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More Mold Making

My last mold making experiment was a good experiment, and if I learned one thing, it’s that the mold should be flexible to allow for the removal of the piece you are casting without destroying the mold or the casting. (Duh!) Instead of ABS I decided to print a mold using flexible filament. Now, to print flexible filament I had to do a small modification to my extruder lever to allow the insertion of a piece of PTFE tubing so that the filament wouldn’t bend over before it fed into the feed gear. Once I did that, I was printing flexible filament (very slowly.)

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I decided to start with something less complex, and used a 2.5D object instead of a 3D object. I had an illustration of a hammer, which seemed to be a simple shape, with no weird inside parts or sharp corners. I started by opening the vector file in Inkscape.

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Once I had the file open I used Inkscape’s dynamic offset feature to extend the shape into a larger piece so I’d have “walls” for my mold.

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I did a Boolean difference between the original and the scaled part to get the wall piece, with the wall pieces being approximately 4mm wide.

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I also created a bottom plate that the wall piece would attach to. I did not make it fit with pins or any other alignment method, I just ended up using tape to hold the pieces together.

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Here are the modeled pieces. The wall piece was easy enough to flex around, but seemed strong enough to hold up for the casting.

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And here are the printed pieces. The flexible filament did not print as well as PLA does, and there were some rough parts on the top of the walls, but it wasn’t going to matter for these purposes.

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I put the two pieces together and applied some masking tape to hold them. Since I was going to use plaster I knew that it didn’t have to be too water-tight to hold the plaster in place.

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I then filled the vessel with the plaster. (Yeah, I have a big bag of plaster on hand for weird reasons, so I occasionally use it, though eventually I want to use concrete for these experiments.)

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After letting the plaster dry for a few days I removed the tape and then pulled off the bottom…

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…and then was able to flex the wall piece enough to get the plaster out of the mold, so that worked pretty well. Again, this was not a complex shape, which really helped as I just had to push the piece straight down through the mold.

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And here’s my (tiny) plaster hammer. I like how it turned out. The edges are not perfect, but then, what is, Right?

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I ended up making two of them, and with one I found that it was fairly easy to shape the edges using tools, so my 2.5D hammer (sort of) became a 3D hammer.

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Simple Wire Bender

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We’ve got a project at Brinn Labs where we need to bend some 16 gauge wire. The wire bends very easily, in fact, too easily, and you can bend it by hand, but you can’t really get nice curves. I looked up “wire benders” and found “fret benders” which people use to curve the frets for guitar building.

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So I found this video titled DIY FRET BENDER – $5 USD FRET BENDER and I was in such a hurry I didn’t even realize the guy provided a bunch of design files! I guess I just often assume people don’t supply files, so I took a screen shot of the design and then dropped it into Inkscape and…

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I just whipped up my own design quickly. Since I didn’t want to screw around with using the CNC machine for this, I just exported the DXF and extruded it in OpenSCAD so I could create an STL file suitable for 3D printing. Since there’s a slot and not just holes, it’s not the most fun thing to make with a drill press. Typically slots require a bit more work than holes, with filing and other time consuming hand tool work that is often best left to machines…

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I designed three parts, and then printed the body and three spacers and six guides. You’ll notice a small lip on the guide piece. That’s to just touch the inside of the bearing so they can roll smoothly. The bearings? Yeah, tear apart that fidget spinner! We’ll need three bearings.

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We’ll also need three 5/16″ bolts and nuts, though you could certainly use 8mm if you’ve got those handy. Hey, look, we’ve now got a wire bender!

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There’s a little room for improvement on this version… The slot could be a little narrower, and I’ve found that without pliers it’s a bit difficult to tighten the nut. I fixed that by 3D printing some nut knobs so it can easily be tightened by hand. (I already had my own nut knob design file, but you can find plenty on Thingiverse and Youmagine.) No photo because I added it later. :/

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This was a really simple build, and since fret benders often cost $50 to $100 (though I saw one for $25 on eBay) this was pretty dirt cheap. I don’t know if it’s up to the task of bending frets, but it should work fine for the wires we need to bend.

