Making High Quality Copies Of Existing Parts Using A Silicone Mold

3D printing has made it incredibly easy to produce small runs of plastic parts, but getting rid of the 3D printed look can be tricky and time-consuming. When you need a smooth and polished finish, or you want to make exact copies of an existing injection molded part, casting resin parts in silicone molds is an excellent option. [Eric Strebel] has plenty of experience with the process, and demonstrates it in detail while creating copies of violin chin rests that are no longer in production. It's an interesting application, where 3D-printed layer lines are not just an aesthetic issue, but something that would irritate the user's skin if present.

Creating silicone molds requires a bit of forethought about the mold design. You want to select the split line to make it as easy as possible to remove the finished parts, while also placing the resin pouring sprue and vents to prevent air bubbles from getting trapped in the mold. In [Erics] case, it's impossible to use a simple planar split line, so he mounts the master part on a block of wood and uses cardboard and modeling clay to create a volume where the second side of the mold will protrude in the first side. It's important to note that sulfur-free clay must be used, otherwise the silicone might not cure.

One side of the silicon mold is cast first, and after curing it is placed back in the mold box with the master part to allow casting the other side of the mold. At this point [Eric] super glues the sprue-former and vent rods to the master parts before molding the second side. A release agent consisting of petroleum jelly and naphtha is added wherever the two sides of the mold will touch, to prevent them from sticking together.

Bubbles are your enemy while resin casting, so ideally you need a vacuum chamber to degas the silicone and resin before casting, and a pressure chamber to allow the resin part to cure. While pouring the silicone for the molds, the mold box is placed on a vibration table to allow any bubbles to rise to the surface. While the entire mold-making and molding process is time-consuming, the copied parts are almost indistinguishable from the original.

[Eric] has also shown us how to make much larger silicone molds in the past. If you find yourself making lots of different-sized mold boxes, it might be worth building an adjustable mold box.

#toolhacks #castingresin #ericstrebel #siliconemold

How To Build With Acrylic Using the Tools You Have

In a perfect world, we'd all have laser cutters and could pop intricate designs out of acrylic sheets with just a few clicks of the mouse. But in reality, most of us have to make do with the pedestrian tools we have at hand. For many, that might even mean everything has to be done by hand. Luckily, [Eric Strebel] has been working on a series of videos that cover how you can make professional looking parts out of acrylic using a wide array of common tools.

Solvent welding hand-cut pieces of acrylic.

The first video demonstrates how a simple cube can be constructed by a band saw, a table saw, and if need be, with hand tools. You might think the two power saws would have similar results, but as [Eric] explains, the table saw ends up being far more accurate and requires less post-processing to get a smooth edge. Ideally you'd run the cut pieces through a router to bevel them, but that's a tall order for many home gamers.

As for the hand tool approach, scoring and snapping the sheets ends up making a surprisingly clean break that can actually be cleaner than the edge you'd get with a power tool. No matter how you cut them, [Eric] shows the proper way to apply the water-like solvent to your acrylic pieces to create a strong and visually attractive bond.

The next video in the series covers more advanced techniques that can still be pulled off without a top-of-the-line workshop. Sure the water-cooled acrylic bender he has is pretty slick, but if you can't afford the $100 USD gadget, he shows you how to get similar results with an old toaster oven that you can pick up from the thrift store or even the side of the road. With some hand-made jigs and molds, you can warp and flex the heated plastic into whatever shape your project needs. Combining the tips from both videos, you might be surprised at what can be created with little more than a ruler, some hot air, and the appropriate techniques.

These are just the latest in a long line of fantastic videos that [Eric Strebel] has produced about at-home design and fabrication. Whether its making a two part silicone mold or creating functional prototypes out of foam board, there's an excellent chance that he's covered a topic you've wanted to learn more about.

#howto #toolhacks #acrylic #bendingacrylic #cutting #ericstrebel #handtools #tools