Project Blog

I’ve played around with printing multiple colors using a single extruder, but by and large all the multi-color action was restricted to a single layer. There’s a good reason for this: every color change takes time, and having 2 or more colors run throughout the part would require a color change ON EVERY LAYER.

But I had to try. I had a great idea: a fairly understated bottle opener with different color text embedded on each side. To the uninitiated it’s a neat little thing, but to people who know 3D printing its a: “wait, what? how did you do that?”

Well, here’s “how I did that.” It took a LOT of time. I didn’t call it “The Saturday Killer” for nothing.

The Basic Idea:

Create a bottle opener with some multi-color text on the side. I chose a reference to the classic Simpsons line: “Beer. Cause Of. Solution To. Problems.” I knew it would be a complicated task, but it turned out to be even more complicated than I thought.

Step 1: Generate a separate STL for each color

Having already created the opener in OpenSCAD, this step was straight-forward. Position text on the sides (more on the font later,)

…use the Difference Command to create an opener with word holes,

…and use the intersection command to get a text object to fill each of those holes.

Step 2: Split each STL into printable segments

For the different colors to dovetail correctly, they can only be printed 2 layers at a time. To split the objects from step 1 into two-layer slices I used the difference command to remove all but a 2 layer section.


I then Generated an STL, moved the cubes, and repeated until I had all my slices.

Step 3: !#@$%@#$: Realize that this is way more complicated than you first thought.

Because you’re interlacing two or more STLs, how things are skeined becomes really important. If you’ve got a curve in the Z direction, or a transition that happens within a layer, things may skein one way for one color, but in a different way for the mating color.

So I needed to do a LOT more work, mainly on the text. I tried using a stock thingiverse font at first, but all the rounded corners were a killer, and I couldn’t get it to size correctly to an even number of layers. So I rolled my own:

If you look closely you’ll see that the text is blocky. This was done to confuse Skeinforge a little as possible. There are no diagonals or curves anywhere, and all transitions and openings take into account the layer thickness, as well as the width of the extrusion. This way there’s less confusion about how much plastic goes where, and the different colors are more likely to dovetail correctly.

Another thing that I added was a solid bar behind all the text. This caused the tool path to be much more continuous, resulting in nice, smooth letters.

Step 4: Actually Print

Now that all these parts were created they just needed to be printed out sequentially, with the Z-offset being adjusted at the appropriate time. My main aha moment during this process was that you need to turn off raft when skeining all but the first print, otherwise you get way too much plastic laid down.

I -of course- learned this the hard way. I first tried printing 4 openers at a time, and by the time I got to the middle of the opener there was so much plastic that the extruder started to catch leading to misalignment.

I scrapped that print and started printing a single opener, realizing the raft thing just after I started. The results were much better:

Step 5: Enjoy

I’m really proud of this thing, but I spent WAY too much time creating it. Hopefully this quick post did a good-enough job of explaining the process. I wanted to share this project, but for my sanity I just need to be DONE.

opener: http://www.thingiverse.com/thing:12592
font: http://thingiverse.com/thing:12618

I’ve been making bottle openers for friends, and I recently struck upon the perfect design for my friend Matt. For some reason, he still pines for a hockey team that left our home state in 1997 (THEN won the Stanley Cup.) His opener got a Whalers Logo:

Up to this point, all my openers have been single color. But combine the fact that I’m jealous of the new dual extruder with the fact that Matt was my Best Man, and I decided that this time I would go the extra mile.

The procedure was straight-forward, and a huge pain in the butt:

• First I printed a blank opener in the base color
• Then I adjusted the Z-Height of the Thingomatic by 5.76mm (the height of the opener base)
• When I switched the color to blue and printed the tail, the printer deposited the plastic on the white base as if it were the build platform
• After switching colors AGAIN, I printed the W and the opener was done

This was a fairly simple multi-color design, but by breaking up the model ahead of time, this technique could be used for any part.

I recently posted an improved bottle opener design to Thingiverse. Unlike the mighty bottle opener, this is one that I’m proud to give out, and people are happy to receive.

Because I did the model in OpenSCAD, it turns out to be really easy to create personal, one-of-a-kind gifts for my friends. In this post I’ll go through the steps I took to make an opener for my friend deWit. He skis, and he’s pretty good:

Ok, maybe he’s really good. Anyway, this has been my favorite skiing picture since it was taken a few years back. I thought it might be nice to capture some of this awesomeness in opener form.

Step 1: Get the image into Inkscape

The first thing I did was use the Windows snipping tool to copy into Inkscape just the section I wanted.

Step 2: Trace

Using the Bezier tool I then created a rough outline of what I wanted to print. This was going on a pretty small area, so I couldn’t get that much detail. Also important to note, I only used straight lines. No splines; they don’t seem to work in the upcoming steps.

Step 3: Save as DXF

Having served its purpose, I deleted the image to leave just the outline. I then saved the file as a DXF into my OpenSCAD directory.

Step 4: Import into OpenSCAD

This was the only painful part. Getting the DXF into OpenSCAD is a simple matter of calling the linear_extrude function. The problem is that the scale, position, and rotation of theDXF were way off. As a result I also needed to add scale, rotate, and translate commands to get the DXF stuff into place.

The code selected in the image above moves the part by [-89,86,thickness], rotates it 90 degrees, and scales by 70% on the x and y axes.

Once I was happy with the placement I exported to STL and moved over to ReplicatorG.

Step 5: Check the GCODE

Just because I drew this outline didn’t mean that that’s exactly what would get printed by the Makerbot. We’re working with a 0.5mm stream here, and some details may have been lost. Luckily you can visualize the gcode before the part gets printed.

In the Skeinforge profile, I made sure that SkeinLayer was turned on. This brings up a tool path visualization after the gcode is generated. Going to the last layer showed me the tool path I was interested in:

So here we can see that I lost some important detail. The ski-poles and backpack straps are missing. Time to tweak!

Step 6: Tweak

When I traced out the poles and straps I made them too thin. As a result Skeinforge just ignored them. By editing the nodes on my path I was able to make the tin spots a little thicker. I then repeated steps 3-5 and was rewarded with this:

OK! Printing time.

Step 7: Print!

Aaaand done. Pretty cool right? Maybe not as cool as hucking air off the wall at Kirkwood, but I’m pretty happy with the results. As you can see the detail is pretty poor, but that’s the nature of the medium and the size of the canvas.

This one is really pushing the limit of what you can fit into that tiny space. Here’s two more that I did that might give you a better idea of what can be accomplished if you choose an image that doesn’t require as much detail:

I’ve been having a lot of fun making these. It’s feels great to be able to give an inexpensive gift that’s personal and useful.