Molding & Casting a Prop Bracer

The mold and final cast part.

The mold and final cast part.

As someone who has gone to GenCon quite a few years and knows several of the GMs of major events, I’ve started getting asked to make props…  This year I have decided to expand my experiences in molding and casting in order to make one of the props.  The prop requested was a “Bracer that looks like it is made of Amber – part of the shell of an insect”.  Thankfully I was afforded quite a bit of creative leeway beyond that.

 

In the past I have used Smooth-on products, but one of the members of the Makerspace mentioned they were a distributor for Alumilite, so I thought I would give them a try.  This was my first experience with most of the Alumilite products.

 

I ordered the following supplies:

UMR 12 oz.

Alumilite Dye 1 oz. Red

Alumilite Dye 1 oz. Yellow

Mold Putty – 15 2 lb. Lt. Blue

Amazing Clear Cast 2 gal. Kit Clear

Synthetic Clay

 

Other items I used:

PVC Pipe form

A form made out of a 3″ PVC pipe shaped to look like a human arm.

3” Diameter PVC Pipe – Approximately 18” long

3” Diameter Hose Clamp

Plaster Bandages

Vaseline

Disposable Mixing Containers

Stir Sticks

Steel Wire (to hold the mold together)

Syringe

Drinking Straw

 

I wanted to make a “generic” bracer that would fit either arm, not a right or left arm bracer, so I didn’t want to do a life cast of my arm first – it would be too specific.  Instead I picked up a piece of 3” pvc pipe, cut a section out of most of it (leaving a part connected) and then used a hose clamp to tighten the open end down.  It turned into a really good stand-in for a human arm.  The shape is close enough that it is recognizable, but is not left or right arm specific.  (Note that the screws in the picture were added at a later stage)

 

Once I had the basic form for the arm, I used the synthetic clay to create the shape of the bracer.  I was going for an organic look, so I wanted curves and no sharp edges.  The biggest challenge I had was trying to smooth out the sculpt.  I still need to figure out the right technique.  Sadly, I forgot to take pictures of the sculpted bracer.

 

The form and original covered with mold putty.

The form and original covered with mold putty.

Once I had the sculpture complete, I added some screws around the edges as alignment points.  I was careful to make sure the heads were close to the PVC so they would not get stuck in the molding material.  Then I got to try my first new material – the Mold Putty.  I really liked the idea of it – take two parts, hand-mix, then just push it onto the original.  It essentially worked exactly that way.  I thought the mixed consistency was almost perfect for my application.  Unfortunately, the biggest difficulty is being sure not to trap air in it – particularly when placing a second mixed batch next to an already placed batch.  I ended up with some imperfections in the final mold because of this.  Would I use it again?  Yes, but I think I may also try other approaches – either a box and pourable rubber, or brush-on rubber.

 

The mold with half of the mother mold present.

The mold with half of the mother mold present.

Given the way I wanted to cast the bracer – standing vertically – I wanted to make sure that I was able to hold the rubber mold to the arm form well.  So, using the plaster bandages, I made a two-part “mother mold” for the rubber mold.  First, I coated everything with Vaseline as a release agent, then I covered half of the arm piece with plaster bandaging, making sure the edges were particularly strong, and that the top edge, where I would be creating the second half of the mold, was also quite smooth.  After the first half of the mother mold cured, I then coated the edge of the plaster with Vaseline to make sure the other half would not stick to the first half.  Once I was done placing the Vaseline, I then coated the other half with plaster bandages.

 

Once all of the plaster dried, I used a sharpie and drew lines across the edges of the plaster.  These lines are so that I could realign them easily after I took the mold apart to remove the original sculpt.

 

After I removed the original sculpt, I realized I forgot something major…  A way to get the resin into the mold.  Oops!  After a bit of thought, I decided the easiest way to get the resin in would be to drill some holes through the PVC pipe and pour it in that way.  Ideally, I would have designed pour holes and vent holes into the original design of the sculpt.  Something to remember for the next one!  In order to try to control the fluid a bit better, I used straws to extend the holes out.  Bendy straws would have been good – I’m not sure how effective straight straws were.

 

Using the volume of clay from the original sculpt, I did a rough guess at how much resin would be needed to fill the mold (~12oz).  I measured out 6oz of each of the two parts, added one drop of red and six drops of yellow to one of them, then mixed it.  I used a syringe to suck up the mixed resin and transfer it into the mold.  It worked quite well, although it was a bit disconcerting because of the number of bubbles that were exposed during the suction process.  Thankfully, as soon as the resin reached normal pressure the bubbles disappeared.