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If I get around to it I’ll clean up the files and release them. You never know when you might need to bend some wire!

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3D Printing (on fabric!)

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I finally got around to 3D printing on fabric. It worked out okay. I need to experiment a bit more to perfect it, but for a first attempt, it worked out okay.

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I used OpenSCAD to design a bump, and then made a field of bumps. (It’s a low-poly half sphere, actually. Really simple to do in OpenSCAD.)

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Also really easy to generate a bunch of them in OpenSCAD by using two for loops. I know OpenSCAD isn’t for everyone, but if you think in code, it might work for you.

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I used this organza fabric to print onto. It’s a mesh material, so the process of printing on it involves printing a few layers, then pausing the print, moving the print head out of the way, laying down the fabric, securing it to the bed, then continuing the print. The fabric gets embedded within the layers of the print.

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My Maker Select Plus did not allow me to pause the print and move the extruder using the on screen controls, so I added some custom gcode to my print. Cura has a post-processing plugin that allows you to inject gcode bits into your script. I had make an edit to get it to work with my printer. And then I actually made my own version so I don’t lost the changes when I upgrade Cura next time.

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So what use is this? It allows you to wrap a print around something. It an be used to create fake armor for cosplay, or to wrap anything cylindrical, or add an interesting texture to something. Over at Milwaukee Makerspace we may have something in the works for Maker Faire Milwaukee this year.

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Stay Tuned!

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CAD Things…

Stand

I recently had to design a simple cabinet to serve as a stand for a mill/lathe. I thought about pulling out some rulers and triangles (yes, I used to actually do drafting with pencils and paper) but instead I decided to try using OpenSCAD.

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I used specific colors in my design, of course when you actually render a thing in OpenSCAD the color goes away, but you can export the different views just fine without rendering. Here are the various view of the thing. Oh, since OpenSCAD is a “unit-less” thing which mostly outputs in millimeters (at least for STL files) I just assumed the units were inches.

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I used the OpenSCAD “scale” feature to scale up the thing by 25.4 times in each direction, which means my 1 millimeter became 1 inch.

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But in a real drawing you plan to hand to someone you need dimensions for things. While there’s been some experimentation in adding them, there just doesn’t seem to be an easy way to show dimensions of things in OpenSCAD. I resorted to printing out paper and marking it up… with a pencil.

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I probably need to learn how to use FreeCAD for this sort of thing. I’m sure I can easily add dimensions with it. One of the really interesting things about FreeCAD is that it has an OpenSCAD Module. You can import a CSG file which you’ve exported from OpenSCAD, and you can just open .scad files as well.

Much more to explore here… stay tuned!

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Adjustable Rectangular Mount

Adjustable Rectangular Mount v1

I finally got around to creating a parametric version of the 3D printed mount I’ve been using for the past few years. Typically I’d just open a previously designed thing in OpenSCAD, make some adjustments, and export an STL to print. Eventually I realized that I should just create a bunch of variables so I can easily just make minor adjustments each time and not have to do a bunch of find & replace operations.

The result is Adjustable Rectangular Mount v1 which you can find on Thingiverse and Youmagine.

It’s a work in progress, and it still needs some tweaking, but I figured it was worth releasing to the world. (Hey, make it better if you can!) It doesn’t work for all sizes and configurations, but for most of my needs, it’s good enough.

Adjustable Rectangular Mount v1

I should probably do more research on how to improve things by reading through other OpenSCAD code, but as mentioned, you’ve gotta start somewhere. I’ll probably be using this one quite a bit in the future, and I’ll update it as I can.

This mount specifically expects that you can use screws (or bolts) to mount it to a surface you can screw into or drill through. I also often add some double-sided foam tape to the inside of the mount and stick it directly to the object being mounted.