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Vinten Tripod Leg Lock

I was doing a video shoot with Ben Nelson for Brown Dog Gadgets last week and I noticed his Vinten tripod leg had an issue staying locked in place… Seems one of the leg lock pieces had broke in half. It seemed liked a perfect reason to fire up OpenSCAD and get the 3D printer spitting out a new part.

In the photo above you can see the new part in silver, and the two original parts on the other legs, in black.

It took two prints to get an acceptable fit. The first was a little too wide and wouldn’t quite fit in place. I tweaked the file just a bit and the second version worked well. I’ll walk through the process a bit below.

For an organic shape like this I usually start by putting it on a desktop scanner to get the profile. This one is curvy, and I’m not big on drawing curves in OpenSCAD, but I am big on scanning in an object and then tracing it in Inkscape. I did a few scans and even then I edited the image a bit to adjust the contrast.

I import the images into Inkscape, each layered directly on top of each other, then add another layer on top of that to do the drawing. I can then easily switch out the image below and compare things. For a symmetrical drawing like this I really just need to draw half of it, then I just dupe and flip to make the other half and combine them into one.

Once I have a vector file created I export that and then import it into an OpenSCAD file where I can extrude it changing it from a 2D shape to a 3D shape. Creating a solid object is the goal. Once I’ve got a solid object I can start knocking holes in it and adding angles by subtracting with various shapes. (The reddish parts are all subtractions or differences from the main piece.)

And yes, the above image does appear to be some sort of special forces TIE Fighter from the Star Wars universe.

Here’s our final piece, ready to be rendered, sliced, and printed. The original part had some pockets on the top and bottom, but since they were not required for functionality I left them out.

Ben installed it and briefly tested it and it seemed to work, though time will tell if it holds up under stress. (Also, this one is PLA so if he leaves the tripod in a hot car, it might soften and fail.) I’ll probably print a few more for him to keep in the tripod bag in case this one does fail in the field.

If you want to print one of these, you can grab the file from Vinten Tripod Leg Lock and have fun!

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STL to SVG

Sometimes I need a 2D vector version of something that is a 3D model. Here’s how I do it. First, if there is an STL file, I load that into OpenSCAD.

For this model I wanted a top view so I could use the hole pattern to laser cut a mounting plate.

I select Show Axes because I’m gonna need that later…

The axes will show the center of the canvas, and luckily our model is centered…

Change the view from Perspective to Orthogonal

If you don’t know the difference between perspective view and orthogonal view, do some research I guess. (I probably learned about them in 7th grade drafting class.) Otherwise, switch between the views and it should make sense…

Okay, next I view the object from the front. Looks good!

I then add the translate command so that I can move the object in 3D space, and I lower it down, in this case 10mm, because the center line is where it will be cut.

The line projection(cut=true) then cuts a slice at the zero point in the Z axis… But we’re not done yet.

(Oh, if you choose cut=false you’ll just get the whole object, not a slice at a specific cross section of it.)

Here we can see what it looks like at an angle, which might make a bit more sense…

Let’s switch from orthogonal back to perspective view… Not required, but I’ll do it anyway.

Back to the top view… and now with the projection you can see the slice we took from the 3D model.

The next step is important… we need to Render the file! You can’t export the SVG file until you render your model.

The model will change… in this case you can see the shapes are now green with red outlines.

And now we can Export as SVG. (You could also use DXF if you need to, though that’s a garbage format I tend to avoid.)

Here’s the SVG open in Inkscape. Brilliant! I can now add to it, and my hole pattern is spaced properly for the mount I want to make. Excellent.

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Ball Feeder Mechanism

Here’s this week’s progress on the wax ball feeder mechanism. These are actually 2D files that were laser cut, but I sort of like the look of making them 2.5D so you can see the dimensionality.

Oh, to make the 3D render I exported a DXF file from Inkscape, load it into OpenSCAD and then use the linear_extrude function.

And yeah, these files are already outdated as there was one mistake (which I fixed with the bandsaw) and I’ve assembled it and found room for improvement.

You can see some earlier iterations here, here, here, here, here, here, and here. Which is to say, if you want to see minor updates with very little context, follow @raster on The Instagram.

You’ll notice an issue with the balls getting stuck in the chute, so there’s a bit of work to do there. I’ve got a few ideas, just need time to test them.

And don’t worry, at some point this might all make sense, once you see the rest of the thing. Or maybe it won’t… who knows!?

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Quick 3D Sketches

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I’ve found that I prefer firing up OpenSCAD and writing some lines of code to actually trying to sketch simple 3D objects on paper. I grabbed a notepad and thought I could knock out a sketch, but then decided I preferred a model I could spin around and easily edit, and in no time I had what I needed.

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I’ve found that mocking up cabinets in OpenSCAD works for me. These are not final plans to fabricate something, just quick sketches to communicate ideas with others.

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Casting Wax Balls

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I made wax balls, and it worked, and I did it using 3D printed molds. I won’t get into why I want/need wax balls in this post, but I swear it has nothing to do with candle making or bath bombs. (These balls are about 12mm in diameter.)

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I originally modeled one ball with one sprue, and then used the loop function of OpenSCAD to make a series of them in a row, slightly overlapping the sprues.

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My original plan was to make silicone molds (like I did with this wax stick) and went as far as creating a positive and a mold box, but along the way I thought about just using a 3D printed mold…

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Here’s the 3D printed mold created using PLA filament. The holes are for bolting the two pieces together using 3mm hardware. (I used tape in the earlier versions, but it did not work well.)

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I didn’t need to fill all the bolt holes, but wanted a few options so I could get tight clamping. Wax doesn’t have the same low viscosity of something like water, but when melted is a bit runny, so I just want to make sure I can keep it from leaking out too much.

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Once the mold is assembled it’s just a matter of melting some wax and pouring it into the mold. I’ve had a few balls with air pockets when demolding, so I’ve taken to sticking a thin piece of wire in to stir around the wax in an attempt to remove the air. (I do have a vacuum pump which I’ve considered trying to use, but the chamber is currently too small to fit much in it.)

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Hey, wax balls! Originally I tried spraying the mold with mold release, but I don’t think it helped much. What does help is putting the cooled molds into the freezer for a bit (this is a known trick for getting wax candles out of glass jars.) It helps solidify the wax enough to make it come out fairly easily. I do break a few every now and then but a lot less than before I used the freezer method.

The other great thing about using 3D printed molds is that I can very easily (and cheaply) make a whole bunch of molds, which is good, because I may need a few thousand wax balls…