts from aluminum to measure. I prepared some very detailed specs for him and what I got back matched those dimensions exactly:

I couldn’t believe the accuracy with wich Myron replicated my diagrams. This is truly the work of a master. Thank you so much, Myron!

The molding process for this piece was no different than the rest: Put it on a board in a mold box and fill it up with silicone. The one thing I had to be careful with was the speed with which I poured the rubber inside the mold. Pouring in a thin stream I carefully filled the box, paying close attention not to trap any air bubbles while covering all those ridges and crevices.

And here’s the final mold. While molding all the other pieces, I actually made a number of emitter molds so that I could later make several castings at once.

Molding the rest of the pieces was very straight forward. By now you know the drill, so I’m not going to repeat it once more. Just enjoy the pictures:

You’ll notice here that I sometimes used clay as a base for the pieces. The plasticine acted as a light adhesive and also prevented the silicone from creeping under the prototypes thus creating a thin rubber film which can make the demolding process problematic.

Looking at this last piece, which is the “end cap” of the Neutrino Probe, I realized that painting – or more precisely masking – this component would be quite elaborate since the disc at the top has a different color than the rest. Have a look at the original to see what I mean:

So I decided in the last minute not to include the back disc in the actual “end cap” casting, but to add it later and use the real deal (more on that in an upcoming blog post).

Instead of removing the disc from my original master model (the one which I turned from wood here), I used a resin casting of said master model to preserve the original.

If something had gone wrong, I simply had made another pull from the mold and started over. But, thankfully, there were no problems. First, I shaved off the majority of the top disc using my belt sander like this:

Then I used sandpaper stapled to a board to gently remove the rest. Wet sanding makes for a smoother surface.

After some priming and more sanding, the surface was perfectly smooth.

I noticed however, that the whole element was not tall enough and did not match the original prototype. I simply sanded off too much of the bottom of the casting to make the surface smooth.

So I used styrene to extend the element like this:

A few layers of putty and primer later, with a little sanding in between, the new “end cap” was finished and ready to be molded.

And here are all of the Neutrino Probe molds with their respective prototypes. Seven pieces in total, which is quite a lot, now that I’m looking at all of them together.

In the next blog post I will cover the casting process for these parts and the unique problems I had to solve to make that happen.

As always, if you want to follow my work more closely, you can follow me on Twitter (@trekprops) to get more frequent updates on what is happening in my workshop.

If you have any questions or observations, you can of course also E-Mail me or leave a comment below. I’m looking forward to hearing your thoughts!

Sometimes, you want to finish something as quickly as possible. You desperately want to make progress, feel the urge to get back to it continuously and yet you can’t find any time to do just that. You just can’t, and every step takes forever as a result. That pretty much sums up the situation I’m in right now with this project.

Anyhow, as you can see I finally did manage to take the next step by finishing another important part of the tool – the business end! It’s a very detailed piece that consists of four separate parts right now (I’m not sure yet how I’m going to mold it though). And four very tiny parts I might add. The smallest one is only 5 mm in width!

This is by the way the part of the probe that was originally made from a disassembled nose hair trimmer. Unfortunately, despite my best efforts I wasn’t able to identify the exact model or even manufacturer of that trimmer, so I couldn’t use the original and had to scratch-build something instead. It was one hell of a lot of tedious work, but – to be honest – the result is probably nicer and cleaner than any found item, which makes the whole thing worthwhile in my book.

But, judge for yourself. To refresh your memory, here’s the front part of the original prop as well as the schematics I did as preparation for this project:

And here are the pictures of my finished multi-part piece:

So, let’s get down to business. How did I create these parts? Here we go:

It all started with some more or less precisely cut pieces of styrene, my material of choice when it comes to scratch-building stuff.

They would make up the body of the largest piece. Which is round. Which meant that I had to sculpt it somehow since I didn’t have anything that I could’ve used as a base piece.

So I marked an appropriate line for the outer curvature on all pieces and cut them with an X-acto knife.

As you can see, I also cut some material away at the top to make it easier to create a recession there later.