 

The raw bracer prop as removed from the mold.

The raw bracer prop as removed from the mold.

The resin takes 24 hours to cure.  24 hours wondering if it turned out.

 

And after that full day of waiting, I de-molded it.  Quite the pleasant surprise!  I think it may have slightly too much red, so I’ll have to correct that for my next iteration.  I’m still debating about sanding and buffing it in order to get it to be more glass-like.

Hot Stuff! Aluminum Pour Night.

 

To quote the Iron Worker on THE SIMPSONS,  “Hot stuff, coming through!”
I was pretty excited that I finally made it down to the Milwaukee Makerspace last night to attend an aluminum pour! I’ve seen a couple of the videos and really wanted to get in on some of that hot metal casting. I have what’s called a “speed-ring”, a metal ring that holds a soft-box for photographic lighting, and I wanted to make a copy of it.

So far, much of the casting has been using a “lost-styrofoam” method. A shape is carved from foam and set in sand, and the aluminum melts the foam as it’s poured in. But I wanted a COPY of an existing item. I asked Bret about it, and he said we could try an experiment of pretty much just pressing the ring down into some sand. An X channel was then added in the middle as a point for the aluminum to pour into and spread out into the shape.

I built a wood box for my item, and we filled it with oily sand, packed it in there, and added the X-trough. My item didn’t pull out of the sand quite as well as I had hoped, but hey, it’s an experiment…

Outside, the aluminum furnace was roaring away, heating aluminum to a delightful orange liquid. The first pour made it through Kevin’s FEAR art piece, my piece, and another members. Later, a second pour took care of Phil’s hand-casting series (which turned out great!)  and the rest went into an ingot mold.

Once my piece was cool enough, we pulled it out to take a look at the results. Not perfect, but not bad for a first time, and an experimental casting at that. There was quite a bit of extra metal, but most of that could be easily trimmed off with the bandsaw. Other members were taking photos of their work. It was obvious that everyone was pretty proud of their individual castings. Even without being the one pouring out twenty pounds of molten metal, it was still a pretty macho experience just to be part of.

If you too want to come play with crazy hot metal, come on down to the Makerspace next time we do an aluminum pour!

Aluminium Casting Night

This past Thursday was another great aluminium pour! I came prepared with a mold I made at work (benefits of working at a minerals company). I can’t show you guys the cast I made, cause it’s a Christmas present, but I can show you the pour!

Be on the look out on the Milwaukee Makerspace Calendar for future Aluminium pours on Thursday night at 7:00, or just come on by any Tuesday or Thursday night at 7:00 pm for our Open Meeting and Builder’s Night Out. See ya there!

Makerspace Aluminum Casting Foundry

I arrived at the Makerspace on Thursday without an idea of what I would cast in metal, and in less than two hours I was removing my piece from the steaming petrobond! Check out the fruit of two hours of labor cast in metal!

That’s right! The Milwaukee Makerspace had its first (and second) aluminum pour on Thursday! Thanks to the hard work of several members, the Makerspace now has a fully functional aluminum casting foundry.  The custom built propane and diesel powered furnace melted an entire #16 crucible of aluminum in less than 20 minutes.  Check out Brant’s video to see our fearless foundry foreman leading the two pours!

To get the foundry running quickly, we’ve started out by using a lost-styrofoam casting method.  That is, styrofoam is carved into the desired shape and then a sprue and vents are attached with hot glue(!).  This assembly is placed in a wooden form, and is surrounded by tightly packed petrobond, an oil bonded, reusable sand.   Then, the molten aluminum is poured directly onto the styrofoam sprue.  The styrofoam is instantly vaporized by the 1250 degree Fahrenheit aluminum, which fills the void in the petrobond formerly occupied by the styrofoam. The air and perhaps even some of the styrofoam residue escapes from the mold through the vents.  We’ll be phasing in bonded sand and lost wax casting soon, so stay tuned for those details.

Eventually we’ll be having aluminum casting classes; however, we’re definitely going to be having aluminum pours on alternate Thursday evenings for the next few months.  Join our mailing list / google group to get more details.  Metal pours are spectacular to watch, so feel free to stop by to see the action around 7 or 8 pm, or join the Makerspace and participate!

Spin Casting

So we recently got a spin caster in the space.

image

Jason H and I are working towards doing our first casts. To that end I’ve milled out a wax Star Trek logo that I hope to cast into a gift for my sister-in-law this holiday season. It will have an EL panel behind it and will be worn as a brouch.

image