Browsing posts in: LaserCutter

Candle lantern design thoughts…

I’ve been spending some time doing a design in Fusion 360 for a laser-cuttable lantern, and I’ve discovered a few things. I’m recording them here to help others and to remind myself when I come back to this in a few months/years.

I started with a simple outline drawing of a tree that I wanted to use as the inset for the side panels:

Alder

I need to get that into Fusion in a way that works. Here’s what I came up with

From 2d to 3d

There are a couple of different approaches to doing this. If you have something that is simple, I recommend the “trace it yourself method”. In this, you insert the picture into Fusion as a Canvas (Insert->Attached Canvas), and then draw an outline in a sketch using it as a guide. I used splines and did a reindeer and rabbit outline pretty quickly, and then nice part is that manipulating the splines after that is simple and quick.

That was going to be a ton of work with the branches and I was both lazy and worried that it would be too complex to work well. So I took the alternate approach:

  1. Load the image into Inkscape and save it as an SVG.
  2. Use SVGtostl.com, upload the svg, and specify how thick you want it to be. You will be able to change this later though it’s a pain, so try to get close.
  3. In Fusion, in a new design, choose Insert->Insert Mesh, and choose the file.
  4. Switch from model mode to mesh mode.
  5. In the browser tree, right-click on the mesh and choose “properties”. My trees end up with 13000 facets, which is about 3 times as many facets as I wanted.
  6. Use the modify->remesh and modify->reduce options to get down the count that you want. You will probably have to experiment a bit to get it to work right. Start with Remesh, and preserve sharp edges and boundaries. You now have a mesh.
  7. Switch from mesh mode to patch mode
  8. Select the mesh in the browser
  9. Modify->mesh to brep. This is changing from the mesh representation – which you can’t really modify in Fusion – to the brep representation, which you can. This may take a while. At this point, you have both a mesh and brep version of the object in the tree. Delete the mesh version as it’s just taking up memory.
  10. If you look at the brep version, it has a ton of faces on it. This will slow things down, so it’s nice to clean up the faces. Modify->merge, choose “select chain”, and then click on one of the front faces. That should select all the faces.
  11. Click “ok. That’s going to sit and spit for quite a while, but eventually it should finish and you should just see one common face. Or maybe Fusion will hang and you’ll have to restart it.
  12. Convert the resulting body to a component, and save it.

Using the resulting design

The resulting design is very complex and will likely kill Fusion. It tried to use it to create panels for all four sides of the lantern, and that was a full failure; it would take a full 30 seconds to render.

What I ended up instead was doing the full design in Fusion without the complex branches. It looks something like this:

image

I designed one side of the lantern and then used pattern on path to duplicate it around 4 sides to make sure everything worked, and then used it to cut the top and bottom for the tab holes.

Then, I took the original side that I designed, converted it to a component, and did the compositing of the side and the branches in a design that only had those parts. That worked well from a performance standpoint and since all four sides are identical, I can just cut the single one four times.

To get this to work I had to move the components so they were okay left/right, use align to move the frame so the front is coplanar to the front of the branches, and then extrude a couple tools to cut off the branches where they were too wide for the frame.

image

Cutting on 2.7mm plywood (was supposed to be 3mm….) took about 5 minutes for each side, and a couple of minutes for the top and bottom.

Here’s a totally uncleaned/unsanded version. It would also look nicer if I taped the wood to protect it:

image



Chemistry nameplate

A somewhat belated present for my wife – belated because my Glowforge had to go back to the shop.

I wanted to do something chemistry-related for her. In the past I’ve bought her a few items like the MadeWithMolecules jewelry, but we all know that gifts that are handmade mean oh so much more.

So, I came up with a concept; a nameplate for her office with some sort of relevant compound on it, and ideally that compound would wrap over the top of her name.

The problem is that most organic compounds were either too complex or structurally inconvenient for the layout. I settled on dopamine, which looks like this:

Image result for dopamine

Which is fairly simple, except that I wanted to show all the atoms, so it really looks something like this:

Image result for dopamine model

I pulled out Visio and started playing around to see if I could get a two-dimensional representation that worked. And I did a bit of searching to find out atomic sizes and expected bond lengths, so that it could be accurate – which is a bit silly given that it pretends that atoms are round balls, but you get the idea.

Here’s what I ended up with:

image

Where:

  • Green = Oxygen (oxygen cylinders are green)
  • Blue = Hydrogen (because water is blue)
  • Grey = Carbon (it would be black, but the nameplate background is black)
  • Nitrogen = Yellow (because I like yellow and it looks good against black)

The atomic sizes and bond lengths are as close as I could get them. The bond angles are also mostly right, except for the two carbon/hydrogen bonds at the top; you have to pretend those are a 3-d projection.

I did a laser test engrave of that on some cheap plexiglass, and that worked okay, so I ordered up some 1/8” cast acrylic for the final version.

Unfortunately, the acrylic I ordered had plastic film protection rather than paper protection, and that plastic melted into the acrylic when I went to etch it, so the results sucked. About this time, my Glowforge went into permanent “too cold” state, so it had to go back, and then there were the holidays…

I eventually finished the prototype and gave it to my wife, and we agreed on two things. First, it was a little too small, and second, the saturated blue I used for the hydrogen atoms was too dark. So, here’s the remake of the production version, starting with the acrylic straight off the cutter:

IMG_9029

One of my challenges was figuring out how to paint it; a few tests showed that a brush was too big, and even a toothpick was too big; the bonds next to the tiny hydrogen atoms are *tiny*, and it’s important not to bleed paint from one area to another. I found some acrylic paint bottles, but they still had bit tips.

Finally, I found these:

image

These are syringes and tips that are sold as glue applicators. The tips are known as “Luer Lock” tips, and the twist right into the syringes. And this kit goes all the way to 25 gauge, which is *tiny*.

So, those showed up while waiting for the Glowforge, and then I had already purchased some acrylic paint from Michael’s:

image

If you are using the smallest tips, it’s pretty hard to suck paint up through them, so I used a big tip, pulled some paint into the syringe, and then switched to the smaller tip. It takes very small amounts of paint to do this; I have a lot more than I need here:

image

The technique is pretty simple; you put the tip into the corners and then carefully flow the paint into the corners to try to cover all of the walls in the paint, and after that you fill in the recess. I found that it made sense to work from different directions.

Partway through the name:

IMG_9031

Done with white (the bonds were a bitch, as I expected). This would look better but I didn’t clean the fine gauge tips well enough after the first version, so the ones I wanted to use were plugged.

IMG_9032

Done with paint. Those white spots are specular reflections from the track lights above my workbench

IMG_9033

Dry paint.

IMG_9034

And, finally, after the backing is removed:

IMG_9035

The coloring isn’t perfect; there are some spots where the black shows through, and in this light you can see the texture the laser cutter left. But overall, I think it’s pretty good, and it looks better in real life than in this shot.