Then I arranged them in a circular way to build a kind of skeleton structure and glued them together using plastic glue.

The next step was to fill the spaces between the “ribs” with putty to “put some meat on the bones” as it were.

Then the sanding began. Oh, boy. The sanding – that’s the kind of work that I’d like to have an assistant do for me or something. On the other hand it gives you great control over the final shape of your piece. The downside is that it takes a long time. A very long time. And especially so if you’re only one bit as anal about a perfect surface as I am…

While sanding the outer surface of this part I also paid some attention to the top side of it where I needed to have a pretty substantial indentation with a thin lip around it. To achieve this I used a mini-dremel with an appropriate attachment to remove material from both the surface inside as well as the “walls”.

Here is an intermediary result. Looks pretty nice already, doesn’t it?

On to the next part, which is essentially the same deal as the first one, except smaller and with a more straight profile. And when I say smaller I mean like 9,5 mm tall! That’s pretty tough to even hold in your hands (depending on what kind of hands you have of course). But holding it while trying to leave some room for sandpaper to work on it? Yep, you guessed it – that’s not easy to say the least. To illustrate: I even had to use tweezers to glue the “styrene skeleton” parts in place, which were only a couple of millimeters in width.

Here’s another preliminary result, this time a bit smoother. As you can see, I used spot putty on the smaller piece to fill in tiny holes and gaps.

And this is where Murphy came into play. It turned out that I had miscalculated something or simply had visually misjudged the proportions of this small piece. Anyway, it was evident that it was too thin and I had to somehow make it thicker – or wider if you look at it from the side.

Sounds easy, but how should I do that? Well, after thinking about it for a bit I decided to simply add material by gluing small strips of styrene to the side of it and fill it with putty as before. Yay, more sanding! Not exactly what I wanted to do but it sure did the trick:

After that small setback, I moved on to the next part, which is a kind of add-on to the first, “big” base piece. I made it basically from four small strips of styrene, which I glued together and sanded in shape.

A little putty to hide the seams:

A little sanding – done.

So, here are all of the three pieces that had been done at that point:

Next, I had to make the small, narrow part fit into the bigger base. So, I cut a piece out of the side of it and added some putty back in to make the new surface nice and smooth. Again, I used my mini-dremel to do that, this time with a small circular saw attached to it. I also used various small files to work on that slot.

While working on any of these pieces, by the way, I sprayed light coats of automotive primer on them all the time to reveal small blemishes, scratches or any kind of unevenness that needed to be fixed.

It wasn’t until I had created this slot that I noticed how deep I had carved the indentation into that big piece from above. Clearly too much! When put together, the final element of the prop would not have looked very good like that. So I had no choice but to improvise again and insert a round piece of styrene to raise the level of that surface a bit. This of course meant that I also had to putty it to blend it to the “walls” inside:

A lot of sanding later – and I mean a LOT of sanding later – the mistake was corrected and the surface both inside and outside was smooth as an androids butt. Also, the small add-on piece fit in its place perfectly.

To finish this piece off I had only one thing left to do and that was to create tiny grooves on the outside as a bit of detailing to give it some structure and make it interesting, not to mention match it with the original of course! To do that I cut tiny pieces of tape and put them on where I wanted the grooves to be.

Then I applied several coats of primer to add some material to the outside.

Then I removed the tape and voilà – micro-detailing!

Last but not least I had to tackle the emitter tip, which proved to be extra challenging. What I needed was a very small piece with very specific measurements and three tiny rings around it. At first I had no idea how to achieve this, but then decided to try to sculpt the tip from air curing clay which worked out quite well.

The three rings around the tip gave me a headache though. How the hell should I sculpt those by hand? It seemed impossible. Then I had the idea to wrap a bit of wire around it to at least get an approximation of what I wanted. It would be a short spiral instead of three separate rings, but that was the best I could think of. And it turned out that it worked really well and looks very nice even if it’s not perfect. After all, it’s only a very small part of the final prop…

So, here’s the final result again:

Note that I added a small indentation on top of the middle sized piece as well, similar to the one on the big base piece to create a small lip and a place for the emitter tip to fit in.

