Archive | 3DPrinting

Cascade Window Shoe Replacement

Continuing adventures in 3d printing, I had a double pane window fail and got a $1,100 quote to replace it. In the end the failure was the “shoe” locking mechanism inside the counter-weight system. Although there is no counter-weight like a windows from the 1700’s that Nash might have installed, but four coil springs. The rest of the window was fine. I designed and printed replacement parts which you can find here on thingiverse.

Nash, by the way, designed all those beautiful houses around Regent’s Park. Notice the sash windows. These have counter-weights in them, or at least did a few hundred years ago:

The original shoe in my (crappier, more modern) windows used a fairly small amount of plastic at the most stressed part of the design. Failure of decade-old plastic mechanical parts appears to be a common thing, and it looked as if designed to fail exactly when the warranty expired.

I wonder if the designers were designing this to fail on purpose or really thought the thing would last. It’s possible they thought the plastic wouldn’t become so brittle, yet it’s clear they were minimizing the amount of material used to make it. This reminds me of a carrier furnace I used to own where they made the drip pan out of a rusting metal. Some bad design is so egregiously bad it strays in to being plain immoral, like the Bronco roof which couldn’t support its own weight and would kill you if it rolled.

The wonderful thing about 3d printing is, nobody has to design these things ever again and you can go print them out of titanium if you want to.

Iteration as Evolution

In Sheffield I once saw a selection of table forks in a museum. They were arranged over time, maybe 200 or 300 years of forks. From the left to the right they evolved from long two-pronged meat stabbing devices in to the short four-printed fork we know today.

To deal with a sump pump issue I had need to make a 1 1/4 inch pipe connect to a US garden hose. Such a thing didn’t exist on Thingiverse as far as I could find, so I hacked one together.

Here’s versions 1 though 6 of that connector. What’s interesting to me is that this is how I, and I think most people, actually build things. In a Taleb-esque random search rather than any real top-down design that JustWorks(TM) the first time you try it. It’s the messy real-world process of learning-by-doing.

  1. Version 1 on the far left was from Thingiverse. It assumed the hose had no screw connector and instead would be jammed inside, which was wrong. The pipe on the bottom was too narrow to actually fit in the 1 1/4 inch pipe.
  2. V2 was made with the OpenSCAD thread library. The thread part was too narrow because I measure the wrong thing. The pipe was too fat because it conformed to the outer, not inner dimensions of the pipe.
  3. V3 fixed the screw top, nearly. It was still a little too narrow, maybe due to plastic oozing effects or something. The bottom was too narrow because I mixed up radius and diameter.
  4. V4’s screw was perfect, but the bottom was too thick due to plastic expansion from the printing process
  5. V5, same problem
  6. V6 I shortened it a little and use some plumbers tape and it worked great

Each iteration took about an hour to print and test over a few days. You can download it at Thingiverse.

It’s better to just START and iterate than to sit around thinking about problems.

3D Printing Bar End Plugs

Continuing the theme of 3d printing… One of my bikes lost its bar end plugs, the holes on the ends here:

To me, these looked approximately like two circles joined by straight lines. Or, sort of an egg-shape. Enter 3D printing! Here’s my hacky model:

And here it is printed:

And two of them, one white, one green, on the bike:

This is sort-of pointless-yet-fun 3d printing, which so far has been the majority of it (the exception being the lever).

All the files are on Thingiverse here.

Access to Tools

This YayLabs Play and Freeze Ice Cream Ball Ice Cream Maker has two identical screw lids on opposite sides of a sphere. In one you put heavy cream and whatever else you want in your ice-cream. In the other you put lots of ice and rock salt. The salt lowers the melting point of the ice, dragging the cream colder than where water would otherwise freeze. You roll the ball around and after 10 minutes or so, have ice-cream.

The problem is that due to various thermal effects the lids get very stuck. Like, hitting-them-with-a-hammer-doesn’t-work stuck. My first theory was to make a cylinder with a notch in it and hope that provided enough grip top open the thing. So I designed and then 3D printed this in 30 minutes:

Which goes on like this:

And of course, that didn’t work. So I added a handle for a lever using OpenSCAD:

Then put it through the printing process using Simplify3D:

Ending up with a basic lever tool:

Which works great!

This isn’t solid plastic. Simplify3D prints a three-dimensional crosshatch mesh inside the solid and it apparently has more than enough strength to open the ice-cream maker. It took about 5.5 hours to print and a few dollars of plastic. I was hoping that some similar tool already existed, with a variable width on the notch piece, to open things like this (or CameklBak’s for example!) But, I couldn’t find anything with my various searches.

I can’t help but think back to The Whole Earth Catalog – Access to Tools:

Making your own tools is a powerful experience, physical tools like my lever thing or ephemeral like software. Try it.

It also made me wonder if this is approximately how things will work out when we get to Mars – shipping lots of 3D printers instead of parts since the cost of delivery will be pretty high and we don’t really have a clue what they’ll need on the ground.

The total design time was about 10 minutes, and the code is all static numbers which reflect the rough measurements of the lids. It helps if you already know some geometry and have the OpenSCAD cheat sheet open.

Someone could take it and make it a more generic tool for various lids by putting different cylinder-notch combinations down the length of the tool, instead of just one at one end. It could also use both sides. Or, various cylinders with a notch on top to take a lever. The lever could be printed or use some common size, like a screwdriver that you could slot in to use as a lever.

The obvious thing to do would be to print a nut in to the top of the cylinder so you can use a wrench. I don’t think it’s very likely the 3D printed plastic would handle the stress of that however. Presumably things like this exist in metal already somewhere, and we can print in various metals today too.

The length of the lever is about the limit of what my printer can print – about 20cm or so, which is less than a foot.

The files are all here on Thingiverse.

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