Seeing those four parts together now that they’re finished, I’m very satisfied with this part of the probe and I think it goes very well with the main parts I did a while back:

I’m sure it’ll be a great prop when it’s all done. And I sure hope that I’ll be able to make some more progress in the near future, too!

What do you think? The good, the bad and the ugly – I’d love to hear back from you in any case, either via a comment below or via eMail!

Also, if you want to watch my prop-related activities more closely you should follow me on Twitter. Every time I’m in my workshop, you’ll know it instantly and see what I’m doing in real-time before anyone else can read about it here on the blog. Sounds like something you might enjoy? Follow me @trekprops and get the inside scoop!

Modulor direct link: UHU plast, special (#154907S)

With every building project, there’s one essential question: What material am I gonna use? Well, in prop building there’s most of the time only one answer to this question and that is “styrene“. Styrene is nothing more than sheets of plastic which is available in several thicknesses. It is also used in other model building efforts, for example architectural models.

So, the first step of building the prototype was to cut out all of the needed pieces from styrene (I used styrene with a thickness of 1 mm). After I had determined the shape of these parts by drawing a blueprint, I printed them out and glued them onto the sheet of styrene using spray glue. Next up was cutting the pieces which I did using a sharp precision knife. After scorching the sheet two or three times, they can easily be broken off along a straight edge.

After that it’s no problem to remove the paper from the styrene. If it doesn’t come off easily, simply put it in luke warm water for a few minutes. Then, the edges of the styrene parts had to be sanded lightly to create clean edges. The opening which would later become the display window proved to be especially difficult. A lot of sanding work was necessary to achieve really straight lines and rounded corners. Very useful in this step was sanding under running water which requires a special kind of sandpaper but results in very little dust and a very smooth edge.

Here are all 24 seperate pieces which I marked with the respective codes to know which one belonged where.

To see if these pieces could fit together to result in the object of my wishes, I did a test fit and glued them together using removable masking tape:

Styrene is best glued together with a special plastic glue which joins the parts permanently:

I filled the inside of this open box with putty to gain additional material for the later sanding process of the corners and edges. I wanted to prevent creating a hole in the body which I would not be able to close again.

After I had closed the body, I sanded the hole object roughly to remove all of the sharp edges and corners.

Next up was the handle. Here I also did a test fit first to determine how I would have to glue the pieces together. Because the handle would have been too thin consisting of 1 mm styrene, I glued two identically shaped parts together to make it thicker.

To perfectly fit the handle onto the main body, I actually attached the respective parts to it while glueing them together.

As you can see, the edges of the handle were very raw. Because of this I again had to use putty and a lot of time to give the handle a sleek shape and a smooth surface. The complex form obviously didn’t make this easy for me. However, the time was well spent as you can see here:

Fits like a glove! However, the main body being curved and the inside of the handle being straight, small holes were visible in between which again had to be filled and sanded smooth.

After that, the complete body had to be sanded very carefully to make every surface smooth and to achieve the desired degree of roundness on all edges and corners. Because silicone rubber transfers each and every imperfection to the mold very rigorously, the master model has be as perfect as the final kit or prop is supposed to be. Mistakes made here are being carried all the way through to the final product and then have to be corrected on each casted part anew. So, a lot of work can be saved here by thinking everything through and doing things right.

I here fabricated one set of greeblies, which are normally being put on as the last step in the buildup of a prop, to see what the final look of the prop would be:

In the same way I did the handle, I also made the scanner array on the top of the prop above the recessed display area. This way I could simply plunge it on and then attach it.

Even if it doesn’t look that way, the construction of such a prop from scratch using the methods shown here is a lot of work! Sanding is by far the most time consuming task because you always spot another small blemish which has to be repaired or areas you are not satisfied with. Also, the whole process requires a lot of patience because it just takes very long if you want to do it right. Anyhow, the effort is well worth it especially when you see yourself making progress and getting the project somewhere.

So far, so good. The master model is finished. Next is Part II in which I describe how I made the silicone mold.